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1997 Microchip Technology Inc. December 1997 /DS33023A
PICmicro™
Mid-Range MCU Family
Reference Manual
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December 1997 /DS33023A
1997 Microchip Technology Inc.
Internationally Recognized Quality
System Certifications
Microchip’ s Quality System embodies the requirements
of ISO9001:1994. Our Microchip Chandler and Tempe
Design and Manuf acturing facilities ha v e been certified
to ISO 9001. The Microchip Kaohsiung Test facility, and
primary Assembly houses have been certified to ISO
9002. ISO certification plans are in-process for an esti-
mated certification grant by year-end 1997. In addition,
Microchip has received numerous customer certifica-
tions, including a Delco issued certificate of compliance
to AEC-A100/QS9000.
Microchip received ISO 9001 Quality System certifica-
tion for its worldwide headquar ters, design, and wafer
fabrication facilities in January, 1997. Our field-pro-
grammab le PICmicro™ 8-bit MCUs , Serial EEPROMs ,
related specialty memory products and development
systems conform to the stringent quality standards of
the International Standard Organization (ISO).
“All rights reser ved. Copyright © 1997, Microchip Technology
Incorporated, USA. Information contained in this publication
regarding device applications and the like is intended through
suggestion only and may be superseded by updates. No rep-
resentation or warranty is given and no liability is assumed by
Microchip Technology Incorporated with respect to the accu-
racy or use of such infor mation, or infringement of patents or
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erwise. Use of Microchip’s products as critical components in
life support systems is not authorized except with express
written approval by Microchip. No licenses are conveyed,
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The Microchip logo and name are registered trademarks of
Microchip Technology Inc. in the U.S.A. and other countries.
All rights reserved. All other trademarks mentioned herein are
the property of their respective companies. No licenses are
conveyed, implicitly or otherwise, under any intellectual prop-
erty rights.
Trademarks
The Microchip name, logo, PIC, K
EE
L
OQ
, PICMASTER,
PICSTART, PRO MATE, and SEEVAL are registered
trademarks of Microchip Technology Incorporated in the
U.S.A.
MPLAB, PICmicro, ICSP and In-Circuit Serial Programming
are trademarks of Microchip Technology Incorporated.
Serialized Quick-Tur n Production is a Service Mar k of Micro-
chip Technology Incorporated.
All other trademarks mentioned herein are property of their
respective companies.
1997 Microchip Technology Inc. DS00097D-page iii
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SECTION 1. INTRODUCTION 1-1
Introduction .......................................................................................................................................................1-2
Manual Objective ..............................................................................................................................................1-3
Device Structure ...............................................................................................................................................1-4
Development Support .......................................................................................................................................1-6
Device Varieties ...............................................................................................................................................1-7
Style and Symbol Conventions ......................................................................................................................1-12
Related Documents ........................................................................................................................................1-14
Related Application Notes ..............................................................................................................................1-17
Revision History .............................................................................................................................................1-18
SECTION 2. OSCILLATOR 2-1
Introduction .......................................................................................................................................................2-2
Oscillator Configurations ..................................................................................................................................2-2
Crystal Oscillators / Ceramic Resonators .........................................................................................................2-4
External RC Oscillator ....................................................................................................................................2-12
Internal 4 MHz RC Oscillator ..........................................................................................................................2-13
Effects of Sleep Mode on the On-chip Oscillator ............................................................................................2-17
Effects of Device Reset on the On-chip Oscillator .........................................................................................2-17
Design Tips ....................................................................................................................................................2-18
Related Application Notes ..............................................................................................................................2-19
Revision History .............................................................................................................................................2-20
SECTION 3. RESET 3-1
Introduction .......................................................................................................................................................3-2
Power-on Reset (POR), Power-up Timer (PWRT),
Oscillator Start-up Timer (OST), Brown-out Reset (BOR), and Parity Error Reset (PER) ..............................3-4
Registers and Status Bit Values .....................................................................................................................3-10
Design Tips ....................................................................................................................................................3-16
Related Application Notes ..............................................................................................................................3-17
Revision History .............................................................................................................................................3-18
SECTION 4. ARCHITECTURE 4-1
Introduction .......................................................................................................................................................4-2
Clocking Scheme/Instruction Cycle ..................................................................................................................4-5
Instruction Flow/Pipelining ................................................................................................................................4-6
I/O Descriptions ................................................................................................................................................4-7
Design Tips ....................................................................................................................................................4-12
Related Application Notes ..............................................................................................................................4-13
Revision History .............................................................................................................................................4-14
Table of Contents
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SECTION 5. CPU AND ALU 5-1
Introduction .......................................................................................................................................................5-2
General Instruction Format ...............................................................................................................................5-4
Central Processing Unit (CPU) .........................................................................................................................5-4
Instruction Clock ...............................................................................................................................................5-4
Arithmetic Logical Unit (ALU) ...........................................................................................................................5-5
STATUS Register .............................................................................................................................................5-6
OPTION_REG Register ...................................................................................................................................5-8
PCON Register .................................................................................................................................................5-9
Design Tips ....................................................................................................................................................5-10
Related Application Notes ..............................................................................................................................5-11
Revision History .............................................................................................................................................5-12
SECTION 6. MEMORY ORGANIZATION 6-1
Introduction .......................................................................................................................................................6-2
Program Memory Organization ........................................................................................................................6-2
Data Memory Organization ..............................................................................................................................6-8
Initialization .....................................................................................................................................................6-14
Design Tips ....................................................................................................................................................6-16
Related Application Notes ..............................................................................................................................6-17
Revision History .............................................................................................................................................6-18
SECTION 7. DATA EEPROM 7-1
Introduction .......................................................................................................................................................7-2
Control Register ...............................................................................................................................................7-3
EEADR ............................................................................................................................................................. 7-4
EECON1 and EECON2 Registers ....................................................................................................................7-4
Reading the EEPROM Data Memory ...............................................................................................................7-5
Writing to the EEPROM Data Memory .............................................................................................................7-5
Write Verify .......................................................................................................................................................7-6
Protection Against Spurious Writes ..................................................................................................................7-7
Data EEPROM Operation During Code Protected Configuration ....................................................................7-7
Initialization .......................................................................................................................................................7-7
Design Tips ......................................................................................................................................................7-8
Related Application Notes ................................................................................................................................7-9
Revision History .............................................................................................................................................7-10
SECTION 8. INTERRUPTS 8-1
Introduction .......................................................................................................................................................8-2
Control Registers ..............................................................................................................................................8-5
Interrupt Latency ............................................................................................................................................8-10
INT and External Interrupts ............................................................................................................................8-10
Context Saving During Interrupts ...................................................................................................................8-11
Initialization .....................................................................................................................................................8-14
Design Tips ....................................................................................................................................................8-16
Related Application Notes ..............................................................................................................................8-17
Revision History .............................................................................................................................................8-18
Table of Contents
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SECTION 9. I/O PORTS 9-1
Introduction .......................................................................................................................................................9-2
PORTA and the TRISA Register ......................................................................................................................9-4
PORTB and the TRISB Register ......................................................................................................................9-6
PORTC and the TRISC Register ......................................................................................................................9-8
PORTD and the TRISD Register ......................................................................................................................9-9
PORTE and the TRISE Register ....................................................................................................................9-10
PORTF and the TRISF Register ....................................................................................................................9-11
PORTG and the TRISG Register ...................................................................................................................9-12
GPIO and the TRISGP Register .....................................................................................................................9-13
I/O Programming Considerations ...................................................................................................................9-14
Initialization .....................................................................................................................................................9-16
Design Tips ....................................................................................................................................................9-17
Related Application Notes ..............................................................................................................................9-19
Revision History .............................................................................................................................................9-20
SECTION 10. PARALLEL SLAVE PORT 10-1
Introduction .....................................................................................................................................................10-2
Control Register .............................................................................................................................................10-3
Operation ........................................................................................................................................................10-4
Operation in Sleep Mode ................................................................................................................................10-5
Effect of a Reset .............................................................................................................................................10-5
PSP Waveforms .............................................................................................................................................10-5
Design Tips ....................................................................................................................................................10-6
Related Application Notes ..............................................................................................................................10-7
Revision History .............................................................................................................................................10-8
Table of Contents
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SECTION 11. TIMER0 11-1
Introduction .....................................................................................................................................................11-2
Control Register .............................................................................................................................................11-3
Operation ........................................................................................................................................................11-4
TMR0 Interrupt ...............................................................................................................................................11-5
Using Timer0 with an External Clock .............................................................................................................11-6
TMR0 Prescaler .............................................................................................................................................11-7
Design Tips ..................................................................................................................................................11-10
Related Application Notes ............................................................................................................................11-11
Revision History ...........................................................................................................................................11-12
SECTION 12. TIMER1 12-1
Introduction .....................................................................................................................................................12-2
Control Register .............................................................................................................................................12-3
Timer1 Operation in Timer Mode ...................................................................................................................12-4
Timer1 Operation in Synchronized Counter Mode .........................................................................................12-4
Timer1 Operation in Asynchronous Counter Mode ........................................................................................12-5
Timer1 Oscillator ............................................................................................................................................12-7
Sleep Operation .............................................................................................................................................12-9
Resetting Timer1 Using a CCP Trigger Output ..............................................................................................12-9
Resetting of Timer1 Register Pair (TMR1H:TMR1L) ......................................................................................12-9
Timer1 Prescaler ............................................................................................................................................12-9
Initialization ...................................................................................................................................................12-10
Design Tips ..................................................................................................................................................12-12
Related Application Notes ............................................................................................................................12-13
Revision History ...........................................................................................................................................12-14
SECTION 13. TIMER2 13-1
Introduction .....................................................................................................................................................13-2
Control Register .............................................................................................................................................13-3
Timer Clock Source ........................................................................................................................................13-4
Timer (TMR2) and Period (PR2) Registers ....................................................................................................13-4
TMR2 Match Output .......................................................................................................................................13-4
Clearing the Timer2 Prescaler and Postscaler ...............................................................................................13-4
Sleep Operation .............................................................................................................................................13-4
Initialization .....................................................................................................................................................13-5
Design Tips ....................................................................................................................................................13-6
Related Application Notes ..............................................................................................................................13-7
Revision History .............................................................................................................................................13-8
SECTION 14. COMPARE/CAPTURE/PWM (CCP) 14-1
Introduction .....................................................................................................................................................14-2
Control Register .............................................................................................................................................14-3
Capture Mode .................................................................................................................................................14-4
Compare Mode ...............................................................................................................................................14-6
PWM Mode .....................................................................................................................................................14-8
Initialization ...................................................................................................................................................14-12
Design Tips ..................................................................................................................................................14-15
Related Application Notes ............................................................................................................................14-17
Revision History ...........................................................................................................................................14-18
Table of Contents
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SECTION 15. SYNCHRONOUS SERIAL PORT (SSP) 15-1
Introduction .....................................................................................................................................................15-2
Control Registers ............................................................................................................................................15-3
SPI Mode ........................................................................................................................................................15-6
SSP I
2
C Operation .......................................................................................................................................15-16
Initialization ...................................................................................................................................................15-26
Design Tips ..................................................................................................................................................15-28
Related Application Notes ............................................................................................................................15-29
Revision History ...........................................................................................................................................15-30
SECTION 16. BASIC SYCHRONOUS SERIAL PORT (BSSP) 16-1
Introduction .....................................................................................................................................................16-2
Control Registers ............................................................................................................................................16-3
SPI Mode ........................................................................................................................................................16-6
SSP I
2
C Operation .......................................................................................................................................16-15
Initialization ...................................................................................................................................................16-23
Design Tips ..................................................................................................................................................16-24
Related Application Notes ............................................................................................................................16-25
Revision History ...........................................................................................................................................16-26
SECTION 17. MASTER SYNCHRONOUS SERIAL PORT (MSSP) 17-1
Introduction .....................................................................................................................................................17-2
Control Register .............................................................................................................................................17-4
SPI Mode ........................................................................................................................................................17-9
SSP I
2
C™ Operation ....................................................................................................................................17-18
Connection Considerations for I
2
C Bus ........................................................................................................17-56
Initialization ...................................................................................................................................................17-57
Design Tips ..................................................................................................................................................17-58
Related Application Notes ............................................................................................................................17-59
Revision History ...........................................................................................................................................17-60
SECTION 18. USART 18-1
Introduction .....................................................................................................................................................18-2
Control Registers ............................................................................................................................................18-3
USART Baud Rate Generator (BRG) .............................................................................................................18-5
USART Asynchronous Mode .........................................................................................................................18-8
USART Synchronous Master Mode .............................................................................................................18-15
USART Synchronous Slave Mode ...............................................................................................................18-19
Initialization ...................................................................................................................................................18-21
Design Tips ..................................................................................................................................................18-22
Related Application Notes ............................................................................................................................18-23
Revision History ...........................................................................................................................................18-24
Table of Contents
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SECTION 19. VOLTAGE REFERENCE 19-1
Introduction .....................................................................................................................................................19-2
Control Register .............................................................................................................................................19-3
Configuring the Voltage Reference ................................................................................................................19-4
Voltage Reference Accuracy/Error .................................................................................................................19-5
Operation During Sleep ..................................................................................................................................19-5
Effects of a Reset ...........................................................................................................................................19-5
Connection Considerations ............................................................................................................................19-6
Initialization .....................................................................................................................................................19-7
Design Tips ....................................................................................................................................................19-8
Related Application Notes ..............................................................................................................................19-9
Revision History ...........................................................................................................................................19-10
SECTION 20. COMPARATOR 20-1
Introduction .....................................................................................................................................................20-2
Control Register .............................................................................................................................................20-3
Comparator Configuration ..............................................................................................................................20-4
Comparator Operation ....................................................................................................................................20-6
Comparator Reference ...................................................................................................................................20-6
Comparator Response Time ..........................................................................................................................20-8
Comparator Outputs .......................................................................................................................................20-8
Comparator Interrupts ....................................................................................................................................20-9
Comparator Operation During SLEEP ...........................................................................................................20-9
Effects of a RESET ........................................................................................................................................20-9
Analog Input Connection Considerations .....................................................................................................20-10
Initialization ...................................................................................................................................................20-11
Design Tips ..................................................................................................................................................20-12
Related Application Notes ............................................................................................................................20-13
Revision History ...........................................................................................................................................20-14
SECTION 21. 8-BIT A/D CONVERTER 21-1
Introduction .....................................................................................................................................................21-2
Control Registers ............................................................................................................................................21-3
Operation ........................................................................................................................................................21-5
A/D Acquisition Requirements ........................................................................................................................21-6
Selecting the A/D Conversion Clock ..............................................................................................................21-8
Configuring Analog Port Pins .........................................................................................................................21-9
A/D Conversions ..........................................................................................................................................21-10
A/D Operation During Sleep .........................................................................................................................21-12
A/D Accuracy/Error .......................................................................................................................................21-13
Effects of a RESET ......................................................................................................................................21-13
Use of the CCP Trigger ................................................................................................................................21-14
Connection Considerations ..........................................................................................................................21-14
Transfer Function .........................................................................................................................................21-14
Initialization ...................................................................................................................................................21-15
Design Tips ..................................................................................................................................................21-16
Related Application Notes ............................................................................................................................21-17
Revision History ...........................................................................................................................................21-18
Table of Contents
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SECTION 22. BASIC 8-BIT A/D CONVERTER 22-1
Introduction .....................................................................................................................................................22-2
Control Registers ............................................................................................................................................22-3
A/D Acquisition Requirements ........................................................................................................................22-6
Selecting the A/D Conversion Clock ..............................................................................................................22-8
Configuring Analog Port Pins .......................................................................................................................22-10
A/D Conversions ..........................................................................................................................................22-11
A/D Operation During Sleep .........................................................................................................................22-14
A/D Accuracy/Error .......................................................................................................................................22-15
Effects of a RESET ......................................................................................................................................22-16
Connection Considerations ..........................................................................................................................22-16
Transfer Function .........................................................................................................................................22-16
Initialization ...................................................................................................................................................22-17
Design Tips ..................................................................................................................................................22-18
Related Application Notes ............................................................................................................................22-19
Revision History ...........................................................................................................................................22-20
SECTION 23. 10-BIT A/D CONVERTER 23-1
Introduction .....................................................................................................................................................23-2
Control Register .............................................................................................................................................23-3
Operation ........................................................................................................................................................23-5
A/D Acquisition Requirements ........................................................................................................................23-6
Selecting the A/D Conversion Clock ..............................................................................................................23-8
Configuring Analog Port Pins .........................................................................................................................23-9
A/D Conversions ..........................................................................................................................................23-10
Operation During Sleep ................................................................................................................................23-14
Effects of a Reset .........................................................................................................................................23-14
A/D Accuracy/Error .......................................................................................................................................23-15
Connection Considerations ..........................................................................................................................23-16
Transfer Function .........................................................................................................................................23-16
Initialization ...................................................................................................................................................23-17
Design Tips ..................................................................................................................................................23-18
Related Application Notes ............................................................................................................................23-19
Revision History ...........................................................................................................................................23-20
SECTION 24. SLOPE A/D 24-1
Introduction .....................................................................................................................................................24-2
Control Registers ............................................................................................................................................24-3
Conversion Process .......................................................................................................................................24-6
Other Analog Modules ..................................................................................................................................24-12
Calibration Parameters .................................................................................................................................24-13
Design Tips ..................................................................................................................................................24-14
Related Application Notes ............................................................................................................................24-15
Revision History ...........................................................................................................................................24-16
Table of Contents
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PAGE
SECTION 25. LCD 25-1
Introduction .....................................................................................................................................................25-2
Control Register .............................................................................................................................................25-3
LCD Timing ....................................................................................................................................................25-6
LCD Interrupts ..............................................................................................................................................25-12
Pixel Control .................................................................................................................................................25-13
Voltage Generation ......................................................................................................................................25-15
Operation During Sleep ................................................................................................................................25-16
Effects of a Reset .........................................................................................................................................25-17
Configuring the LCD Module ........................................................................................................................25-17
Discrimination Ratio .....................................................................................................................................25-18
LCD Voltage Generation ..............................................................................................................................25-20
Contrast ........................................................................................................................................................25-22
LCD Glass ....................................................................................................................................................25-22
Initialization ...................................................................................................................................................25-23
Design Tips ..................................................................................................................................................25-24
Related Application Notes ............................................................................................................................25-25
Revision History ...........................................................................................................................................25-26
SECTION 26. WATCHDOG TIMER AND SLEEP MODE 26-1
Introduction .....................................................................................................................................................26-2
Control Register .............................................................................................................................................26-3
Watchdog Timer (WDT) Operation .................................................................................................................26-4
SLEEP (Power-Down) Mode ..........................................................................................................................26-7
Initialization .....................................................................................................................................................26-9
Design Tips ..................................................................................................................................................26-10
Related Application Notes ............................................................................................................................26-11
Revision History ...........................................................................................................................................26-12
SECTION 27. DEVICE CONFIGURATION BITS 27-1
Introduction .....................................................................................................................................................27-2
Configuration Word Bits .................................................................................................................................27-4
Program Verification/Code Protection ............................................................................................................27-8
ID Locations ...................................................................................................................................................27-9
Design Tips ..................................................................................................................................................27-10
Related Application Notes ............................................................................................................................27-11
Revision History ...........................................................................................................................................27-12
SECTION 28. IN-CIRCUIT SERIAL PROGRAMMING™ 28-1
Introduction .....................................................................................................................................................28-2
Entering In-Circuit Serial Programming Mode ................................................................................................28-3
Application Circuit ...........................................................................................................................................28-4
Programmer ...................................................................................................................................................28-6
Programming Environment .............................................................................................................................28-6
Other Benefits ................................................................................................................................................28-7
Field Programming of PICmicro OTP MCUs ..................................................................................................28-8
Field Programming of FLASH PICmicros .....................................................................................................28-10
Design Tips ..................................................................................................................................................28-12
Related Application Notes ............................................................................................................................28-13
Revision History ...........................................................................................................................................28-14
Table of Contents
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SECTION 29. INSTRUCTION SET 29-1
Introduction .....................................................................................................................................................29-2
Instruction Formats .........................................................................................................................................29-4
Special Function Registers as Source/Destination ........................................................................................29-6
Q Cycle Activity ..............................................................................................................................................29-7
Instruction Descriptions ..................................................................................................................................29-8
Design Tips ..................................................................................................................................................29-45
Related Application Notes ............................................................................................................................29-47
Revision History ...........................................................................................................................................29-48
SECTION 30. ELECTRICAL SPECIFICATIONS 30-1
Introduction .....................................................................................................................................................30-2
Absolute Maximums .......................................................................................................................................30-3
Device Selection Table ...................................................................................................................................30-4
Device Voltage Specifications ........................................................................................................................30-5
Device Current Specifications ........................................................................................................................30-6
Input Threshold Levels ...................................................................................................................................30-9
I/O Current Specifications ............................................................................................................................30-10
Output Drive Levels ......................................................................................................................................30-11
I/O Capacitive Loading .................................................................................................................................30-12
Data EEPROM / Flash .................................................................................................................................30-13
LCD ..............................................................................................................................................................30-14
Comparators and Voltage Reference ...........................................................................................................30-15
Timing Parameter Symbology ......................................................................................................................30-16
Example External Clock Timing Waveforms and Requirements ..................................................................30-17
Example Power-up and Reset Timing Waveforms and Requirements ........................................................30-19
Example Timer0 and Timer1 Timing Waveforms and Requirements ...........................................................30-20
Example CCP Timing Waveforms and Requirements .................................................................................30-21
Example Parallel Slave Port (PSP) Timing Waveforms and Requirements .................................................30-22
Example SSP and Master SSP SPI Mode Timing Waveforms and Requirements ......................................30-23
Example SSP I
2
C Mode Timing Waveforms and Requirements ..................................................................30-27
Example Master SSP I
2
C Mode Timing Waveforms and Requirements ......................................................30-30
Example USART/SCI Timing Waveforms and Requirements ......................................................................30-32
Example 8-bit A/D Timing Waveforms and Requirements ...........................................................................30-34
Example 10-bit A/D Timing Waveforms and Requirements .........................................................................30-36
Example Slope A/D Timing Waveforms and Requirements .........................................................................30-38
Example LCD Timing Waveforms and Requirements ..................................................................................30-40
Related Application Notes ............................................................................................................................30-41
Revision History ...........................................................................................................................................30-42
SECTION 31. DEVICE CHARACTERISTICS 31-1
Introduction .....................................................................................................................................................31-2
Characterization vs. Electrical Specification ...................................................................................................31-2
DC and AC Characteristics Graphs and Tables .............................................................................................31-2
Revision History ...........................................................................................................................................31-22
Table of Contents
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SECTION 32. DEVELOPMENT TOOLS 32-1
Introduction .....................................................................................................................................................32-2
The Integrated Development Environment (IDE) ...........................................................................................32-3
MPLAB Software Language Support .............................................................................................................32-6
MPLAB-SIM Simulator Software ....................................................................................................................32-8
MPLAB Emulator Hardware Support ..............................................................................................................32-9
MPLAB Programmer Support .......................................................................................................................32-10
Supplemental Tools ......................................................................................................................................32-11
Development Boards ....................................................................................................................................32-12
Development Tools for Other Microchip Products ........................................................................................32-14
Related Application Notes ............................................................................................................................32-15
Revision History ...........................................................................................................................................32-16
SECTION 33. CODE DEVELOPMENT 33-1
Revision History .............................................................................................................................................33-2
SECTION 34. APPENDIX 34-1
I
2
C
Overview ...............................................................................................................................................34-2
List of LCD Glass Manufacturers ................................................................................................................. 34-11
Device Enhancement ...................................................................................................................................34-13
Revision History ........................................................................................................................................... 34-19
SECTION 35. GLOSSARY 35-1
Revision History ...........................................................................................................................................35-14
Table of Contents
1997 Microchip Technology Inc. DS31001A page 1-1
Introduction
1
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Section 1. Introduction
HIGHLIGHTS
This section of the manual contains the following major topics:
1.1 Introduction....................................................................................................................1-2
1.2 Manual Objective ...........................................................................................................1-3
1.3 Device Structure ............................................................................................................1-4
1.4 Development Support....................................................................................................1-6
1.5 De vice V arieties..............................................................................................................1-7
1.6 Style and Symbol Conventions....................................................................................1-12
1.7 Related Documents .....................................................................................................1-14
1.8 Related Application Notes............................................................................................1-17
1.9 Revision History...........................................................................................................1-18
PICmicro MID-RANGE MCU FAMILY
DS31001A-page 1-2
1997 Microchip Technology Inc.
1.1 Introduction
Microchip is the Embedded Control Solutions Company
. The company’s focus is on products
that meet the needs of the embedded control market. We are a leading supplier of:
8-bit General Purpose Microcontrollers (PICmicro™ MCUs)
Speciality and standard non-volatile memory devices
Security devices (K
EE
L
OQ®
)
Application specific standard products
Please request a Microchip Product Line Card f or a listing of all the interesting products that we
hav e to off er. This literature can be obtained from your local sales office , or downloaded from the
Microchip web site (www.microchip.com).
In the past, 8-bit MCU users were fix ed on the traditional MCU model for production, a R OM device
was required. Microchip has been the leader in changing this perception by showing that OTP
de vices can give a better lifetime product cost compared to ROM versions .
Microchip has a strength is in EPROM technology. That made it the memory technology of choice
for the PICmicro MCU’s program memory. Microchip has minimized the cost difference between
EPROM and ROM memory technology, and therefore Microchip can pass these benefits onto our
customers. This is not true f or other MCU vendors, and is seen in the price diff erence between their
EPROM and ROM versions .
The growth of Microchip’s 8-bit MCU market share is a testament to the PICmicro MCUs ability to
meet the needs of many. This growth has made the PICmicro architecture one of the top three
architectures av ailab le in the gener al market today. This g rowth w as fueled b y the Microchip vision
of the benefits of a low cost OTP solution. Some of the benefits for the customer include:
Quick time to market
Allows code changes to product, during production run
No Non-Recurring Engineering (NRE) charges f or Mask Revisions
Ability to easily serialize the product
Ability to store calibration data, without additional hardware
Better able to maximize PICmicro MCU inventory
Less risk, since the same device is used f or development as well as for production.
Microchip’ s PICmicro 8-bit MCUs off er a price/performance ratio that allows them to be considered
for any traditional 8-bit MCU application as well as some traditional 4-bit applications (Base-Line
f amily), dedicated logic replacement and lo w-end DSP applications (High-End family). These fea-
tures and price-performance mix make PICmicro MCUs an attractive solution for most applications.
1997 Microchip Technology Inc. DS31001A-page 1-3
Section 1. Introduction
Introduction
1
1.2 Manual Objective
PICmicro devices are grouped by the size of their Instruction Word. The three current PICmicro
families are:
1. Base-Line: 12-bit Instruction Word length
2. Mid-Range: 14-bit Instruction Word length
3. High-End: 16-bit Instruction Word length
This manual focuses on the Mid-Range devices, which are also referred to as the PIC16CXXX
MCU family.
The operation of the PIC16CXXX MCU f amily architecture and peripheral modules is explained,
but does not co ver the specifics of each de vice. Theref ore, it is not intended to replace the de vice
data sheets, but complement them. In other words, this guide supplies the general details and
operation of the PICmicro architecture and peripheral modules, while the data sheet s give spe-
cific details such as device memory mapping.
Initialization e xamples are given throughout this man ual. These examples sometimes need to be
written as device specific as opposed to family generic, though they are valid for most other
devices. Some modifications may be required f or devices with v ariations in register file mappings.
Note: The first few Mid-Range devices have minor device variations when compared to
this general description. We have tried to descr ibe these variations throughout this
manual. Please refer to the specific device data sheet for complete infor mation on
the device.
PICmicro MID-RANGE MCU FAMILY
DS31001A-page 1-4 1997 Microchip Technology Inc.
1.3 Device Structure
Each part of a device can be placed into one of three groups:
1. Core
2. Peripherals
3. Special Features
1.3.1 The Core
The core pertains to the basic features that are required to make the device operate. These
include:
1. Device Oscillator Revision “DS31002A”
2. Reset logic Revision “DS31003A”
3. CPU (Central Processing Unit) operation Revision “DS31005A”
4. ALU (Arithmetic Logical Unit) operation Revision “DS31005A”
5. Device memory map organization Revision “DS31006A”
6. Interrupt operation Revision “DS31008A”
7. Instruction set Revision “DS31029A”
1.3.2 Peripherals
P eripherals are the features that add a diff erentiation from a microprocessor . These ease in inter-
facing to the external world (such as general purpose I/O, LCD drivers, A/D inputs, and PWM
outputs), and internal tasks such as keeping different time bases (such as timers). The peripher-
als that are discussed are:
1. General purpose I/O Revision “DS31009A”
2. Timer0 Re vision “DS31011A”
3. Timer1 Re vision “DS31012A”
4. Timer2 Re vision “DS31013A”
5. Capture, Compare, and PWM (CCP) Revision “DS31014A”
6. Synchronous Serial Port (SSP) Revision “DS31015A”
7. Basic Synchronous Serial Port (SSP) Revision “DS31016A”
8. Master Synchronous Serial Port (MSSP) Revision “DS31017A”
9. USART (SCI) Revision “DS31018A”
10. Voltage References Revision “DS31019A”
11. Comparators Re vision “DS31020A”
12. 8-bit Analog to Digital (A/D) Revision “DS31021A”
13. Basic 8-bit Analog to Digital (A/D) Revision “DS31022A”
14. 10-bit Analog to Digital (A/D) Revision “DS31023A”
15. Slope Analog to Digital (A/D) w/ Thermister Revision “DS31024A”
16. Liquid Crystal Display (LCD) Drivers Revision “DS31025A”
17. Parallel Slave Port (PSP) Revision “DS31010A”
1997 Microchip Technology Inc. DS31001A-page 1-5
Section 1. Introduction
Introduction
1
1.3.3 Special Features
Special features are the unique features that help to do one or more of the following things:
Decrease system cost
Increase system reliability
Increase design flexibility
The Mid-Range PICmicro MCUs off er sev eral f eatures that help achiev e these goals. The special
features discussed are:
1. Device Configuration bits Revision “DS31027A”
2. On-chip Power-on Reset (POR) Revision “DS31003A”
3. Brown-out Reset (BOR) logic Revision “DS31003A”
4. W atchdog Timer Re vision “DS31026A”
5. Low power mode (Sleep) Revision “DS31026A”
6. Internal RC device oscillator Revision “DS31002A”
7. In-Circuit Serial Programming™ (ICSP™) Revision “DS31028A”
PICmicro MID-RANGE MCU FAMILY
DS31001A-page 1-6 1997 Microchip Technology Inc.
1.4 Development Support
Microchip offers a wide range of development tools that allow users to efficiently develop and
debug application code . Microchip’ s de v elopment tools can be brok en down into four categories:
1. Code generation
2. Software debug
3. Device programmer
4. Product evaluation boards
All tools developed by Microchip operate under the MPLAB™ Integrated Development Environ-
ment (IDE), while some third party tools may not. The code generation tools include:
MPASM
MPLAB-C
MP-DriveWay™
These software de v elopment programs include de vice header files . Each header file defines the
register names (as shown in the de vice data sheet) to the specified address or bit location. Using
the header files eases code migration, and reduces the tediousness of memorizing a register’s
address or a bit’s position in a register.
Tools which ease in debugging software are:
PICMASTER® In-Circuit Emulator
ICEPIC In-Circuit Emulator
MPLAB-SIM Software Simulator
After generating and deb ugging the application software, the de vice will need to be programmed.
Microchip offers two levels of programmers:
1. PICSTART Plus programmer
2. PROMATE II programmer
Demonstration boards allow the developer of software code to evaluate the capability and suit-
ability of the device to the application. The demo boards offered are:
PICDEM-1
PICDEM-2
PICDEM-3
PICDEM-14A
A full description of each of Microchip’s development tools is discussed in the “Development
Tools” section. As new tools are developed, product briefs and user guides may be obtained
from the Microchip web site (www.microchip.com) or from your local Microchip Sales Office.
Code de velopment recommendations and techniques are provided in the “Code De velopment”
section.
Microchip offers other reference tools to speed the development cycle. These include:
Application Notes
Reference Designs
Microchip web site
Microchip BBS
Local Sales Offices with Field Application Support
Corporate Support Line
Additional avenues of assistance can be found in many Web User Groups including the MIT
reflector PIClist. The Microchip web site lists other sites that may be useful references.
Note: Microchip strongly recommends that the supplied header files be used in the source
code of your program. This eases code migration as well as increases the quality
and depth of the technical support that Microchip can offer.
1997 Microchip Technology Inc. DS31001A-page 1-7
Section 1. Introduction
Introduction
1
1.5 Device Varieties
Once the functional requirements of the device are specified, some other decisions need to be
made. These include:
Memory technology
Operating voltage
Operating temperature range
Operating frequency
Packaging
Microchip has a large number of options and option combinations, one of which should fulfill y our
requirements.
1.5.1 Memory Varieties
Memor y technology has no effect on the logical operation of a device. Due to the different pro-
cessing steps required, some electrical characteristics may v ary between devices with the same
f eature set/pinout but with diff erent memory technologies. An e xample is the electrical character-
istic VIL (Input Low Voltage), which may ha ve some diff erence between a typical EPROM device
and a typical ROM device.
Each device has a variety of frequency ranges and packaging options available. Depending on
application and production requirements, the proper device options can be identified using the
inf ormation in the Product Selection System section at the end of each data sheet. When placing
orders, please use the “Product Identification System” at the back of the data sheet to specify the
correct part number.
When discussing the functionality of the device, the memor y technology and the voltage range
do not matter. Microchip offers three program memory types. The memor y type is designated in
the part number by the first letter(s) after the family affiliation designators.
1. C, as in PIC16CXXX. These devices have EPROM type memory.
2. CR, as in PIC16CRXXX. These devices have ROM type memory.
3. F, as in PIC16FXXX. These devices have Flash type memory.
1.5.1.1 EPROM
Microchip f ocuses on Erasable Programmab le Read Only Memory (EPROM) technology to giv e
the customers flexibility throughout their entire design cycle. With this technology Microchip
offers various packaging options as well as services.
1.5.1.2 Read Only Memory (ROM) Devices
Microchip offers a masked Read Only Memory (ROM) version of several of the highest volume
parts, thus giving customers a lower cost option for high volume, mature products.
ROM devices do not allow serialization information in the program memory space.
For information on submitting ROM code, please contact your local Microchip sales office.
1.5.1.3 Flash Memory Devices
These devices are electr ically erasable, and can therefore be offered in a low cost plastic pack-
age. Being electrically erasable, these devices can be both erased and reprogrammed without
removal from the circuit. A device will have the same specifications whether it is used for proto-
type development, pilot programs, or production.
PICmicro MID-RANGE MCU FAMILY
DS31001A-page 1-8 1997 Microchip Technology Inc.
1.5.2 Operating Voltage Range Options
All Mid-Range PICmicro™ MCUs operate over the standard voltage range. Devices are also
off ered which operate ov er an e xtended v oltage range (and reduced frequency range). Table 1-1
shows all possib le memory types and voltage range designators f or the PIC16CXXX MCU family.
The designators are in bold typeface.
Table 1-1: Device Memory Type and Voltage Range Designators
As you can see in Table 1-2, Microchip specifications its extended range devices at a more con-
ser vative voltage range until device characterization has ensured they will be able to meet the
goal of their final design specifications.
Table 1-2: Typical Voltage Ranges for Each Device Type
Memory Type Voltage Range
Standard Extended
EPROM PIC16CXXX PIC16LCXXX
ROM PIC16CRXXX PIC16LCRXXX
Flash PIC16FXXX PIC16LFXXX
Note:Not all memory types may be available for a particular device.
T ypical V oltage Range (1) EPROM ROM Flash
Standard C4.5 - 6.0V CR 4.5 - 6.0V F4.5 - 6.0V
Extended Before device characterization LC 3.0 - 6.0V LCR 3.0 - 6.0V LF 3.0 - 6.0V
Final specification (2) LC 2.5 - 6.0V LCR 2.5 - 6.0V LF 2.0 - 6.0V
Note 1: De vices fabricated in Microchip’s 120K Process Technology will have a maximum limit on VDD of 5.5V. New
device data sheets will specify Microchip’s technology designation
2: This voltage range depends on the results of device characterization.
1997 Microchip Technology Inc. DS31001A-page 1-9
Section 1. Introduction
Introduction
1
1.5.3 Packaging V arieties
Depending on the development phase of your project, one of three package types would be used:
The first is a de vice with an erasure window . Typically these are f ound in packages with a ceramic
body. These devices are used for the development phase, since the device’s program memory
can be erased and reprogrammed many times.
The second package type is a lo w cost plastic pac kage . This package type is used in production
where device cost is to be kept to a minimum.
Lastly, there is the DIE option. A DIE is an unpackaged device that has been tested. DIEs are
used in low cost designs and designs where board space is at a minimum. Table 1-3 shows a
quick summary of this.
Table 1-3: Typical Package Uses
Package Type Typical Usage
Windowed Development Mode
Plastic Production
DIE Special Applications, such as those which require minimum board space
PICmicro MID-RANGE MCU FAMILY
DS31001A-page 1-10 1997 Microchip Technology Inc.
1.5.3.4 UV Erasable Devices
The UV erasable version of EPROM program memor y devices is optimal for prototype develop-
ment and pilot programs.
These de vices can be erased and reprogrammed to any of the configur ation modes. Third party
programmers are also available; refer to Microchip’s
Third Party Guide
(DS00104) for a list of
sources.
The amount of time required to completely erase a UV erasable device depends on: the wave-
length of the light, its intensity, distance from UV source, the process technology of the device
(how small are the memory cells).
1.5.3.5 One-Time-Programmable (OTP) Devices
The availability of OTP devices is especially useful for customers expecting code changes and
updates.
OTP devices, packaged in plastic packages, permit the user to program them once. In addition
to the program and data EPROM memories, the configuration bits must be programmed.
1.5.3.6 Flash Devices
A Flash de vice allo ws its memory to be changed by an electric charge. This means that the sys-
tem can be designed so that programming may be performed in-circuit. Since no window is
required, the lower cost plastic packages can used for these devices.
1.5.3.7 EEPROM Devices
An EEPROM device allows its memor y to be erased by an electric charge. This means that the
system can be designed so that erasure and reprogr amming may be performed in-circuit. Since
no window is required, the lower cost plastic packages can used for these devices.
Note: Fluorescent lights and sunlight both emit ultra violet light at the er asure wav elength.
Leaving a UV erasable device’s window uncovered could cause, over time, the
devices memory cells to become erased. The erasure time for a fluorescent light is
about three years , while sunlight requires only about one week. To pre vent the mem-
or y cells from losing data, an opaque label should be placed over the erasure win-
dow.
1997 Microchip Technology Inc. DS31001A-page 1-11
Section 1. Introduction
Introduction
1
1.5.3.8 ROM Devices
ROM devices have their program memory fix ed at the time of the silicon manufacture. Since the
program memory cannot be changed, the device can be housed in the lower cost plastic pack-
age.
1.5.3.9 DIE
The DIE option allows the board siz e to become as small as physically possible . The DIE Support
document (DS30258) explains general information about using and designing with DIE. There
are also individual specification sheets that detail DIE specific infor mation. Manufacturing with
DIE requires special knowledge and equipment. This means that the number of manufacturing
houses that support DIE will be limited. If y ou decide to use the DIE option, please research y our
manufacturing sites to ensure that they will be able to meet the specializ ed requirements of DIE
use.
1.5.3.10 Specialized Services
F or OTP customers with established code, Microchip offers two specialized services. These two
services, Quick Turn Production Programming and Serialized Quick Tur n Production Program-
ming, that allow customers to shorten their manufacturing cycle time.
1.5.3.11 Quick Turn Production (QTP) Programming
Microchip offers this programming service for factory production orders. This service is made
av ailable for users who choose not to program a medium to high quantity of units and whose code
patterns have stabilized. The devices are identical to the OTP devices but with all EPROM loca-
tions and configuration options already programmed by the factor y. Certain code and prototype
verification procedures apply before production shipments are available. Please contact your
local Microchip sales office for more details.
1.5.3.12 Serialized Quick Turn Production (SQTPSM) Programming
Microchip offers a this unique programming service where a few user-defined locations in each
device are programmed with different serial numbers. The serial numbers may be random,
pseudo-random or sequential.
Serial programming allows each device to have a unique number which can serve as an
entry-code, password or ID number.
PICmicro MID-RANGE MCU FAMILY
DS31001A-page 1-12 1997 Microchip Technology Inc.
1.6 Style and Symbol Conventions
Throughout this document, certain style and f ont format changes are used. Most f ormat changes
imply a distinction should be made for the emphasized text. The MCU industry has many symbols
and non-conventional word definitions/abbreviations. Table 1-4 provides a description for many
of the conv entions contained in this document. A glossary is provided in the “Glossary” section,
which contains more word and abbreviation definitions that are used throughout this manual.
1.6.1 Document Conventions
Table 1-4 defines some of the symbols and terms used throughout this manual.
Table 1-4: Document Conventions
Symbol or Term Description
set To force a bit/register to a value of logic ‘1’.
clear To force a bit/register to a value of logic ‘0’.
reset 1) To force a register/bit to its default state.
2) A condition in which the device places itself after a device reset
occurs. Some bits will be forced to ‘0’ (such as interrupt enable bits),
while others will be forced to ‘1’ (such as the I/O data direction bits).
0xnn or nnh Designates the number ‘nn’ in the hexadecimal number system. These
conventions are used in the code examples.
B’bbbbbbbb’ Designates the number ‘bbbbbbbb’ in the binary number system. This
convention is used in the text and in figures and tables.
R-M-W Read - Modify - Write. This is when a register or port is read, then the
value is modified, and that value is then written back to the register or
port. This action can occur from a single instruction (such as bit set file,
BSF) or a sequence of instructions.
: (colon) Used to specify a range, or the concatenation of registers / bits / pins.
An e xample is TMR1H:TMR1L is the concatenation of two 8-bit registers
to form a 16-bit timer value, while SSPM3:SSPM0 are 4-bits used to
specify the mode of the SSP module. Concatenation order (left-right)
usually specifies a positional relationship (MSb to LSb, higher to lower).
< > Specifies bit(s) locations in a particular register.
An e xample is SSPCON<SSPM3:SSPM0> (or SSPCON<3:0>) specifies
the register and associated bits or bit positions.
Courier Font Used f or code examples , binary numbers, and f or Instruction Mnemonics
in the text.
Times Font Used for equations and variables.
Times, Bold Font,
Italics
Used in explanatory text for items called out from a graphic/equa-
tion/example.
Note Notes present information that we wish to reemphasize, either to help
you avoid a common pitfall, or make you aware of operating differences
between some de vice f amily members . A Note is alwa ys in a shaded box
(as below), unless used in a table, where it is at the bottom of the table
(as in this table).
Note: This is a note in a note box.
Caution(1) A caution statement describes a situation that could potentially damage
software or equipment.
Warning(1) A warning statement describes a situation that could potentially cause
personnel harm.
Note 1: The inf ormation in a caution or a warning is provided for y our protection. Please read
each caution and warning carefully.
1997 Microchip Technology Inc. DS31001A-page 1-13
Section 1. Introduction
Introduction
1
1.6.2 Electrical Specifications
Throughout this manual there will be ref erences to electrical specification parameter numbers . A
parameter number represents a unique set of characteristics and conditions that is consistent
between every data sheet, though the actual parameter value may vary from device to device.
The “Electrical Specifications” section sho ws all the specifications that are documented f or all
devices. No one device has all these specifications. This section is intended to let you know the
types of parameters that Microchip specifies. The value of each specification is device depen-
dent, though we strongly attempt to keep them consistent across all devices.
Table 1-5: Electrical Specification Parameter Numbering Convention
Parameter
Number
Format Comment
Dxxx DC Specification
Axxx DC Specification for Analog peripherals
xxx Timing (AC) Specification
PDxxx Device Programming DC Specification
Pxxx Device Programming Timing (AC) Specification
Legend: xxx: represents a number.
PICmicro MID-RANGE MCU FAMILY
DS31001A-page 1-14 1997 Microchip Technology Inc.
1.7 Related Documents
Microchip , as well as other sources, off ers additional documentation which can aid in y our de v el-
opment with PICmicro MCUs. These lists contain the most common documentation but other
documents ma y also be a v ailab le . Please check the Microchip w eb site (www.micr ochip.com) f or
the latest published technical documentation.
1.7.1 Microchip Documentation
The following documents are available from Microchip. Many of these documents provide appli-
cation specific infor mation that give actual examples of using, programming and designing with
PICmicro MCUs.
1. MPASM User’s Guide (DS33014)
This document explains how to use Microchip’s MPASM assembler.
2. MPLAB™-C Compiler User’s Guide (DS51014)
This document explains how to use Microchip’s MPLAB-C C compiler.
3. MPLAB User’s Guide (DS51025)
This document e xplains how to use Microchip’s MPLAB Integrated De velopment En viron-
ment.
4. MPLAB Editor User’s Guide (DS30420)
This document explains how to use Microchip’s MPLAB built-in editor.
5. PICMASTER® User’s Guide (DS30421)
This document explains how to use Microchip’s PICMASTER In-Circuit Emulator.
6. MPSIM User’s Guide (DS30027)
This document explains how to use Microchip’s MPLAB Simulator.
7. PRO MATE® User’s Guide (DS30082)
This document explains how to use Microchip’s PRO MATE universal programmer.
8. PICSTART®-Plus User’s Guide (DS51028)
This document explains how to use Microchip’s PICSTART-Plus low-cost universal pro-
grammer.
9.
fuzzy
TECH®-MP User’s Guide (DS30389)
This document explains how to use the
fuzzy
TECH-MP fuzzy logic code generator.
10. MP-DriveWay™ User’s Guide (DS51027)
This document explains how to use the MP-DriveWay code generator.
11.
fuzzy
TECH-MP Fuzzy Logic Handbook (DS30238)
This document explains the basics of
fuzzy
TECH-MP fuzzy.
12. Embedded Control Handbook Volume I (DS00092)
This document contains a plethora of application notes. This is useful for insight on how
to use the device (or par ts of it) as well as getting star ted on your par ticular application
due to the availability of extensive code files.
13. Embedded Control Handbook Volume II (DS00167)
This document contains the Math Libraries for PICmicro MCUs.
14. In-Circuit Serial Programming Guide™ (DS30277)
This document discusses implementing In-Circuit Serial Programming.
15. PICDEM-1 User’s Guide (DS351079)
This document explains how to use Microchip’s PICDEM-1 demo board.
16. PICDEM-2 User’s Guide (DS30374)
This document explains how to use Microchip’s PICDEM-2 demo board.
17. PICDEM-3 User’s Guide (DS33015)
This document explains how to use Microchip’s PICDEM-3 demo board.
18. Third Party Guide (DS00104)
This document lists Microchip’s third parties, as well as various consultants.
19. DIE Support (DS30258)
This document gives information on using Microchip products in DIE form.
1997 Microchip Technology Inc. DS31001A-page 1-15
Section 1. Introduction
Introduction
1
1.7.2 Third Party Documentation
There are several documents available from third party sources around the world. Microchip
does not review these documents for technical accuracy, however they may be a helpful source
for understanding the operation of Microchip MCU devices. This is not necessar ily a complete
list, but are the documents that w e were a ware of at the time of printing. For more inf ormation on
how to contact some of these sources, as well as any new sources that we become aware of,
please visit the Microchip web site.
DOCUMENT LANGUAGE
The PIC16C5X Microcontroller: A Practical Approach to
Embedded Control
Bill Rigby/ Terry Dalby, Tecksystems Inc.
0-9654740-0-3............................................................................................................English
Easy PIC'n
David Benson, Square 1 Electronics
0-9654162-0-8............................................................................................................English
A Beginners Guide to the Microchip PIC®
Nigel Gardner, Bluebird Electronics
1-899013-01-6............................................................................................................English
PIC Microcontroller Operation and Applications
DN de Beer, Cape Technikon.....................................................................................English
Digital Systems and Programmable Interface Controllers
WP Verburg, Pretoria Technikon ................................................................................English
Mikroprozessor PIC16C5X
Michael Rose, Hüthig
3-7785-2169-1...........................................................................................................German
Mikroprozessor PIC17C42
Michael Rose, Hüthig
3-7785-2170-5...........................................................................................................German
Les Microcontrolleurs PIC et mise en oeuvre
Christian Tavernier , Dunod
2-10-002647-X............................................................................................................French
Micontrolleurs PIC a structure RISC
C.F. Urbain, Publitronic
2-86661-058-X............................................................................................................French
New Possibilities with the Microchip PIC
RIGA .........................................................................................................................Russian
PICmicro MID-RANGE MCU FAMILY
DS31001A-page 1-16 1997 Microchip Technology Inc.
DOCUMENT LANGUAGE
PIC16C5X/71/84 Development and Design, Part 1
United Tech Electronic Co. Ltd
957-21-0807-7.......................................................................................................... Chinese
PIC16C5X/71/84 Development and Design, Part 2
United Tech Electronic Co. Ltd
957-21-1152-3.......................................................................................................... Chinese
PIC16C5X/71/84 Development and Design, Part 3
United Tech Electronic Co. Ltd
957-21-1187-6.......................................................................................................... Chinese
PIC16C5X/71/84 Development and Design, Part 4
United Tech Electronic Co. Ltd
957-21-1251-1.......................................................................................................... Chinese
PIC16C5X/71/84 Development and Design, Part 5
United Tech Electronic Co. Ltd
957-21-1257-0.......................................................................................................... Chinese
PIC16C84 MCU Architecture and Software Development
ICC Company
957-8716-79-6.......................................................................................................... Chinese
1997 Microchip Technology Inc. DS31001A-page 1-17
Section 1. Introduction
Introduction
1
1.8 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically f or the PIC16CXXX Mid-Range MCU family (that is the y
may be wr itten for the Base-Line, or the High-End families), but the concepts are pertinent, and
could be used (with modification and possible limitations). The current application notes related
to an introduction to Microchip’s PICmicro MCUs are:
Title Application Note #
A Comparison of Low End 8-bit Microcontrollers AN520
PIC16C54A EMI Results AN577
Continuous Improvement AN503
Improving the Susceptibility of an Application to ESD AN595
Plastic Packaging and the Effects of Surface Mount Soldering Techniques AN598
PICmicro MID-RANGE MCU FAMILY
DS31001A-page 1-18 1997 Microchip Technology Inc.
1.9 Revision History
Revision A
This is the initial released revision of Microchip’s PICmicro MCUs Introduction.
1997 Microchip Technology Inc. DS31002A page 2-1
M
Oscillator
2
Section 2. Oscillator
HIGHLIGHTS
This section of the manual contains the following major topics:
2.1 Introduction....................................................................................................................2-2
2.2 Oscillator Configurations................................................................................................2-2
2.3 Crystal Oscillators / Ceramic Resonators......................................................................2-4
2.4 External RC Oscillator..................................................................................................2-12
2.5 Internal 4 MHz RC Oscillator .......................................................................................2-13
2.6 Effects of Sleep Mode on the On-chip Oscillator .........................................................2-17
2.7 Effects of Device Reset on the On-chip Oscillator.......................................................2-17
2.8 Design Tips..................................................................................................................2-18
2.9 Related Application Notes............................................................................................2-19
2.10 Revision History...........................................................................................................2-20
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-2 1997 Microchip Technology Inc.
2.1 Introduction
The internal oscillator circuit is used to generate the device clock. The device clock is required
for the device to execute instructions and for the peripherals to function. Four device clock peri-
ods generate one internal instruction clock (TCY) cycle.
There are up to eight diff erent modes which the oscillator ma y ha v e. There are two modes which
allow the selection of the internal RC oscillator clock out (CLKOUT) to be driv en on an I/O pin, or
allow that I/O pin to be used for a general purpose function. The oscillator mode is selected by
the de vice configuration bits . The de vice configur ation bits are nonv olatile memory locations and
the operating mode is determined by the v alue written during de vice programming. The oscillator
modes are:
LP Low Frequency (Power) Crystal
XT Crystal/Resonator
HS High Speed Crystal/Resonator
RC External Resistor/Capacitor (same as EXTRC with CLKOUT)
EXTRC External Resistor/Capacitor
EXTRC External Resistor/Capacitor with CLKOUT
INTRC Internal 4 MHz Resistor/Capacitor
INTRC Internal 4 MHz Resistor/Capacitor with CLKOUT
These oscillator options are made av ailab le to allow a single device type the flexibility to fit appli-
cations with different oscillator requirements. The RC oscillator option saves system cost while
the LP cr ystal option saves power. Configuration bits are used to select the various options. For
more details on the device configuration bits, see the “Device Characteristics” section.
2.2 Oscillator Configurations
2.2.1 Oscillator Types
Mid-Range devices can have up to eight different oscillator modes. The user can program up to
three de vice configuration bits (FOSC2, FOSC1 and FOSC0) to select one of these eight modes:
LP Low Frequency (Power) Crystal
XT Crystal/Resonator
HS High Speed Crystal/Resonator
RC External Resistor/Capacitor (same as EXTRC with CLKOUT)
EXTRC External Resistor/Capacitor
EXTRC External Resistor/Capacitor with CLKOUT
INTRC Internal 4 MHz Resistor/Capacitor
INTRC Internal 4 MHz Resistor/Capacitor with CLKOUT
The main diff erence between the LP, XT, and HS modes is the gain of the internal inverter of the
oscillator circuit which allows the different frequency ranges. Table 2-1 and Table 2-2 give infor-
mation to aid in selecting an oscillator mode. In general, use the oscillator option with the low est
possible gain which still meet specifications. This will result in lower dynamic currents (IDD). The
frequency range of each oscillator mode is the recommended (tested) frequency cutoffs, b ut the
selection of a different gain mode is acceptable as long as a thorough validation is perfor med
(voltage, temperature, component variations (Resistor, Capacitor, and internal microcontroller
oscillator circuitry)).
The RC mode and the EXTRC with CLK OUT mode ha ve the same functionality. The y are named
like this to help describe their operation vs. the other oscillator modes.
1997 Microchip Technology Inc. DS31002A-page 2-3
Section 2. Oscillator
Oscillator
2
Table 2-1: Selecting the Oscillator Mode for Devices with FOSC1:FOSC0
Table 2-2: Selecting the Oscillator Mode for Devices with FOSC2:FOSC0
Configuration bits
FOSC1:FOSC0 OSC
Mode
OSC
Feedback
Inverter
Gain
Comment
1 1 RC Least expensive solution for device oscillation
(only an external resistor and capacitor is
required). Most variation in time-base.
Device’s default mode.
1 0 HS High Gain High frequency application.
Oscillator circuit’s mode consumes the most
current of the three crystal modes.
0 1 XT Medium Gain Standard crystal/resonator frequency.
Oscillator circuit’s mode consumes the middle
current of the three crystal modes.
0 0 LP Low Gain Low power/frequency applications.
Oscillator circuit’s mode consumes the least
current of the three crystal modes.
Configuration
bits
FOSC2:FOSC0
OSC
Mode
OSC
Feedback
Inverter
Gain
Comment
1 1 1 EXTRC
with
CLKOUT
Inexpensive solution for device oscillation. Most
variation in timebase. CLKOUT is enabled on
pin. Device’s default mode.
1 1 0 EXTRC Inexpensive solution for device oscillation. Most
variation in timebase.
CLKOUT is disabled (use as I/O) on pin.
1 0 1 INTRC
with
CLKOUT
Least expensive solution for device oscillation.
4 MHz oscillator, which can be tuned.
CLKOUT is enabled on pin.
1 0 0 INTRC Least expensive solution for device oscillation.
4 MHz oscillator, which can be tuned.
CLKOUT is disabled (use as I/O) on pin.
0 1 1 Reserved
0 1 0 HS High Gain High frequency application.
Oscillator circuit’s mode consumes the most
current of the three crystal modes.
0 0 1 XT Medium Gain Standard crystal/resonator frequency.
Oscillator circuit’s mode consumes the middle
current of the three crystal modes.
0 0 0 LP Low Gain Low power/frequency applications.
Oscillator circuit’s mode consumes the least
current of the three crystal modes.
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-4 1997 Microchip Technology Inc.
2.3 Crystal Oscillators / Ceramic Resonators
In XT, LP or HS modes a crystal or ceramic resonator is connected to the OSC1 and OSC2 pins
to establish oscillation (Figure 2-1). The PICmicro oscillator design requires the use of a parallel
cut crystal. Using a series cut crystal may give a frequency out of the crystal manufacturer’s
specifications. When in XT, LP or HS modes, the device can have an external clock source drive
the OSC1 pin (Figure 2-3).
Figure 2-1: Crystal or Ceramic Resonator Operation (HS, XT or LP Oscillator Mode)
C1
C2
XTAL
OSC2
Rs
(1)
OSC1
R
F
(2) SLEEP
To internal logic (3)
PIC16CXXX
To internal logic (3)
Note 1: A series resistor, RS, may be required for AT strip cut crystals.
2: The feedback resistor, RF, is typically in the range of 2 to 10 MΩ.
3: Depending on the device, the buffer to the internal logic may be
either before or after the oscillator inverter.
1997 Microchip Technology Inc. DS31002A-page 2-5
Section 2. Oscillator
Oscillator
2
2.3.1 Oscillator / Resonator Start-up
As the device voltage increases from VSS, the oscillator will start its oscillations. The time
required for the oscillator to start oscillating depends on many factors. These include:
Crystal / resonator frequency
Capacitor values used (C1 and C2 in Figure 2-1)
De vice VDD rise time
System temperature
Series resistor value (and type) if used (Rs in Figure 2-1)
Oscillator mode selection of de vice (which selects the gain of the internal oscillator inverter)
Crystal quality
Oscillator circuit layout
System noise
Figure 2-2 graphs an example oscillator / resonator start-up. The peak-to-peak voltage of the
oscillator wavefor m can be quite low (less than 50% of device VDD) where the waveform is cen-
tered at VDD/2 (refer to parameters D033 and D043 in the “Electrical Specifications” section).
Figure 2-2: Example Oscillator / Resonator Start-up Characteristics
Voltage
Crystal Start-up Time Time
De vice VDD
Maximum VDD of System
0V
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-6 1997 Microchip Technology Inc.
2.3.2 Component Selection
Figure 2-1 is a diagram of the devices cr ystal or ceramic resonator circuitr y. The resistance for
the f eedback resistor , RF, is typically within the 2 to 10 M range. This v aries with device voltage ,
temperature, and process v ariations. A series resistor , Rs, may be required if an AT strip cut crys-
tal is used. Be sure to include the device’s operating voltage and the de vice’s manufacturing pro-
cess when determining resistor requirements. As you can see in Figure 2-1, the connection to
the de vice’s internal logic is device dependent. See the applicab le data sheet for de vice specifics.
The typical values of capacitors ( C1, C2) are given in Table 2-3 and Table 2-4. Each de vice’ s data
sheet will give the specific values that Microchip tested.
Table 2-3: Typical Capacitor Selection for Ceramic Resonators
Ranges tested:
Mode Frequency
C1
/
C2
(1)
XT 455 kHz
2.0 MHz
4.0 MHz
22 - 100 pF
15 - 68 pF
15 - 68 pF
HS 8.0 MHz
16.0 MHz
20.0 MHz
10 - 68 pF
10 - 22 pF
TBD
Resonators used:
455 kHz Panasonic EFO-A455K04B ±0.3%
2.0 MHz Murata Erie CSA2.00MG ±0.5%
4.0 MHz Murata Erie CSA4.00MG ±0.5%
8.0 MHz Murata Erie CSA8.00MT ±0.5%
16.0 MHz Murata Erie CSA16.00MX ±0.5%
20.0 MHz TBD TBD
Note 1: Recommended values of C1 and C2 are identical to the ranges tested above.
Higher capacitance increases the stability of the oscillator but also increases the
start-up time. These values are for design guidance only. Since each resonator has
its own characteristics, the user should consult the resonator man ufacturer for appro-
priate values of external component or verify oscillator performance.
2: All resonators tested required external capacitors.
1997 Microchip Technology Inc. DS31002A-page 2-7
Section 2. Oscillator
Oscillator
2
Table 2-4: Typical Capacitor Selection for Crystal Oscillator
Mode Freq
C1
(1)
C2
(1)
LP 32 kHz
200 kHz 68 - 100 pF
15 - 30 pF 68 - 100 pF
15 - 30 pF
XT 100 kHz
2 MHz
4 MHz
68 - 150 pF
15 - 30 pF
15 - 30 pF
150 - 200 pF
15 - 30 pF
15 - 30 pF
HS 8 MHz
10 MHz
20 MHz
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
Crystals used:
32.768 kHz Epson C-001R32.768K-A ± 20 PPM
100 kHz Epson C-2 100.00 KC-P ± 20 PPM
200 kHz STD XTL 200.000 kHz ± 20 PPM
2.0 MHz ECS ECS-20-S-2 ± 50 PPM
4.0 MHz ECS ECS-40-S-4 ± 50 PPM
10.0 MHz ECS ECS-100-S-4 ± 50 PPM
20.0 MHz ECS ECS-200-S-4 ± 50 PPM
Note 1: Higher capacitance increases the stability of the oscillator but also increases the
start-up time. These values are for design guidance only. A series resistor, Rs, may
be required in HS mode as well as XT mode to avoid overdriving crystals with low
drive level specification. Since each crystal has its own characteristics, the user
should consult the crystal manufacturer for appropriate values of external compo-
nents or verify oscillator performance.
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-8 1997 Microchip Technology Inc.
2.3.3 Tuning the Oscillator Circuit
Since Microchip devices have wide operating ranges (frequency, voltage, and temperature;
depending on the par t and version ordered) and exter nal components (cr ystals, capacitors,...),
of varying quality and manuf acture; validation of operation needs to be performed to ensure that
the component selection will comply with the requirements of the application.
There are many f actors that go into the selection and arrangement of these external components.
These factors include:
amplifier gain
desired frequency
resonant frequency(s) of the crystal
temperature of operation
supply voltage range
start-up time
stability
crystal life
power consumption
simplification of the circuit
use of standard components
combination which results in fewest components
1997 Microchip Technology Inc. DS31002A-page 2-9
Section 2. Oscillator
Oscillator
2
2.3.3.1 Determining Best Values for Crystals, Clock Mode, C1, C2, and Rs
The best method for selecting components is to apply a little knowledge and a lot of trial, mea-
surement, and testing.
Crystals are usually selected by their parallel resonant frequency only, however other parame-
ters may be impor tant to your design, such as temperature or frequency tolerance. Application
Note AN588 is an e xcellent ref erence if y ou would lik e to know more about crystal operation and
their ordering information.
The PICmicros™ internal oscillator circuit is a parallel oscillator circuit, which requires that a par-
allel resonant crystal be selected. The load capacitance is usually specified in the 20 pF to 32 pF
range. The crystal will oscillate closest to the desired frequency with capacitance in this range. It
ma y be necessary to sometimes juggle these values a bit, as described later , in order to achie v e
other benefits.
Clock mode is primarily chosen by using the FOSC par ameter specification (parameter 1A) in the
device’s data sheet, based on frequency. Clock modes (except RC) are simply gain selections,
lower gain for lower frequencies, higher gain for higher frequencies. It is possible to select a
higher or lower gain, if desired, based on the specific needs of the oscillator circuit.
C1 and C2 should also be initially selected based on the load capacitance as suggested by the
crystal manufacturer and the tables supplied in the device data sheet. The values given in the
Microchip data sheet can only be used as a starting point, since the crystal manufacturer , supply
voltage, and other factors already mentioned may cause your circuit to differ from the one used
in the factory characterization process.
Ideally, the capacitance is chosen (within the r ange of the recommended crystal load preferab ly)
so that it will oscillate at the highest temperature and low est VDD that the circuit will be expected
to perf orm under . High temperature and low VDD both ha ve a limiting aff ect on the loop gain, such
that if the circuit functions at these e xtremes, the designer can be more assured of proper oper-
ation at other temperatures and supply voltage combinations. The output sine wave should not
be clipped in the highest gain environment (highest VDD and lowest temperature) and the sine
output amplitude should be great enough in the low est gain environment (lowest VDD and highest
temperature) to cov er the logic input requirements of the cloc k as listed in the de vice data sheet.
A method for improving star t-up is to use a value of C2 greater than C1. This causes a greater
phase shift across the crystal at power-up, which speeds oscillator start-up.
Besides loading the crystal for proper frequency response, these capacitors can have the effect
of lowering loop gain if their value is increased. C2 can be selected to affect the overall gain of
the circuit. A higher C2 can lower the gain if the crystal is being over driven (see also discussion
on Rs). Capacitance values that are too high can store and dump too much current through the
cr ystal, so C1 and C2 should not become excessively large. Unfor tunately, measuring the watt-
age through a crystal is tricky b usiness , but if you do not stray too far from the suggested v alues
you should not have to be concerned with this.
A series resistor , Rs, is added to the circuit if, after all other external components are selected to
satisf action, the crystal is still being over driv en. This can be determined by looking at the OSC2
pin, which is the driven pin, with an oscilloscope. Connecting the probe to the OSC1 pin will load
the pin too much and negativ ely aff ect perf ormance. Remember that a scope probe adds its o wn
capacitance to the circuit, so this may have to be accounted for in your design, i.e. if the circuit
worked best with a C2 of 20 pF and scope probe was 10 pF, a 30 pF capacitor may actually be
called f or. The output signal should not be clipping or squashed. Overdriving the crystal can also
lead to the circuit jumping to a higher harmonic level or even crystal damage.
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-10 1997 Microchip Technology Inc.
The OSC2 signal should be a nice clean sine wave that easily spans the input minimum and max-
imum of the clock input pin (4V to 5V peak to peak for a 5V VDD is usually good). An easy way
to set this is to again test the circuit at the minimum temperature and maximum VDD that the
design will be e xpected to perform in, then look at the output. This should be the maximum ampli-
tude of the clock output. If there is clipping or the sine wave is squashing near VDD and VSS at
the top and bottom, and increasing load capacitors will risk too much current through the crystal
or push the value too far from the manufacturer’s load specification, then add a trimpot between
the output pin and C2, and adjust it until the sine wa ve is clean. K eeping it fairly close to maximum
amplitude at the low temperature and high VDD combination will assure this is the maximum
amplitude the cr ystal will see and prevent overdriving. A ser ies resistor, Rs, of the closest stan-
dard value, can now be inserted in place of the trimpot. If Rs is too high, perhaps more than
20k ohms, the input will be too isolated from the output, making the clock more susceptible to
noise. If you find a value this high is needed to prevent overdriving the crystal, try increasing C2
to compensate. Tr y to get a combination where Rs is around 10k or less, and load capacitance
is not too far from the 20 pF or 32 pF manufacturer specification.
2.3.3.1.1 Start-up
The most difficult time f or the oscillator to start-up is when waking up from sleep . This is because
the load capacitors have both par tially charged to some quiescent value, and phase differential
at wak e-up is minimal. Thus, more time is required to achieve stable oscillation. Remember also
that low v oltage, high temperatures, and the lower frequency clock modes also impose limitations
on loop gain, which in turn affects start-up. Each of the following factors makes thing worse:
a low frequency design (with its low gain clock mode)
a quiet environment (such as a battery operated device)
operating outside the noisy RF area (such as in a shielded box)
low voltage
high temperature
waking up from sleep.
Noise actually helps a design for oscillator start-up, since it helps kick start the oscillator.
2.3.4 External Clock Input
If the PICmicro’ s internal oscillator is not being used, and the device will be driv en from an e xter-
nal clock, be sure to set the oscillator mode to one of the crystal modes (LP, XT, or HS). That is,
something other than one of the RC modes, since RC mode will fight with the injected input. Ide-
ally you would select the mode that corresponds to the frequency injected, but this is of less
impor tance here since the clock is only driving its inter nal logic, and not a cr ystal loop circuit. It
ma y be possible to select a clock mode lo w er than would be needed by an oscillator circuit, and
thereby sa v e some of the po wer that would be used exercising the inv erting amplifier . Make sure
the OSC2 signal amplitude covers the needed logic thresholds of the device.
Figure 2-3: External Device Clock Input Operation (HS, XT or LP Oscillator Modes)
clock from
external system PIC16CXXX
OSC1
OSC2
Open
Note 1: A resistor to ground may be used to reduce system noise.
This may increase system current.
(1)
1997 Microchip Technology Inc. DS31002A-page 2-11
Section 2. Oscillator
Oscillator
2
2.3.5 External Crystal Oscillator Circuit for Device Clock
Sometimes more than one device needs to be clocked from a single crystal. Since Microchip
does not recommend connecting other logic to the PICmicro’ s internal oscillator circuit, an exter-
nal crystal oscillator circuit is recommended. Each de vice will then hav e an external clock source,
and the number of de vices that can be driven will depend on the buff er drive capability. This circuit
is also useful when more than one device (PICmicro) needs to operate synchronously to each
other.
Either a prepackaged oscillator can be used or a simple oscillator circuit with TTL gates can be
built. Prepac kaged oscillators provide a wide operating range and better stability. A well-designed
crystal oscillator will pro vide good performance with TTL gates. Two types of crystal oscillator cir-
cuits can be used; one with series resonance, or one with parallel resonance.
Figure 2-4 shows implementation of an external parallel resonant oscillator circuit. The circuit is
designed to use the fundamental frequency of the crystal. The 74AS04 inverter performs the
180-degree phase shift that a parallel oscillator requires. The 4.7 k resistor provides the nega-
tive feedback for stability. The 10 k potentiometer biases the 74AS04 in the linear region.
Figure 2-4: External Parallel Resonant Crystal Oscillator Circuit
Figure 2-5 shows an e xternal series resonant oscillator circuit. This circuit is also designed to use
the fundamental frequency of the crystal. The inver ter perfor ms a 180-degree phase shift in a
series resonant oscillator circuit. The 330 k resistors provide the negative feedback to bias the
inverters in their linear region.
Figure 2-5: External Series Resonant Crystal Oscillator Circuit
When the device is clocked from an exter nal clock source (as in Figure 2-4 or Figure 2-5) then
the microcontroller’s oscillator must be configured for LP, XT or HS mode (Figure 2-3).
20 pF
+5V
20 pF
10k
4.7 k
10 k
74AS04
XTAL
10 k
74AS04
CLKIN
To Other
Devices
PIC16CXXX
330 k
74AS04 74AS04 PIC16CXXX
CLKIN
To Other
Devices
XTAL
330 k
74AS04
0.1 µF
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-12 1997 Microchip Technology Inc.
2.4 External RC Oscillator
F or timing insensitiv e applications the “EXTRC” device option offers additional cost savings. The
RC oscillator frequency is a function of; the supply voltage, the resistor (REXT) and capacitor
(CEXT) values , and the operating temperature. In addition to this , the oscillator frequency will vary
from unit to unit due to normal process parameter variation. Furthermore, the difference in lead
frame capacitance between pac kage types will also affect the oscillation frequency, especially for
low CEXT values. The user also needs to take into account variation due to tolerance of external
REXT and CEXT components used. Figure 2-6 shows how the RC combination is connected to a
PIC16CXXX. For REXT values below 2.2 k, oscillator operation may become unstable, or stop
completely. For very high REXT values (e.g. 1 M), the oscillator becomes sensitive to noise,
humidity and leakage. Thus, we recommend keeping REXT between 3 k and 100 k.
Figure 2-6: EXTRC Oscillator Mode
Although the oscillator will operate with no external capacitor (CEXT = 0 pF), we recommend
using values above 20 pF for noise and stability reasons. With no or small external capacitance,
the oscillation frequency can vary dramatically due to changes in e xternal capacitances, such as
PCB trace capacitance and package lead frame capacitance.
See characterization data for RC frequency variation from part to part due to normal process
variation. The variation is larger for larger resistance (since leakage current variation will affect
RC frequency more f or large R) and for smaller capacitance (since v ariation of input capacitance
will affect RC frequency more).
See characterization data for var iation of oscillator frequency due to VDD for given REXT/CEXT
values as well as frequency variation due to operating temperature for given REXT, CEXT, and
VDD values.
The oscillator frequency, divided by 4, is available on the OSC2/CLKOUT pin, and can be used
for test pur poses or to synchronize other logic (see Figure 4-3: "Clock/Instruction Cycle" in
the “Architecture” section, for waveform).
2.4.1 RC Start-up
As the de vice voltage increases, the RC will start its oscillations immediately after the pin voltage
levels meet the input threshold specifications (parameters D032 and D042 in the “Electrical
Specifications” section). The time required for the RC to start oscillating depends on many fac-
tors. These include:
Resistor value used
Capacitor value used
De vice VDD rise time
System temperature
OSC2/CLKOUT
CEXT
VDD
REXT
VSS
PIC16CXXX
OSC1
Fosc/4 (1)
Internal
clock
Fosc
Note 1: This output may also be able to be configured as a general purpose I/O pin.
1997 Microchip Technology Inc. DS31002A-page 2-13
Section 2. Oscillator
Oscillator
2
2.5 Internal 4 MHz RC Oscillator
The internal RC oscillator (not on all devices) provides a fixed 4 MHz (nominal) system clock at
VDD = 5V and 25°C , see the device data sheet’ s “Electrical Specifications” section f or inf ormation
on variation over voltage and temperature.
The value in the OSCCAL register is used to tune the frequency of the internal RC oscillator . The
calibration value that Microchip programs into the device will “trim” the internal oscillator to
remov e process variation from the oscillator frequency. The CAL3:CAL0 bits are used f or fine cal-
ibration within a frequency window. Higher values of CAL3:CAL0 (from 0000 to 1111) yields
higher clock speeds.
When a 4 MHz internal RC oscillator frequency cannot be achieved by a CAL3:CAL0 value, the
RC oscillator frequency can be increased or decreased by an offset frequency. The CALFST and
CALSLW bits are used to enable a positiv e or negative frequency offset to place the internal RC
frequency within the CAL3:CAL0 trim window.
Setting the CALFST bit offsets the internal RC for a higher frequency, while setting the CALSL W
bit offsets the internal RC for a lower frequency.
Upon a device reset, the OSCCAL register is forced to the midpoint value (CAL3:CAL0 = 7h,
CALFST and CALSLW providing no offset).
Register 2-1: OSCCAL Register
R/W-0 R/W-1 R/W-1 R/W-1 R/W-0 R/W-0 U-0 U-0
CAL3 CAL2 CAL1 CAL0 CALFST CALSLW
bit 7 bit 0
bit 7:4 CAL3:CAL0: Internal RC Oscillator Calibration bits
0000 = Lowest clock frequency within the trim range
1111 = Highest clock frequency within the trim range
bit 3 CALFST: Oscillator Range Offset bit
1 = Increases the frequency of the internal RC oscillator into the CAL3:CAL0 trim window
0 = No offset provided
bit 2 CALSLW: Oscillator Range Offset bit
1 = Decreases the frequency of the internal RC oscillator into the CAL3:CAL0 trim window
0 = No offset provided
Note: When both bits are set, the CALFST bit overrides the CALSLW bit.
bit 1:0 Unimplemented: Read as '0'
Note: These bits should be written as ‘0’ when modifying the OSCCAL register, for com-
patibility with future devices.
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note: OSCCAL is used to remove process variation from the internal RC oscillator of the
device. The OSCCAL value should not be modified from the Microchip supplied
value , and all timing critical functions should be adjusted by the application softw are.
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-14 1997 Microchip Technology Inc.
Figure 2-7 shows the possib le device frequencies from the uncalibrated point (at V DD = 5V, 25°C,
and OSCCAL = 70h), and the changes achievable by the OSCCAL register.
Figure 2-7: Ideal Internal RC Oscillator Frequency vs. OSCCAL Register Value
Figure 2-8 shows an example of a device where by selecting one of the CAL3:CAL0 values, the
frequency can corrected to 4 MHz. These bits can be considered the fine trimming of the
frequency. Sometimes the device frequency at the uncalibrated point cannot be corrected to 4
MHz by the fine trimming of the CAL3:CAL0 bits v alue. Theref ore two additional bits are a vailab le
which give a large frequency offset (positive and negative) to move the frequency within the
range where the fine trimming can work. These bits are the CALSLW and CALFST bits, which
offset the internal RC frequency. The action of these bits are shown in Figure 2-9, and
Figure 2-10.
Figure 2-8: CAL3:CAL0 Trimming of Internal RC Oscillator Frequency Offset
Frequency
CAL3:CAL0 = 07h
CALFST = 0
CALSLW = 0
See X-axis
CAL3:CAL0
Trim Window
CAL3:CAL0 = Fh
CALFST = 1
CALSLW = x
CAL3:CAL0 = 0h
CALFST = 0
CALSLW = 1
CAL3:CAL0 = 0h
CALFST = 0
CALSLW = 0
CAL3:CAL0 = Fh
CALFST = 0
CALSLW = 0
4 MHz
(slowest frequency) (fastest frequency)
Frequency
CAL3:CAL0
Trim Window
4 MHz ± 1.5%
CAL3:CAL0 = 0000 CAL3:CAL0 = 1111
Internal RC
Frequency at
> 4 MHz
< 4 MHz
One of the 16 possible calibration points
(@ 5V, 25˚C)
device reset
CALFST = 0
CALFLW = 0
CAL3:CAL0 = 7h
1997 Microchip Technology Inc. DS31002A-page 2-15
Section 2. Oscillator
Oscillator
2
Figure 2-9: CALFST Positive Internal RC Oscillator Frequency Offset
Figure 2-10: CALSLW Negative Internal RC Oscillator Frequency Offset
CAL3:CAL0
Trim Window
CAL3:CAL0 = 0000 CAL3:CAL0 = 1111
Internal RC
Frequency at
CALFST offset
Internal RC
Frequency with
CALFST = 1
CALSLW = x
Frequency
4 MHz ± 1.5%
< 4 MHz
(@ 5V, 25˚C)
One of the 16 possible CAL3:CAL0 calibration points
device reset
CALFST = 0
CALFLW = 0
Frequency
CAL3:CAL0
Trim Window
CAL3:CAL0 = 0000 CAL3:CAL0 = 1111
Internal RC
Frequency at
Internal RC
Frequency with
CALSLW = 1
CALFST = 0
CALSLW offset
device reset
One of the 16 possible CAL3:CAL0 calibration points
4 MHz ± 1.5%
> 4 MHz
(@ 5V, 25˚C)
CALSLW = 0
CALFST = 0
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-16 1997 Microchip Technology Inc.
A calibration instruction is programmed into the last address of the implemented program
memor y. This instruction contains the calibration value for the internal RC oscillator. This value
is programmed as a RETLW XX instruction where XX is the calibration value. In order to retrieve
the calibration v alue, issue a CALL YY instruction where YY is the last location in the device’ s user
accessible prog ram memory. The calibration value is now loaded in the W register. The program
should then perf orm a MOVWF OSCCAL instruction to load the value into the internal RC oscillator
calibration register. Table 2-5 shows the location of the calibration value depending on the size
of the program memory.
Table 2-5: Calibration Value Location
2.5.1 Clock Out
The internal RC oscillator can be configured to provide a clock out signal on the CLKOUT pin
when the configuration word address (2007h) is programmed with FOSC2, FOSC1, FOSC0
equal to 101 for Internal RC or 111 for External RC. CLKOUT, which is divided by 4, can be
used for test purposes or to synchronize other logic.
When the calibration v alue of the internal RC oscillator is accidently erased, the cloc k out f eature
allows the user to determine what the calibration value should be. This is achieved by writing a
program which modifies (increments/decrements) the value of the OSCCAL register. When the
CLKOUT pin is at 4 MHz (± 1.5%) at 5V and 25˚C, the OSCCAL register has the correct calibra-
tion value. This value then needs to be written to a por t or shifted out ser ially, so that the value
can be written down and programmed into the calibration location.
Program
Memory Size
(Words)
Calibration V alue
Location
512 1FFh
1K 3FFh
2K 7FFh
4K FFFh
8K 1FFFh
Note 1: Erasing the device (windowed devices) will also erase the factory programmed
calibration value for the internal oscillator.
Prior to erasing a windowed device, the internal oscillator calibration value must be
saved. It is a good idea to wr ite this value on the package of the device to ensure
that the calibration value is not accidently lost.
This sav ed valued must be restored into program memory calibration location bef ore
programming the device.
Note 2: OSCCAL<1:0> are unimplemented and should be written as ‘0’. This will help
ensure compatibility with future devices.
1997 Microchip Technology Inc. DS31002A-page 2-17
Section 2. Oscillator
Oscillator
2
2.6 Effects of Sleep Mode on the On-chip Oscillator
When the device executes a SLEEP instruction, the on-chip clocks and oscillator are turned off
and the device is held at the beginning of an instr uction cycle (Q1 state). With the oscillator off,
the OSC1 and OSC2 signals will stop oscillating. Since all the transistor switching currents ha ve
been remov ed, sleep mode achie ves the lo west current consumption of the de vice (only leakage
currents). Enabling any on-chip feature that will operate during sleep will increase the current
consumed during sleep. The user can w ake from SLEEP through e xternal reset, Watchdog Timer
Reset or through an interrupt.
Table 2-6: OSC1 and OSC2 Pin States in Sleep Mode
2.7 Effects of Device Reset on the On-chip Oscillator
De vice resets have no effect on the on-chip crystal oscillator circuitry. The oscillator will contin ue
to operate as it does under normal execution. While in reset, the device logic is held at the Q1
state so that when the device exits reset, it is at the beginning of an instruction cycle.
The OSC2 pin, when used as the external clockout (EXTRC mode), will be held low during
reset, and as soon as the MCLR pin is at VIH (input high voltage), the RC will start to oscillate.
See Table 3-1, in the “Reset” section, for time-outs due to Sleep and MCLR reset.
2.7.1 Power-up Delays
There are two timers that offer necessary delays on power-up. One is the Oscillator Start-up
Timer, OST, intended to k eep the chip in RESET until the crystal oscillator is stable. The other is
the Power-up Timer (PWRT), which provides a fixed delay of 72 ms (nominal) on power-up only
(POR and BOR). The PWRT is designed to keep the part in RESET while the power supply sta-
bilizes. With these two timers on-chip, most applications need no external reset circuitry. For
additional information on reset operation, see the “Reset” section.
OSC Mode OSC1 Pin OSC2 Pin
EXTRC Floating, e xternal resistor should
pull high At logic low
INTRC N.A. N.A.
LP, XT, and HS Feedback inverter disabled, at
quiescent voltage level Feedback inverter disabled, at
quiescent voltage level
See Table 3-1, in the “Reset” section, for time-outs due to Sleep and MCLR reset.
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-18 1997 Microchip Technology Inc.
2.8 Design Tips
Question 1:
When looking at the OSC2 pin after power -up with an oscilloscope, there is
no clock. What can cause this?
Answer 1:
1. Executing a SLEEP instruction with no source for wake-up (such as, WDT, MCLR, or an
Interrupt). Verify that the code does not put device to sleep without pro viding for wak e-up.
If it is possible, tr y waking it up with a low pulse on MCLR. Powering up with MCLR held
low will also give the crystal oscillator more time to start-up, but the Program Counter will
not advance until the MCLR pin is high.
2. The wrong clock mode is selected for the desired frequency. For a blank device, the
default oscillator is EXTRC. Most parts come with the clock selected in the default RC
mode, which will not start oscillation with a crystal or resonator . Verify that the clock mode
has been programmed correctly.
3. The proper power-up sequence has not been f ollowed. If a CMOS part is powered through
an I/O pin prior to power-up, bad things can happen (latch up , improper start-up etc.) It is
also possible for brown-out conditions, noisy power lines at start-up, and slow VDD rise
times to cause problems. Tr y powering up the device with nothing connected to the I/O,
and power-up with a known, good, fast-rise, power supply. It is not as much of a problem
as it ma y sound, but the possibility exists . Ref er to the power-up inf ormation in the de vice
data sheet for considerations on brown-out and power-up sequences.
4. The C1 and C2 capacitors attached to the crystal have not been connected properly or are
not the correct values. Make sure all connections are correct. The device data sheet val-
ues f or these components will almost alwa ys get the oscillator running, they just might not
be the optimal values for your design.
Question 2:
The PICmicro starts, but runs at a frequency m uch higher than the resonant
frequency of the crystal.
Answer 2:
The gain is too high for this oscillator circuit. Refer to subsection 2.3 “Crystal Oscillators /
Ceramic Resonators” to aid in the selection of C2 (ma y need to be higher) Rs (ma y be needed)
and clock mode (wrong mode may be selected). This is especially possible for low frequency
crystals, like the common 32.768 kHz.
Question 3:
The design runs fine, but the frequency is slightly off, what can be done to
adjust this?
Answer 3:
Changing the value of C1 has some aff ect on the oscillator frequency. If a SERIES resonant crys-
tal is used, it will resonate at a diff erent frequency than a PARALLEL resonant crystal of the same
frequency call-out.
Question 4:
The board works fine, then suddenly quits, or loses time.
Answer 4:
Other than the obvious software checks that should be done to investigate losing time, it is pos-
sible that the amplitude of the oscillator output is not high enough to reliab ly trigger the oscillator
input.
Question 5:
I’m using a device with the internal RC oscillator and I have accidently
erased the calibration value. What can I do?
Answer 5:
If the frequency of the device does not matter, you can continue to use the device.
If the frequency of the device does matter, you can purchase a new windowed device, or follow
the suggestion in subsection 2.5.1 “Clock Out.
1997 Microchip Technology Inc. DS31002A-page 2-19
Section 2. Oscillator
Oscillator
2
2.9 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the oscillator
are:
Title Application Note #
PIC16/17 Oscillator Design Guide AN588
Low Power Design using PIC16/17 AN606
PICmicro MID-RANGE MCU FAMILY
DS31002A-page 2-20 1997 Microchip Technology Inc.
2.10 Revision History
Revision A
This is the initial released revision of the PICmicro oscillators description.
1997 Microchip Technology Inc. DS31003A page 3-1
M
Reset
3
Section 3. Reset
HIGHLIGHTS
This section of the manual contains the following major topics:
3.1 Introduction....................................................................................................................3-2
3.2 Power-on Reset (POR), Power-up Timer (PWRT), Oscillator Start-up Timer (OST),
Brown-out Reset (BOR), and Parity Error Reset (PER).................................................3-4
3.3 Registers and Status Bit Values...................................................................................3-10
3.4 Design Tips..................................................................................................................3-16
3.5 Related Application Notes............................................................................................3-17
3.6 Revision History...........................................................................................................3-18
PICmicro MID-RANGE MCU FAMILY
DS31003A-page 3-2 1997 Microchip Technology Inc.
3.1 Introduction
The reset logic is used to place the device into a known state. The source of the reset can be
determined by using the device status bits. The reset logic is designed with features that reduce
system cost and increase system reliability.
Devices differentiate between various kinds of reset:
a) Power-on Reset (POR)
b) MCLR reset during normal operation
c) MCLR reset during SLEEP
d) WDT reset during normal operation
e) Brown-out Reset (BOR)
f) Parity Error Reset (PER)
Most registers are unaffected by a reset; their status is unknown on POR and unchanged by all
other resets. The other registers are forced to a “reset state” on Power-on Reset, MCLR, WDT
reset, Brown-out Reset, Parity Error Reset, and on MCLR reset during SLEEP.
The on-chip parity bits that can be used to verify the contents of program memory.
Most registers are not aff ected by a WDT w ake-up , since this is vie wed as the resumption of nor-
mal operation. Status bits T O, PD, POR, BOR, and PER are set or cleared differently in different
reset situations as indicated in Table 3-2. These bits are used in softw are to determine the nature
of the reset. See Table 3-4 for a full description of the reset states of all registers.
A simplified block diagram of the on-chip reset circuit is shown in Figure 3-1. This block diagram
is a superset of reset features. To determine the features that are available on a specific device,
please refer to the device’s Data Sheet.
All new devices will have a noise filter in the MCLR reset path to detect and ignore small pulses .
See parameter 30 in the “Electrical Specifications” section for pulse width specification.
Note: While the PICmicro™ is in a reset state, the internal phase clock is held at Q1
(beginning of an instruction cycle).
1997 Microchip Technology Inc. DS31003A-page 3-3
Section 3. Reset
Reset
3
Figure 3-1: Simplified Block Diagram of a Super-set On-chip Reset Circuit
S
RQ
MCLR / VPP Pin (3)
VDD
OSC1/
WDT
Module
VDD rise
detect
OST/PWRT
On-chip(1)
RC OSC
WDT Time-out
Power-on Reset
OST
PWRT
Chip_Reset
10-bit Ripple-counter
Enable OST
Enable PWRT (4)
SLEEP
See Table 3-1 for time-out situations.
Note 1: This is a separate oscillator from the RC oscillator of the CLKIN pin or the INTRC oscillator.
2: Features in dashed boxes not available on all devices, see device’s Data Sheet.
3: In some devices, this pin may be configured as a general purpose Input.
4: The early PICmicro devices hav e the configuration bit defined as PWR TE = 1 is enab led, while all other
devices the configuration bit is defined as PWRTE = 0 is enabled.
Brown-out
Reset BODEN
CLKIN
Pin
10-bit Ripple-counter
Program
Memory
Parity
MPEEN
MCLRE
Weak Pull-up (2)
VDD
MCLRE
I/O Pull-up
Enable
(2)
(2)
(2)
PICmicro MID-RANGE MCU FAMILY
DS31003A-page 3-4 1997 Microchip Technology Inc.
3.2 Power-on Reset (POR), Power-up Timer (PWRT),
Oscillator Start-up Timer (OST), Brown-out Reset (BOR), and Parity Error Reset (PER)
3.2.1 Power-on Reset (POR)
A Power-on Reset pulse is generated on-chip when VDD rise is detected. To take advantage of
the POR, just tie the MCLR pin directly (or through a resistor) to VDD as shown in Figure 3-2. This
will eliminate exter nal RC components usually needed to create a Power-on Reset. A minimum
rise time for VDD is required. See parameter D003 and parameter D004 in the “Electrical Spec-
ifications” section for details.
Figure 3-2: Using On-Chip POR
When the device exits the reset condition (begins normal operation), the device oper ating param-
eters (voltage , frequency, temperature, etc.) must be within their operating ranges , otherwise the
de vice will not function correctly. Ensure the delay is long enough to get all oper ating parameters
within specification.
Figure 3-3 shows a possib le POR circuit for a slow po wer supply ramp up . The e xternal P ower-on
Reset circuit is only required if VDD power-up time is too slow. The diode, D, helps discharge the
capacitor quickly when VDD powers down.
Figure 3-3: External Power-on Reset Circuit (For Slow VDD Power-up)
VDD
MCLR
PIC16CXXX
VDD
R (1)
Note: The resistor is optional.
C
R
D
VDD
MCLR
PIC16CXXX
VDD
Note: R < 40 k is recommended to ensure that the voltage drop across R does not
exceed 0.2V. A larger voltage drop will degrade VIH level on the MCLR/VPP pin.
VDD
1997 Microchip Technology Inc. DS31003A-page 3-5
Section 3. Reset
Reset
3
3.2.2 Power-up Timer (PWRT)
The Power-up Timer provides a nominal 72 ms delay on Power-on Reset (POR) or Brown-out
Reset (BOR), see parameter 33 in the “Electrical Specifications” section. The P o wer-up Timer
operates on a dedicated internal RC oscillator. The device is kept in reset as long as the PWRT
is active. The PWRT delay allows VDD to rise to an acceptable level. The power-up timer enable
configuration bit can enable/disable the Power-up Timer. The Power-up Timer should always be
enabled when Brown-out Reset is enabled. The polarity of the Power-up Timer configuration bit
is now PWRTE = 0 for enabled, while the initial definition of the bit was PWRTE = 1 for enabled.
Since all new de vices will use the PWR TE = 0 f or enab led, the te xt will describe the operation for
such devices. Please refer to the individual Data Sheet to ensure the correct polarity for this bit.
The power-up time delay will vary from device to device due to VDD, temperature, and process
variations. See DC parameters for details.
3.2.3 Oscillator Start-up Timer (OST)
The Oscillator Star t-Up Timer (OST) provides a 1024 oscillator cycle delay (from OSC1 input)
after the PWR T delay is o ver . This ensures that the crystal oscillator or resonator has started and
is stable.
The OST time-out is invoked only for XT, LP and HS modes and only on Power-on Reset,
Brown-out Reset, or wake-up from SLEEP.
The OST counts the oscillator pulses on the OSC1/CLKIN pin. The counter only starts increment-
ing after the amplitude of the signal reaches the oscillator input thresholds. This delay allows the
crystal oscillator or resonator to stabiliz e bef ore the de vice e xits the OST dela y. The length of the
time-out is a function of the crystal/resonator frequency.
Figure 3-4 shows the operation of the OST circuit in conjunction with the po wer-up timer. F or lo w
frequency crystals this start-up time can become quite long. That is because the time it tak es the
low frequency oscillator to start oscillating is longer than the power-up timer’s delay. So the time
from when the power-up timer times-out, to when the oscillator starts to oscillate is a dead time.
There is no minimum or maximum time for this dead time (
T
DEADTIME
).
Figure 3-4: Oscillator Start-up Time
VDD
MCLR
Oscillator
OST TIME_OUT
PWRT TIME_OUT
INTERNAL RESET
TOSC1
TOST
TPWRT
POR or BOR Trip Point
Tosc1 = time for the crystal oscillator to react to an oscillation level detectable by the
Oscillator Start-up Timer (OST).
TOST = 1024TOSC.
TDEADTIME
PICmicro MID-RANGE MCU FAMILY
DS31003A-page 3-6 1997 Microchip Technology Inc.
3.2.4 Power-up Sequence
On power-up, the time-out sequence is as follows: First the internal POR is detected, then, if
enabled, the PWRT time-out is invoked. After the PWRT time-out is over, the OST is activated.
The total time-out will vary based on oscillator configuration and PWR TE bit status. For e xample ,
in RC mode with the PWR TE bit set (PWR T disabled), there will be no time-out at all. Figure 3-5,
Figure 3-6 and Figure 3-7 depict time-out sequences.
Since the time-outs occur from the internal POR pulse, if MCLR is kept low long enough, the
time-outs will expire. Then bringing MCLR high will begin execution immediately (Figure 3-7).
This is useful for testing purposes or to synchronize more than one device operating in parallel.
If the device voltage is not within the electrical specifications by the end of a time-out, the
MCLR/VPP pin must be held low until the v oltage is within the de vice specification. The use of an
external RC delay is sufficient for many of these applications.
Table 3-1 shows the time-outs that occur in various situations, while Figure 3-5 through
Figure 3-8 show four different cases that can happen on powering up the device.
Table 3-1: Time-out in Various Situations
Figure 3-5: Time-out Sequence on Power-up (MCLR Tied to VDD)
Oscillator
Configuration
Power-up Timer Brown-out Reset Wake-up
from
SLEEP
Enabled Disabled
XT, HS, LP 72 ms + 1024TOSC 1024TOSC 72 ms + 1024TOSC 1024TOSC
RC 72 ms (1) 72 ms (1)
Note 1: Devices with the Internal/External RC option have a nominal 250 µs delay.
TPWRT
TOST
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
OST TIME-OUT
INTERNAL RESET
1997 Microchip Technology Inc. DS31003A-page 3-7
Section 3. Reset
Reset
3
Figure 3-6: Time-out Sequence on Power-up (MCLR not Tied to VDD): Case 1
Figure 3-7: Time-out Sequence on Power-up (MCLR not Tied to VDD): Case 2
Figure 3-8: Slow Rise Time (MCLR Tied to VDD)
TPWRT
TOST
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
OST TIME-OUT
INTERNAL RESET
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
OST TIME-OUT
INTERNAL RESET
TPWRT
TOST
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
OST TIME-OUT
INTERNAL RESET
0V 5V
TPWRT
TOST
PICmicro MID-RANGE MCU FAMILY
DS31003A-page 3-8 1997 Microchip Technology Inc.
3.2.5 Brown-out Reset (BOR)
On-chip Brown-out Reset circuitry places the device into reset when the device voltage falls
below a trip point (BVDD). This ensures that the de vice does not continue program e x ecution out-
side the valid oper ation range of the device. Brown-out resets are typically used in AC line appli-
cations or large battery applications where large loads ma y be s witched in (such as automotiv e),
and cause the device voltage to temporarily fall below the specified operating minimum.
The BODEN configuration bit can disable (if clear/programmed) or enable (if set) the Brown-out
Reset circuitry. If VDD falls belo w BVDD (Typically 4.0V, parameter D005 in the “Electrical Spec-
ifications” section), for greater than parameter 35, the brown-out situation will reset the chip. A
reset is not guaranteed to occur if VDD falls belo w BVDD f or less than parameter 35 . The chip will
remain in Brown-out Reset until VDD rises above BVDD. The Power-up Timer will now be inv ok ed
and will keep the chip in reset an additional 72 ms . If VDD drops below BVDD while the Power-up
Timer is running, the chip will go back into Reset and the Power-up Timer will be re-initialized.
Once VDD rises above BVDD, the Power-up Timer will again start a 72 ms time delay. Figure 3-9
shows typical Brown-out situations.
With the BODEN bit set, all voltages below BVDD will hold the device in the reset state. This
includes during the power-up sequence.
Figure 3-9: Brown-out Situations
Note: Bef ore using the on-chip brown-out for a voltage supervisory function (monitor bat-
tery deca y), please revie w the electrical specifications to ensure that they meet your
requirements.
72 ms
VDD
Internal
Reset
BVDD
VDD
Internal
Reset 72 ms
<72 ms
72 ms
BVDD
VDD
Internal
Reset
BVDD
1997 Microchip Technology Inc. DS31003A-page 3-9
Section 3. Reset
Reset
3
Some devices do not have the on-chip bro wn-out circuit, and in other cases there are some appli-
cations where the Brown-out Reset trip point of the device may not be at the desired level.
Figure 3-10 and Figure 3-11 are two examples of external circuitry that may be implemented.
Each needs to be evaluated to determine if they match the requirements of the application.
Figure 3-10: External Brown-out Protection Circuit 1
Figure 3-11: External Brown-out Protection Circuit 2
This circuit will activate reset when VDD goes below (Vz + 0.7V)
where Vz = Zener voltage.
Note 1: Internal Brown-out Reset circuitry should be disabled when using this circuit.
2: Resistors should be adjusted for the characteristics of the transistor.
VDD
33 k
10 k
40 k
VDD
MCLR
PIC16CXXX
Q1
R2 40 k
VDD
MCLR
PIC16CXXX
R1
Q1
VDD
Note 1: This brown-out circuit is less expensive, albeit less accurate. Transistor Q1 turns
off when VDD is below a certain level such that:
2: Internal Brown-out Reset circuitry should be disabled when using this circuit.
3: Resistors should be adjusted for the characteristics of the transistor.
VDD R1
R1 + R2 = 0.7V
PICmicro MID-RANGE MCU FAMILY
DS31003A-page 3-10 1997 Microchip Technology Inc.
3.3 Registers and Status Bit Values
Table 3-2: Status Bits and Their Significance
POR BOR(1) TO PD Condition
0x11Power-on Reset
0x0xIllegal, T O is set on POR
0xx0Illegal, PD is set on POR
1(2) 011Brown-out Reset
1(2) 1(2) 01WDT Reset
1(2) 1(2) 00WDT W ake-up
1(2) 1(2) uuMCLR reset during normal operation
1(2) 1(2) 10MCLR reset during SLEEP
Legend: u = unchanged, x = unknown, - = unimplemented bit, reads as ‘0’.
Note 1: Not all devices have BOR circuitry.
2: These bits are unchanged for the giv en conditions, and when initializ ed (set) after a
POR or a BOR will read as a '1'.
1997 Microchip Technology Inc. DS31003A-page 3-11
Section 3. Reset
Reset
3
Table 3-3: Initialization Condition for Special Registers
Condition Program
Counter STATUS
Register PCON
Register
Power-on Reset 000h 0001 1xxx u--- -10x
MCLR reset during normal operation 000h 000u uuuu u--- -uuu
MCLR reset during SLEEP 000h 0001 0uuu u--- -uuu
WDT reset 000h 0000 1uuu u--- -uuu
WDT Wake-up PC + 1 uuu0 0uuu u--- -uuu
Brown-out Reset 000h 0001 1uuu u--- -uu0
Interrupt Wake-up from SLEEP PC + 1(1) uuu1 0uuu u--- -uuu
Legend: u = unchanged, x = unknown, - = unimplemented bit, reads as ‘0’.
Note 1: When the wak e-up is due to an interrupt and global enable bit, GIE, is set the PC is
loaded with the interrupt vector (0004h) after execution of PC+1.
2: If a status bit is not implemented, that bit will be read as ‘0’.
PICmicro MID-RANGE MCU FAMILY
DS31003A-page 3-12 1997 Microchip Technology Inc.
Table 3-4: Initialization Conditions for Special Function Registers
Register Power-on Reset
Brown-out Reset
MCLR Reset during:
- normal operation
- SLEEP or
WDT Reset
Wake-up from SLEEP
through:
- interrupt
- WDT time-out
ADCAPL 0000 0000 0000 0000 uuuu uuuu
ADCAPH 0000 0000 0000 0000 uuuu uuuu
ADCON0 0000 00-0 0000 00-0 uuuu uu-u
ADCON1 ---- -000 ---- -000 ---- -uuu
ADRES xxxx xxxx uuuu uuuu uuuu uuuu
ADTMRL 0000 0000 0000 0000 uuuu uuuu
ADMRH 0000 0000 0000 0000 uuuu uuuu
CCP1CON --00 0000 --00 0000 --uu uuuu
CCP2CON 0000 0000 0000 0000 uuuu uuuu
CCPR1L xxxx xxxx uuuu uuuu uuuu uuuu
CCPR1H xxxx xxxx uuuu uuuu uuuu uuuu
CCPR2L xxxx xxxx uuuu uuuu uuuu uuuu
CCPR2H xxxx xxxx uuuu uuuu uuuu uuuu
CMCON 00-- 0000 00-- 0000 uu-- uuuu
EEADR xxxx xxxx uuuu uuuu uuuu uuuu
EECON1 ---0 x000 ---0 q000 ---0 uuuu
EECON2 -- -
EEDATA xxxx xxxx uuuu uuuu uuuu uuuu
FSR xxxx xxxx uuuu uuuu uuuu uuuu
GPIO --xx xxxx --uu uuuu --uu uuuu
I2CADD 0000 0000 0000 0000 uuuu uuuu
I2CBUF xxxx xxxx uuuu uuuu uuuu uuuu
I2CCON 0000 0000 0000 0000 uuuu uuuu
I2CSTAT --00 0000 --00 0000 --uu uuuu
INDF -- -
INTCON 0000 000x 0000 000u uuuu uuuu(1)
LCDCON 00-0 0000 00-0 0000 uu-u uuuu
LCDD00 to LCDD15 xxxx xxxx uuuu uuuu uuuu uuuu
LCDPS ---- 0000 ---- 0000 ---- uuuu
LCDSE 1111 1111 1111 1111 uuuu uuuu
OPTION_REG 1111 1111 1111 1111 uuuu uuuu
OSCCAL 0111 00-- uuuu uu-- uuuu uu--
PCL 0000 0000 0000 0000 PC + 1(2)
PCLATH ---0 0000 ---0 0000 ---u uuuu
PCON ---- --0u ---- --uu ---- --uu
PIE1 0000 0000 0000 0000 uuuu uuuu
PIE2 ---- ---0 ---- ---0 ---- ---u
PIR1 0000 0000 0000 0000 uuuu uuuu
Legend: u = unchanged, x = unknown, - = unimplemented bit, reads as ‘0’,q = value depends on condition.
Note 1: One or more bits in INTCON and/or PIR1 will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIE bit is set, the PC is loaded with the interrupt
vector (0004h).
3: See Table 3-3 for reset value for specific condition.
1997 Microchip Technology Inc. DS31003A-page 3-13
Section 3. Reset
Reset
3
PIR2 ---- ---0 ---- ---0 ---- ---u
PORTA --xx xxxx --uu uuuu --uu uuuu
PORTB xxxx xxxx uuuu uuuu uuuu uuuu
PORTC xxxx xxxx uuuu uuuu uuuu uuuu
PORTD xxxx xxxx uuuu uuuu uuuu uuuu
PORTE ---- -xxx ---- -uuu ---- -uuu
PORTF 0000 0000 0000 0000 uuuu uuuu
PORTG 0000 0000 0000 0000 uuuu uuuu
PR2 1111 1111 1111 1111 1111 1111
PREFA 0000 0000 0000 0000 uuuu uuuu
PREFB 0000 0000 0000 0000 uuuu uuuu
RCSTA 0000 -00x 0000 -00x uuuu -uuu
RCREG 0000 0000 0000 0000 uuuu uuuu
SLPCON 0011 1111 0011 1111 uuuu uuuu
SPBRG 0000 0000 0000 0000 uuuu uuuu
SSPBUF xxxx xxxx uuuu uuuu uuuu uuuu
SSPCON 0000 0000 0000 0000 uuuu uuuu
SSPADD 0000 0000 0000 0000 uuuu uuuu
SSPSTAT 0000 0000 0000 0000 uuuu uuuu
STATUS 0001 1xxx 000q quuu(3) uuuq quuu(3)
T1CON --00 0000 --uu uuuu --uu uuuu
T2CON -000 0000 -000 0000 -uuu uuuu
TMR0 xxxx xxxx uuuu uuuu uuuu uuuu
TMR1L xxxx xxxx uuuu uuuu uuuu uuuu
TMR1H xxxx xxxx uuuu uuuu uuuu uuuu
TMR2 0000 0000 0000 0000 uuuu uuuu
TRIS --11 1111 --11 1111 --uu uuuu
TRISA --11 1111 --11 1111 --uu uuuu
TRISB 1111 1111 1111 1111 uuuu uuuu
TRISC 1111 1111 1111 1111 uuuu uuuu
TRISD 1111 1111 1111 1111 uuuu uuuu
TRISE 0000 -111 0000 -111 uuuu -uuu
TRISF 1111 1111 1111 1111 uuuu uuuu
TRISG 1111 1111 1111 1111 uuuu uuuu
TXREG 0000 0000 0000 0000 uuuu uuuu
TXSTA 0000 -010 0000 -010 uuuu -uuu
VRCON 000- 0000 000- 0000 uuu- uuuu
Wxxxx xxxx uuuu uuuu uuuu uuuu
Table 3-4: Initialization Conditions for Special Function Registers (Cont.d)
Register Power-on Reset
Brown-out Reset
MCLR Reset during:
- normal operation
- SLEEP or
WDT Reset
Wake-up from SLEEP
through:
- interrupt
- WDT time-out
Legend: u = unchanged, x = unknown, - = unimplemented bit, reads as ‘0’,q = value depends on condition.
Note 1: One or more bits in INTCON and/or PIR1 will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIE bit is set, the PC is loaded with the interrupt
vector (0004h).
3: See Table 3-3 for reset value for specific condition.
PICmicro MID-RANGE MCU FAMILY
DS31003A-page 3-14 1997 Microchip Technology Inc.
3.3.1 Power Control (PCON) and STATUS Registers
The Power Control (PCON) register contains a status bit to allow differentiation between a
P o wer-on Reset (POR) to an e xternal MCLR Reset or WDT Reset. It also contains a status bit to
determine if a Brown-out Reset (BOR) occurred. The power control/status register, PCON has
up to four bits.
The BOR (Brown-out Reset) bit, is unknown on a Power-on-reset. It must initially be set by the
user and check ed on subsequent resets to see if BOR = '0' indicating that a Brown-out Reset has
occurred. The BOR status bit is a “don’t care” bit and is not necessarily predictable if the
brown-out circuit is disabled (by clearing the BODEN bit in the Configuration word).
The POR (P o wer-on Reset) bit, is cleared on a P o wer-on Reset and is unaff ected otherwise. The
user sets this bit following a Power-on Reset. On subsequent resets if POR is ‘0’, it will indicate
that a Power-on Reset must have occurred.
The PER (P arity Error Reset) bit, is cleared on a P arity Error Reset and must be set by user soft-
ware. It will also be set on a Power-on Reset.
The MPEEN (Memory Parity Error Enable) bit, reflects the status of the MPEEN bit in configur a-
tion word. It is unaffected by any reset or interrupt.
Register 3-1: PCON Register
Note: BOR is unknown on Power-on Reset. It must then be set by the user and checked
on subsequent resets to see if BOR is clear, indicating a brown-out has occurred.
The BOR status bit is a don't care and is not necessarily predictable if the brown-out
circuit is disabled (by clearing the BODEN bit in the Configuration word).
R-u U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0
MPEEN PER POR BOR
bit 7 bit 0
bit 7 MPEEN: Memory Parity Error Circuitry Status bit
This bit reflects the value of the MPEEN configuration bit.
bit 6:3 Unimplemented: Read as '0'
bit 2 PER: Memory Parity Error Reset Status bit
1 = No parity error reset occurred
0 = A program memory fetch parity error occurred
(must be set in software after a Power-on Reset or Parity Error Reset occurs)
bit 1 POR: Power-on Reset Status bit
1 = No Power-on Reset occurred
0 = A Power-on Reset occurred (must be set in software after a Power-on Reset occurs)
bit 0 BOR: Brown-out Reset Status bit
1 = No Brown-out Reset occurred
0 = A Brown-out Reset occurred (must be set in software after a Brown-out Reset or
Power-on Reset occurs)
Legend
R = Readable bit W = Writable bit u = unchanged bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note: Not all bits may be implemented.
1997 Microchip Technology Inc. DS31003A-page 3-15
Section 3. Reset
Reset
3
The STATUS register contains two bits (TO and PD), which when used in conjunction with the
PCON register bits provide the user with enough inf ormation to determine the cause of the reset.
Register 3-2: STATUS Register
R/W-0 R/W-0 R/W-0 R-1 R-1 R/W-x R/W-x R/W-x
IRP RP1 RP0 TO PD ZDC C
bit 7 bit 0
bit 7 IRP: Register Bank Select bit (used for indirect addressing)
1 = Bank 2, 3 (100h - 1FFh)
0 = Bank 0, 1 (00h - FFh)
For devices with only Bank0 and Bank1 the IRP bit is reserved, always maintain this bit clear.
bit 6:5 RP1:RP0: Register Bank Select bits (used for direct addressing)
11 = Bank 3 (180h - 1FFh)
10 = Bank 2 (100h - 17Fh)
01 = Bank 1 (80h - FFh)
00 = Bank 0 (00h - 7Fh)
Each bank is 128 bytes. For devices with only Bank0 and Bank1 the IRP bit is reserved,
always maintain this bit clear.
bit 4 TO: Time-out bit
1 = After power-up, CLRWDT instruction, or SLEEP instruction
0 = A WDT time-out occurred
bit 3 PD: Power-down bit
1 = After power-up or by the CLRWDT instruction
0 = By execution of the SLEEP instruction
bit2 Z: Zero bit
1 = The result of an arithmetic or logic operation is zero
0 = The result of an arithmetic or logic operation is not zero
bit 1 DC: Digit carr y/borrow bit (ADDWF, ADDLW, SUBLW, SUBWF instructions) (for borrow the polarity
is reversed)
1 = A carry-out from the 4th low order bit of the result occurred
0 = No carry-out from the 4th low order bit of the result
bit 0 C: Carry/borrow bit (ADDWF, ADDLW,SUBLW,SUBWF instructions)
1 = A carry-out from the most significant bit of the result occurred
0 = No carry-out from the most significant bit of the result occurred
Note: For borrow the polarity is reversed. A subtraction is executed by adding the two’s
complement of the second operand. For rotate (RRF, RLF) instructions, this bit is
loaded with either the high or low order bit of the source register.
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31003A-page 3-16 1997 Microchip Technology Inc.
3.4 Design Tips
Question 1:
When m y system is subjected to an en vironment with ESD and EMI, it oper -
ates erratically.
Answer 1:
If the device you are using does not hav e filtering to the on-chip master clear circuit (Appendix C),
ensure that proper e xternal filtering is placed on the MCLR pin to remove narro w pulses . Electri-
cal Specification parameter 35 specifies the pulse width required to cause a reset.
Question 2:
With JW (windowed) de vices my system resets and operates pr operly. With
an OTP device, my system does not operate properly.
Answer 2:
The most common reason f or this is that the windo wed device (JW) has not had its window cov-
ered. The bac kground light causes the de vice to power-up in a diff erent state than would typically
be seen in a device where no light is present. In most cases all the General Purpose RAM and
Special Function Registers were not initialized properly.
1997 Microchip Technology Inc. DS31003A-page 3-17
Section 3. Reset
Reset
3
3.5 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to Resets are:
Title Application Note #
P ower-up Troub le Shooting AN607
Power-up Considerations AN522
PICmicro MID-RANGE MCU FAMILY
DS31003A-page 3-18 1997 Microchip Technology Inc.
3.6 Revision History
Revision A
This is the initial released revision of the Reset description.
1997 Microchip Technology Inc. DS31004A page 4-1
M
Architecture
4
Section 4. Architecture
HIGHLIGHTS
This section of the manual contains the following major topics:
4.1 Introduction....................................................................................................................4-2
4.2 Clocking Scheme/Instruction Cycle ...............................................................................4-5
4.3 Instruction Flow/Pipelining.............................................................................................4-6
4.4 I/O Descriptions .............................................................................................................4-7
4.5 Design Tips..................................................................................................................4-12
4.6 Related Application Notes............................................................................................4-13
4.7 Revision History...........................................................................................................4-14
PICmicro MID-RANGE MCU FAMILY
DS31004A-page 4-2 1997 Microchip Technology Inc.
4.1 Introduction
The high perfor mance of the PICmicro™ devices can be attributed to a number of architectural
features commonly found in RISC microprocessors. These include:
Harvard architecture
Long W ord Instructions
Single W ord Instructions
Single Cycle Instructions
Instruction Pipelining
Reduced Instruction Set
Register File Architecture
Orthogonal (Symmetric) Instructions
Figure 4-2 shows a simple core memory bus arrangement for Mid-Range MCU devices.
Harvard Architecture:
Harv ard architecture has the program memory and data memory as separate memories and are
accessed from separate b uses. This improv es bandwidth ov er traditional v on Neumann architec-
ture in which program and data are fetched from the same memory using the same bus. To exe-
cute an instruction, a von Neumann machine must mak e one or more (generally more) accesses
across the 8-bit bus to f etch the instruction. Then data ma y need to be f etched, operated on, and
possibly written. As can be seen from this description, that bus can be e xtremely conjested. While
with a Harvard architecture, the instruction is fetched in a single instruction cycle (all 14-bits).
While the program memory is being accessed, the data memor y is on an independent bus and
can be read and written. These separated buses allow one instruction to execute while the next
instruction is fetched. A comparison of Harvard vs. von-Neumann architectures is shown in
Figure 4-1.
Figure 4-1: Harvard vs. von Neumann Block Architectures
Long W ord Instructions:
Long word instructions hav e a wider (more bits) instruction bus than the 8-bit Data Memory Bus.
This is possible because the tw o b uses are separ ate . This further allows instructions to be sized
differently than the 8-bit wide data word which allows a more efficient use of the program mem-
ory, since the program memory width is optimized to the architectural requirements.
Single W ord Instructions:
Single Word instruction opcodes are 14-bits wide making it possible to have all single word
instructions. A 14-bit wide program memory access bus fetches a 14-bit instruction in a single
cycle. With single word instructions, the number of words of program memor y locations equals
the number of instructions for the device. This means that all locations are valid instructions.
Typically in the von Neumann architecture, most instructions are multi-byte. In general, a device
with 4-KBytes of program memory would allow approximately 2K of instructions. This 2:1 r atio is
generalized and dependent on the application code. Since each instruction may take multiple
bytes, there is no assurance that each location is a valid instruction.
Program
Memory
Data
Memory
Program
Memory
and
Data
CPU CPU 8
814
Harvard von-Neumann
1997 Microchip Technology Inc. DS31004A-page 4-3
Section 4. Architecture
Architecture
4
Instruction Pipeline:
The instruction pipeline is a two-stage pipeline which ov erlaps the fetch and e x ecution of instruc-
tions. The f etch of the instruction takes one TCY, while the ex ecution takes another TCY. However,
due to the overlap of the fetch of current instruction and execution of previous instruction, an
instruction is fetched and another instruction is executed every single TCY.
Single Cycle Instructions:
With the Program Memory bus being 14-bits wide, the entire instruction is fetched in a single
machine cycle (TCY). The instr uction contains all the infor mation required and is executed in a
single cycle. There may be a one cycle delay in execution if the result of the instruction modified
the contents of the Program Counter. This requires the pipeline to be flushed and a new instruc-
tion to be fetched.
Reduced Instruction Set:
When an instruction set is well designed and highly or thogonal (symmetric), fewer instructions
are required to perf orm all needed tasks. With fe wer instructions, the whole set can be more rap-
idly learned.
Register File Architecture:
The register files/data memory can be directly or indirectly addressed. All special function regis-
ters, including the program counter, are mapped in the data memory.
Orthogonal (Symmetric) Instructions:
Orthogonal instructions make it possible to carry out any operation on any register using any
addressing mode. This symmetrical nature and lack of “special instructions” make programming
simple yet efficient. In addition, the learning curve is reduced significantly. The mid-range instruc-
tion set uses only two non-register oriented instructions, which are used for tw o of the cores f ea-
tures. One is the SLEEP instruction which places the device into the low est pow er use mode. The
other is the CLRWDT instruction which verifies the chip is operating properly by preventing the
on-chip Watchdog Timer (WDT) from overflowing and resetting the device.
PICmicro MID-RANGE MCU FAMILY
DS31004A-page 4-4 1997 Microchip Technology Inc.
Figure 4-2: General Mid-range PICmicro Block Diagram
EPROM
Program
Memory
8K x 14
13 Data Bus 8
14
Program
Bus
Instruction reg
Program Counter
8 Level Stack
(13-bit)
RAM
File
Registers
368 x 8
Direct Addr 7
RAM Addr (1) 9
Addr MUX
Indirect
Addr
FSR reg
STATUS reg
MUX
ALU
W reg
Power-up
Timer
Oscillator
Start-up Timer
Power-on
Reset
Watchdog
Timer
Instruction
Decode &
Control
Timing
Generation
OSC1/CLKIN
OSC2/CLKOUT
MCLR VDD, VSS
PORTA
PORTB
PORTC
PORTD
PORTE
RA4
RA5
RC0
RC1
RC2
RC3
RC4
RC5
RC6
RC7
8
8
Brown-out
Reset (2)
Note 1: The high order bits of the Direct Address for the RAM are from the STATUS register.
2: Not all devices have this feature, please refer to device data sheet.
3: Many of the general purpose I/O pins are multiplexed with one or more peripheral module functions.
The multiplexing combinations are device dependent.
USARTs
CCPs Comparators Synchronous
A/DTimer0 Timer1 Timer2
Serial Port
RA3
RA2
RA1
RA0
8
3
up to
up to
RB0/INT
RB1
RB2
RB3
RB4
RB5
RB6
RB7
RD0
RD1
RD2
RD3
RD4
RD5
RD6
RD7
Data EEPROM
up to
256 x 8
Other LCD Drivers
Voltage
Reference
Modules
Peripheral Modules (Note 3)
PORTF RF0
RF1
RF2
RF3
RF4
RF5
RF6
RF7
PORTG RG0
RG1
RG2
RG3
RG4
RG5
RG6
RG7
Parallel
Slave Port
General Purpose I/O
RE0
RE1
RE2
RE3
RE4
RE5
RE6
RE7
Internal
RC clock (2)
(Note 3)
1997 Microchip Technology Inc. DS31004A-page 4-5
Section 4. Architecture
Architecture
4
4.2 Clocking Scheme/Instruction Cycle
The clock input (from OSC1) is internally divided by four to generate four non-overlapping
quadrature clocks, namely Q1, Q2, Q3, and Q4. Inter nally, the program counter (PC) is incre-
mented every Q1, and the instr uction is fetched from the program memory and latched into the
instruction register in Q4. The instruction is decoded and executed during the following Q1
through Q4. The clocks and instruction execution flow are illustrated in Figure 4-3, and
Example 4-1.
Figure 4-3: Clock/Instruction Cycle
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
Q1
Q2
Q3
Q4
PC
OSC2/CLKOUT
(RC mode)
PC PC+1 PC+2
Fetch INST (PC)
Execute INST (PC-1) Fetch INST (PC+1)
Execute INST (PC) Fetch INST (PC+2)
Execute INST (PC+1)
Internal
phase
clock
TCY1TCY2TCY3
PICmicro MID-RANGE MCU FAMILY
DS31004A-page 4-6 1997 Microchip Technology Inc.
4.3 Instruction Flow/Pipelining
An “Instruction Cycle” consists of four Q cycles (Q1, Q2, Q3, and Q4). F etch takes one instruction
cycle while decode and e xecute takes another instruction cycle. Ho wev er , due to Pipelining, each
instruction effectively executes in one cycle. If an instruction causes the program counter to
change (e.g. GOTO) then an extra cycle is required to complete the instruction (Example 4-1).
The instruction fetch begins with the program counter incrementing in Q1.
In the execution cycle, the fetched instruction is latched into the “Instruction Register (IR)” in
cycle Q1. This instruction is then decoded and executed during the Q2, Q3, and Q4 cycles. Data
memory is read during Q2 (operand read) and written during Q4 (destination write).
Example 4-1 shows the operation of the two stage pipeline for the instruction sequence shown.
At time TCY0, the first instruction is f etched from progr am memory. During TCY1, the first instruc-
tion executes while the second instruction is fetched. During TCY2, the second instruction exe-
cutes while the third instruction is fetched. During TCY3, the f ourth instruction is fetched while the
third instruction (CALL SUB_1) is executed. When the third instruction completes execution, the
CPU forces the address of instruction f our onto the Stack and then changes the Program Counter
(PC) to the address of SUB_1. This means that the instruction that was fetched during TCY3 needs
to be “flushed” from the pipeline. During TCY4, instruction four is flushed (e x ecuted as a NOP) and
the instruction at address SUB_1 is fetched. Finally during TCY5, instruction five is executed and
the instruction at address SUB_1 + 1 is fetched.
Example 4-1: Instruction Pipeline Flow
All instructions are single cycle, except for any program branches. These take two cycles since the fetch
instruction is “flushed” from the pipeline while the new instruction is being fetched and then executed.
TCY0TCY1TCY2TCY3TCY4TCY5
1. MOVLW 55h Fetch 1 Execute 1
2. MOVWF PORTB Fetch 2 Execute 2
3. CALL SUB_1 Fetch 3 Execute 3
4. BSF PORTA, BIT3 (Forced NOP) Fetch 4 Flush
5. Instruction @ address SUB_1 Fetch SUB_1 Execute SUB_1
Fetch SUB_1 + 1
1997 Microchip Technology Inc. DS31004A-page 4-7
Section 4. Architecture
Architecture
4
4.4 I/O Descriptions
Table 4-1 giv es a brief description of the functions that may be m ultiplex ed to a port pin. Multiple
functions ma y exist on one port pin. When multiple xing occurs, the peripheral module’ s functional
requirements ma y f orce an ov erride of the data direction (TRIS bit) of the port pin (such as in the
A/D and LCD modules).
Table 4-1: I/O Descriptions
Pin Name Pin
Type Buffer
Type Description
Analog Input Channels
AN0 I Analog
AN1 I Analog
AN2 I Analog
AN3 I Analog
AN4 I Analog
AN5 I Analog
AN6 I Analog
AN7 I Analog
AN8 I Analog
AN9 I Analog
AN10 I Analog
AN11 I Analog
AN12 I Analog
AN13 I Analog
AN14 I Analog
AN15 I Analog
AVDD P P Analog Power
AVSS P P Analog Ground
C1 I Analog LCD V oltage Generation
C2 I Analog LCD V oltage Generation
CCP1 I/O ST Capture1 input/Compare1 output/PWM1 output
CCP2 I/O ST Capture2 input/Compare2 output/PWM2 output.
CDAC O Analog A/D ramp current source output. Normally connected to external
capacitor to generate a linear voltage ramp.
CK I/O ST USART Synchronous Clock, always associated with TX pin function
(See related TX, RX, DT)
CLKIN I ST/CMOS External clock source input. Always associated with pin function
OSC1. (See related OSC1/CLKIN, OSC2/CLKOUT pins)
CLKOUT O Oscillator crystal output. Connects to crystal or resonator in crystal
oscillator mode. In RC mode, OSC2 pin outputs CLKOUT which has
1/4 the frequency of OSC1, and denotes the instruction cycle rate.
Always associated with OSC2 pin function. (See related OSC2,
OSC1)
CMPA O Comparator A output
CMPB O Comparator B output
Legend: TTL = TTL-compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels
SM = SMBus compatible input. An external resistor is required if this pin is used as an output
NPU = N-channel pull-up PU = Weak internal pull-up
No-P diode = No P-diode to VDD AN = Analog input or output
I = input O = output
P = Power L = LCD Driver
PICmicro MID-RANGE MCU FAMILY
DS31004A-page 4-8 1997 Microchip Technology Inc.
COM0 L LCD Common Driver0
COM1 L LCD Common Driver1
COM2 L LCD Common Driver2
COM3 L LCD Common Driver3
CS I TTL chip select control for parallel slave port (See related RD and WR)
DT I/O ST USART Synchronous Data. Always associated RX pin function. (See
related RX, TX, CK)
GP is a bi-directional I/O port. Some pins of port GP can be software
programmed for internal weak pull-ups on the inputs.
GP0 I/O TTL/ST TTL input buffer as general purpose I/O, Schmitt Trigger input buffer
when used as the serial programming mode.
GP1 I/O TTL/ST TTL input buffer as general pur pose I/O, Schmitt Tr igger input buffer
when used as the serial programming mode.
GP2 I/O ST
GP3 I TTL
GP4 I/O TTL
GP5 I/O TTL
INT I ST External Interrupt
MCLR/VPP I/P ST Master clear (reset) input or programming voltage input. This pin is
an active low reset to the device.
NC These pins should be left unconnected.
OSC1 I ST/CMOS Oscillator crystal input or external clock source input. ST buff er when
configured in RC mode. CMOS otherwise.
OSC2 O Oscillator crystal output. Connects to crystal or resonator in crystal
oscillator mode. In RC mode, OSC2 pin outputs CLKOUT which has
1/4 the frequency of OSC1, and denotes the instruction cycle rate.
PBTN I ST Input with weak pull-up resistor , can be used to gener ate an interrupt.
PSP0 I/O TTL Parallel Slave Port for interfacing to a microprocessor port. These
pins have TTL input buffers when PSP module is enabled.
PSP1 I/O TTL
PSP2 I/O TTL
PSP3 I/O TTL
PSP4 I/O TTL
PSP5 I/O TTL
PSP6 I/O TTL
PSP7 I/O TTL PORTA is a bi-directional I/O port.
RA0 I/O TTL
RA1 I/O TTL
RA2 I/O TTL
RA3 I/O TTL
RA4 I/O ST RA4 is an open drain when configured as output.
RA5 I/O TTL
Table 4-1: I/O Descriptions (Cont.d)
Pin Name Pin
Type Buffer
Type Description
Legend: TTL = TTL-compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels
SM = SMBus compatible input. An external resistor is required if this pin is used as an output
NPU = N-channel pull-up PU = Weak internal pull-up
No-P diode = No P-diode to VDD AN = Analog input or output
I = input O = output
P = Power L = LCD Driver
1997 Microchip Technology Inc. DS31004A-page 4-9
Section 4. Architecture
Architecture
4
PORTB is a bi-directional I/O port. PORTB can be software pro-
grammed for internal weak pull-ups on all inputs.
RB0 I/O TTL
RB1 I/O TTL
RB2 I/O TTL
RB3 I/O TTL
RB4 I/O TTL Interrupt on change pin.
RB5 I/O TTL Interrupt on change pin.
RB6 I/O TTL/ST Interrupt on change pin. Serial programming clock. TTL input
buffer as general purpose I/O, Schmitt Trigger input buffer when
used as the serial programming clock.
RB7 I/O TTL/ST Interrupt on change pin. Serial programming data. TTL input
buffer as general purpose I/O, Schmitt Trigger input buffer when
used as the serial programming data.
PORTC is a bi-directional I/O port.
RC0 I/O ST
RC1 I/O ST
RC2 I/O ST
RC3 I/O ST
RC4 I/O ST
RC5 I/O ST
RC6 I/O ST
RC7 I/O ST
RD I TTL Read control for parallel slave port (See also WR and CS pins)
PORTD is a bi-directional I/O port.
RD0 I/O ST
RD1 I/O ST
RD2 I/O ST
RD3 I/O ST
RD4 I/O ST
RD5 I/O ST
RD6 I/O ST
RD7 I/O ST PORTE is a bi-directional I/O port.
RE0 I/O ST
RE1 I/O ST
RE2 I/O ST
RE3 I/O ST
RE4 I/O ST
RE5 I/O ST
RE6 I/O ST
RE7 I/O ST
Table 4-1: I/O Descriptions (Cont.d)
Pin Name Pin
Type Buffer
Type Description
Legend: TTL = TTL-compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels
SM = SMBus compatible input. An external resistor is required if this pin is used as an output
NPU = N-channel pull-up PU = Weak internal pull-up
No-P diode = No P-diode to VDD AN = Analog input or output
I = input O = output
P = Power L = LCD Driver
PICmicro MID-RANGE MCU FAMILY
DS31004A-page 4-10 1997 Microchip Technology Inc.
REFA O CMOS Programmable reference A output.
REFB O CMOS Programmable reference B output.
PORTF is a digital input or LCD Segment Driver Port
RF0 I/O ST
RF1 I/O ST
RF2 I/O ST
RF3 I/O ST
RF4 I/O ST
RF5 I/O ST
RF6 I/O ST
RF7 I/O ST PORTG is a digital input or LCD Segment Driver Port
RG0 I/O ST
RG1 I/O ST
RG2 I/O ST
RG3 I/O ST
RG4 I/O ST
RG5 I/O ST
RG6 I/O ST
RG7 I/O ST
RX I ST USART Asynchronous Receive
SCL I/O ST Synchronous serial clock input/output for I2C mode.
SCLA I/O ST Synchronous serial clock for I2C interface.
SCLB I/O ST Synchronous serial clock for I2C interface.
SDA I/O ST I2C Data I/O
SDAA I/O ST Synchronous serial data I/O for I2C interface
SDAB I/O ST Synchronous serial data I/O for I2C interface
SCK I/O ST Synchronous serial clock input/output for SPI mode.
SDI I ST SPI Data In
SDO O SPI Data Out (SPI mode)
SS I ST SPI Slave Select input
SEG00 to
SEG31 I/L ST LCD Segment Driver00 through Driver31.
SUM O AN AN1 summing junction output. This pin can be connected to an exter-
nal capacitor for averaging small duration pulses.
T0CKI I ST Timer0 external clock input
T1CKI I ST Timer1 external clock input
T1OSO O CMOS Timer1 oscillator output
T1OSI I CMOS Timer1 oscillator input
TX O USART Asynchronous Transmit (See related RX)
Table 4-1: I/O Descriptions (Cont.d)
Pin Name Pin
Type Buffer
Type Description
Legend: TTL = TTL-compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels
SM = SMBus compatible input. An external resistor is required if this pin is used as an output
NPU = N-channel pull-up PU = Weak internal pull-up
No-P diode = No P-diode to VDD AN = Analog input or output
I = input O = output
P = Power L = LCD Driver
I2C is a trademark of Philips Corporation.
1997 Microchip Technology Inc. DS31004A-page 4-11
Section 4. Architecture
Architecture
4
VLCD1 P LCD Voltage
VLCD2 P LCD Voltage
VLCD3 P LCD Voltage
VLCD ADJ I Analog LCD V oltage Generation
VREF I Analog Analog High Voltage Reference input.
DR reference voltage output on devices with comparators.
VREF+ I Analog Analog High Voltage Reference input.
Usually multiplexed onto an analog pin.
VREF- I Analog Analog Low Voltage Reference input.
Usually multiplexed onto an analog pin.
VREG O This pin is an output to control the gate of an external N-FET
for voltage regulation.
VSS P Ground reference for logic and I/O pins.
VDD P Positive supply for logic and I/O pins.
WR I TTL Write control for parallel slave port (See CS and RD pins also).
Table 4-1: I/O Descriptions (Cont.d)
Pin Name Pin
Type Buffer
Type Description
Legend: TTL = TTL-compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels
SM = SMBus compatible input. An external resistor is required if this pin is used as an output
NPU = N-channel pull-up PU = Weak internal pull-up
No-P diode = No P-diode to VDD AN = Analog input or output
I = input O = output
P = Power L = LCD Driver
PICmicro MID-RANGE MCU FAMILY
DS31004A-page 4-12 1997 Microchip Technology Inc.
4.5 Design Tips
No related design tips at this time.
1997 Microchip Technology Inc. DS31004A-page 4-13
Section 4. Architecture
Architecture
4
4.6 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to Architecture
are:
Title Application Note #
No related application notes at this time.
PICmicro MID-RANGE MCU FAMILY
DS31004A-page 4-14 1997 Microchip Technology Inc.
4.7 Revision History
Revision A
This is the initial released revision of the PICmicro’s Architecture description.
1997 Microchip Technology Inc. DS31005A page 5-1
M
CPU and ALU
5
Section 5. CPU and ALU
HIGHLIGHTS
This section of the manual contains the following major topics:
5.1 Introduction....................................................................................................................5-2
5.2 General Instruction Format............................................................................................5-4
5.3 Central Processing Unit (CPU)......................................................................................5-4
5.4 Instruction Clock ............................................................................................................5-4
5.5 Arithmetic Logical Unit (ALU).........................................................................................5-5
5.6 STATUS Register ...........................................................................................................5-6
5.7 OPTION_REG Register.................................................................................................5-8
5.8 PCON Register..............................................................................................................5-9
5.9 Design Tips..................................................................................................................5-10
5.10 Related Application Notes............................................................................................5-11
5.11 Revision History...........................................................................................................5-12
PICmicro MID-RANGE MCU FAMILY
DS31005A-page 5-2 1997 Microchip Technology Inc.
5.1 Introduction
The Central Processing Unit (CPU) is responsib le f or using the inf ormation in the program mem-
ory (instructions) to control the operation of the device. Many of these instructions operate on
data memory. To operate on data memory, the Arithmetic Logical Unit (ALU) is required. In addi-
tion to performing arithmetical and logical operations, the ALU controls status bits (which are
found in the STATUS register). The result of some instructions force status bits to a v alue depend-
ing on the state of the result.
The machine codes that the CPU recognizes are show in Table 5-1 (as well as the instruction
mnemonics that the MPASM uses to generate these codes).
1997 Microchip Technology Inc. DS31005A-page 5-3
Section 5. CPU and ALU
CPU and ALU
5
Table 5-1: Mid-Range MCU Instruction Set
Mnemonic,
Operands Description Cycles 14-Bit Instruction Word Status
Bits
Affected Notes
MSb LSb
BYTE-ORIENTED FILE REGISTER OPERATIONS
ADDWF
ANDWF
CLRF
CLRW
COMF
DECF
DECFSZ
INCF
INCFSZ
IORWF
MOVF
MOVWF
NOP
RLF
RRF
SUBWF
SWAPF
XORWF
f, d
f, d
f
-
f, d
f, d
f, d
f, d
f, d
f, d
f, d
f
-
f, d
f, d
f, d
f, d
f, d
Add W and f
AND W with f
Clear f
Clear W
Complement f
Decrement f
Decrement f, Skip if 0
Increment f
Increment f, Skip if 0
Inclusive OR W with f
Move f
Move W to f
No Operation
Rotate Left f through Carry
Rotate Right f through Carry
Subtract W from f
Swap nibbles in f
Exclusive OR W with f
1
1
1
1
1
1
1(2)
1
1(2)
1
1
1
1
1
1
1
1
1
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
0111
0101
0001
0001
1001
0011
1011
1010
1111
0100
1000
0000
0000
1101
1100
0010
1110
0110
dfff
dfff
lfff
0xxx
dfff
dfff
dfff
dfff
dfff
dfff
dfff
lfff
0xx0
dfff
dfff
dfff
dfff
dfff
ffff
ffff
ffff
xxxx
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
0000
ffff
ffff
ffff
ffff
ffff
C,DC,Z
Z
Z
Z
Z
Z
Z
Z
Z
C
C
C,DC,Z
Z
1,2
1,2
2
1,2
1,2
1,2,3
1,2
1,2,3
1,2
1,2
1,2
1,2
1,2
1,2
1,2
BIT-ORIENTED FILE REGISTER OPERATIONS
BCF
BSF
BTFSC
BTFSS
f, b
f, b
f, b
f, b
Bit Clear f
Bit Set f
Bit Test f, Skip if Clear
Bit Test f, Skip if Set
1
1
1 (2)
1 (2)
01
01
01
01
00bb
01bb
10bb
11bb
bfff
bfff
bfff-
bfff
ffff
ffff
ffff
ffff
1,2
1,2
3
3
LITERAL AND CONTROL OPERATIONS
ADDLW
ANDLW
CALL
CLRWDT
GOTO
IORLW
MOVLW
RETFIE
RETLW
RETURN
SLEEP
SUBLW
XORLW
k
k
k
-
k
k
k
-
k
-
-
k
k
Add literal and W
AND literal with W
Call subroutine
Clear W atchdog Timer
Go to address
Inclusive OR literal with W
Move literal to W
Return from interrupt
Return with literal in W
Return from Subroutine
Go into standby mode
Subtract W from literal
Exclusive OR literal with W
1
1
2
1
2
1
1
2
2
2
1
1
1
11
11
10
00
10
11
11
00
11
00
00
11
11
111x
1001
0kkk
0000
1kkk
1000
00xx
0000
01xx
0000
0000
110x
1010
kkkk
kkkk
kkkk
0110
kkkk
kkkk
kkkk
0000
kkkk
0000
0110
kkkk
kkkk
kkkk
kkkk
kkkk
0100
kkkk
kkkk
kkkk
1001
kkkk
1000
0011
kkkk
kkkk
C,DC,Z
Z
TO,PD
Z
TO,PD
C,DC,Z
Z
Note 1: When an I/O register is modified as a function of itself ( e.g., MOVF PORTB, 1), the value used will be that
value present on the pins themselves. For example, if the data latch is '1' for a pin configured as input and is
driven low by an external device, the data will be written back with a '0'.
2: If this instruction is executed on the TMR0 register (and, where applicable, d = 1), the prescaler will be
cleared if assigned to the Timer0 Module.
3: If Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The
second cycle is executed as a NOP.
PICmicro MID-RANGE MCU FAMILY
DS31005A-page 5-4 1997 Microchip Technology Inc.
5.2 General Instruction Format
The Mid-Range MCU instructions can be broken down into four general formats as shown in
Figure 5-1. As can be seen the opcode f or the instruction v aries from 3-bits to 6-bits. This v ariable
opcode size is what allows 35 instructions to be implemented.
Figure 5-1: General Format for Instructions
5.3 Central Processing Unit (CPU)
The CPU can be thought of as the “br ains” of the device. It is responsible for fetching the correct
instruction for execution, decoding that instruction, and then executing that instruction.
The CPU sometimes works in conjunction with the ALU to complete the ex ecution of the instruc-
tion (in arithmetic and logical operations).
The CPU controls the program memory address bus, the data memory address bus, and
accesses to the stack.
5.4 Instruction Clock
Each instruction cycle (TCY) is comprised of four Q cycles (Q1-Q4). The Q cycle time is the same
as the device oscillator cycle time (TOSC). The Q cycles provide the timing/designation for the
Decode, Read, Process Data, Write, etc., of each instruction cycle. The f ollo wing diagram sho ws
the relationship of the Q cycles to the instruction cycle.
The four Q cycles that make up an instruction cycle (TCY) can be generalized as:
Q1: Instruction Decode Cycle or forced No operation
Q2: Instruction Read Data Cycle or No operation
Q3: Process the Data
Q4: Instruction Write Data Cycle or No operation
Each instruction will show a detailed Q cycle operation for the instruction.
Figure 5-2: Q Cycle Activity
Byte-oriented file register operations
13 8 7 6 0 d = 0 for destination W
OPCODE d f (FILE #) d = 1 for destination f
f = 7-bit file register address
Bit-oriented file register operations
13 10 9 7 6 0
OPCODE b (BIT #) f (FILE #) b = 3-bit bit address
f = 7-bit file register address
Literal and control operations
13 8 7 0
OPCODE k (literal) k = 8-bit immediate value
13 11 10 0
OPCODE k (literal) k = 11-bit immediate value
General
CALL and GOTO instructions only
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
TCY1TCY2TCY3
Tosc
1997 Microchip Technology Inc. DS31005A-page 5-5
Section 5. CPU and ALU
CPU and ALU
5
5.5 Arithmetic Logical Unit (ALU)
PICmicro MCUs contain an 8-bit ALU and an 8-bit working register. The ALU is a general pur-
pose arithmetic and logical unit. It performs arithmetic and Boolean functions between the data
in the working register and any register file.
Figure 5-3: Operation of the ALU and W Register
The ALU is 8-bits wide and is capable of addition, subtraction, shift and logical operations. Unless
otherwise mentioned, arithmetic operations are two's complement in nature. In two-operand
instructions, typically one operand is the working register (W register). The other operand is a file
register or an immediate constant. In single operand instructions, the operand is either the W reg-
ister or a file register.
The W register is an 8-bit w orking register used for ALU oper ations . It is not an addressable reg-
ister.
Depending on the instruction executed, the ALU may affect the values of the Carry (C), Digit
Carry (DC), and Zero (Z) bits in the STATUS register . The C and DC bits operate as a borrow bit
and a digit borrow out bit, respectively, in subtraction. See the SUBLW and SUBWF instructions for
examples.
W Register
Register
File
8
d bit, or from instruction
8
8
8-bit literal
(from instruction word)
d = '0' or d = '1'
(SFR’s)
and
General
Purpose
RAM
(GPR)
ALU
Literal Instructions
8
8
Special
Function
Registers
8-bit register value
(from direct or indirect
address of instruction)
PICmicro MID-RANGE MCU FAMILY
DS31005A-page 5-6 1997 Microchip Technology Inc.
5.6 STATUS Register
The STATUS register, sho wn in Figure 5-1, contains the arithmetic status of the ALU, the RESET
status and the bank select bits for data memory. Since the selection of the Data Memor y banks
is controlled by this register, it is required to be present in every bank. Also , this register is in the
same relative position (offset) in each bank (see Figure 6-5: “Register File Map” in the “Mem-
ory Organization” section).
The STATUS register can be the destination for any instruction, as with any other register. If the
STATUS register is the destination for an instruction that affects the Z, DC or C bits , then the write
to these three bits is disabled. These bits are set or cleared according to the device logic. Fur-
thermore, the TO and PD bits are not writable. Therefore, the result of an instruction with the
STATUS register as destination may be different than intended.
For example, CLRF STATUS will clear the upper-three bits and set the Z bit. This leaves the
STATUS register as 000u u1uu (where u = unchanged).
It is recommended, therefore, that only BCF, BSF, SWAPF and MOVWF instructions are used to
alter the STATUS register because these instr uctions do not affect the Z, C or DC bits from the
STATUS register. For other instructions, not affecting any status bits, see Table 5-1.
Note 1: Some devices do not require the IRP and RP1 (STATUS<7:6>) bits. These bits are
not used by the Section 5. CPU and ALU and should be maintained clear. Use of
these bits as general purpose R/W bits is NOT recommended, since this ma y affect
upward code compatibility with future products.
Note 2: The C and DC bits operate as a borrow and digit borro w bit, respectively, in subtrac-
tion.
1997 Microchip Technology Inc. DS31005A-page 5-7
Section 5. CPU and ALU
CPU and ALU
5
Register 5-1: STATUS Register
R/W-0 R/W-0 R/W-0 R-1 R-1 R/W-x R/W-x R/W-x
IRP RP1 RP0 TO PD ZDC C
bit 7 bit 0
bit 7 IRP: Register Bank Select bit (used for indirect addressing)
1 = Bank 2, 3 (100h - 1FFh)
0 = Bank 0, 1 (00h - FFh)
For devices with only Bank0 and Bank1 the IRP bit is reserved, always maintain this bit clear.
bit 6:5 RP1:RP0: Register Bank Select bits (used for direct addressing)
11 = Bank 3 (180h - 1FFh)
10 = Bank 2 (100h - 17Fh)
01 = Bank 1 (80h - FFh)
00 = Bank 0 (00h - 7Fh)
Each bank is 128 bytes. For devices with only Bank0 and Bank1 the IRP bit is reserved,
always maintain this bit clear.
bit 4 TO: Time-out bit
1 = After power-up, CLRWDT instruction, or SLEEP instruction
0 = A WDT time-out occurred
bit 3 PD: Power-down bit
1 = After power-up or by the CLRWDT instruction
0 = By execution of the SLEEP instruction
bit2 Z: Zero bit
1 = The result of an arithmetic or logic operation is zero
0 = The result of an arithmetic or logic operation is not zero
bit 1 DC: Digit carr y/borrow bit (ADDWF, ADDLW, SUBLW, SUBWF instructions) (for borrow the polarity
is reversed)
1 = A carry-out from the 4th low order bit of the result occurred
0 = No carry-out from the 4th low order bit of the result
bit 0 C: Carry/borrow bit (ADDWF, ADDLW,SUBLW,SUBWF instructions)
1 = A carry-out from the most significant bit of the result occurred
0 = No carry-out from the most significant bit of the result occurred
Note: For borrow the polarity is reversed. A subtraction is executed by adding the two’s
complement of the second operand. For rotate (RRF, RLF) instructions, this bit is
loaded with either the high or low order bit of the source register.
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31005A-page 5-8 1997 Microchip Technology Inc.
5.7 OPTION_REG Register
The OPTION_REG register is a readable and writable register which contains v arious control bits
to configure the TMR0/WDT prescaler, the external INT Interrupt, TMR0, and the weak pull-ups
on PORTB.
Register 5-2: OPTION_REG Register
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0
bit 7 bit 0
bit 7 RBPU: PORTB Pull-up Enable bit
1 = PORTB pull-ups are disabled
0 = PORTB pull-ups are enabled by individual port latch values
bit 6 INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of INT pin
0 = Interrupt on falling edge of INT pin
bit 5 T0CS: TMR0 Clock Source Select bit
1 = Transition on T0CKI pin
0 = Internal instruction cycle clock (CLKOUT)
bit 4 T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on T0CKI pin
0 = Increment on low-to-high transition on T0CKI pin
bit 3 PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
bit 2-0 PS2:PS0: Prescaler Rate Select bits
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
000
001
010
011
100
101
110
111
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
Bit Value TMR0 Rate WDT Rate
Note: To achieve a 1:1 prescaler assignment for the TMR0 register, assign the prescaler
to the Watchdog Timer.
1997 Microchip Technology Inc. DS31005A-page 5-9
Section 5. CPU and ALU
CPU and ALU
5
5.8 PCON Register
The Power Control (PCON) register contains flag bit(s), that together with the TO and PD bits,
allows the user to differentiate between the device resets.
Register 5-3: PCON Register
Note 1: BOR is unknown on Power-on Reset. It must then be set by the user and checked
on subsequent resets to see if BOR is clear, indicating a brown-out has occurred.
The BOR status bit is a don't care and is not necessarily predictable if the brown-out
circuit is disabled (by clearing the BODEN bit in the Configuration word).
Note 2: It is recommended that the POR bit be cleared after a power-on reset has been
detected, so that subsequent power-on resets may be detected.
R-u U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0
MPEEN PER POR BOR
bit 7 bit 0
bit 7 MPEEN: Memory Parity Error Circuitry Status bit
This bit reflects the value of the MPEEN configuration bit.
bit 6:3 Unimplemented: Read as '0'
bit 2 PER: Memory Parity Error Reset Status bit
1 = No error occurred
0 = A program memory fetch parity error occurred
(must be set in software after a Power-on Reset occurs)
bit 1 POR: Power-on Reset Status bit
1 = No Power-on Reset occurred
0 = A Power-on Reset occurred (must be set in software after a Power-on Reset occurs)
bit 0 BOR: Brown-out Reset Status bit
1 = No Brown-out Reset occurred
0 = A Brown-out Reset occurred (must be set in software after a Brown-out Reset occurs)
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31005A-page 5-10 1997 Microchip Technology Inc.
5.9 Design Tips
Question 1:
My program algorithm does not seem to function correctly.
Answer 1:
1. The destination of the instruction may be specifying the W register (d = 0) instead of the
file register (d = 1).
2. The register bank select bits (RP1:RP0 or IRP) ma y not be properly selected. Also if inter-
rupts are used, the register bank select bits may not be properly restored when e xiting the
interrupt handler.
Question 2:
I cannot seem to modify the STATUS register flags.
Answer 2:
if the STATUS register is the destination for an instruction that affects the Z, DC, or C bits, the
write to these bits is disabled. These bits are set or cleared based on device logic. Therefore, to
modify bits in the STATUS register it is recommended to use the BCF and BSF instructions.
1997 Microchip Technology Inc. DS31005A-page 5-11
Section 5. CPU and ALU
CPU and ALU
5
5.10 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the CPU or
the ALU are:
Title Application Note #
Fixed Point Routines AN617
IEEE 754 Compliant Floating Point Routines AN575
Digital Signal Processing with the PIC16C74 AN616
Math Utility Routines AN544
Implementing IIR Digital Filters AN540
Implementation of Fast Fourier Transforms AN542
Tone Generation AN543
Servo Control of a DC Brushless Motor AN532
Implementation of the Data Encryption Standard using the PIC17C42 AN583
PIC16C5X / PIC16CXX Utility Math Routines AN526
Real Time Operating System for PIC16/17 AN585
PICmicro MID-RANGE MCU FAMILY
DS31005A-page 5-12 1997 Microchip Technology Inc.
5.11 Revision History
Revision A
This is the initial released revision of the CPU and ALU description.
1997 Microchip Technology Inc. DS31006A page 6-1
Memory
Organization
6
M
Section 6. Memory Organization
HIGHLIGHTS
This section of the manual contains the following major topics:
6.1 Introduction....................................................................................................................6-2
6.2 Program Memory Organization......................................................................................6-2
6.3 Data Memory Organization............................................................................................6-8
6.4 Initialization..................................................................................................................6-14
6.5 Design Tips..................................................................................................................6-16
6.6 Related Application Notes............................................................................................6-17
6.7 Revision History...........................................................................................................6-18
PICmicro MID-RANGE MCU FAMILY
DS31006A-page 6-2 1997 Microchip Technology Inc.
6.1 Introduction
There are two memory blocks in the Section 6. Memory Organization; prog ram memory and data
memor y. Each block has its own bus, so that access to each block can occur dur ing the same
oscillator cycle.
The data memory can further be broken down into General Purpose RAM and the Special Func-
tion Registers (SFRs). The operation of the SFRs that control the “core” are described here. The
SFRs used to control the peripheral modules are described in the section discussing each indi-
vidual peripheral module.
6.2 Program Memory Organization
Mid-Range MCU de vices have a 13-bit prog r am counter capable of addressing an 8K x 14 pro-
gram memory space. The width of the program memory bus (instruction word) is 14-bits. Since
all instructions are a single word, a device with an 8K x 14 prog ram memory has space for 8K of
instructions. This makes it much easier to determine if a device has sufficient program memor y
for a desired application.
This program memory space is divided into four pages of 2K words each (0h - 7FFh, 800h -
FFFh, 1000h - 17FFh, and 1800h - 1FFFh). Figure 6-1 shows the program memory map as well
as the 8 le vel deep hardw are stac k. Depending on the device , only a portion of this memory may
be implemented. Please refer to the device data sheet for the available memory.
To jump between the program memory pages, the high bits of the Program Counter (PC) must
be modified. This is done by writing the desired value into a SFR called PCLATH (Program
Counter Latch High). If sequential instructions are executed, the program counter will cross the
page boundaries without any user intervention. For devices that have less than 8K words,
accessing a location above the physically implemented address will cause a wraparound. That
is, in a 4K-word device accessing 17FFh actually addresses 7FFh. 2K-w ord devices (or less) do
not require paging.
1997 Microchip Technology Inc. DS31006A-page 6-3
Section 6. Memory Organization
Memory
Organization
6
Figure 6-1: Architectural Program Memory Map and Stack
PC<12:8>
13
0000h
0004h
0005h
07FFh
0800h
1FFFh
Stack Level 1
Stack Level 8
Reset Vector
Interrupt V ector
On-chip Program
On-chip Program
Memory (Page 1)
Memory (Page 0)
CALL, RETURN
RETFIE, RETLW
On-chip Program
Memory (Page 2)
On-chip Program
Memory (Page 3)
0FFFh
1000h
17FFh
1800h
2K
4K
6K
8K
PC<12:0> PCL
PCLATH
Note 1: Not all devices implement the entire program memory space
2: Calibration Data may be programmed into program memory locations.
PICmicro MID-RANGE MCU FAMILY
DS31006A-page 6-4 1997 Microchip Technology Inc.
6.2.1 Reset Vector
On any device, a reset forces the Program Counter (PC) to address 0h. We call this address the
“Reset Vector Address” since this is the address that program execution will branch to when a
device reset occurs.
Any reset will also clear the contents of the PCLATH register. This means that any branch at the
Reset Vector Address (0h) will jump to that location in PAGE0 of the program memory.
6.2.2 Interrupt Vector
When an interrupt is acknowledged the PC is f orced to address 0004h. W e call this the “Interrupt
Vector Address”. When the PC is forced to the interrupt vector, the PCLATH register is not mod-
ified. Once in the service interrupt routine (ISR), this means that before any write to the PC, the
PCLATH register should be written with the value that will specify the desired location in program
memory. Before the PCLATH register is modified b y the Interrupt Service Routine (ISR) the con-
tents of the PCLATH may need to be sa ved, so it can be restored before returning from the ISR.
6.2.3 Calibration Information
Some devices have calibration information stored in their program memory. This information is
programmed b y Microchip when the de vice is under final test. The use of these values allo ws the
application to achie ve better results . The calibration inf ormation is typically at the end of program
memory, and is implemented as a RETLW instruction with the literal value being the specified cal-
ibration information.
Note: For windowed devices, write down all calibration values BEFORE erasing. This
allows the device’s calibration values to be restored when the device is re-pro-
grammed. When possible writing the values on the package is recommended.
1997 Microchip Technology Inc. DS31006A-page 6-5
Section 6. Memory Organization
Memory
Organization
6
6.2.4 Program Counter (PC)
The program counter (PC) specifies the address of the instruction to f etch for ex ecution. The PC
is 13-bits wide. The low b yte is called the PCL register . This register is readab le and writable. The
high byte is called the PCH register. This register contains the PC<12:8> bits and is not directly
readable or writable. All updates to the PCH register go through the PCLATH register.
Figure 6-2 shows the four situations for the loading of the PC. Situation 1 shows how the PC is
loaded on a write to PCL (PCLATH<4:0> PCH). Situation 2 shows how the PC is loaded during
a GOTO instruction (PCLATH<4:3> PCH). Situation 3 shows how the PC is loaded during a
CALL instruction (PCLATH<4:3> PCH), with the PC loaded (PUSHed) onto the Top of Stack.
Situation 4 shows how the PC is loaded during one of the return instructions where the PC
loaded (POPed) from the Top of Stack.
Figure 6-2: Loading of PC In Different Situations
PC 12 8 7 0
5PCLATH<4:0>
PCLATH ALU result
Opcode <10:0>
8
PC 12 11 10 0
11
PCLATH<4:3>
PCH PCL
87
2
PCLATH
PCH PCL
Situation 1 - Instruction with PCL as destination
Situation 2 - GOTO Instruction
STACK (13-bits x 8)
Top of STACK
STACK (13-bits x 8)
Top of STACK
Opcode <10:0>
PC 12 11 10 0
11
PCLATH<4:3>
87
2
PCLATH
PCH PCL
Situation 3 - CALL Instruction STACK (13-bits x 8)
Top of STACK
Opcode <10:0>
PC 12 11 10 0
11
87
PCLATH
PCH PCL
Situation 4 - RETURN, RETFIE, or RETLW Instruction STACK (13-bits x 8)
Top of STACK
13
13
Note: PCLATH is never updated with the contents of PCH.
PICmicro MID-RANGE MCU FAMILY
DS31006A-page 6-6 1997 Microchip Technology Inc.
6.2.4.1 Computed GOTO
A computed GOTO is accomplished by adding an offset to the program counter (ADDWF PCL).
When doing a table read using a computed GOTO method, care should be exercised if the table
location crosses a PCL memory boundary (each 256 byte block).
6.2.5 Stack
The stack allows a combination of up to 8 program calls and interrupts to occur. The stack con-
tains the return address from this branch in program execution.
Mid-Range MCU de vices have an 8-level deep x 13-bit wide hardw are stack. The stack space is
not part of either program or data space and the stac k pointer is not readable or writab le. The PC
is PUSHed onto the stack when a CALL instruction is executed or an interrupt causes a branch.
The stack is POP ed in the e vent of a RETURN, RETLW or a RETFIE instruction e xecution. PCLATH
is not modified when the stack is PUSHed or POPed.
After the stack has been PUSHed eight times , the ninth push overwrites the value that w as stored
from the first push. The tenth push overwrites the second push (and so on). An example of the
overwriting of the stack is shown in Figure 6-3.
Figure 6-3: Stack Modification
Note: Any write to the Program Counter (PCL), will cause the lower five bits of the PCLATH
to be loaded into PCH.
Push1 Push9
Push2 Push10
Push3
Push4
Push5
Push6
Push7
Push8
Top of STACK
STACK
Note 1: There are no status bits to indicate stack overflow or stack underflow conditions.
Note 2: There are no instructions/mnemonics called PUSH or POP. These are actions that
occur from the execution of the CALL, RETURN, RETLW, and RETFIE instructions,
or the vectoring to an interrupt address.
1997 Microchip Technology Inc. DS31006A-page 6-7
Section 6. Memory Organization
Memory
Organization
6
6.2.6 Program Memory Paging
Some devices have program memory sizes greater then 2K words, but the CALL and GOTO
instructions only have a 11-bit address range. This 11-bit address range allows a branch within
a 2K program memory page size. To allow CALL and GOTO instructions to address the entire 1K
program memory address range, there must be another tw o bits to specify the progr am memory
page. These paging bits come from the PCLATH<4:3> bits (Figure 6-2). When doing a CALL or
GOTO instruction, the user must ensure that page bits (PCLATH<4:3>) are programmed so that
the desired program memory page is addressed (Figure 6-2). When one of the return instruc-
tions is executed, the entire 13-bit PC is POPed from the stack. Therefore, manipulation of the
PCLATH<4:3> is not required for the return instructions.
Example 6-1 shows the calling of a subroutine in page 1 of the program memory. This example
assumes that PCLATH is saved and restored by the interrupt service routine (if interrupts are
used).
Example 6-1: Call of a Subroutine in Page1 from Page0
Note: Devices with program memory sizes 2K words and less, ignore both paging bits
(PCLATH<4:3>), which are used to access program memory when more than one
page is available. The use of PCLATH<4:3> as general purpose read/write bits (for
these de vices) is not recommended since this may affect upward compatibility with
future products.
Devices with program memory sizes between 2K words and 4K words, ignore the
paging bit (PCLATH<4>), which is used to access program memory pages 2 and 3
(1000h - 1FFFh). The use of PCLATH<4> as a general pur pose read/write bit (for
these de vices) is not recommended since this may affect upward compatibility with
future products.
ORG 0x500
BSF PCLATH,3 ; Select Page1 (800h-FFFh)
CALL SUB1_P1 ; Call subroutine in Page1 (800h-FFFh)
: ;
: ;
ORG 0x900 ;
SUB1_P1: ; called subroutine Page1 (800h-FFFh)
: ;
RETURN ; return to Call subroutine in Page0 (000h-7FFh)
;
PICmicro MID-RANGE MCU FAMILY
DS31006A-page 6-8 1997 Microchip Technology Inc.
6.3 Data Memory Organization
Data memor y is made up of the Special Function Registers (SFR) area, and the General Pur-
pose Registers (GPR) area. The SFRs control the operation of the device, while GPRs are the
general area for data storage and scratch pad operations.
The data memory is bank ed for both the GPR and SFR areas. The GPR area is banked to allow
greater than 96 bytes of general pur pose RAM to be addressed. SFRs are for the registers that
control the peripheral and core functions. Banking requires the use of control bits for bank selec-
tion. These control bits are located in the STATUS Register (STATUS<7:5>). Figure 6-5 shows
one of the data memory map organizations, this organization is device dependent.
To move v alues from one register to another register , the value m ust pass through the W register .
This means that for all register-to-register moves, two instruction cycles are required.
The entire data memory can be accessed either directly or indirectly. Direct addressing may
require the use of the RP1:RP0 bits. Indirect addressing requires the use of the File Select Reg-
ister (FSR). Indirect addressing uses the Indirect Register P ointer (IRP) bit of the STATUS regis-
ter for accesses into the Bank0 / Bank1 or the Bank2 / Bank3 areas of data memory.
6.3.1 General Purpose Registers (GPR)
Some Mid-Range MCU de vices ha ve banked memory in the GPR area. GPRs are not initialized
by a Power-on Reset and are unchanged on all other resets.
The register file can be accessed either directly, or using the File Select Register FSR, indirectly.
Some devices have areas that are shared across the data memory banks, so a read / write to
that area will appear as the same location (value) regardless of the current bank. W e ref er to this
area as the Common RAM.
6.3.2 Special Function Registers (SFR)
The SFRs are used by the CPU and Peripheral Modules for controlling the desired operation of
the device. These registers are implemented as static RAM.
The SFRs can be classified into two sets, those associated with the “core” function and those
related to the peripheral functions. Those registers related to the “core” are described in this sec-
tion, while those related to the operation of the peripheral features are described in the section
of that peripheral feature.
All Mid-Range MCU devices have banked memory in the SFR area. Switching between these
banks requires the RP0 and RP1 bits in the STATUS register to be configured for the desired
bank. Some SFRs are initialized by a Power-on Reset and other resets, while other SFRs are
unaffected.
The register file can be accessed either directly, or using the File Select Register FSR, indirectly.
Note: The Special Function Register (SFR) Area may have General Purpose Registers
(GPRs) mapped in these locations.
1997 Microchip Technology Inc. DS31006A-page 6-9
Section 6. Memory Organization
Memory
Organization
6
6.3.3 Banking
The data memory is partitioned into four banks. Each bank contains General Purpose Registers
and Special Function Registers. Switching between these banks requires the RP0 and RP1 bits
in the STATUS register to be configured for the desired bank when using direct addressing. The
IRP bit in the STATUS register is used for indirect addressing.
Table 6-1: Direct and Indirect Addressing of Banks
Each Bank e xtends up to 7Fh (128 bytes). The lower locations of each bank are reserved f or the
Special Function Registers. Above the Special Function Registers are General Pur pose Regis-
ters. All data memory is implemented as static RAM. All Banks may contain special function reg-
isters. Some “high use” special function registers from Bank0 are mirrored in the other banks for
code reduction and quicker access.
Through the evolution of the products, there are a f ew variations in the la yout of the Data Memory .
The data memory organization that will be the standard for all new devices is shown in
Figure 6-5. This Memory map has the last 16-bytes mapped across all memory banks. This is to
reduce the software o v erhead f or conte xt switching. The registers in bold will be in ev ery device .
The other registers are peripheral dependent. Not every peripheral’s registers are shown,
because some file addresses hav e a diff erent registers from those shown. As with all the figures,
tables , and specifications presented in this reference guide, v erify the details with the device spe-
cific data sheet.
Figure 6-4: Direct Addressing
Accessed
Bank Direct
(RP1:RP0) Indirect
(IRP)
00 00
10 1
21 01
31 1
Data
Memory
Direct Addressing
bank select location select
RP1 RP0 6 0
from opcode
00 01 10 11
7Fh
00h
7Fh Bank0 Bank1 Bank2 Bank3
PICmicro MID-RANGE MCU FAMILY
DS31006A-page 6-10 1997 Microchip Technology Inc.
Figure 6-5: Register File Map
File
Address File
Address File
Address File
Address
INDF 00h INDF 80h INDF 100h INDF 180h
TMR0 01h OPTION_REG 81h TMR0 101h OPTION_REG 181h
PCL 02h PCL 82h PCL 102h PCL 182h
STATUS 03h STATUS 83h STATUS 103h STATUS 183h
FSR 04h FSR 84h FSR 104h FSR 184h
PORTA 05h TRISA 85h 105h 185h
PORTB 06h TRISB 86h PORTB 106h TRISB 186h
PORTC 07h TRISC 87h PORTF 107h TRISF 187h
PORTD 08h TRISD 88h PORTG 108h TRISG 188h
PORTE 09h TRISE 89h 109h 189h
PCLATH 0Ah PCLATH 8Ah PCLATH 10Ah PCLATH 18Ah
INTCON 0Bh INTCON 8Bh INTCON 10Bh INTCON 18Bh
PIR1 0Ch PIE1 8Ch 10Ch 18Ch
PIR2 0Dh PIE2 8Dh 10Dh 18Dh
TMR1L 0Eh PCON 8Eh 10Eh 18Eh
TMR1H 0Fh OSCCAL 8Fh 10Fh 18Fh
T1CON 10h 90h 110h 190h
TMR2 11h 91h 111h 191h
T2CON 12h PR2 92h 112h 192h
SSPBUF 13h SSPADD 93h 113h 193h
SSPCON 14h SSPATAT 94h 114h 194h
CCPR1L 15h 95h 115h 195h
CCPR1H 16h 96h 116h 196h
CCP1CON 17h 97h 117h 197h
RCSTA 18h TXSTA 98h 118h 198h
TXREG 19h SPBRG 99h 119h 199h
RCREG 1Ah 9Ah 11Ah 19Ah
CCPR2L 1Bh 9Bh 11Bh 19Bh
CCPR2H 1Ch 9Ch 11Ch 19Ch
CCP2CON 1Dh 9Dh 11Dh 19Dh
ADRES 1Eh 9Eh 11Eh 19Eh
ADCON0 1Fh ADCON1 9Fh 11Fh 19Fh
General
Purpose
Registers (2)
20h General
Purpose
Registers (3)
A0h
EFh
General
Purpose
Registers (3)
120h
16Fh
General
Purpose
Registers (3)
1A0h
1EFh
7Fh
Mapped in
Bank0
70h - 7Fh (4)
F0h
FFh
Mapped in
Bank0
70h - 7Fh (4)
170h
17Fh
Mapped in
Bank0
70h - 7Fh (4)
1F0h
1FFh
Bank0 Bank1 Bank2 (5) Bank3
(5)
Note 1: Registers in BOLD will be present in every device.
2: Not all locations may be implemented. Unimplemented locations will read as '0'.
3: These locations may not be implemented. Depending on the device, accesses to the unimplemented loca-
tions operate differently. Please refer to the specific device data sheet for details.
4: Some device do not map these registers into Bank0. In devices where these registers are mapped into
Bank0, these registers are referred to as common RAM
5: Some devices may not implement these banks. Locations in unimplemented banks will read as ’0’.
6: General Purpose Registers (GPRs) may be located in the Special Function Register (SFR) area.
1997 Microchip Technology Inc. DS31006A-page 6-11
Section 6. Memory Organization
Memory
Organization
6
The map in Figure 6-6 shows the register file memory map of some 18-pin devices.
Unimplemented registers will read as '0'.
Figure 6-6: Register File Map
File
Address File
Address
INDF 00h INDF 80h
TMR0 01h OPTION_REG 81h
PCL 02h PCL 82h
STATUS 03h STATUS 83h
FSR 04h FSR 84h
PORTA 05h TRISA 85h
PORTB 06h TRISB 86h
07h PCON 87h
ADCON0 /
EEDATA (2) 08h ADCON1 /
EECON1 (2) 88h
ADRES /
EEADR (2) 09h ADRES /
EECON2 (2) 89h
PCLATH 0Ah PCLATH 8Ah
INTCON 0Bh INTCON 8Bh
General
Purpose
Registers (3)
0Ch
7Fh
General
Purpose
Registers (4)
8Ch
FFh
Bank0 Bank1
Note 1: Registers in BOLD will be present in every device.
2: These registers may not be implemented, or are implemented as other registers in
some devices.
3: Not all locations may be implemented. Unimplemented locations will read as ’0’.
4: These locations are unimplemented in Bank1. Access to these unimplemented
locations will access the corresponding Bank0 register.
PICmicro MID-RANGE MCU FAMILY
DS31006A-page 6-12 1997 Microchip Technology Inc.
6.3.4 Indirect Addressing, INDF, and FSR Registers
Indirect addressing is a mode of addressing data memor y where the data memory address in
the instruction is not fixed. An SFR register is used as a pointer to the data memory location that
is to be read or written. Since this pointer is in RAM, the contents can be modified by the pro-
gram. This can be useful for data tables in the data memory. Figure 6-7 shows the operation of
indirect addressing. This shows the moving of the value to the data memor y address specified
by the value of the FSR register.
Indirect addressing is possible b y using the INDF register . Any instruction using the INDF register
actually accesses the register pointed to by the File Select Register , FSR. Reading the INDF reg-
ister itself indirectly (FSR = '0') will read 00h. Writing to the INDF register indirectly results in a
no-operation (although status bits may be affected). An effective 9-bit address is generated by
the concatenation of the IRP bit (STA TUS<7>) with the 8-bit FSR register , as shown in Figure 6-8.
Figure 6-7: Indirect Addressing
Opcode Address
File Address = INDF
FSR
Instruction
Executed
Instruction
Fetched
RAM
Opcode File IRP
RP1:RP0 9
9
7
2
9
Address = 0h
Address != 0
1997 Microchip Technology Inc. DS31006A-page 6-13
Section 6. Memory Organization
Memory
Organization
6
Figure 6-8: Indirect Addressing
Example 6-2 shows a simple use of indirect addressing to clear RAM (locations 20h-2Fh) in a
minimum number of instructions. A similar concept could be used to move a defined number of
bytes (block) of data to the USART transmit register (TXREG). The starting address of the block
of data to be transmitted could easily be modified by the program.
Example 6-2: Indirect Addressing
Data
Memory
Indirect Addressing
IRP FSR register
70
bank select location select
00 01 10 11 00h
7Fh
00h
7Fh Bank0 Bank1 Bank2 Bank3
BCF STATUS, IRP ; Indirect addressing Bank0/1
MOVLW 0x20 ; Initialize pointer to RAM
MOVWF FSR ;
NEXT CLRF INDF ; Clear INDF register
INCF FSR,F ; Inc pointer
BTFSS FSR,4 ; All done?
GOTO NEXT ; NO, clear next
CONTINUE ;
: ; YES, continue
PICmicro MID-RANGE MCU FAMILY
DS31006A-page 6-14 1997 Microchip Technology Inc.
6.4 Initialization
Example 6-3 shows how the bank switching occurs for Direct addressing, while Example 6-4
shows some code to do initialization (clearing) of General Purpose RAM.
Example 6-3: Bank Switching
CLRF STATUS ; Clear STATUS register (Bank0)
: ;
BSF STATUS, RP0 ; Bank1
: ;
BCF STATUS, RP0 ; Bank0
: ;
MOVLW 0x60 ; Set RP0 and RP1 in STATUS register, other
XORWF STATUS, F ; bits unchanged (Bank3)
: ;
BCF STATUS, RP0 ; Bank2
: ;
BCF STATUS, RP1 ; Bank0
1997 Microchip Technology Inc. DS31006A-page 6-15
Section 6. Memory Organization
Memory
Organization
6
Example 6-4: RAM Initialization
CLRF STATUS ; Clear STATUS register (Bank0)
MOVLW 0x20 ; 1st address (in bank) of GPR area
MOVWF FSR ; Move it to Indirect address register
Bank0_LP
CLRF INDF0 ; Clear GPR at address pointed to by FSR
INCF FSR ; Next GPR (RAM) address
BTFSS FSR, 7 ; End of current bank ? (FSR = 80h, C = 0)
GOTO Bank0_LP ; NO, clear next location
;
; Next Bank (Bank1)
; (** ONLY REQUIRED IF DEVICE HAS A BANK1 **)
;
MOVLW 0xA0 ; 1st address (in bank) of GPR area
MOVWF FSR ; Move it to Indirect address register
Bank1_LP
CLRF INDF0 ; Clear GPR at address pointed to by FSR
INCF FSR ; Next GPR (RAM) address
BTFSS STATUS, C ; End of current bank? (FSR = 00h, C = 1)
GOTO Bank1_LP ; NO, clear next location
;
; Next Bank (Bank2)
; (** ONLY REQUIRED IF DEVICE HAS A BANK2 **)
;
BSF STATUS, IRP ; Select Bank2 and Bank3
; for Indirect addressing
MOVLW 0x20 ; 1st address (in bank) of GPR area
MOVWF FSR ; Move it to Indirect address register
Bank2_LP
CLRF INDF0 ; Clear GPR at address pointed to by FSR
INCF FSR ; Next GPR (RAM) address
BTFSS FSR, 7 ; End of current bank? (FSR = 80h, C = 0)
GOTO Bank2_LP ; NO, clear next location
;
; Next Bank (Bank3)
; (** ONLY REQUIRED IF DEVICE HAS A BANK3 **)
;
MOVLW 0xA0 ; 1st address (in bank) of GPR area
MOVWF FSR ; Move it to Indirect address register
Bank3_LP
CLRF INDF0 ; Clear GPR at address pointed to by FSR
INCF FSR ; Next GPR (RAM) address
BTFSS STATUS, C ; End of current bank? (FSR = 00h, C = 1)
GOTO Bank3_LP ; NO, clear next location
: ; YES, All GPRs (RAM) is cleared
PICmicro MID-RANGE MCU FAMILY
DS31006A-page 6-16 1997 Microchip Technology Inc.
6.5 Design Tips
Question 1:
Program execution seems to get lost.
Answer 1:
When a device with more then 2K words of program memory is used, the calling of subroutines
ma y require that the PCLATH register be loaded prior to the CALL (or GOTO) instruction to specify
the correct program memory page that the routine is located on. The following instructions will
correctly load PCLATH register, regardless of the program memory location of the label SUB_1.
MOVLW HIGH (SUB_1) ; Select Program Memory Page of
MOVWF PCLATH ; Routine.
CALL SUB_1 ; Call the desired routine
:
:
SUB_1 : ; Start of routine
:
RETURN ; Return from routine
Question 2:
I need to initialize RAM to ’0’s. What is an easy way to do that?
Answer 2:
Example 6-4 shows this . If the device y ou are using does not use all 4 data memory banks, some
of the code may be removed.
1997 Microchip Technology Inc. DS31006A-page 6-17
Section 6. Memory Organization
Memory
Organization
6
6.6 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-r ange MCU family (that is they may be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to memory are:
Title Application Note #
Implementing a Table Read AN556
PICmicro MID-RANGE MCU FAMILY
DS31006A-page 6-18 1997 Microchip Technology Inc.
6.7 Revision History
Revision A
This is the initial released revision of the Memory Organization description.
1997 Microchip Technology Inc. DS31007A page 7-1
M
Data EEPROM
7
Section 7. Data EEPROM
HIGHLIGHTS
This section of the manual contains the following major topics:
7.1 Introduction....................................................................................................................7-2
7.2 Control Register.............................................................................................................7-3
7.3 EEADR...........................................................................................................................7-4
7.4 EECON1 and EECON2 Registers.................................................................................7-4
7.5 Reading the EEPROM Data Memory ............................................................................7-5
7.6 Writing to the EEPROM Data Memory...........................................................................7-5
7.7 Write V erify.....................................................................................................................7-6
7.8 Protection Against Spurious Writes ...............................................................................7-7
7.9 Data EEPROM Operation During Code Protected Configuration..................................7-7
7.10 Initialization....................................................................................................................7-7
7.11 Design Tips ....................................................................................................................7-8
7.12 Related Application Notes..............................................................................................7-9
7.13 Revision History...........................................................................................................7-10
PICmicro MID-RANGE MCU FAMILY
DS31007A-page 7-2 1997 Microchip Technology Inc.
7.1 Introduction
The EEPROM data memory is readable and writable during normal operation (full VDD range).
This memor y is not directly mapped in the register file space. Instead it is indirectly addressed
through the Special Function Registers. There are f our SFRs used to read and write this memory .
These registers are:
EECON1
EECON2 (not a physically implemented register)
EEDATA
EEADR
EED ATA holds the 8-bit data for read/write, and EEADR holds the address of the EEPROM loca-
tion being accessed. The 8-bit EEADR register can access up to 256 locations of Data EEPROM.
The EEADR register can be thought of as the indirect addressing register of the Data EEPROM.
EECON1 contains the control bits, while EECON2 is the register used to initiate the read/write.
Some de vices will implement less then the entire memory map . The address range alwa ys starts
at 0h, and goes throughout the memory a vailable. Table 7-1 shows some of the possible common
device memory sizes and the address range for those sizes.
Table 7-1: Possible Data EEPROM Memory Sizes
The EEPROM data memory allows byte read and write. A byte write automatically erases the
location and writes the new data (erase before write). The EEPROM data memory is rated for
high erase/write cycles. The write time is controlled by an on-chip timer. The wr ite-time will vary
with voltage and temperature as well as from chip to chip. Please refer to the AC specifications
for exact limits.
When the de vice is code protected, the CPU may continue to read and write the data EEPROM
memory. The device programmer can no longer access this memory.
Data EEPROM
Size (1) Address Range
64 0h - 3Fh
128 0h - 7Fh
256 0h - FFh
Note 1: Presently, devices are only offered with 64
bytes of Data EEPROM.
1997 Microchip Technology Inc. DS31007A-page 7-3
Section 7. Data EEPROM
Data EEPROM
7
7.2 Control Register
Register 7-1: EECON1 Register
U-0 U-0 U-0 R/W-1 R/W-1 R/W-x R/S-0 R/S-x
EEIF (1) WRERR WREN WR RD
bit 7 bit 0
bit 7:5 Unimplemented: Read as '0'
bit 4 EEIF: EEPROM Write Operation Interrupt Flag bit
1 = The write operation completed (must be cleared in software)
0 = The write operation is not complete or has not been started
bit 3 WRERR: EEPROM Error Flag bit
1 = A write operation is prematurely terminated
(any MCLR reset or any WDT reset during normal operation)
0 = The write operation completed
bit 2 WREN: EEPROM Write Enable bit
1 = Allows write cycles
0 = Inhibits write to the data EEPROM
bit 1 WR: Write Control bit
1 = initiates a write cycle. The bit is cleared by hardware once write is complete.
The WR bit can only be set (not cleared) in software.
0 = Write cycle to the data EEPROM is complete
bit 0 RD: Read Control bit
1 = Initiates an EEPROM read. Read takes one cycle. RD is cleared in hardware.
The RD bit can only be set (not cleared) in software.
0 = Does not initiate an EEPROM read
Legend
R = Readable bit W = Writable bit S = Settable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note 1: Future devices will have this bit in the PIR register.
PICmicro MID-RANGE MCU FAMILY
DS31007A-page 7-4 1997 Microchip Technology Inc.
7.3 EEADR
The EEADR register can address up to a maximum of 256 bytes of data EEPROM.
The unused address bits are decoded. This means that these bits must always be '0' to ensure
that the address is in the Data EEPROM memory space.
7.4 EECON1 and EECON2 Registers
EECON1 is the control register with five low order bits physically implemented. The upper-three
bits are unimplemented and read as '0's.
Control bits RD and WR initiate read and write, respectively. These bits cannot be cleared, only
set, in software. They are cleared in hardware at completion of the read or wr ite operation. The
inability to clear the WR bit in software prevents the accidental, premature termination of a write
operation.
The WREN bit, when set, will allow a write operation. On power-up, the WREN bit is clear. The
WRERR bit is set when a write operation is interrupted by a MCLR reset or a WDT time-out reset
during normal operation. In these situations, following reset, the user can check the WRERR bit
and rewrite the location. The data and address will be unchanged in the EEDATA and
EEADR registers.
Interrupt flag bit EEIF is set when write is complete. It must be cleared in software.
EECON2 is not a physical register. Reading EECON2 will read all '0's. The EECON2 register is
used exclusively in the Data EEPROM write sequence.
1997 Microchip Technology Inc. DS31007A-page 7-5
Section 7. Data EEPROM
Data EEPROM
7
7.5 Reading the EEPROM Data Memory
To read a data memory location, the user must write the address to the EEADR register and then
set control bit RD (EECON1<0>). The data is available, in the ver y next instruction cycle, in the
EED ATA register; therefore it can be read b y the next instruction. EED ATA will hold this value until
another read or until it is written to by the user (during a write operation).
Example 7-1: Data EEPROM Read
7.6 Writing to the EEPROM Data Memory
To write an EEPROM data location, the user must first write the address to the EEADR register
and the data to the EED ATA register. Then the user must f ollo w a specific sequence to initiate the
write for each byte.
Example 7-2: Data EEPROM Write
The write will not initiate if the above sequence is not exactly followed (wr ite 55h to EECON2,
write AAh to EECON2, then set WR bit) f or each b yte. W e strongly recommend that interrupts be
disabled during this code segment.
Additionally, the WREN bit in EECON1 must be set to enable write. This mechanism prevents
accidental writes to data EEPROM due to errant (unexpected) code execution (i.e., lost pro-
grams). The user should keep the WREN bit clear at all times, except when updating EEPROM.
The WREN bit is not cleared by hardware
After a write sequence has been initiated, clear ing the WREN bit will not affect this write cycle.
The WR bit will be inhibited from being set unless the WREN bit is set.
At the completion of the write cycle, the WR bit is cleared in hardware and the EE Write Complete
Interrupt Flag bit (EEIF) is set. The user can either enable this interrupt or poll this bit. EEIF m ust
be cleared by software.
BCF STATUS, RP0 ; Bank0
MOVLW CONFIG_ADDR ; Any location in Data EEPROM memory space
MOVWF EEADR ; Address to read
BSF STATUS, RP0 ; Bank1
BSF EECON1, RD ; EE Read
BCF STATUS, RP0 ; Bank0
MOVF EEDATA, W ; W = EEDATA
BSF STATUS, RP0 ; Bank1
BCF INTCON, GIE ; Disable INTs.
BSF EECON1, WREN ; Enable Write
Required
Sequence
MOVLW 55h ;
MOVWF EECON2 ; 55h must be written to EECON2
MOVLW AAh ; to start write sequence
MOVWF EECON2 ; Write AAh
BSF EECON1,WR ; Set WR bit begin write
BSF INTCON, GIE ; Enable INTs.
PICmicro MID-RANGE MCU FAMILY
DS31007A-page 7-6 1997 Microchip Technology Inc.
7.7 Write Verify
Depending on the application, good programming practice may dictate that the value written to
the Data EEPROM be verified (Example 7-3) as the value that was intended to be written. This
should be used in applications where an EEPROM bit will be stressed near the specification limit.
The Total Endurance disk will help determine your comfort level.
Example 7-3: Write Verify
BCF STATUS, RP0 ; Bank0
: ; Any code can go here
: ;
MOVF EEDATA, W ; Must be in Bank0
BSF STATUS, RP0 ; Bank1
READ
BSF EECON1, RD ; YES, Read the value written
BCF STATUS, RP0 ; Bank0
;
; Is the value written (in W reg) and read (in EEDATA) the same?
;
SUBWF EEDATA, W ;
BTFSS STATUS, Z ; Is difference 0?
GOTO WRITE_ERR ; NO, Write error
: ; YES, Good write
: ; Continue program
1997 Microchip Technology Inc. DS31007A-page 7-7
Section 7. Data EEPROM
Data EEPROM
7
7.8 Protection Against Spurious Writes
There are conditions when the device may not want to write to the data EEPROM memor y. To
protect against spurious EEPROM writes, v arious mechanisms have been b uilt-in. On power-up ,
WREN is cleared. Also, the Power-up Timer (72 ms duration) prevents EEPROM write.
The write initiate sequence and the WREN bit together help prevent an accidental write during
brown-outs, power glitches, and software malfunction.
7.9 Data EEPROM Operation During Code Protected Configuration
When the de vice is code protected, the CPU is able to read and write data to the Data EEPROM.
F or ROM devices , there are two code protection bits. One f or the ROM prog ram memory and one
f or the Data EEPR OM memory. See the Device Progr amming Specification f or more information
about these bits.
7.10 Initialization
The Data EEPROM module does not have an initialization sequence such as other modules. To
do a read of the Data EEPROM refer to Example 7-1. To do a write to the Data EEPROM refer
to Example 7-2, and to verify that the write completed successfully refer to Example 7-3.
As for the General Pur pose RAM, it is a good idea to initialize all Data EEPROM locations to a
known state. This initialization may take place at the time of device programming or an applica-
tion diagnostic mode, since on reset you may not want the Data EEPROM to be cleared.
An Application Diagnostic mode ma y be a condition on the I/O pins that the de vice tests f or after
the de vice power-ups . Then depending on this mode, the de vice would do some diagnostic func-
tion. The state for the I/O pins w ould need to be something that would not be possible without the
injected levels to force this diagnostic mode.
PICmicro MID-RANGE MCU FAMILY
DS31007A-page 7-8 1997 Microchip Technology Inc.
7.11 Design Tips
Question 1:
Why do the data EEPROM locations not contain the data that I wrote?
Answer 1:
There are a few possibilities, but the most likely is that you did not exactly follow the write
sequence as shown in Example 7-2. If you are using this code segment ensure that all interrupts
are disabled during this sequence.
Question 2:
Why is the data in the data EEPROM is getting corrupted?
Answer 2:
The data will only change when a Data EEPROM write occurs. Inadvertent writes may occur
when the de vice is in a bro wn-out condition (out of oper ating specification) and the device is not
being f orced to the reset state . During a brown-out, either the internal brown-out circuitry should
be enabled (when available) or external circuitr y should be used to reset the PICmicro MCU to
ensure that no data EEPROM writes occur when the device is out of the valid operating range.
1997 Microchip Technology Inc. DS31007A-page 7-9
Section 7. Data EEPROM
Data EEPROM
7
7.12 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to data
EEPROM are:
Title Application Note #
EEPROM Endurance Tutorial AN601
How to get 10 Million Cycles out of your Microchip Serial EEPROM AN602
Basic Serial EEPROM Operation AN536
Everything a System Engineer needs to know about Serial EEPROM Endurance AN537
Using the Microchip Endurance Predictive Software AN562
PICmicro MID-RANGE MCU FAMILY
DS31007A-page 7-10 1997 Microchip Technology Inc.
7.13 Revision History
Revision A
This is the initial released revision of the Data EEPROM description.
1997 Microchip Technology Inc. DS31008A page 8-1
M
Interrupts
8
Section 8. Interrupts
HIGHLIGHTS
This section of the manual contains the following major topics:
8.1 Introduction....................................................................................................................8-2
8.2 Control Registers...........................................................................................................8-5
8.3 Interrupt Latency..........................................................................................................8-10
8.4 INT and External Interrupts..........................................................................................8-10
8.5 Context Saving During Interrupts.................................................................................8-11
8.6 Initialization..................................................................................................................8-14
8.7 Design Tips..................................................................................................................8-16
8.8 Related Application Notes............................................................................................8-17
8.9 Revision History...........................................................................................................8-18
PICmicro MID-RANGE MCU FAMILY
DS31008A-page 8-2 1997 Microchip Technology Inc.
8.1 Introduction
PICmicro MCUs can hav e man y sources of interrupt. These sources generally include one inter-
rupt source for each peripheral module, though some modules may generate multiple interrupts
(such as the USART module). The current interrupts are:
INT Pin Interrupt (external interrupt)
TMR0 Overflow Interrupt
PORTB Change Interrupt (pins RB7:RB4)
Comparator Change Interrupt
Parallel Slave Port Interrupt
USART Interrupts
Receive Interrupt
Transmit Interrupt
A/D Conversion Complete Interrupt
LCD Interrupt.
Data EEPROM Write Complete Interrupt
Timer1 Overflow Interrupt
Timer2 Overflow Interrupt
CCP Interrupt
SSP Interrupt
There is a minimum of one register used in the control and status of the interrupts. This register
is:
INTCON
Additionally, if the de vice has peripheral interrupts, then it will hav e registers to enable the periph-
eral interrupts and registers to hold the interrupt flag bits. Depending on the device, the registers
are:
PIE1
PIR1
PIE2
PIR2
We will gener ically refer to these registers as PIR and PIE. If future devices provide more inter-
rupt sources, they will be supported by additional register pairs, such as PIR3 and PIE3.
The Interrupt Control Register, INTCON, records individual flag bits for core interrupt requests.
It also has various individual enable bits and the global interrupt enable bit.
1997 Microchip Technology Inc. DS31008A-page 8-3
Section 8. Interrupts
Interrupts
8
The Global Interrupt Enable bit, GIE (INTCON<7>), enables (if set) all un-masked interrupts or
disables (if cleared) all interrupts. Individual interrupts can be disabled through their correspond-
ing enable bits in the INTCON register. The GIE bit is cleared on reset.
The “return from interrupt” instruction, RETFIE, e xits the interrupt routine as well as sets the GIE
bit, which allows any pending interrupt to execute.
The INTCON register contains these interrupts: INT Pin Interrupt, the RB P ort Change Interrupt,
and the TMR0 Overflow Interrupt. The INTCON register also contains the Peripheral Interrupt
Enable bit, PEIE. The PEIE bit will enable/disable the peripheral interrupts from vectoring when
the PEIE bit is set/cleared.
When an interrupt is responded to, the GIE bit is cleared to disable any further interrupt, the
return address is pushed into the stack and the PC is loaded with 0004h. Once in the interr upt
service routine the source(s) of the interrupt can be determined by polling the interrupt flag bits.
Generally the interrupt flag bit(s) must be cleared in software before re-enabling the global inter-
rupt to avoid recursive interrupts.
Once in the interrupt service routine the source(s) of the interrupt can be deter mined by polling
the interrupt flag bits. Individual interrupt flag bits are set regardless of the status of their
corresponding mask bit or the GIE bit.
Note 1: Individual interrupt flag bits are set regardless of the status of their corresponding
mask bit or the GIE bit.
Note 2: When an instruction that clears the GIE bit is executed, any interrupts that were
pending f or ex ecution in the next cycle are ignored. The CPU will execute a NOP in
the cycle immediately following the instruction which clears the GIE bit. The inter-
rupts which were ignored are still pending to be serviced when the GIE bit is set
again.
PICmicro MID-RANGE MCU FAMILY
DS31008A-page 8-4 1997 Microchip Technology Inc.
Figure 8-1: Interrupt Logic
TMR1IE
TMR1IF
TMR2IE
TMR2IF
INTF
INTE
RBIF
RBIE
T0IF
T0IE
GIE
PEIE
Wake-up (If in SLEEP mode)
Interrupt to CPU
INTCON RegisterPIR/PIE Registers
ADCIE
ADCIF
ADIE
ADIF
CCP1IE
CCP1IF
CCP2IE
CCP2IF
CMIE
CMIF
EEIE
EEIF
LCDIE
LCDIF
PBIE
PBIF
PSPIE
PSPIF
RCIE
RCIF
SSPIE
SSPIF
OVFIE
OVFIF
TXIE
TXIF
GPIF
GPIE
(EEIE 2)
Note 1: This shows all current Interrupt bits (at time of manual printing) for
all PICmicro Mid-Range MCUs. Which bits pertain to a specific
device is dependent upon the device type and peripherals imple-
mented. See specific device data sheet.
2: Some of the original Mid-Range devices had only one peripheral
module. These devices do not have the PEIE bit, and have the mod-
ule enable bit in the INTCON register.
(ADIE 2)
Clear GIE bit
1997 Microchip Technology Inc. DS31008A-page 8-5
Section 8. Interrupts
Interrupts
8
8.2 Control Registers
Generally devices have a minimum of three registers associated with interrupts. The INTCON
register which contains Global Interrupt Enable bit, GIE, as well as the Peripheral Interrupt
Enable bit, PEIE, and the PIE / PIR register pair which enable the peripheral interrupts and dis-
play the interrupt flag status.
8.2.1 INTCON Register
The INTCON Register is a readable and writable register which contains v arious enable and flag
bits.
Register 8-1: INTCON Register
Note: Interrupt flag bits get set when an interrupt condition occurs regardless of the state
of its corresponding enable bit or the global enable bit, GIE (INTCON<7>).This
feature allows for software polling.
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
GIE PEIE (3) T0IE INTE (2) RBIE (1,
2) T0IF INTF (2) RBIF (1, 2)
bit 7 bit 0
bit 7 GIE: Global Interrupt Enable bit
1 = Enables all un-masked interrupts
0 = Disables all interrupts
bit 6 PEIE: Peripheral Interrupt Enable bit
1 = Enables all un-masked peripheral interrupts
0 = Disables all peripheral interrupts
bit 5 T0IE: TMR0 Overflow Interrupt Enable bit
1 = Enables the TMR0 overflow interrupt
0 = Disables the TMR0 overflow interrupt
bit 4 INTE: INT External Interrupt Enable bit
1 = Enables the INT external interrupt
0 = Disables the INT external interrupt
bit 3 RBIE (1): RB Port Change Interrupt Enable bit
1 = Enables the RB port change interrupt
0 = Disables the RB port change interrupt
bit 2 T0IF: TMR0 Overflow Interrupt Flag bit
1 = TMR0 register has overflowed (must be cleared in software)
0 = TMR0 register did not overflow
bit 1 INTF: INT External Interrupt Flag bit
1 = The INT external interrupt occurred (must be cleared in software)
0 = The INT external interrupt did not occur
bit 0 RBIF (1): RB Port Change Interrupt Flag bit
1 = At least one of the RB7:RB4 pins changed state (must be cleared in software)
0 = None of the RB7:RB4 pins have changed state
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note 1: In some devices , the RBIE bit ma y also be kno wn as GPIE and the RBIF bit ma y be
know as GPIF.
Note 2: Some devices may not have this feature. For those devices this bit is reserved.
Note 3: In devices with only one peripheral interrupt, this bit may be EEIE or ADIE.
PICmicro MID-RANGE MCU FAMILY
DS31008A-page 8-6 1997 Microchip Technology Inc.
8.2.2 PIE Register(s)
Depending on the number of peripheral interrupt sources, there ma y be multiple P eripheral Inter-
rupt Enable registers (PIE1, PIE2). These registers contain the individual enable bits for the
Per ipheral interrupts. These registers will be gener ically referred to as PIE. If the device has a
PIE register, The PEIE bit must be set to enable any of these peripheral interrupts.
Although, the PIE register bits have a general bit location with each register, future devices may
not have consistent placement. Bit location inconsistencies will not be a problem if you use the
supplied Microchip Include files for the symbolic use of these bits. This will allow the Assem-
bler/Compiler to automatically take care of the placement of these bits by specifying the correct
register and bit name.
Note: Bit PEIE (INTCON<6>) must be set to enable any of the peripheral interrupts.
1997 Microchip Technology Inc. DS31008A-page 8-7
Section 8. Interrupts
Interrupts
8
Register 8-2: PIE Register
R/W-0
(Note 1)
bit 7 bit 0
bit TMR1IE: TMR1 Overflow Interrupt Enable bit
1 = Enables the TMR1 overflow interrupt
0 = Disables the TMR1 overflow interrupt
bit TMR2IE: TMR2 to PR2 Match Interrupt Enable bit
1 = Enables the TMR2 to PR2 match interrupt
0 = Disables the TMR2 to PR2 match interrupt
bit CCP1IE: CCP1 Interrupt Enable bit
1 = Enables the CCP1 interrupt
0 = Disables the CCP1 interrupt
bit CCP2IE: CCP2 Interrupt Enable bit
1 = Enables the CCP2 interrupt
0 = Disables the CCP2 interrupt
bit SSPIE: Synchronous Serial Port Interrupt Enable bit
1 = Enables the SSP interrupt
0 = Disables the SSP interrupt
bit RCIE: USART Receive Interrupt Enable bit
1 = Enables the USART receive interrupt
0 = Disables the USART receive interrupt
bit TXIE: USART Transmit Interrupt Enable bit
1 = Enables the USART transmit interrupt
0 = Disables the USART transmit interrupt
bit ADIE: A/D Converter Interrupt Enable bit
1 = Enables the A/D interrupt
0 = Disables the A/D interrupt
bit ADCIE: Slope A/D Converter comparator Trip Interrupt Enable bit
1 = Enables the Slope A/D interrupt
0 = Disables the Slope A/D interrupt
bit OVFIE: Slope A/D TMR Overflow Interrupt Enable bit
1 = Enables the Slope A/D TMR overflow interrupt
0 = Disables the Slope A/D TMR overflow interrupt
bit PSPIE: Parallel Slave Port Read/Write Interrupt Enable bit
1 = Enables the PSP read/write interrupt
0 = Disables the PSP read/write interrupt
bit EEIE: EE Write Complete Interrupt Enable bit
1 = Enables the EE write complete interrupt
0 = Disables the EE write complete interrupt
bit LCDIE: LCD Interrupt Enable bit
1 = Enables the LCD interrupt
0 = Disables the LCD interrupt
bit CMIE: Comparator Interrupt Enable bit
1 = Enables the Comparator interrupt
0 = Disables the Comparator interrupt
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note 1: The bit position of the enable bits is device dependent. Please refer to the device
data sheet for bit placement.
PICmicro MID-RANGE MCU FAMILY
DS31008A-page 8-8 1997 Microchip Technology Inc.
8.2.3 PIR Register(s)
Depending on the number of peripheral interrupt sources, there ma y be multiple P eripheral Inter-
rupt Flag registers (PIR1, PIR2). These registers contain the individual flag bits f or the peripheral
interrupts. These registers will be generically referred to as PIR.
Although, the PIR bits hav e a gener al bit location within each register, future devices ma y not be
able to be consistent with that. It is recommended that you use the supplied Microchip Include
files for the symbolic use of these bits. This will allow the Assembler/Compiler to automatically
take care of the placement of these bits within the specified register.
Note 1: Interrupt flag bits get set when an interrupt condition occurs regardless of the state
of its corresponding enable bit or the global enable bit, GIE (INTCON<7>).
Note 2: User software should ensure the appropriate interrupt flag bits are cleared (by soft-
ware) prior to enabling an interrupt, and after servicing that interrupt.
Register 8-3: PIR Register
R/W-0
(Note 1)
bit 7 bit 0
bit TMR1IF: TMR1 Overflow Interrupt Flag bit
1 = TMR1 register overflowed (must be cleared in software)
0 = TMR1 register did not overflow
bit TMR2IF: TMR2 to PR2 Match Interrupt Flag bit
1 = TMR2 to PR2 match occurred (must be cleared in software)
0 = No TMR2 to PR2 match occurred
bit CCP1IF: CCP1 Interrupt Flag bit
Capture Mode
1 = A TMR1 register capture occurred (must be cleared in software)
0 = No TMR1 register capture occurred
Compare Mode
1 = A TMR1 register compare match occurred (must be cleared in software)
0 = No TMR1 register compare match occurred
PWM Mode
Unused in this mode
bit CCP2IF: CCP2 Interrupt Flag bit
Capture Mode
1 = A TMR1 register capture occurred (must be cleared in software)
0 = No TMR1 register capture occurred
Compare Mode
1 = A TMR1 register compare match occurred (must be cleared in software)
0 = No TMR1 register compare match occurred
PWM Mode
Unused in this mode
bit SSPIF: Synchronous Serial Port Interrupt Flag bit
1 = The transmission/reception is complete
0 = Waiting to transmit/receive
bit RCIF: USART Receive Interrupt Flag bit
1 = The USART receive buffer, RCREG, is full (cleared when RCREG is read)
0 = The USART receive buffer is empty
bit TXIF: USART Transmit Interrupt Flag bit
1 = The USART transmit buffer, TXREG, is empty (cleared when TXREG is written)
0 = The USART transmit buffer is full
bit ADIF: A/D Converter Interrupt Flag bit
1 = An A/D conversion completed (must be cleared in software)
0 = The A/D conversion is not complete
1997 Microchip Technology Inc. DS31008A-page 8-9
Section 8. Interrupts
Interrupts
8
bit ADCIF: Slope A/D Converter Comparator Trip Interrupt Flag bit
1 = An A/D conversion completed (must be cleared in software)
0 = The A/D conversion is not complete
bit OVFIF: Slope A/D TMR Overflow Interrupt Flag bit
1 = Slope A/D TMR overflowed (must be cleared in software)
0 = Slope A/D TMR did not overflow
bit PSPIF: Parallel Slave Port Read/Write Interrupt Flag bit
1 = A read or a write operation has taken place (must be cleared in software)
0 = No read or write has occurred
bit EEIF: EE Write Complete Interrupt Flag bit
1 = The data EEPROM write operation is complete (must be cleared in software)
0 = The data EEPROM write operation is not complete
bit LCDIF: LCD Interrupt Flag bit
1 = LCD interrupt has occurred (must be cleared in software)
0 = LCD interrupt has not occurred
bit CMIF: Comparator Interrupt Flag bit
1 = Comparator input has changed (must be cleared in software)
0 = Comparator input has not changed
Register 8-3: PIR Register (Cont’d)
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note 1: The bit position of the flag bits is device dependent. Please refer to the device data
sheet for bit placement.
PICmicro MID-RANGE MCU FAMILY
DS31008A-page 8-10 1997 Microchip Technology Inc.
8.3 Interrupt Latency
Interrupt latency is defined as the time from the interr upt event (the interr upt flag bit gets set) to
the time that the instruction at address 0004h starts execution (when that interrupt is enabled).
For synchronous interrupts (typically internal), the latency is 3TCY.
For asynchronous interr upts (typically external), such as the INT or Port RB Change Interrupt,
the interrupt latency will be 3 - 3.75TCY (instruction cycles). The exact latency depends upon
when the interrupt event occurs (Figure 8-2) in relation to the instruction cycle.
The latency is the same for both one and two cycle instructions.
8.4 INT and External Interrupts
The external interrupt on the INT pin is edge triggered: either rising if the INTEDG bit
(OPTION<6>) is set, or f alling, if the INTEDG bit is clear. When a v alid edge appears on the INT
pin, the INTF flag bit (INTCON<1>) is set. This interrupt can be enabled/disabled b y setting/clear-
ing the INTE enable bit (INTCON<4>). The INTF bit must be cleared in software in the interrupt
service routine before re-enabling this interrupt. The INT interrupt can wake-up the processor
from SLEEP, if the INTE bit was set prior to going into SLEEP. The status of the GIE bit decides
whether or not the processor branches to the interrupt vector following wake-up. See the
“Watchdog Timer and Sleep Mode” section for details on SLEEP and for timing of wake-up
from SLEEP through INT interrupt.
Figure 8-2: INT Pin and Other External Interrupt Timing
Q2Q1 Q3 Q4 Q2Q1 Q3 Q4 Q2Q1 Q3 Q4 Q2Q1 Q3 Q4 Q2Q1 Q3 Q4
OSC1
CLKOUT
INT pin
INTF flag
(INTCON<1>)
GIE bit
(INTCON<7>)
INSTRUCTION FLOW
PC
Instruction
fetched
Instruction
executed
Interrupt Latency
PC PC+1 PC+1 0004h 0005h
Inst (0004h) Inst (0005h)
Dummy Cycle
Inst (PC) Inst (PC+1)
Inst (PC-1) Inst (0004h)
Dummy Cycle
Inst (PC)
1
4
51
Note 1: INTF flag is sampled here (every Q1).
2: Interrupt latency = 3-4 TCY where TCY = instruction cycle time.
Latency is the same whether Instruction (PC) is a single cycle or a 2-cycle instruction.
3: CLKOUT is available only in RC oscillator mode.
4: For minimum width of INT pulse, refer to AC specs.
5: INTF is enabled to be set anytime during the Q4-Q1 cycles.
2
3
Note: Any interrupts caused by e xternal signals (such as timers, capture , change on port)
will have similar timing.
1997 Microchip Technology Inc. DS31008A-page 8-11
Section 8. Interrupts
Interrupts
8
8.5 Context Saving During Interrupts
During an interr upt, only the retur n PC value is saved on the stack. Typically, users may wish to
sav e key registers during an interrupt e.g. W register and STATUS register. This has to be imple-
mented in software.
The action of saving inf ormation is commonly referred to as “PUSHing, while the action of restor-
ing the infor mation before the return is commonly referred to as “POPing. These (PUSH, POP)
are not instruction mnemonics, but are conceptual actions . This action can be implemented by a
sequence of instructions. For ease of code transportability, these code segments can be made
into MACROs (see MPASM Assembler User’s Guide for details on creating macros).
Example 8-1 stores and restores the STATUS and W registers for devices with common RAM
(such as the PIC16C77). The user register , W_TEMP, must be defined across all banks and must
be defined at the same offset from the bank base address (i.e., W_TEMP is defined at 0x70 -
0x7F in Bank0). The user register, STATUS_TEMP, must be defined in Bank0, in this example
STATUS_TEMP is also in Bank0.
The steps of Example 8-1:
1. Stores the W register regardless of current bank.
2. Stores the STATUS register in Bank0.
3. Executes the Interrupt Service Routine (ISR) code.
4. Restores the STATUS (and bank select bit register).
5. Restores the W register.
If additional locations need to be saved before executing the Interrupt Service Routine (ISR)
code, the y should be saved after the STATUS register is saved (step 2), and restored before the
STATUS register is restored (step 4).
Example 8-1: Saving the STATUS and W Registers in RAM
(for Devices with Common RAM)
MOVWF W_TEMP ; Copy W to a Temporary Register
; regardless of current bank
SWAPF STATUS,W ; Swap STATUS nibbles and place
; into W register
MOVWF STATUS_TEMP ; Save STATUS to a Temporary register
; in Bank0
:
: (Interrupt Service Routine (ISR) )
:
SWAPF STATUS_TEMP,W ; Swap original STATUS register value
; into W (restores original bank)
MOVWF STATUS ; Restore STATUS register from
; W register
SWAPF W_TEMP,F ; Swap W_Temp nibbles and return
; value to W_Temp
SWAPF W_TEMP,W ; Swap W_Temp to W to restore original
; W value without affecting STATUS
PICmicro MID-RANGE MCU FAMILY
DS31008A-page 8-12 1997 Microchip Technology Inc.
Example 8-2 stores and restores the STATUS and W registers f or de vices without common RAM
(such as the PIC16C74A). The user register, W_TEMP, must be defined across all banks and
must be defined at the same offset from the bank base address (i.e., W_TEMP is defined at 0x70
- 0x7F in Bank0). The user register, STATUS_TEMP, must be defined in Bank0.
Within the 70h - 7Fh range (Bank0), where ver W_TEMP is e xpected the corresponding locations
in the other banks should be dedicated for the possible saving of the W register.
The steps of Example 8-2:
1. Stores the W register regardless of current bank.
2. Stores the STATUS register in Bank0.
3. Executes the Interrupt Service Routine (ISR) code.
4. Restores the STATUS (and bank select bit register).
5. Restores the W register.
If additional locations need to be saved before executing the Interrupt Service Routine (ISR)
code, the y should be saved after the STATUS register is saved (step 2), and restored before the
STATUS register is restored (step 4).
Example 8-2: Saving the STATUS and W Registers in RAM
(for Devices without Common RAM)
MOVWF W_TEMP ; Copy W to a Temporary Register
; regardless of current bank
SWAPF STATUS,W ; Swap STATUS nibbles and place
; into W register
BCF STATUS,RP0 ; Change to Bank0 regardless of
; current bank
MOVWF STATUS_TEMP ; Save STATUS to a Temporary register
; in Bank0
:
: (Interrupt Service Routine (ISR) )
:
SWAPF STATUS_TEMP,W ; Swap original STATUS register value
; into W (restores original bank)
MOVWF STATUS ; Restore STATUS register from
; W register
SWAPF W_TEMP,F ; Swap W_Temp nibbles and return
; value to W_Temp
SWAPF W_TEMP,W ; Swap W_Temp to W to restore original
; W value without affecting STATUS
1997 Microchip Technology Inc. DS31008A-page 8-13
Section 8. Interrupts
Interrupts
8
Example 8-3 stores and restores the STATUS and W registers for devices with general purpose
RAM only in Bank0 (such as the PIC16C620). The Bank must be tested bef ore sa ving any of the
user registers. , W_TEMP, must be defined across all banks and must be defined at the same
offset from the bank base address. The user register , STATUS_TEMP, must be defined in Bank0.
The steps of Example 8-3:
1. Test current bank.
2. Stores the W register regardless of current bank.
3. Stores the STATUS register in Bank0.
4. Executes the Interrupt Service Routine (ISR) code.
5. Restores the STATUS (and bank select bit register).
6. Restores the W register.
If additional locations need to be saved before executing the Interrupt Service Routine (ISR)
code, the y should be saved after the STATUS register is saved (step 2), and restored before the
STATUS register is restored (step 4).
Example 8-3: Saving the STATUS and W Registers in RAM
(for Devices with General Purpose RAM Only in Bank0)
Push
BTFSS STATUS, RP0 ; In Bank 0?
GOTO RP0CLEAR ; YES,
BCF STATUS, RP0 ; NO, Force to Bank 0
MOVWF W_TEMP ; Store W register
SWAPF STATUS, W ; Swap STATUS register and
MOVWF STATUS_TEMP ; store in STATUS_TEMP
BSF STATUS_TEMP, 1 ; Set the bit that corresponds to RP0
GOTO ISR_Code ; Push completed
RP0CLEAR
MOVWF W_TEMP ; Store W register
SWAPF STATUS, W ; Swap STATUS register and
MOVWF STATUS_TEMP ; store in STATUS_TEMP
;
ISR_Code
:
: (Interrupt Service Routine (ISR) )
:
;
Pop
SWAPF STATUS_TEMP, W ; Restore Status register
MOVWF STATUS ;
BTFSS STATUS, RP0 ; In Bank 1?
GOTO Restore_WREG ; NO,
BCF STATUS, RP0 ; YES, Force Bank 0
SWAPF W_TEMP, F ; Restore W register
SWAPF W_TEMP, W ;
BSF STATUS, RP0 ; Back to Bank 1
RETFIE ; POP completed
Restore_WREG
SWAPF W_TEMP, F ; Restore W register
SWAPF W_TEMP, W ;
RETFIE ; POP completed
PICmicro MID-RANGE MCU FAMILY
DS31008A-page 8-14 1997 Microchip Technology Inc.
8.6 Initialization
Example 8-4 shows the initialization and enab ling of de vice interrupts, where PIE1_MASK1 value
is the value to write into the interrupt enable register.
Example 8-5 shows how to create macro definitions for functions. Macros must be defined
bef ore they are used. F or deb ugging ease, it may help if macros are placed in other files that are
included at assembly time. This allows the source to be viewed without all the clutter of the
required macros. These files must be included before the macro is used, but it simplifies deb ug-
ging, if all include files are done at the top of the source file. Example 8-6 shows this structure.
Example 8-7 shows a typical Interrupt Ser vice Routine structure. This ISR uses macros for the
saving and restoring of registers before the execution of the interrupt code.
Example 8-4: Initialization and Enabling of Interrupts
Example 8-5: Register Saving / Restoring as Macros
PIE1_MASK1 EQU B‘01101010’ ; This is the Interrupt Enable
: ; Register mask value
:
CLRF STATUS ; Bank0
CLRF INTCON ; Disable interrupts and clear some flags
CLRF PIR1 ; Clear all flag bits
BSF STATUS, RP0 ; Bank1
MOVLW PIE1_MASK1 ; This is the initial masking for PIE1
MOVWF PIE1 ;
BCF STATUS, RP0 ; Bank0
BSF INTCON, GIE ; Enable Interrupts
PUSH_MACRO MACRO ; This Macro Saves register contents
MOVWF W_TEMP ; Copy W to a Temporary Register
; regardless of current bank
SWAPF STATUS,W ; Swap STATUS nibbles and place
; into W register
MOVWF STATUS_TEMP ; Save STATUS to a Temporary register
; in Bank0
ENDM ; End this Macro
;
POP_MACRO MACRO ; This Macro Restores register contents
SWAPF STATUS_TEMP,W ; Swap original STATUS register value
; into W (restores original bank)
MOVWF STATUS ; Restore STATUS register from
; W register
SWAPF W_TEMP,F ; Swap W_Temp nibbles and return
; value to W_Temp
SWAPF W_TEMP,W ; Swap W_Temp to W to restore original
; W value without affecting STATUS
ENDM ; End this Macro
1997 Microchip Technology Inc. DS31008A-page 8-15
Section 8. Interrupts
Interrupts
8
Example 8-6: Source File Template
Example 8-7: Typical Interrupt Service Routine (ISR)
LIST p = p16C77 ; List Directive,
; Revision History
;
#INCLUDE <P16C77.INC> ; Microchip Device Header File
;
#INCLUDE <MY_STD.MAC> ; Include my standard macros
#INCLUDE <APP.MAC> ; File which includes macros specific
; to this application
; Specify Device Configuration Bits
__CONFIG _XT_OSC & _PWRTE_ON & _BODEN_OFF & _CP_OFF & _WDT_ON
;
org 0x00 ; Start of Program Memory
RESET_ADDR : ; First instruction to execute after a reset
end
org ISR_ADDR ;
PUSH_MACRO ; MACRO that saves required context registers,
; or in-line code
CLRF STATUS ; Bank0
BTFSC PIR1, TMR1IF ; Timer1 overflow interrupt?
GOTO T1_INT ; YES
BTFSC PIR1, ADIF ; NO, A/D interrupt?
GOTO AD_INT ; YES, do A/D thing
: ; NO, do this for all sources
: ;
BTFSC PIR1, LCDIF ; NO, LCD interrupt
GOTO LCD_INT ; YES, do LCD thing
BTFSC INTCON, RBIF ; NO, Change on PORTB interrupt?
GOTO PORTB_INT ; YES, Do PortB Change thing
INT_ERROR_LP1 ; NO, do error recovery
GOTO INT_ERROR_LP1 ; This is the trap if you enter the ISR
; but there were no expected
; interrupts
T1_INT ; Routine when the Timer1 overflows
: ;
BCF PIR1, TMR1IF ; Clear the Timer1 overflow interrupt flag
GOTO END_ISR ; Ready to leave ISR (for this request)
AD_INT ; Routine when the A/D completes
: ;
BCF PIR1, ADIF ; Clear the A/D interrupt flag
GOTO END_ISR ; Ready to leave ISR (for this request)
LCD_INT ; Routine when the LCD Frame begins
: ;
BCF PIR1, LCDIF ; Clear the LCD interrupt flag
GOTO END_ISR ; Ready to leave ISR (for this request)
PORTB_INT ; Routine when PortB has a change
: ;
END_ISR ;
POP_MACRO ; MACRO that restores required registers,
; or in-line code
RETFIE ; Return and enable interrupts
PICmicro MID-RANGE MCU FAMILY
DS31008A-page 8-16 1997 Microchip Technology Inc.
8.7 Design Tips
Question 1:
An algorithm does not give the correct results.
Answer 1:
Assuming that the algorithm is correct and that interrupts are enabled during the algorithm,
ensure that are registers that are used by the algorithm and by the interrupt service routine are
saved and restored. If not some registers may be corrupted by the execution of the ISR.
Question 2:
My system seems to lock up.
Answer 2:
If interrupts are being used, ensure that the interr upt flag is cleared after servicing that interrupt
(but before executing the RETFIE instruction). If the interr upt flag remains set when the RETFIE
instruction is ex ecuted, program e xecution immediately returns to the interrupt v ector, since there
is an outstanding enabled interrupt.
1997 Microchip Technology Inc. DS31008A-page 8-17
Section 8. Interrupts
Interrupts
8
8.8 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to this section
are:
Title Application Note #
Using the PortB Interrupt On Change as an External Interrupt AN566
PICmicro MID-RANGE MCU FAMILY
DS31008A-page 8-18 1997 Microchip Technology Inc.
8.9 Revision History
Revision A
This is the initial released revision of the interrupt description.
1997 Microchip Technology Inc. DS31009A page 9-1
M
I/O Ports
9
Section 9. I/O Ports
HIGHLIGHTS
This section of the manual contains the following major topics:
9.1 Introduction....................................................................................................................9-2
9.2 PORTA and the TRISA Register ....................................................................................9-4
9.3 PORTB and the TRISB Register....................................................................................9-6
9.4 PORTC and the TRISC Register....................................................................................9-8
9.5 PORTD and the TRISD Register....................................................................................9-9
9.6 PORTE and the TRISE Register..................................................................................9-10
9.7 PORTF and the TRISF Register ..................................................................................9-11
9.8 PORTG and the TRISG Register.................................................................................9-12
9.9 GPIO and the TRISGP Register ..................................................................................9-13
9.10 I/O Programming Considerations.................................................................................9-14
9.11 Initialization..................................................................................................................9-16
9.12 Design Tips ..................................................................................................................9-17
9.13 Related Application Notes............................................................................................9-19
9.14 Revision History...........................................................................................................9-20
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-2 1997 Microchip Technology Inc.
9.1 Introduction
General purpose I/O pins can be considered the simplest of peripherals. They allow the
PICmicro™ to monitor and control other devices. To add flexibility and functionality to a device,
some pins are multiplexed with an alternate function(s). These functions depend on which
peripheral features are on the device. In general, when a per ipheral is functioning, that pin may
not be used as a general purpose I/O pin.
F or most ports, the I/O pin’s direction (input or output) is controlled by the data direction register,
called the TRIS register. TRIS<x> controls the direction of PORT<x>. A ‘1’ in the TRIS bit corre-
sponds to that pin being an input, while a ‘0’ corresponds to that pin being an output. An easy
way to remember is that a ‘1’ looks like an I (input) and a ‘0’ looks like an O (output).
The PORT register is the latch for the data to be output. When the PORT is read, the de vice reads
the levels present on the I/O pins (not the latch). This means that care should be taken with
read-modify-write commands on the ports and changing the direction of a pin from an input to an
output.
Figure 9-1 shows a typical I/O port. This does not take into account peripheral functions that ma y
be multiple x ed onto the I/O pin. Reading the POR T register reads the status of the pins whereas
writing to it will write to the port latch. All write operations (such as BSF and BCF instructions) are
read-modify-write operations. Therefore a write to a por t implies that the port pins are read, this
value is modified, and then written to the port data latch.
Figure 9-1: Typical I/O Port
Data bus
WR PORT
WR TRIS
RD PORT
Data Latch
TRIS Latch
P
VSS
I/O pin
Note: I/O pin has protection diodes to VDD and VSS.
Q
D
Q
CK
Q
D
Q
CK
QD
EN
N
VDD
RD TRIS Schmitt
Trigger
TTL or
1997 Microchip Technology Inc. DS31009A-page 9-3
Section 9. I/O Ports
I/O Ports
9
When peripheral functions are multiple xed onto general I/O pins, the functionality of the I/O pins
may change to accommodate the requirements of the per ipheral module. Examples of this are
the Analog-to-Digital (A/D) converter and LCD driver modules, which force the I/O pin to the
peripheral function when the device is reset. In the case of the A/D, this prev ents the de vice from
consuming excess current if any analog levels were on the A/D pins after a reset occurred.
With some peripherals, the TRIS bit is overridden while the peripheral is enabled. Therefore,
read-modify-write instr uctions (BSF, BCF, XORWF) with TRIS as destination should be avoided.
The user should refer to the corresponding peripheral section for the correct TRIS bit settings.
POR T pins ma y be m ultiple xed with analog inputs and analog VREF input. The operation of each
of these pins is selected, to be an analog input or digital I/O, by clearing/setting the control bits
in the ADCON1 register (A/D Control Register1). When selected as an analog input, these pins
will read as ‘0’s.
The TRIS registers control the direction of the port pins, even when they are being used as ana-
log inputs. The user must ensure the TRIS bits are maintained set when using the pins as analog
inputs.
Note 1: If pins are multiple x ed with Analog inputs , then on a Power-on Reset these pins are
configured as analog inputs, as controlled by the ADCON1 register. Reading por t
pins configured as analog inputs read a ‘0’.
Note 2: If pins are multiple xed with compar ator inputs, then on a P o wer-on Reset these pins
are configured as analog inputs, as controlled b y the CMCON register. Reading port
pins configured as analog inputs read a ‘0’.
Note 3: If pins are multiplexed with LCD driver segments, then on a Power-on Reset these
pins are configured as LCD driver segments, as controlled by the LCDSE register.
To configure the pins as a digital port, the corresponding bits in the LCDSE register
must be cleared. Any bit set in the LCDSE register overrides any bit settings in the
corresponding TRIS register .
Note 4: Pins may be m ultiple xed with the P ar allel Slav e P ort (PSP). For the PSP to function,
the I/O pins must be configured as digital inputs and the PSPMODE bit must be set.
Note 5: At present the Parallel Slave Port (PSP) is only multiplexed onto PORTD and
POR TE. The microprocessor port becomes enabled when the PSPMODE bit is set.
In this mode, the user must make sure that the TRISE bits are set (pins are config-
ured as digital inputs) and that POR TE is configured for digital I/O . POR TD will over-
ride the values in the TRISD register. In this mode the PORTD and PORTE input
buffers are TTL. The control bits for the PSP operation are located in TRISE.
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-4 1997 Microchip Technology Inc.
9.2 PORTA and the TRISA Register
The RA4 pin is a Schmitt Trigger input and an open drain output. All other RA port pins hav e TTL
input le vels and full CMOS output driv ers. All pins hav e data direction bits (TRIS registers) which
can configure these pins as output or input.
Setting a TRISA register bit puts the corresponding output driver in a hi-impedance mode . Clear-
ing a bit in the TRISA register puts the contents of the output latch on the selected pin(s).
Example 9-1: Initializing PORTA
Figure 9-2: Block Diagram of RA3:RA0 and RA5 Pins
CLRF STATUS ; Bank0
CLRF PORTA ; Initialize PORTA by clearing output
; data latches
BSF STATUS, RP0 ; Select Bank1
MOVLW 0xCF ; Value used to initialize data direction
MOVWF TRISA ; PORTA<3:0> = inputs PORTA<5:4> = outputs
; TRISA<7:6> always read as '0'
Data bus
WR PORT
WR TRIS
RD PORT
Data Latch
TRIS Latch
P
VSS
I/O pin
To Peripheral Module(s)
Note: I/O pin has protection diodes to VDD and VSS.
Q
D
Q
CK
Q
D
Q
CK
QD
EN
N
Analog
input
mode TTL
VDD
RD TRIS or ST
input
buffer
1997 Microchip Technology Inc. DS31009A-page 9-5
Section 9. I/O Ports
I/O Ports
9
Figure 9-3: Block Diagram of RA4 Pin
Data Bus
WR PORT
WR TRIS
RD PORT
Data Latch
TRIS Latch
Schmitt
Trigger
input
buffer
N
VSS
To Peripheral Module
Note: I/O pin has protection diodes to VSS only.
Q
D
Q
CK
Q
D
Q
CK
QD
EN
RD TRIS
RA4 pin
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-6 1997 Microchip Technology Inc.
9.3 PORTB and the TRISB Register
PORTB is an 8-bit wide bi-directional por t. The corresponding data direction register is TRISB.
Setting a bit in the TRISB register puts the corresponding output driver in a high-impedance input
mode. Clearing a bit in the TRISB register puts the contents of the output latch on the selected
pin(s).
Example 9-2: Initializing PORTB
Each of the PORTB pins has a weak internal pull-up. A single control bit can turn on all the
pull-ups. This is performed by clearing bit RBPU (OPTION<7>). The weak pull-up is automati-
cally turned off when the port pin is configured as an output. The pull-ups are disabled on a
Power-on Reset.
Figure 9-4: Block Diagram of RB3:RB0 Pins
CLRF STATUS ; Bank0
CLRF PORTB ; Initialize PORTB by clearing output
; data latches
BSF STATUS, RP0 ; Select Bank1
MOVLW 0xCF ; Value used to initialize data direction
MOVWF TRISB ; PORTB<3:0> = inputs, PORTB<5:4> = outputs
; PORTB<7:6> = inputs
Data Latch
RBPU(2) P
VDD
QD
CK
QD
CK
QD
EN
Data bus
WR Port
WR TRIS
RD TRIS
RD Port
weak
pull-up
RD Port
To Peripheral Module
I/O
pin(1)
TTL
Input
Buffer
Schmitt Trigger
Buffer
TRIS Latch
Note 1: I/O pins have diode protection to VDD and VSS.
2: To enable weak pull-ups , set the appropriate TRIS bit(s) and clear
the RBPU bit (OPTION<7>).
1997 Microchip Technology Inc. DS31009A-page 9-7
Section 9. I/O Ports
I/O Ports
9
Four of PORTB’s pins, RB7:RB4, have an interrupt on change feature. Only pins configured as
inputs can cause this interrupt to occur (i.e. any RB7:RB4 pin configured as an output is e xcluded
from the interrupt on change compar ison). The input pins (of RB7:RB4) are compared with the
old value latched on the last read of PORTB. The “mismatch” outputs of RB7:RB4 are OR’ed
together to generate the RB Port Change Interrupt with flag bit RBIF (INTCON<0>).
This interrupt can wake the device from SLEEP. The user, in the interr upt service routine, can
clear the interrupt in the following manner:
a) Any read or write of PORTB. This will end the mismatch condition.
b) Clear flag bit RBIF.
A mismatch condition will continue to set flag bit RBIF. Reading PORTB will end the mismatch
condition, and allow flag bit RBIF to be cleared.
This interrupt on mismatch feature, together with software configurable pull-ups on these four
pins allow easy interface to a keypad and make it possible for wake-up on key-depression.
The interrupt on change feature is recommended f or w ak e-up on ke y depression and oper ations
where PORTB is only used for the interrupt on change feature. Polling of PORTB is not recom-
mended while using the interrupt on change feature.
Figure 9-5: Block Diagram of RB7:RB4 Pins
Data Latch
From other
RBPU(2) P
VDD
I/O
QD
CK
QD
CK
QD
EN
QD
EN
Data bus
WR Port
WR TRIS
Set RBIF
TRIS Latch
RD TRIS
RD Port
RB7:RB4 pins
weak
pull-up
RD Port
Latch
TTL
Input
Buffer
pin(1)
ST
Buffer
RB7:RB6 in serial programming mode
Q3
Q1
Note 1: I/O pins have diode protection to VDD and VSS.
2: To enable weak pull-ups, set the appropriate TRIS bit(s)
and clear the RBPU bit (OPTION<7>).
3: In sleep mode the device is in Q1 state.
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-8 1997 Microchip Technology Inc.
9.4 PORTC and the TRISC Register
PORTC is an 8-bit bi-directional port. Each pin is individually configurable as an input or output
through the TRISC register. PORTC pins have Schmitt Trigger input buffers.
When enabling peripheral functions , care should be tak en in defining TRIS bits for each PORTC
pin. Some peripherals ov erride the TRIS bit to mak e a pin an output, while other peripherals o ver-
ride the TRIS bit to make a pin an input.
Example 9-3: Initializing PORTC
Figure 9-6: PORTC Block Diagram (Peripheral Output Override)
CLRF STATUS ; Bank0
CLRF PORTC ; Initialize PORTC by clearing output
; data latches
BSF STATUS, RP0 ; Select Bank1
MOVLW 0xCF ; Value used to initialize data direction
MOVWF TRISC ; PORTC<3:0> = inputs, PORTC<5:4> = outputs
; PORTC<7:6> = inputs
Data Latch
TRIS Latch
RD TRIS
P
VSS
Q
D
Q
CK
Q
D
Q
CK
QD
EN
N
VDD
0
1
RD PORT
WR PORT
WR TRIS
Schmitt
Trigger
Peripheral input
Peripheral OE(2)
Data Bus
PORT/PERIPHERAL Select(1)
Peripheral Data-out
RD PORT
Note 1: Port/Peripheral select signal selects between port data and peripheral output.
2: Peripheral OE (output enable) is only activated if peripheral select is active.
3: I/O pins have diode protection to VDD and VSS.
I/O pin
1997 Microchip Technology Inc. DS31009A-page 9-9
Section 9. I/O Ports
I/O Ports
9
9.5 PORTD and the TRISD Register
POR TD is an 8-bit port with Schmitt Trigger input buffers. Each pin is individually configur ab le as
an input or output.
Example 9-4: Initializing PORTD
Figure 9-7: Typical PORTD Block Diagram (in I/O Port Mode)
CLRF STATUS ; Bank0
CLRF PORTD ; Initialize PORTD by clearing output
; data latches
BSF STATUS, RP0 ; Select Bank1
MOVLW 0xCF ; Value used to initialize data direction
MOVWF TRISD ; PORTD<3:0> = inputs, PORTD<5:4> = outputs
; PORTD<7:6> = inputs
Data Bus
WR PORT
WR TRIS
RD PORT
Data Latch
TRIS Latch
Schmitt
Trigger
input
buffer
Note: I/O pins have protection diodes to VDD and VSS.
Q
D
Q
CK
Q
D
Q
CK
QD
EN
I/O pin
RD TRIS
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-10 1997 Microchip Technology Inc.
9.6 PORTE and the TRISE Register
POR TE can be up to an 8-bit port with Schmitt Trigger input buff ers . Each pin is individually con-
figurable as an input or output.
Example 9-5: Initializing PORTE
Figure 9-8: Typical PORTE Block Diagram (in I/O Port Mode)
CLRF STATUS ; Bank0
CLRF PORTE ; Initialize PORTE by clearing output
; data latches
BSF STATUS, RP0 ; Select Bank1
MOVLW 0x03 ; Value used to initialize data direction
MOVWF TRISE ; PORTE<1:0> = inputs, PORTE<7:2> = outputs
Data Bus
WR PORT
WR TRIS
RD PORT
Data Latch
TRIS Latch
Schmitt
Trigger
input
buffer
Q
D
Q
CK
Q
D
Q
CK
QD
EN
I/O pin
RD TRIS
Note: I/O pins have protection diodes to VDD and VSS.
Note: On some de vices with POR TE, the upper bits of the TRISE register are used f or the
Parallel Slave Port control and status bits.
1997 Microchip Technology Inc. DS31009A-page 9-11
Section 9. I/O Ports
I/O Ports
9
9.7 PORTF and the TRISF Register
PORTF is a digital input only por t. Each pin is multiplexed with an LCD segment driver. These
pins have Schmitt Trigger input buffers.
Example 9-6: Initializing PORTF
Figure 9-9: PORTF LCD Block Diagram
BCF STATUS, RP0 ; Select Bank2
BSF STATUS, RP1 ;
BCF LCDSE, SE16 ; Make all PORTF
BCF LCDSE, SE12 ; digital inputs
RD PORT
Schmitt
Trigger
input
buffer
QD
EN
Digital Input/
LCDSE<n>
LCD Segment Data
LCD Segment LCD Output pin
Data Bus
RD TRIS
VDD
Output Enable
Note: I/O pins have protection diodes to VDD and VSS.
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-12 1997 Microchip Technology Inc.
9.8 PORTG and the TRISG Register
PORTG is a digital input only por t. Each pin is multiplexed with an LCD segment driver. These
pins have Schmitt Trigger input buffers.
Example 9-7: Initializing PORTG
Figure 9-10: PORTG LCD Block Diagram
BCF STATUS, RP0 ; Select Bank2
BSF STATUS, RP1 ;
BCF LCDSE, SE27 ; Make all PORTG
BCF LCDSE, SE20 ; and PORTE<7> digital inputs
RD PORT
Schmitt
Trigger
input
buffer
QD
EN
Digital Input/
LCDSE<n>
LCD Segment Data
LCD Segment Output Enable LCD Output pin
Data Bus
RD TRIS
VDD
1997 Microchip Technology Inc. DS31009A-page 9-13
Section 9. I/O Ports
I/O Ports
9
9.9 GPIO and the TRISGP Register
GPIO is an 8-bit I/O register. Only the low order six bits are implemented (GP5:GP0). Bits 7 and
6 are unimplemented and read as ‘0’s. Any GPIO pin (except GP3) can be programmed
individually as input or output. The GP3 pin is an input only pin.
The TRISGP register controls the data direction for GPIO pins. A ‘1’ in a TRISGP register bit
puts the corresponding output driver in a hi-impedance mode. A ‘0’ puts the contents of the
output data latch on the selected pins, enab ling the output b uff er. The exceptions are GP3 which
is input only and its TRIS bit will always read as '1'. Upon reset, the TRISGP register is all ‘1’s,
making all pins inputs.
A read of the GPIO por t, reads the pins not the output data latches. Any input must be present
until read by an input instruction (e.g., MOVF GPIO,W). The outputs are latched and remain
unchanged until the output latch is rewritten.
Example 9-8: Initializing GPIO
Figure 9-11: Block Diagram of GP5:GP0 Pins
The configuration word can set several I/O’s to alternate functions. When acting as alternate
functions the pins will read as ‘0’ during por t read. The GP0, GP1, and GP3 pins can be config-
ured with weak pull-ups and also with interrupt on change. The interrupt on change and weak
pull-up functions are not pin selectable. Interrupt on change is enabled by setting INTCON<3>.
If the de vice configuration bits select one of the external oscillator modes, the GP4 and GP5 pin’ s
GPIO functions are overridden and these pins are used for the oscillator.
CLRF STATUS ; Bank0
CLRF GPIO ; Initialize GPIO by clearing output
; data latches
BSF STATUS, RP0 ; Select Bank1
MOVLW 0xCF ; Value used to initialize data direction
MOVWF TRISGP ; GP<3:0> = inputs GP<5:4> = outputs
; TRISGP<7:6> always read as '0'
Note 1: I/O pins have protection diodes to VDD and VSS.
Data
Bus
QD
Q
CK
QD
Q
CK P
N
WR
Port
TRIS ‘f
Data
TRIS
RD Port
VSS
VDD
I/O
pin(1)
W
Reg
Latch
Latch
Reset
GP3 is input only with no data latch and no output drivers.
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-14 1997 Microchip Technology Inc.
9.10 I/O Programming Considerations
When using the ports (and GPIO) as I/O , design considerations need to be tak en into account to
ensure that the operation is as intended.
9.10.1 Bi-directional I/O Ports
Any instruction which perf orms a write operation actually does a read followed by a write opera-
tion. The BCF and BSF instr uctions, for example, read the register into the CPU, execute the bit
operation, and write the result back to the register . Caution must be used when these instructions
are applied to a port with both inputs and outputs defined. For example, a BSF operation on bit5
of PORTB will cause all eight bits of PORTB to be read into the CPU. Then the BSF operation
takes place on bit5 and PORTB is written to the output latches. If another bit of PORTB is used
as a bi-directional I/O pin (e.g., bit0) and it is defined as an input at this time, the input signal
present on the pin itself would be read into the CPU and re written to the data latch of this partic-
ular pin, ov erwriting the pre vious content. As long as the pin stays in the input mode , no prob lem
occurs. However, if bit0 is switched to an output, the content of the data latch may now be
unknown.
Reading the port register, reads the values of the port pins. Writing to the port register writes the
value to the port latch. When using read-modify-write instructions (ex. BCF, BSF, etc.) on a port,
the value of the port pins is read, the desired operation is performed on this value , and the v alue
is then written to the port latch.
Example 9-9 shows the effect of two sequential read-modify-write instructions on an I/O port.
Example 9-9: Read-Modify-Write Instructions on an I/O Port
A pin configured as an output, actively driving a Low or High should not be driven from external
devices at the same time in order to change the level on this pin (“wired-or, “wired-and”). The
resulting high output currents may damage the chip.
; Initial PORT settings: PORTB<7:4> Inputs
; PORTB<3:0> Outputs
; PORTB<7:6> have external pull-ups and are not connected to other circuitry
;
; PORT latch PORT pins
; ---------- ---------
BCF PORTB, 7 ; 01pp pppp 11pp pppp
BCF PORTB, 6 ; 10pp pppp 11pp pppp
BSF STATUS, RP0 ;
BCF TRISB, 7 ; 10pp pppp 11pp pppp
BCF TRISB, 6 ; 10pp pppp 10pp pppp
;
; Note that the user may have expected the pin values to be 00pp ppp.
; The 2nd BCF caused RB7 to be latched as the pin value (high).
1997 Microchip Technology Inc. DS31009A-page 9-15
Section 9. I/O Ports
I/O Ports
9
9.10.2 Successive Operations on an I/O Port
The actual write to an I/O port happens at the end of an instruction cycle, whereas for reading,
the data must be valid at the beginning of the instruction cycle (Figure 9-12). Therefore, care
must be e x ercised if a write f ollo wed b y a read oper ation is carried out on the same I/O port. The
sequence of instructions should be such to allow the pin voltage to stabilize (load dependent)
bef ore the next instruction which causes that file to be read into the CPU is e x ecuted. Otherwise,
the pre vious state of that pin may be read into the CPU r ather than the new state. When in doubt,
it is better to separate these instructions with a NOP or another instruction not accessing this I/O
port.
Figure 9-12: Successive I/O Operation
Figure 9-13 shows the I/O model which causes this situation. As the effective capacitance (C)
becomes larger, the r ise/fall time of the I/O pin increases. As the device frequency increases or
the effective capacitance increases, the possibility of this subsequent PORTx read-modify-write
instruction issue increases. This effective capacitance includes the effects of the board traces.
The best way to address this is to add an series resistor at the I/O pin. This resistor allows the
I/O pin to get to the desired level before the next instruction.
The use of NOP instructions between the subsequent PORTx read-modify-write instructions, is a
lower cost solution, but has the issue that the number of NOP instructions is dependent on the
effective capacitance C and the frequency of the device.
Figure 9-13: I/O Connection Issues
PC PC + 1 PC + 2 PC + 3
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Instruction
fetched
RB7:RB0
MOVWF PORTB
write to
PORTB NOP
Port pin
sampled here
NOP
MOVF PORTB,W
Instruction
executed MOVWF PORTB
write to
PORTB
NOP
MOVF PORTB,W
PC
TPD
This example shows a write to PORTB followed by a read from PORTB.
Note: Data setup time = (0.25TCY - TPD)
whereTCY = instruction cycle
TPD = propagation delay
Therefore, at higher clock frequencies, a write followed by a read may be
problematic due to external capacitance.
PIC16CXXX
I/O
C(1)
Q4 Q1 Q2 Q3 Q4 Q1
VIL
BSF PORTx, PINy
Q2 Q3
BSF PORTx, PINz
PORTx, PINy
Read PORTx, PINy as low
BSF PORTx, PINz clears the value
to be driven on the PORTx, PINy pin.
Note: This is not a capacitor to ground, but the effectiv e capac-
itive loading on the trace.
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-16 1997 Microchip Technology Inc.
9.11 Initialization
See the section describing each port for examples of initialization of the ports.
Note: It is recommended that when initializing the port, the data latch (PORT register)
should be initialized first, and then the data direction (TRIS register). This will elim-
inate a possible pin glitch, since the PORT data latch values power up in a random
state.
1997 Microchip Technology Inc. DS31009A-page 9-17
Section 9. I/O Ports
I/O Ports
9
9.12 Design Tips
Question 1:
Code will not toggle any I/O por ts, but the oscillator is running. What can I
be doing wrong?
Answer 1:
1. Have the TRIS registers been initialized properly? These registers can be written to
directly in the second bank (Bank1). In most cases the user is not switching to Bank1
(BSF STATUS,RP0) before writing zeros to the TRIS register.
2. If you are setting up the TRIS registers properly in Bank1 (RP0 = 1), you may not be
returning to Bank0 before writing to the ports (BCF STATUS,RP0).
3. Is there a peripheral multiplexed onto those pins that are enabled?
4. Is the W atchdog Timer enabled (done at programming)? If it is enab led, is it being cleared
properly with a CLRWDT instruction at least every 9 ms (or more if prescaled)?
5. Are you using the correct instructions to write to the port? More than one person has used
the MOVF command when they should have used MOVWF.
6. For parts with interrupts, are the interrupts disabled? If not, try disabling them to v erify they
are not interfering.
Question 2:
When m y pr ogram reads a port, I get a different v alue than what I put in the
port register. What can cause this?
Answer 2:
1. When a port is read, it is always the pin that is read, regardless of its being set to input or
output. So if a pin is set to an input, you will read the value on the pin regardless of the
register value.
2. If a pin is set to output, sa y it has a one in the data latch; if it is shorted to ground y ou will
still read a zero on the pin. This is very useful for building fault tolerant systems, or han-
dling I2C™ bus conflicts . (The I2C bus is only driv en lo w, and the pin is tristated for a one.
If the pin is low and you are not driving it, some other device is trying to take the bus).
3. Mid-Range MCU devices all have at least one open drain (or open collector) pin. These
pins can only drive a zero or tristate. For most Mid-Range devices this is pin RA4. Open
drain pins must have a pull-up resistor to have a high state. This pin is useful for driving
odd voltage loads. The pull-up can be connected to a voltage (typically less than VDD)
which becomes the high state.
Question 3:
I have a PIC16CXXX with pin RB0 configured as an interrupt input, but am
not getting interrupted. When I change my routine to poll the pin, it reads
the high input and operates fine. What is the problem?
Answer 3:
PORTB accepts TTL input levels (on most parts), so when you have an input of say 3V (with
VDD = 5V), you will read a one. However the buffer to the interrupt structure from pin RB0 is
Schmitt Trigger, which requires a higher voltage (than TTL input) before the high input is regis-
tered. So it is possible to read a one, but not get the interrupt. The interrupt was given a Schmitt
Trigger input with hysteresis to minimize noise prob lems. It is one thing to hav e short noise spikes
on a pin that is a data input that can potentially cause bad data, but quite another to permit noise
to cause an interrupt, hence the difference.
I2C is a trademark of Philips Corporation.
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-18 1997 Microchip Technology Inc.
Question 4:
When I perform a BCF instruction, other pins get cleared in the port. Why?
Answer 4:
1. Another case where a read-modify-write instruction ma y seem to change other pin v alues
unexpectedly can be illustrated as follows: Suppose you make PORTC all outputs and
drive the pins low. On each of the por t pins is an LED connected to ground, such that a
high output lights it. Across each LED is a 100 µF capacitor. Let's also suppose that the
processor is running very fast, say 20 MHz. Now if you go down the port setting each pin
in order ; BSF PORTC,0 then BSF PORTC,1 then BSF PORTC,2 and so on, you may see
that only the last pin was set, and only the last LED actually turns on. This is because the
capacitors take a while to charge. As each pin was set, the pin before it was not charged
yet and so was read as a zero. This zero is written back out to the port latch (r-m-w,
remember) which clears the bit you just tried to set the instruction before. This is usually
only a concern at high speeds and for successive port operations, but it can happen, so
take it into consideration.
2. If this is on a PIC16C7XX device, you have not configured the I/O pins properly in the
ADCON1 register. If a pin is configured for analog input, any read of that pin will read a
zero, regardless of the voltage on the pin. This is an exception to the normal rule that the
pin state is alwa ys read. You can still configure an analog pin as an output in the TRIS reg-
ister , and drive the pin high or low b y writing to it, but you will alwa ys read a zero . Theref ore
if you e x ecute a Read-Modify-Write instruction (see previous question) all analog pins are
read as zero, and those not directly modified by the instruction will be wr itten back to the
port latch as zero. A pin configured as analog is e xpected to ha ve values that may be nei-
ther high nor low to a digital pin, or floating. Floating inputs on digital pins are a no-no , and
can lead to high current draw in the input buffer, so the input buffer is disabled.
1997 Microchip Technology Inc. DS31009A-page 9-19
Section 9. I/O Ports
I/O Ports
9
9.13 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to I/O ports are:
Title Application Note #
Improving the Susceptibility of an Application to ESD AN595
Clock Design using Low Power/Cost Techniques AN615
Implementing Wake-up on Keystroke AN528
Interfacing to AC Power Lines AN521
Multiplexing LED Drive and a 4 x 4 Keypad Sampling AN529
Using PIC16C5X as an LCD Drivers AN563
Serial Port Routines Without Using TMR0 AN593
Implementation of an Asynchronous Serial I/O AN510
Using the PORTB Interrupt on Change Feature as an External Interrupt AN566
Implementing Wake-up on Keystroke AN522
Apple Desktop Bus AN591
Software Implementation of Asynchronous Serial I/O AN555
Communicating with the I2C Bus using the PIC16C5X AN515
Interfacing 93CX6 Serial EEPROMs to the PIC16C5X Microcontrollers AN530
Logic Powered Serial EEPROMs AN535
Interfacing 24LCXXB Serial EEPROMs to the PIC16C54 AN567
Using the 24XX65 and 24XX32 with Stand-alone PIC16C54 Code AN558
PICmicro MID-RANGE MCU FAMILY
DS31009A-page 9-20 1997 Microchip Technology Inc.
9.14 Revision History
Revision A
This is the initial released revision of the I/O Ports description.
1997 Microchip Technology Inc. DS31010A page 10-1
M
Parallel
Slave Port
10
Section 10. Parallel Slave Port
HIGHLIGHTS
This section of the manual contains the following major topics:
10.1 Introduction..................................................................................................................10-2
10.2 Control Register...........................................................................................................10-3
10.3 Operation .....................................................................................................................10-4
10.4 Operation in Sleep Mode .............................................................................................10-5
10.5 Effect of a Reset...........................................................................................................10-5
10.6 PSP Wa vef orms...........................................................................................................10-5
10.7 Design Tips ..................................................................................................................10-6
10.8 Related Application Notes............................................................................................10-7
10.9 Revision History...........................................................................................................10-8
PICmicro MID-RANGE MCU FAMILY
DS31010A-page 10-2 1997 Microchip Technology Inc.
10.1 Introduction
Some devices have an 8-bit wide Parallel Slave Port (PSP). This port is multiplexed onto one of
the de vices I/O ports. The POR T operates as an 8-bit wide P arallel Slav e P ort, or microprocessor
port, when the PSPMODE control bit is set. In this mode, the input buffers are TTL.
In slav e mode the module is asynchronously readable and writable b y the e xternal world through
RD control input pin and the WR control input pin.
It can directly interface to an 8-bit microprocessor data bus. The external microprocessor can
read or write the PORT latch as an 8-bit latch. Setting the PSPMODE bit enables port pins to be
the RD input, the WR input, and the CS (chip select) input.
There are actually two 8-bit latches, one for data-out (from the PICmicro) and one for data input.
The user writes 8-bit data to PORT data latch and reads data from the port pin latch (note that
they have the same address). In this mode, the TRIS register is ignored, since the microproces-
sor is controlling the direction of data flow.
Figure 10-1 shows the block diagram for the PSP.
Figure 10-1: PORTD and PORTE Block Diagram (Parallel Slave Port)
Note 1: At present the Parallel Slave Port (PSP) is only multiplexed onto PORTD and
POR TE. The microprocessor port becomes enabled when the PSPMODE bit is set.
In this mode, the user must make sure that PORTD and PORTE are configured as
digital I/O. That is, peripheral modules multiplexed onto the PSP functions are dis-
abled (such as the A/D).
When PORTE is configured for digital I/O. PORTD will override the values in the
TRISD register.
Note 2: In this mode the PORTD and PORTE input buffers are TTL. The control bits for the
PSP operation are located in TRISE.
EN
QD
CK
Data bus
WR Port
RD Port
One bit of PORTD
Set interrupt flag
PSPIF
PSP7:PSP0
TTL
TTL
Read
Chip Select
Write
RD
CS
WR
Note: I/O pins have protection diodes to VDD and VSS.
EN
QD
EN
TTL
TTL
1997 Microchip Technology Inc. DS31010A-page 10-3
Section 10. Parallel Slave Port
Parallel
Slave Port
10
10.2 Control Register
Register 10-1: TRISE Register
R-0 R-0 R/W-0 R/W-0 U-0 R/W-1 R/W-1 R/W-1
IBF OBF IBOV PSPMODE TRISE2 TRISE1 TRISE0
bit 7 bit 0
bit 7 IBF: Input Buffer Full Status bit
1 = A word has been received and waiting to be read by the CPU
0 = No word has been received
bit 6 OBF: Output Buffer Full Status bit
1 = The output buffer still holds a previously written word
0 = The output buffer has been read
bit 5 IBOV: Input Buffer Overflow Detect bit (in microprocessor mode)
1 = A write occurred when a previously input word has not been read
(must be cleared in software)
0 = No overflow occurred
bit 4 PSPMODE: Parallel Slave Port Mode Select bit
1 = Parallel slave port mode
0 = General purpose I/O mode
bit 3 Unimplemented: Read as '0'
bit 2 TRISE2: RE2 direction control bit
1 = Input
0 = Output
bit 1 TRISE1: RE1 direction control bit
1 = Input
0 = Output
bit 0 TRISE0: RE0 direction control bit
1 = Input
0 = Output
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31010A-page 10-4 1997 Microchip Technology Inc.
10.3 Operation
A write to the PSP from the external system, occurs when both the CS and WR lines are first
detected low . When either the CS or WR lines become high (edge triggered), the Input Buffer Full
status flag bit IBF (TRISE<7>) is set on the Q4 clock cycle , f ollo wing the next Q2 cycle, to signal
the write is complete. The interr upt flag bit, PSPIF, is also set on the same Q4 clock cycle. The
IBF flag bit is inhibited from being cleared f or additional TCY cycles (see parameter 66). If the IBF
flag bit is cleared by reading the PORTD input latch, and this has to be a read-only instr uction
(i.e., MOVF) and not a read-modify-write instruction. The input Buff er Ov erflow status flag bit IBO V
(TRISE<5>) is set if a second write to the Par allel Slave P ort is attempted when the previous b yte
has not been read out of the buffer.
A read from the PSP from the exter nal system, occurs when both the CS and RD lines are first
detected low. The Output Buffer Full status flag bit OBF (TRISE<6>) is cleared immediately indi-
cating that the PORTD latch was read by the external bus. When either the CS or RD pin
becomes high (edge triggered), the interrupt flag bit PSPIF is set on the Q4 cloc k cycle, f ollowing
the next Q2 cycle, indicating that the read is complete. OBF remains low until data is written to
PORTD by the user firmware.
Input Buffer Full Status Flag bit IBF, is set if a received word is waiting to be read by the CPU.
Once the PORT input latch is read, the IBF bit is cleared. The IBF bit is a read only status bit.
Output Buff er Full Status Flag bit OBF, is set if a word written to POR T latch is w aiting to be read
by the e xternal b us. Once the PORTD output latch is read b y the microprocessor , OBF is cleared.
Input Buffer Overflow Status Flag bit IBOV is set if a second write to the microprocessor port is
attempted when the previous word has not been read by the CPU (the first word is retained in
the buffer).
When not in Parallel Slave Por t mode, the IBF and OBF bits are held clear. However, if flag bit
IBOV was previously set, it must be cleared in the software.
An interrupt is generated and latched into flag bit PSPIF when a read or a write operation is com-
pleted. Interr upt flag bit PSPIF must be cleared by user software and the interrupt can be dis-
abled by clearing interrupt enable bit PSPIE.
Table 10-1: PORTE Functions
Name Function
RD Read Control Input in parallel slave port mode:
RD
1 = Not a read operation
0 = Read operation. Reads PORTD register (if chip selected)
WR Write Control Input in parallel slave port mode:
WR
1 = Not a write operation
0 = Write operation. Writes PORTD register (if chip selected)
CS Chip Select Control Input in parallel slave port mode:
CS
1 = Device is not selected
0 = Device is selected
Note: The PSP may have other functions multiplexed onto the same pins. For the PSP to
operate, the pins must be configured as digital I/O.
1997 Microchip Technology Inc. DS31010A-page 10-5
Section 10. Parallel Slave Port
Parallel
Slave Port
10
10.4 Operation in Sleep Mode
When in sleep mode the microprocessor may still read and wr ite the Parallel Slave Por t. These
actions will set the PSPIF bit. If the PSP interrupts are enab led, this will wak e the processor from
sleep mode so that the PSP data latch may be either read, or wr itten with the next value for the
microprocessor.
10.5 Effect of a Reset
After any reset the PSP is disabled and PORTD and PORTE are forced to their default mode.
10.6 PSP Waveforms
Figure 10-2 shows the waveform for a write from the microprocessor to the PSP, while
Figure 10-3 shows the waveform for a read of the PSP by the microprocessor.
Figure 10-2: Parallel Slave Port Write Waveforms
Figure 10-3: Parallel Slave Port Read Waveforms
Q1 Q2 Q3 Q4
CS
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
WR
RD
IBF
OBF
PSPIF
PORTD<7:0>
Note: The IBF flag bit is inhibited from being cleared until after this point.
Q1 Q2 Q3 Q4
CS
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
WR
IBF
PSPIF
RD
OBF
PORTD<7:0>
PICmicro MID-RANGE MCU FAMILY
DS31010A-page 10-6 1997 Microchip Technology Inc.
10.7 Design Tips
Question 1:
Migrating from the PIC16C74 to the PIC16C74A, the operation of the PSP
seems to have changed.
Answer 1:
Yes, a design change was made so the PIC16C74A is edge sensitive (while the PIC16C74 was
level sensitive). See Appendix C.9 for more information.
1997 Microchip Technology Inc. DS31010A-page 10-7
Section 10. Parallel Slave Port
Parallel
Slave Port
10
10.8 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the Parallel
Slave Port are:
Title Application Note #
Using the 8-bit Parallel Slave Port AN579
PICmicro MID-RANGE MCU FAMILY
DS31010A-page 10-8 1997 Microchip Technology Inc.
10.9 Revision History
Revision A
This is the initial released revision of the Parallel Slave Port description.
1997 Microchip Technology Inc. DS31011A page 11-1
Timer0
11
M
Section 11. Timer0
HIGHLIGHTS
This section of the manual contains the following major topics:
11.1 Introduction..................................................................................................................11-2
11.2 Control Register...........................................................................................................11-3
11.3 Operation .....................................................................................................................11-4
11.4 TMR0 Interrupt.............................................................................................................11-5
11.5 Using Timer0 with an External Clock...........................................................................11-6
11.6 TMR0 Prescaler...........................................................................................................11-7
11.7 Design Tips ................................................................................................................11-10
11.8 Related Application Notes..........................................................................................11-11
11.9 Revision History.........................................................................................................11-12
PICmicro MID-RANGE MCU FAMILY
DS31011A-page 11-2 1997 Microchip Technology Inc.
11.1 Introduction
The Timer0 module has the following features:
8-bit timer/counter
Readable and writable
8-bit software programmable prescaler
Clock source selectable to be external or internal
Interrupt on overflow from FFh to 00h
Edge select for external clock
Figure 11-1 shows a simplified block diagram of the Timer0 module.
Figure 11-1: Timer0 Block Diagram
Note: To achieve a 1:1 prescaler assignment for the TMR0 register, assign the prescaler
to the Watchdog Timer.
Note 1: T0CS, T0SE, PSA, PS2:PS0 (OPTION_REG<5:0>).
2: The prescaler is shared with Watchdog Timer (refer to Figure 11-6 for detailed block diagram).
T0CKI pin
T0SE
0
1
1
0
T0CS
FOSC/4
Programmable
Prescaler
Sync with
Internal
clocks TMR0
PSout
(2 cycle delay)
PSout
Data bus
8
PSA
PS2, PS1, PS0 Set interrupt
flag bit T0IF
on overflow
3
1997 Microchip Technology Inc. DS31011A-page 11-3
Section 11. Timer0
Timer0
11
11.2 Control Register
The OPTION_REG register is a readable and writable register which contains v arious control bits
to configure the TMR0/WDT prescaler, the External INT Interrupt, TMR0, and the weak pull-ups
on PORTB.
Register 11-1: OPTION_REG Register
Note: To achieve a 1:1 prescaler assignment for the TMR0 register, assign the prescaler
to the Watchdog Timer.
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
RBPU (1) INTEDG T0CS T0SE PSA PS2 PS1 PS0
bit 7 bit 0
bit 7 RBPU (1): Weak Pull-up Enable bit
1 = Weak pull-ups are disabled
0 = Weak pull-ups are enabled by individual port latch values
bit 6 INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of INT pin
0 = Interrupt on falling edge of INT pin
bit 5 T0CS: TMR0 Clock Source Select bit
1 = Transition on T0CKI pin
0 = Internal instruction cycle clock (CLKOUT)
bit 4 T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on T0CKI pin
0 = Increment on low-to-high transition on T0CKI pin
bit 3 PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
bit 2:0 PS2:PS0: Prescaler Rate Select bits
000
001
010
011
100
101
110
111
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
Bit Value TMR0 Rate WDT Rate
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note 1: Some devices call this bit GPPU. Devices that have the RBPU bit, have the weak
pull-ups on PORTB, while devices that have the GPPU have the weak pull-ups on
the GPIO Port.
PICmicro MID-RANGE MCU FAMILY
DS31011A-page 11-4 1997 Microchip Technology Inc.
11.3 Operation
Timer mode is selected by clearing the T0CS bit (OPTION<5>). In timer mode, the Timer0 mod-
ule will increment every instr uction cycle (without prescaler). If the TMR0 register is written, the
increment is inhibited for the following two instruction cycles (Figure 11-2 and Figure 11-3). The
user can work around this by writing an adjusted value to the TMR0 register.
Counter mode is selected by setting the T0CS bit (OPTION<5>). In counter mode, Timer0 will
increment either on e very rising or falling edge of the T0CKI pin. The incrementing edge is deter-
mined by the Timer0 Source Edge Select the T0SE bit (OPTION<4>). Clearing the T0SE bit
selects the rising edge. Restrictions on the external clock input are discussed in detail in Subsec-
tion 11.5 “Using Timer0 with an External Clock” .
The prescaler is mutually exclusively shared between the Timer0 module and the Watchdog
Timer. The prescaler assignment is controlled in software by the PSA control bit (OPTION<3>).
Clearing the PSA bit will assign the prescaler to the Timer0 module. The prescaler is not readable
or writable. When the prescaler is assigned to the Timer0 module, prescale v alues of 1:2, 1:4,...,
1:256 are selectable . Subsection 11.6 “TMR0 Prescaler” details the oper ation of the prescaler.
Any write to the TMR0 register will cause a 2 instr uction cycle (2TCY) inhibit. That is, after the
TMR0 register has been written with the new v alue , TMR0 will not be incremented until the third
instruction cycle later (Figure 11-2). When the prescaler is assigned to the Timer0 module, any
write to the TMR0 register will immediately update the TMR0 register and clear the prescaler . The
incrementing of Timer0 (TMR0 and Prescaler) will also be inhibited 2 instruction cycles (TCY). So
if the prescaler is configured as 2, then after a write to the TMR0 register TMR0 will not increment
for 4 Timer0 clocks (Figure 11-3). After that, TMR0 will increment every prescaler number of
clocks later.
Figure 11-2: Timer0 Timing: Internal Clock/No Prescale
Figure 11-3: Timer0 Timing: Internal Clock/Prescale 1:2
PC-1
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
PC
(Program
Counter)
Instruction
Fetch
TMR0
PC PC+1 PC+2 PC+3 PC+4 PC+5 PC+6
T0 T0+1 T0+2 NT0 NT0 NT0 NT0+1 NT0+2 T
0
MO VWF TMR0 MOVF TMR0,WMOVF TMR0,WMOVF TMR0,W MO VF TMR0,WMO VF TMR0,W
Write TMR0
executed Read TMR0
reads NT0 Read TMR0
reads NT0 Read TMR0
reads NT0 Read TMR0
reads NT0 + 1 Read TMR0
reads NT0 + 2
Instruction
Executed
PC-1
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
PC
(Program
Counter)
Instruction
Fetch
TMR0
PC PC+1 PC+2 PC+3 PC+4 PC+5 PC+6
T0 NT0+1
MO VWF TMR0 MO VF TMR0,WMO VF TMR0,WMOVF TMR0,W MO VF TMR0,WMOVF TMR0,W
Write TMR0
executed Read TMR0
reads NT0 Read TMR0
reads NT0 Read TMR0
reads NT0 Read TMR0
reads NT0 Read TMR0
reads NT0 + 1
T0+1 NT0
Instruction
Execute
1997 Microchip Technology Inc. DS31011A-page 11-5
Section 11. Timer0
Timer0
11
11.4 TMR0 Interrupt
The TMR0 interrupt is generated when the TMR0 register overflows from FFh to 00h. This
overflow sets bit T0IF (INTCON<2>). The interrupt can be masked by clearing bit T0IE
(INTCON<5>). Bit T0IF must be cleared in software by the Timer0 module interrupt service rou-
tine before re-enabling this interrupt. The TMR0 interrupt cannot awaken the processor from
SLEEP since the timer is shut-off during SLEEP. See Figure 11-4 for Timer0 interrupt timing.
Figure 11-4: TMR0 Interrupt Timing
Q2Q1 Q3 Q4Q2Q1 Q3 Q4 Q2Q1 Q3 Q4 Q2Q1 Q3 Q4 Q2Q1 Q3 Q4
11
OSC1
CLKOUT(3)
Timer0
T0IF bit
FEh
GIE bit
INSTRUCTION
PC
Instruction
fetched
PC PC +1 PC +1 0004h 0005h
Instruction
executed
Inst (PC)
Inst (PC-1)
Inst (PC+1)
Inst (PC)
Inst (0004h) Inst (0005h)
Inst (0004h)Dummy cycle Dummy cycle
FFh 00h 01h 02h
Note 1: Interrupt flag bit T0IF is sampled here (every Q1).
2: Interrupt latency = 4TCY where TCY = instruction cycle time.
3: CLKOUT is available only in RC oscillator mode.
FLOW
PICmicro MID-RANGE MCU FAMILY
DS31011A-page 11-6 1997 Microchip Technology Inc.
11.5 Using Timer0 with an External Clock
When an exter nal clock input is used for Timer0, it must meet cer tain requirements as detailed
in 11.5.1 “External Clock Synchronization. These requirements ensure the external clock
can be synchronized with the internal phase clock (TOSC). Also, there is a delay in the actual
incrementing of Timer0 after synchronization.
11.5.1 External Clock Synchronization
When no prescaler is used, the e xternal clock input is the same as the prescaler output. The syn-
chronization of T0CKI with the internal phase clocks is accomplished by sampling the prescaler
output on the Q2 and Q4 cycles of the internal phase clocks (Figure 11-5). Therefore, it is nec-
essary f or T0CKI to be high f or at least 2Tosc (and a small RC dela y of 20 ns) and low f or at least
2Tosc (and a small RC delay of 20 ns). Refer to parameters 40 , 41 and 42 in the electrical spec-
ification of the desired device.
When a prescaler is used, the e xternal clock input is divided by an asynchronous ripple-counter
type prescaler so that the prescaler output is symmetrical. For the external clock to meet the
sampling requirement, the ripple-counter must be taken into account. Therefore, it is necessar y
f or T0CKI to hav e a period of at least 4Tosc (and a small RC delay of 40 ns) divided b y the pres-
caler value . The only requirement on T0CKI high and low time is that the y do not violate the min-
imum pulse width requirement of 10 ns. Refer to parameters 40, 41 and 42 in the electrical
specification of the desired device.
11.5.2 TMR0 Increment Delay
Since the prescaler output is synchronized with the internal clocks, there is a small delay from
the time the exter nal clock edge occurs to the time the Timer0 module is actually incremented.
Figure 11-5 shows the delay from the external clock edge to the timer incrementing.
Figure 11-5: Timer0 Timing with External Clock
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
External Clock Input or
Prescaler output (2)
External Clock/Prescaler
Output after sampling
Increment Timer0 (Q4)
Timer0 T0 T0 + 1 T0 + 2
Small pulse
misses sampling
Note 1: Delay from clock input change to Timer0 increment is 3Tosc to 7Tosc. (Duration of Q = Tosc).
Therefore, the error in measuring the interval between two edges on Timer0 input = ±4Tosc max.
2: External clock if no prescaler selected, Prescaler output otherwise.
3: The arrows indicate the points in time where sampling occurs.
(3) (1)
1997 Microchip Technology Inc. DS31011A-page 11-7
Section 11. Timer0
Timer0
11
11.6 TMR0 Prescaler
An 8-bit counter is available as a prescaler for the Timer0 module, or as a postscaler for the
Watchdog Timer (Figure 11-6). For simplicity, this counter is being referred to as “prescaler” in
the Timer0 description. Thus , a prescaler assignment for the Timer0 module means that there is
no postscaler for the Watchdog Timer, and vice-versa.
The PSA and PS2:PS0 bits (OPTION<3:0>) determine the prescaler assignment and prescale
ratio.
When assigned to the Timer0 module, all instructions writing to the TMR0 register (e.g.,
CLRF TMR0, MOVWF TMR0, BSF TMR0,x....etc.) will clear the prescaler. When assigned to WDT,
a CLRWDT instruction will clear the prescaler along with the Watchdog Timer . The prescaler is not
readable or writable.
Figure 11-6: Block Diagram of the Timer0/WDT Prescaler
Note: There is only one prescaler available which is mutually exclusively shared between
the Timer0 module and the Watchdog Timer.
T0CKI pin
T0SE
M
U
X
CLKOUT (=Fosc/4)
SYNC
2
Cycles TMR0 reg
8-bit Prescaler
8 - to - 1MUX
M
U
X
M U X
Watchdog
Timer
PSA
01
0
1
WDT
Time-out
PS2:PS0
8
Note: T0CS, T0SE, PSA, PS2:PS0 are (OPTION_REG<5:0>).
PSA
WDT Enable bit
M
U
X
0
10
1
Data Bus
Set T0IF flag bit
on Overflow
8
PSA
T0CS
PICmicro MID-RANGE MCU FAMILY
DS31011A-page 11-8 1997 Microchip Technology Inc.
11.6.1 Switching Prescaler Assignment
The prescaler assignment is fully under software control, i.e., it can be changed “on the fly” during
program execution.
In Example 11-1, the first modification of the OPTION_REG does not need to be included if the
final desired prescaler is other then 1:1. If the final prescaler value is to be 1:1, then a temporary
prescale value is set (other than 1:!), and the final prescale v alue is set in the last modification of
OPTION_REG.
Example 11-1: Changing Prescaler (Timer0WDT)
To change prescaler from the WDT to the Timer0 module use the sequence shown in
Example 11-2.
Example 11-2: Changing Prescaler (WDTTimer0)
Note: To avoid an unintended device RESET, the following instruction sequence
(shown in Example 11-1) must be executed when changing the prescaler
assignment from Timer0 to the WDT. This sequence must be follo wed e v en if
the WDT is disabled.
1) BSF STATUS, RP0 ;Bank1
Lines 2 and 3 do
NOT have to be
included if the final
desired prescale
value is other than
1:1. If 1:1 is final
desired value, then a
temporary prescale
value is set in lines 2
and 3 and the final
prescale value will
be set in lines 10
and 11.
2) MOVLW b'xx0x0xxx' ;Select clock source and prescale value of
3) MOVWF OPTION_REG ;other than 1:1
4) BCF STATUS, RP0 ;Bank0
5) CLRF TMR0 ;Clear TMR0 and prescaler
6) BSF STATUS, RP1 ;Bank1
7) MOVLW b'xxxx1xxx' ;Select WDT, do not change prescale value
8) MOVWF OPTION_REG ;
9) CLRWDT ;Clears WDT and prescaler
10) MOVLW b'xxxx1xxx' ;Select new prescale value and WDT
11) MOVWF OPTION_REG ;
12) BCF STATUS, RP0 ;Bank0
CLRWDT ; Clear WDT and prescaler
BSF STATUS, RP0 ; Bank1
MOVLW b'xxxx0xxx' ; Select TMR0, new prescale
MOVWF OPTION_REG ; value and clock source
BCF STATUS, RP0 ; Bank0
1997 Microchip Technology Inc. DS31011A-page 11-9
Section 11. Timer0
Timer0
11
11.6.2 Initialization
Since Timer0 has a software programmable clock source, there are two examples to show the
initialization of Timer0 with each source. Example 11-3 shows the initialization for the internal
clock source (timer mode), while Example 11-4 shows the initialization for the external clock
source (counter mode).
Example 11-3: Timer0 Initialization (Internal Clock Source)
Example 11-4: Timer0 Initialization (External Clock Source)
CLRF TMR0 ; Clear Timer0 register
CLRF INTCON ; Disable interrupts and clear T0IF
BSF STATUS, RP0 ; Bank1
MOVLW 0xC3 ; PortB pull-ups are disabled,
MOVWF OPTION_REG ; Interrupt on rising edge of RB0
; Timer0 increment from internal clock
; with a prescaler of 1:16.
BCF STATUS, RP0 ; Bank0
;** BSF INTCON, T0IE ; Enable TMR0 interrupt
;** BSF INTCON, GIE ; Enable all interrupts
;
; The TMR0 interrupt is disabled, do polling on the overflow bit
;
T0_OVFL_WAIT
BTFSS INTCON, T0IF
GOTO T0_OVFL_WAIT
; Timer has overflowed
CLRF TMR0 ; Clear Timer0 register
CLRF INTCON ; Disable interrupts and clear T0IF
BSF STATUS, RP0 ; Bank1
MOVLW 0x37 ; PortB pull-ups are enabled,
MOVWF OPTION_REG ; Interrupt on falling edge of RB0
; Timer0 increment from external clock
; on the high-to-low transition of T0CKI
; with a prescaler of 1:256.
BCF STATUS, RP0 ; Bank0
;** BSF INTCON, T0IE ; Enable TMR0 interrupt
;** BSF INTCON, GIE ; Enable all interrupts
;
; The TMR0 interrupt is disabled, do polling on the overflow bit
;
T0_OVFL_WAIT
BTFSS INTCON, T0IF
GOTO T0_OVFL_WAIT
; Timer has overflowed
PICmicro MID-RANGE MCU FAMILY
DS31011A-page 11-10 1997 Microchip Technology Inc.
11.7 Design Tips
Question 1:
I am implementing a counter/clock, but the clock loses time or is
inaccurate.
Answer 1:
If you are polling TMR0 to see if it has rolled over to zero. You could do this by executing:
wait MOVF TMR0,W ; read the timer into W
BTFSS STATUS,Z ; see if it was zero, if so,
; break from loop
GOTO wait ; if not zero yet, keep waiting
Two possible scenarios to lose clock cycles are:
1. If you are incrementing TMR0 from the internal instruction clock, or an external source that
is about as f ast, the overflo w could occur during the two cycle GOTO, so you could miss it.
In this case the TMR0 source should be prescaled.
Or you could do a test to see if it has rolled o ver b y checking f or less than a nominal value:
Wait movlw 3
subwf TMR0,W
btfsc STATUS,C
goto Wait
2. When writing to TMR0, two instruction clock cycles are lost. Often you ha ve a specific time
period you want to count, say 100 decimal. In that case you might put 156 into TMR0
(256 - 100 = 156). Ho w ever, since two instruction cycles are lost when you write to TMR0
(for internal logic synchronization), you should actually write 158 to the timer.
1997 Microchip Technology Inc. DS31011A-page 11-11
Section 11. Timer0
Timer0
11
11.8 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to Timer0 are:
Title Application Note #
Frequency Counter Using PIC16C5X AN592
A Clock Design using the PIC16C54 for LED Display and Switch Inputs AN590
PICmicro MID-RANGE MCU FAMILY
DS31011A-page 11-12 1997 Microchip Technology Inc.
11.9 Revision History
Revision A
This is the initial released revision of the Timer0 Module description.
1997 Microchip Technology Inc. DS31012A page 12-1
M
Timer1
12
Section 12. Timer1
HIGHLIGHTS
This section of the manual contains the following major topics:
12.1 Introduction..................................................................................................................12-2
12.2 Control Register...........................................................................................................12-3
12.3 Timer1 Operation in Timer Mode .................................................................................12-4
12.4 Timer1 Operation in Synchronized Counter Mode.......................................................12-4
12.5 Timer1 Operation in Asynchronous Counter Mode......................................................12-5
12.6 Timer1 Oscillator..........................................................................................................12-7
12.7 Sleep Operation...........................................................................................................12-9
12.8 Resetting Timer1 Using a CCP Trigger Output ............................................................12-9
12.9 Resetting of Timer1 Register Pair (TMR1H:TMR1L)....................................................12-9
12.10 Timer1 Prescaler..........................................................................................................12-9
12.11 Initialization................................................................................................................12-10
12.12 Design Tips................................................................................................................12-12
12.13 Related Application Notes..........................................................................................12-13
12.14 Revision History.........................................................................................................12-14
PICmicro MID-RANGE MCU FAMILY
DS31012A-page 12-2 1997 Microchip Technology Inc.
12.1 Introduction
The Timer1 module is a 16-bit timer/counter consisting of two 8-bit registers (TMR1H and
TMR1L) which are readable and writable . The TMR1 Register pair (TMR1H:TMR1L) increments
from 0000h to FFFFh and rolls over to 0000h. The Timer1 Interrupt, if enabled, is generated on
overflow which is latched in the TMR1IF interrupt flag bit. This interrupt can be enabled/disabled
by setting/clearing the TMR1IE interrupt enable bit.
Timer1 can operate in one of three modes:
As a synchronous timer
As a synchronous counter
As an asynchronous counter
The operating mode is determined by clock select bit, TMR1CS (T1CON<1>), and the synchro-
nization bit, T1SYNC (Figure 12-1).
In timer mode, Timer1 increments every instruction cycle. In counter mode, it increments on
every rising edge of the external clock input on pin T1CKI.
Timer1 can be turned on and off using theTMR1ON control bit (T1CON<0>).
Timer1 also has an internal “reset input”, which can be generated by a CCP module.
Timer1 has the capability to operate off an e xternal crystal. When the Timer1 oscillator is enab led
(T1OSCEN is set), the T1OSI and T1OSO pins become inputs . That is, their corresponding TRIS
values are ignored.
Figure 12-1: Timer1 Block Diagram
TMR1H TMR1L
T1OSC T1SYNC
TMR1CS
T1CKPS1:T1CKPS0 SLEEP input
T1OSCEN
Enable
Oscillator(1) FOSC/4
Internal
Clock
TMR1ON
on/off
Prescaler
1, 2, 4, 8 Synchronize
det
1
0
0
1
Synchronized
clock input
2
T1OSO/
T1OSI
Note 1: When the T1OSCEN bit is cleared, the inverter and feedback resistor are turned
off. This eliminates power drain.
Set TMR1IF flag bit
on Overflow TMR1
T1CKI
CLR
CCP Special Trigger
1997 Microchip Technology Inc. DS31012A-page 12-3
Section 12. Timer1
Timer1
12
12.2 Control Register
Register 12-1 shows the Timer1 control register.
Register 12-1: T1CON: Timer1 Control Register
U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON
bit 7 bit 0
bit 7:6 Unimplemented: Read as '0'
bit 5:4 T1CKPS1:T1CKPS0: Timer1 Input Clock Prescale Select bits
11 = 1:8 Prescale value
10 = 1:4 Prescale value
01 = 1:2 Prescale value
00 = 1:1 Prescale value
bit 3 T1OSCEN: Timer1 Oscillator Enable bit
1 = Oscillator is enabled
0 = Oscillator is shut off. The oscillator inverter and feedback resistor are turned off to
eliminate power drain
bit 2 T1SYNC: Timer1 External Clock Input Synchronization Select bit
When TMR1CS = 1:
1 = Do not synchronize external clock input
0 = Synchronize external clock input
When TMR1CS = 0:
This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0.
bit 1 TMR1CS: Timer1 Clock Source Select bit
1 = External clock from pin T1OSO/T1CKI (on the rising edge)
0 = Internal clock (FOSC/4)
bit 0 TMR1ON: Timer1 On bit
1 = Enables Timer1
0 = Stops Timer1
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31012A-page 12-4 1997 Microchip Technology Inc.
12.3 Timer1 Operation in Timer Mode
Timer mode is selected by clearing the TMR1CS (T1CON<1>) bit. In this mode, the input clock
to the timer is FOSC/4. The synchronize control bit, T1SYNC (T1CON<2>), has no effect since
the internal clock is always synchronized.
12.4 Timer1 Operation in Synchronized Counter Mode
Counter mode is selected by setting the TMR1CS bit. In this mode the timer increments on e v ery
rising edge of clock input on the T1OSI pin when the oscillator enable bit (T1OSCEN) is set, or
the T1OSO/T1CKI pin when the T1OSCEN bit is cleared.
If the T1SYNC bit is cleared, then the external clock input is synchronized with internal phase
clocks . The synchronization is done after the prescaler stage. The prescaler is an asynchronous
ripple-counter.
In this configuration, during SLEEP mode, Timer1 will not increment even if the external clock is
present, since the synchronization circuit is shut off. The prescaler however will continue to
increment.
12.4.1 External Clock Input Timing for Synchronized Counter Mode
When an e xternal cloc k input is used for Timer1 in synchronized counter mode, it m ust meet cer-
tain requirements. The external clock requirement is due to internal phase clock (Tosc) synchro-
nization. Also, there is a delay in the actual incrementing of TMR1 after synchronization.
When the prescaler is 1:1, the e xternal clock input is the same as the prescaler output. The syn-
chronization of T1CKI with the internal phase clocks is accomplished by sampling the prescaler
output on alternating Tosc clocks of the inter nal phase clocks. Therefore, it is necessary for the
T1CKI pin to be high for at least 2Tosc (and a small RC delay) and low for at least 2Tosc (and a
small RC delay). Refer to parameters 45, 46, and 47 in the “Electrical Specifications” section.
When a prescaler other than 1:1 is used, the e xternal clock input is divided by the asynchronous
ripple-counter prescaler so that the prescaler output is symmetrical. In order for the external
clock to meet the sampling requirement, the ripple-counter must be taken into account. There-
fore, it is necessar y for the T1CKI pin to have a period of at least 4Tosc (and a small RC delay)
divided by the prescaler value. Another requirement on the T1CKI pin high and low time is that
they do not violate the minimum pulse width requirements). Refer to parameters 40, 42, 45, 46,
and 47 in the “Electrical Specifications” section.
1997 Microchip Technology Inc. DS31012A-page 12-5
Section 12. Timer1
Timer1
12
12.5 Timer1 Operation in Asynchronous Counter Mode
If T1SYNC (T1CON<2>) is set, the e xternal clock input is not synchronized. The timer continues
to increment asynchronously to the internal phase clocks. The timer will continue to run during
SLEEP and can generate an interrupt on overflow which will wake-up the processor. However,
special precautions in software are needed to read/write the timer (Subsection 12.5.2 “Reading
and Writing Timer1 in Asynchronous Counter Mode”). Since the counter can operate in
sleep, Timer1 can be used to implement a true real-time clock.
In asynchronous counter mode, Timer1 cannot be used as a time-base for capture or compare
operations.
12.5.1 External Clock Input Timing with Unsynchronized Clock
If the T1SYNC control bit is set, the timer will increment completely asynchronously. The input
clock m ust meet certain minimum high time and low time requirements . Refer to the De vice Data
Sheet Electrical Specifications Section, timing parameters 45, 46, and 47.
12.5.2 Reading and Writing Timer1 in Asynchronous Counter Mode
Reading TMR1H or TMR1L while the timer is running from an exter nal asynchronous clock, will
guarantee a valid read (taken care of in hardware). However, the user should keep in mind that
reading the 16-bit timer in two 8-bit values itself poses certain problems since the timer may
overflow between the reads.
F or writes, it is recommended that the user simply stop the timer and write the desired values . A
write contention may occur b y writing to the timer registers while the register is incrementing. This
may produce an unpredictable value in the timer register.
Reading the 16-bit value requires some care, since two separate reads are required to read the
entire 16-bits. Example 12-1 shows why this may not be a straight forward read of the 16-bit
register.
Example 12-1: Reading 16-bit Register Issues
TMR1 Sequence 1 Sequence 2
Action TMPH:TMPL Action TMPH:TMPL
04FFh READ TMR1L xxxxh READ TMR1H xxxxh
0500h Store in TMPL xxFFh Store in TMPH 04xxh
0501h READ TMR1H xxFFh READ TMR1L 04xxh
0502h Store in TMPH 05FFh Store in TMPL 0401h
PICmicro MID-RANGE MCU FAMILY
DS31012A-page 12-6 1997 Microchip Technology Inc.
Example 12-2 shows a routine to read the 16-bit timer v alue with e xperiencing the issues shown
in Example 12-1. This is useful if the timer cannot be stopped.
Example 12-2: Reading a 16-bit Free-Running Timer
Writing a 16-bit value to the 16-bit TMR1 register is straight forward. First the TMR1L register is
cleared to ensure that there are many Timer1 cloc k/oscillator cycles before there is a rollo ver into
the TMR1H register. The TMR1H register is then loaded, and finally the TMR1L register is loaded.
Example 12-3 shows this:
Example 12-3: Writing a 16-bit Free Running Timer
; All interrupts are disabled
MOVF TMR1H, W ; Read high byte
MOVWF TMPH ;
MOVF TMR1L, W ; Read low byte
MOVWF TMPL ;
MOVF TMR1H, W ; Read high byte
SUBWF TMPH, W ; Sub 1st read with 2nd read
BTFSC STATUS,Z ; Is result = 0
GOTO CONTINUE ; Good 16-bit read
;
; TMR1L may have rolled over between the read of the high and low bytes.
; Reading the high and low bytes now will read a good value.
;
MOVF TMR1H, W ; Read high byte
MOVWF TMPH ;
MOVF TMR1L, W ; Read low byte
MOVWF TMPL ;
; Re-enable the Interrupt (if required)
CONTINUE ; Continue with your code
; All interrupts are disabled
CLRF TMR1L ; Clear Low byte, Ensures no
; rollover into TMR1H
MOVLW HI_BYTE ; Value to load into TMR1H
MOVWF TMR1H, F ; Write High byte
MOVLW LO_BYTE ; Value to load into TMR1L
MOVWF TMR1H, F ; Write Low byte
; Re-enable the Interrupt (if required)
CONTINUE ; Continue with your code
1997 Microchip Technology Inc. DS31012A-page 12-7
Section 12. Timer1
Timer1
12
12.6 Timer1 Oscillator
A cr ystal oscillator circuit is built in between pins T1OSI (input) and T1OSO (amplifier output). It
is enabled by setting the T1OSCEN control bit (T1CON<3>). The oscillator is a low power
oscillator, rated up to 200 kHz operation. It will continue to run during SLEEP. It is primarily
intended f or a 32 kHz crystal, which is an ideal frequency for real-time k eeping. Table 12-1 shows
the capacitor selection for the Timer1 oscillator.
The Timer1 oscillator is identical to the LP oscillator . The user must provide a softw are time delay
to ensure proper oscillator start-up.
Table 12-1: Capacitor Selection for the Timer1 Oscillator
Note: This allows the counter to operate (increment) when the device is in sleep mode,
which allows Timer1 to be used as a real-time clock.
Osc Type Freq C1 C2
LP 32 kHz 33 pF 33 pF
100 kHz 15 pF 15 pF
200 kHz 15 pF 15 pF
Crystals Tested:
32.768 kHz Epson C-001R32.768K-A ± 20 PPM
100 kHz Epson C-2 100.00 KC-P ± 20 PPM
200 kHz STD XTL 200.000 kHz ± 20 PPM
Note 1: Higher capacitance increases the stability of oscillator but also increases the start-up
time.
2: Since each resonator/crystal has its own characteristics, the user should consult the
resonator/crystal manufacturer for appropriate values of external components.
PICmicro MID-RANGE MCU FAMILY
DS31012A-page 12-8 1997 Microchip Technology Inc.
12.6.1 Typical Application
This f eature is typically used in applications where real-time needs to be kept, b ut it is also desir-
able to have the lowest possible power consumption. The Timer1 oscillator allows the device to
be placed in sleep, while the timer continues to increment. When Timer1 overflows the interrupt
could wake-up the device so that the appropriate registers could be updated.
Figure 12-2: Timer1 Application
8
4
4
44 x 4
Keypad
current sink
TMR1
VSS
PIC16CXXX
VDD
32 kHz
Backup
Battery
power-down
detect
T1OSI
T1OSO
OSC1
1997 Microchip Technology Inc. DS31012A-page 12-9
Section 12. Timer1
Timer1
12
12.7 Sleep Operation
When Timer1 is configured for asynchronous operation, the TMR1 registers will continue to
increment for each timer clock (or prescale multiple of clocks). When the TMR1 register over-
flows, the TMR1IF bit will get set, and if enabled generate an interrupt that will wake the
processor from sleep mode.
The Timer1 oscillator will add a delta current, due to the operation of this circuitr y. That is, the
power-down current will no longer only be the leakage current of the device, but also the active
current of the Timer1 oscillator and other Timer1 circuitry.
12.8 Resetting Timer1 Using a CCP Trigger Output
If a CCP module is configured in compare mode to generate a “special event trigger”
(CCP1M3:CCP1M0 = 1011), this signal resets Timer1.
Timer1 must be configured for either timer or synchronized counter mode to take advantage of
the special event trigger feature. If Timer1 is r unning in asynchronous counter mode, this reset
operation may not work, and should not be used.
In the event that a write to Timer1 coincides with a special event trigger from the CCP module,
the write will take precedence.
In this mode of operation, the CCPRxH:CCPRxL register pair effectively becomes the period
register for Timer1.
12.9 Resetting of Timer1 Register Pair (TMR1H:TMR1L)
TMR1H and TMR1L registers are not reset on a POR or any other reset, only b y the CCP special
event triggers.
T1CON register is reset to 00h on a Power-on Reset or a Brown-out Reset. In any other reset,
the register is unaffected.
12.10 Timer1 Prescaler
The prescaler counter is cleared on writes to the TMR1H or TMR1L registers.
Table 12-2: Registers Associated with Timer1 as a Timer/Counter
Note: The special event trigger from the CCP module does not set interrupt flag bit
TMR1IF.
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on
all other
resets
INTCON GIE PEIE T0IE INTE RBIE(2) T0IF INTF RBIF(2) 0000 000x 0000 000u
PIR TMR1IF (1) 00
PIE TMR1IE (1) 00
TMR1L Holding register for the Least Significant Byte of the 16-bit TMR1 register xxxx xxxx uuuu uuuu
TMR1H Holding register for the Most Significant Byte of the 16-bit TMR1 register xxxx xxxx uuuu uuuu
T1CON T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON --00 0000 --uu uuuu
Legend: x = unknown, u = unchanged, - = unimplemented read as '0'.
Shaded cells are not used by the Timer1 module.
Note 1: The placement of this bit is device dependent.
2: These bits may also be named GPIE and GPIF.
PICmicro MID-RANGE MCU FAMILY
DS31012A-page 12-10 1997 Microchip Technology Inc.
12.11 Initialization
Since Timer1 has a software programmable clock source, there are three examples to show the
initialization of each mode. Example 12-4 shows the initialization for the internal clock source,
Example 12-5 shows the initialization f or the e xternal cloc k source, and Example 12-6 shows the
initialization of the external oscillator mode.
Example 12-4: Timer1 Initialization (Internal Clock Source)
Example 12-5: Timer1 Initialization (External Clock Source)
CLRF T1CON ; Stop Timer1, Internal Clock Source,
; T1 oscillator disabled, prescaler = 1:1
CLRF TMR1H ; Clear Timer1 High byte register
CLRF TMR1L ; Clear Timer1 Low byte register
CLRF INTCON ; Disable interrupts
BSF STATUS, RP0 ; Bank1
CLRF PIE1 ; Disable peripheral interrupts
BCF STATUS, RP0 ; Bank0
CLRF PIR1 ; Clear peripheral interrupts Flags
MOVLW 0x30 ; Internal Clock source with 1:8 prescaler
MOVWF T1CON ; Timer1 is stopped and T1 osc is disabled
BSF T1CON, TMR1ON ; Timer1 starts to increment
;
; The Timer1 interrupt is disabled, do polling on the overflow bit
;
T1_OVFL_WAIT
BTFSS PIR1, TMR1IF
GOTO T1_OVFL_WAIT
;
; Timer has overflowed
;
BCF PIR1, TMR1IF
CLRF T1CON ; Stop Timer1, Internal Clock Source,
; T1 oscillator disabled, prescaler = 1:1
CLRF TMR1H ; Clear Timer1 High byte register
CLRF TMR1L ; Clear Timer1 Low byte register
CLRF INTCON ; Disable interrupts
BSF STATUS, RP0 ; Bank1
CLRF PIE1 ; Disable peripheral interrupts
BCF STATUS, RP0 ; Bank0
CLRF PIR1 ; Clear peripheral interrupts Flags
MOVLW 0x32 ; External Clock source with 1:8 prescaler
MOVWF T1CON ; Clock source is synchronized to device
; Timer1 is stopped and T1 osc is disabled
BSF T1CON, TMR1ON ; Timer1 starts to increment
;
; The Timer1 interrupt is disabled, do polling on the overflow bit
;
T1_OVFL_WAIT
BTFSS PIR1, TMR1IF
GOTO T1_OVFL_WAIT
;
; Timer has overflowed
;
BCF PIR1, TMR1IF
1997 Microchip Technology Inc. DS31012A-page 12-11
Section 12. Timer1
Timer1
12
Example 12-6: Timer1 Initialization (External Oscillator Clock Source)
CLRF T1CON ; Stop Timer1, Internal Clock Source,
; T1 oscillator disabled, prescaler = 1:1
CLRF TMR1H ; Clear Timer1 High byte register
CLRF TMR1L ; Clear Timer1 Low byte register
CLRF INTCON ; Disable interrupts
BSF STATUS, RP0 ; Bank1
CLRF PIE1 ; Disable peripheral interrupts
BCF STATUS, RP0 ; Bank0
CLRF PIR1 ; Clear peripheral interrupts Flags
MOVLW 0x3E ; External Clock source with oscillator
MOVWF T1CON ; circuitry, 1:8 prescaler, Clock source
; is asynchronous to device
; Timer1 is stopped
BSF T1CON, TMR1ON ; Timer1 starts to increment
;
; The Timer1 interrupt is disabled, do polling on the overflow bit
;
T1_OVFL_WAIT
BTFSS PIR1, TMR1IF
GOTO T1_OVFL_WAIT
;
; Timer has overflowed
;
BCF PIR1, TMR1IF
PICmicro MID-RANGE MCU FAMILY
DS31012A-page 12-12 1997 Microchip Technology Inc.
12.12 Design Tips
Question 1:
Timer1 does not seem to be keeping accurate time.
Answer 1:
There are a few reasons that this could occur
1. You should never write to Timer1, where that could cause the loss of time. In most cases
that means you should not write to the TMR1L register, but if the conditions are ok, you
ma y write to the TMR1H register . Normally you write to the TMR1H register if you want the
Timer1 overflow interrupt to be sooner then the full 16-bit time-out.
2. You should ensure the your layout uses good PCB layout techniques so that noise does
not couple onto the Timer1 oscillator lines.
1997 Microchip Technology Inc. DS31012A-page 12-13
Section 12. Timer1
Timer1
12
12.13 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to Timer1 are:
Title Application Note #
Using Timer1 in Asynchronous Clock Mode AN580
Low Power Real Time Clock AN582
Yet another Clock using the PIC16C92X AN649
PICmicro MID-RANGE MCU FAMILY
DS31012A-page 12-14 1997 Microchip Technology Inc.
12.14 Revision History
Revision A
This is the initial released revision of the Timer1 module description.
1997 Microchip Technology Inc. DS31013A page 13-1
M
Timer2
13
Section 13. Timer2
HIGHLIGHTS
This section of the manual contains the following major topics:
13.1 Introduction..................................................................................................................13-2
13.2 Control Register...........................................................................................................13-3
13.3 Timer Clock Source......................................................................................................13-4
13.4 Timer (TMR2) and Period (PR2) Registers..................................................................13-4
13.5 TMR2 Match Output.....................................................................................................13-4
13.6 Clearing the Timer2 Prescaler and Postscaler.............................................................13-4
13.7 Sleep Operation...........................................................................................................13-4
13.8 Initialization..................................................................................................................13-5
13.9 Design Tips ..................................................................................................................13-6
13.10 Related Application Notes............................................................................................13-7
13.11 Revision History...........................................................................................................13-8
PICmicro MID-RANGE MCU FAMILY
DS31013A-page 13-2 1997 Microchip Technology Inc.
13.1 Introduction
Timer2 is an 8-bit timer with a prescaler, a postscaler, and a period register. Using the prescaler
and postscaler at their maximum settings, the overflow time is the same as a 16-bit timer.
Timer2 is the PWM time-base when the CCP module(s) is used in the PWM mode.
Figure 13-1 shows a block diagram of Timer2. The postscaler counts the number of times that
the TMR2 register matched the PR2 register. This can be useful in reducing the overhead of the
interrupt service routine on the CPU performance.
Figure 13-1: Timer2 Block Diagram
Comparator
TMR2 Sets flag
TMR2 reg
output (1)
Reset
Postscaler
Prescaler
PR2 reg
2
FOSC/4
1:1 1:16
1:1, 1:4, 1:16
EQ
4
bit TMR2IF
Note: TMR2 register output can be software selected b y the SSP Module as a baud clock.
to
TOUTPS3:TOUTPS0
T2CKPS1:T2CKPS0
1997 Microchip Technology Inc. DS31013A-page 13-3
Section 13. Timer2
Timer2
13
13.2 Control Register
Register 13-1 shows the Timer2 control register.
Register 13-1: T2CON: Timer2 Control Register
U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0
bit
7bit 0
bit 7 Unimplemented: Read as '0'
bit 6:3 TOUTPS3:TOUTPS0: Timer2 Output Postscale Select bits
0000 = 1:1 Postscale
0001 = 1:2 Postscale
1111 = 1:16 Postscale
bit 2 TMR2ON: Timer2 On bit
1 = Timer2 is on
0 = Timer2 is off
bit 1:0 T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits
00 = Prescaler is 1
01 = Prescaler is 4
1x = Prescaler is 16
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31013A-page 13-4 1997 Microchip Technology Inc.
13.3 Timer Clock Source
The Timer2 module has one source of input clock, the device clock (FOSC/4). A prescale option
of 1:1, 1:4 or 1:16 is software selected by control bits T2CKPS1:T2CKPS0 (T2CON<1:0>).
13.4 Timer (TMR2) and Period (PR2) Registers
The TMR2 register is readable and writable, and is cleared on all device resets. Timer2 incre-
ments from 00h until it matches PR2 and then resets to 00h on the ne xt increment cycle . PR2 is
a readable and writable register.
TMR2 is cleared when a WDT, POR, MCLR, or a BOR reset occurs, while the PR2 register is set.
Timer2 can be shut off (disabled from incrementing) by clearing the TMR2ON control bit
(T2CON<2>). This minimizes the power consumption of the module.
13.5 TMR2 Match Output
The match output of TMR2 goes to two sources:
1. Timer2 Postscaler
2. SSP Clock Input
There are four bits which select the postscaler. This allows the postscaler a 1:1 to 1:16 scaling
(inclusive). After the postscaler overflows, the TMR2 interrupt flag bit (TMR2IF) is set to indicate
the Timer2 overflow. This is useful in reducing the softw are o v erhead of the Timer2 interrupt ser-
vice routine, since it will only execute once every postscaler # of matches.
The match output of TMR2 is also routed to the Synchronous Serial Port module, which ma y soft-
ware select this as the clock source for the shift clock.
13.6 Clearing the Timer2 Prescaler and Postscaler
The prescaler and postscaler counters are cleared when any of the following occurs:
a write to the TMR2 register
a write to the T2CON register
any device reset (Power-on Reset, MCLR reset, W atchdog Timer Reset, Brown-out Reset,
or Parity Error Reset)
13.7 Sleep Operation
During sleep, TMR2 will not increment. The prescaler will retain the last prescale count, ready f or
operation to resume after the device wakes from sleep.
Table 13-1: Registers Associated with Timer2
Note: When T2CON is written TMR2 does not clear.
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR, PER
Value on
all other
resets
INTCON GIE PEIE T0IE INTE RBIE T0IF INTF RBIF 0000 000x 0000 000u
PIR TMR2IF (1) 00
PIE TMR2IE (1) 00
TMR2 Timer2 module’s register 0000 0000 0000 0000
T2CON TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 -000 0000
PR2 Timer2 Period Register 1111 1111 1111 1111
Legend: x = unknown, u = unchanged, - = unimplemented read as ‘0'.
Shaded cells are not used by the Timer2 module.
Note 1: The position of this bit is device dependent.
1997 Microchip Technology Inc. DS31013A-page 13-5
Section 13. Timer2
Timer2
13
13.8 Initialization
Example 13-1 shows how to initialize the Timer2 module, including specifying the Timer2 pres-
caler and postscaler.
Example 13-1: Timer2 Initialization
CLRF T2CON ; Stop Timer2, Prescaler = 1:1,
; Postscaler = 1:1
CLRF TMR2 ; Clear Timer2 register
CLRF INTCON ; Disable interrupts
BSF STATUS, RP0 ; Bank1
CLRF PIE1 ; Disable peripheral interrupts
BCF STATUS, RP0 ; Bank0
CLRF PIR1 ; Clear peripheral interrupts Flags
MOVLW 0x72 ; Postscaler = 1:15, Prescaler = 1:16
MOVWF T2CON ; Timer2 is off
BSF T2CON, TMR2ON ; Timer2 starts to increment
;
; The Timer2 interrupt is disabled, do polling on the overflow bit
;
T2_OVFL_WAIT
BTFSS PIR1, TMR2IF ; Has TMR2 interrupt occurred?
GOTO T2_OVFL_WAIT ; NO, continue loop
;
; Timer has overflowed
;
BCF PIR1, TMR2IF ; YES, clear flag and continue.
PICmicro MID-RANGE MCU FAMILY
DS31013A-page 13-6 1997 Microchip Technology Inc.
13.9 Design Tips
No related Design Tips at this time.
1997 Microchip Technology Inc. DS31013A-page 13-7
Section 13. Timer2
Timer2
13
13.10 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the Timer2
Module are:
Title Application Note #
Using the CCP Module AN594
Air Flow Control using Fuzzy Logic AN600
Adaptive Differential Pulse Code Modulation using PICmicros AN643
PICmicro MID-RANGE MCU FAMILY
DS31013A-page 13-8 1997 Microchip Technology Inc.
13.11 Revision History
Revision A
This is the initial released revision of the TImer2 module description.
1997 Microchip Technology Inc. DS31014A page 14-1
M
CCP
14
Section 14. Compare/Capture/PWM (CCP)
HIGHLIGHTS
This section of the manual contains the following major topics:
14.1 Introduction..................................................................................................................14-2
14.2 Control Register...........................................................................................................14-3
14.3 Capture Mode ..............................................................................................................14-4
14.4 Compare Mode ............................................................................................................14-6
14.5 PWM Mode ..................................................................................................................14-8
14.6 Initialization................................................................................................................14-12
14.7 Design Tips ................................................................................................................14-15
14.8 Related Application Notes..........................................................................................14-17
14.9 Revision History.........................................................................................................14-18
PICmicro MID-RANGE MCU FAMILY
DS31014A-page 14-2 1997 Microchip Technology Inc.
14.1 Introduction
Each CCP (Capture/Compare/PWM) module contains a 16-bit register which can operate as a
16-bit capture register , as a 16-bit compare register or as a 10-bit PWM master/sla ve Duty Cycle
register. The CCP modules are identical in operation, with the exception of the operation of the
special event trigger.
Each CCP module has 3 registers. Multiple CCP modules may e xist on a single de vice. Through-
out this section we use generic names for the CCP registers. These generic names are shown
in Table 14-1.
Table 14-1: Specific to Generic CCP Nomenclature
Table 14-2 shows the resources of the CCP modules, in each of its modes. While Table 14-3
shows the interactions between the CCP modules, where CCPx is one CCP module and CCPy
is another CCP module.
Table 14-2: CCP Mode - Timer Resource
Table 14-3: Interaction of Two CCP Modules
Generic Name CCP1 CCP2 Comment
CCPxCON CCP1CON CCP2CON CCP control register
CCPRxH CCPR1H CCPR2H CCP High byte
CCPRxL CCPR1L CCPR2L CCP Low byte
CCPx CCP1 CCP2 CCP pin
CCP Mode Timer Resource
Capture
Compare
PWM
Timer1
Timer1
Timer2
CCPx Mode CCPy Mode Interaction
Capture Capture Same TMR1 time-base .
Capture Compare The compare should be configured for the special event trigger,
which clears TMR1.
Compare Compare The compare(s) should be configured for the special e v ent trigger ,
which clears TMR1.
PWM PWM The PWMs will have the same frequency, and update rate
(TMR2 interrupt).
PWM Capture None
PWM Compare None
1997 Microchip Technology Inc. DS31014A-page 14-3
Section 14. CCP
CCP
14
14.2 Control Register
Register 14-1: CCPxCON Register
U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
DCxB1 DCxB0 CCPxM3 CCPxM2 CCPxM1 CCPxM0
bit 7 bit 0
bit 7:6 Unimplemented: Read as '0'
bit 5:4 DCxB1:DCxB0: PWM Duty Cycle bit1 and bit0
Capture Mode:
Unused
Compare Mode:
Unused
PWM Mode:
These bits are the two LSbs (bit1 and bit0) of the 10-bit PWM duty cycle. The upper eight
bits (DCx9:DCx2) of the duty cycle are found in CCPRxL.
bit 3:0 CCPxM3:CCPxM0: CCPx Mode Select bits
0000 = Capture/Compare/PWM off (resets CCPx module)
0100 = Capture mode, every falling edge
0101 = Capture mode, every rising edge
0110 = Capture mode, every 4th rising edge
0111 = Capture mode, every 16th rising edge
1000 = Compare mode,
Initialize CCP pin Low, on compare match force CCP pin High (CCPIF bit is set)
1001 = Compare mode,
Initialize CCP pin High, on compare match force CCP pin Low (CCPIF bit is set)
1010 = Compare mode,
Generate software interrupt on compare match
(CCPIF bit is set, CCP pin is unaffected)
1011 = Compare mode,
Trigger special event (CCPIF bit is set)
11xx = PWM mode
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31014A-page 14-4 1997 Microchip Technology Inc.
14.3 Capture Mode
In Capture mode, CCPRxH:CCPRxL captures the 16-bit value of the TMR1 register when an
event occurs on pin CCPx. An event is defined as:
Every falling edge
Every rising edge
Every 4th rising edge
Every 16th rising edge
An event is selected by control bits CCPxM3:CCPxM0 (CCPxCON<3:0>). When a capture is
made, the interrupt request flag bit, CCPxIF, is set. The CCPxIF bit must be cleared in software.
If another capture occurs bef ore the value in register CCPRx is read, the pre vious captured value
will be lost.
As can be seen in Figure 14-1, a capture does not reset the 16-bit TMR1 register. This is so
Timer1 can also be used as the timebase for other operations. The time between two captures
can easily be computed as the difference between the value of the second capture that of the
first capture. When Timer1 overflows, the TMR1IF bit will be set and if enabled an interrupt will
occur, allowing the time base to be extended to greater than 16-bits.
14.3.1 CCP Pin Configuration
In Capture mode, the CCPx pin should be configured as an input by setting its corresponding
TRIS bit.
Figure 14-1: Capture Mode Operation Block Diagram
The prescaler can be used to get a very fine average resolution on a constant input frequency.
F or example, if we have a stable input frequency and we set the prescaler to 1:16, then the total
error f or those 16 periods is 1 TCY. This gives an eff ective resolution of TCY/16, which at 20 MHz
is 12.5 ns. This technique is only v alid where the input frequency is “stab le” over the 16 samples .
Without using the prescaler (1:1), each sample would have a resolution of TCY.
Note: Timer1 must be running in timer mode or synchronized counter mode for the CCP
module to use the capture feature. In asynchronous counter mode, the capture
operation may not work.
Note: If the CCPx pin is configured as an output, a write to the port can cause a capture
condition.
CCPRxH CCPRxL
TMR1H TMR1L
Set flag bit CCPxIF
Capture
Enable
Q’s CCPxCON<3:0>
CCPx Pin
Prescaler
÷ 1, 4, 16
and
edge detect
1997 Microchip Technology Inc. DS31014A-page 14-5
Section 14. CCP
CCP
14
14.3.2 Changing Between Capture Modes
When the Capture mode is changed, a capture interrupt may be generated. The user should
keep the CCPxIE bit clear to disable these interrupts and should clear the CCPxIF flag bit
following any such change in operating mode.
14.3.2.1 CCP Prescaler
There are f our prescaler settings , specified b y bits CCPxM3:CCPxM0. Whenever the CCP mod-
ule is turned off, or the CCP module is not in capture mode, the prescaler counter is cleared. This
means that any reset will clear the prescaler counter.
Switching from one capture prescale setting to another ma y generate an interrupt. Also , the pres-
caler counter will not be cleared, therefore the first capture may be from a nonzero prescaler.
Example 14-1 shows the recommended method f or switching between capture prescale settings.
This example also clears the prescaler counter and will not generate the interrupt.
Example 14-1: Changing Between Capture Prescalers
To clear the Capture prescaler count, the CCP module must be configured into any non-capture
CCP mode (Compare, PWM, or CCP off modes).
14.3.3 Sleep Operation
When the de vice is placed in sleep, Timer1 will not increment (since it is in synchronous mode),
but the prescaler will continue to count events (not synchronized). When a specified capture
event occurs, the CCPxIF bit will be set, but the capture register will not be updated. If the CCP
interrupt is enabled, the device will wake-up from sleep. The value in the 16-bit TMR1 register is
not transf erred to the 16-bit capture register , b ut since the timer was not incrementing, this v alue
should not hav e any meaning. Eff ectiv ely, this allo ws the CCP pin to be used as another e xternal
interrupt.
14.3.4 Effects of a Reset
The CCP module is off, and the value in the capture prescaler is forced to 0.
CLRF CCP1CON ; Turn CCP module off
MOVLW NEW_CAPT_PS ; Load the W reg with the new prescaler
; mode value and CCP ON
MOVWF CCP1CON ; Load CCP1CON with this value
PICmicro MID-RANGE MCU FAMILY
DS31014A-page 14-6 1997 Microchip Technology Inc.
14.4 Compare Mode
In Compare mode, the 16-bit CCPRx register value is constantly compared against the TMR1
register pair value. When a match occurs, the CCPx pin is:
Driven High
Driven Low
Remains Unchanged
The action on the pin is based on the value of control bits CCPxM3:CCPxM0 (CCPxCON<3:0>).
At the same time, a compare interrupt is also generated.
Figure 14-2: Compare Mode Operation Block Diagram
Note: Timer1 must be running in Timer mode or Synchronized Counter mode if the CCP
module is using the compare f eature. In Asynchronous Counter mode, the compare
operation may not work.
CCPRxH CCPRxL
TMR1H TMR1L
Comparator
QS
R
Output
Logic
Special Event
Trigger
Set flag bit CCPxIF
match
CCPx Pin
TRIS CCPxCON<3:0>
Mode Select
Output Enable
1997 Microchip Technology Inc. DS31014A-page 14-7
Section 14. CCP
CCP
14
14.4.1 CCP Pin Operation in Compare Mode
The user must configure the CCPx pin as an output by clearing the appropriate TRIS bit.
Selecting the compare output mode, forces the state of the CCP pin to the state that is opposite
of the match state. So if the Compare mode is selected to force the output pin lo w on match, then
the output will be forced high until the match occurs (or the mode is changed).
14.4.2 Software Interrupt Mode
When generate Software Interrupt mode is chosen, the CCPx pin is not affected. Only a CCP
interrupt is generated (if enabled).
14.4.3 Special Event Trigger
In this mode, an internal hardware trigger is generated which may be used to initiate an action.
The special event trigger output of CCPx resets the TMR1 register pair. This allows the CCPRx
register to effectively be a 16-bit programmable period register for Timer1.
For some devices, the special trigger output of the CCP module resets the TMR1 register pair,
and starts an A/D conversion (if the A/D module is enabled).
14.4.4 Sleep Operation
When the de vice is placed in sleep, Timer1 will not increment (since in synchronous mode), and
the state of the module will not change. If the CCP pin is driving a value, it will continue to dr ive
that value. When the device wakes-up, it will continue form this state.
14.4.5 Effects of a Reset
The CCP module is off.
Note: Clearing the CCPxCON register will force the CCPx compare output latch to the
default low level. This is not the Port I/O data latch.
Note: The special event trigger will not set the Timer1 interrupt flag bit, TMR1IF.
PICmicro MID-RANGE MCU FAMILY
DS31014A-page 14-8 1997 Microchip Technology Inc.
14.5 PWM Mode
In Pulse Width Modulation (PWM) mode, the CCPx pin produces up to a 10-bit resolution PWM
output. Since the CCPx pin is multiplexed with the PORT data latch, the corresponding TRIS bit
must be cleared to make the CCPx pin an output.
Figure 14-3 shows a simplified block diagram of the CCP module in PWM mode.
F or a step by step procedure on ho w to set up the CCP module for PWM oper ation, see Subsec-
tion 14.5.3 “Set-up for PWM Operation.
Figure 14-3: Simplified PWM Block Diagram
A PWM output (Figure 14-4) has a time-base (period) and a time that the output stays high (duty
cycle). The frequency of the PWM is the inverse of the period (1/period).
Figure 14-4: PWM Output
Note: Clearing the CCPxCON register will force the CCPx PWM output latch to the def ault
low level. This is not the port I/O data latch.
CCPRxL
CCPRxH (Slave)
Comparator
TMR2
Comparator
PR2
RQ
S
Duty cycle registers CCPxCON<5:4>
Clear Timer, CCPx pin
and latch the Duty Cycle
TRIS<y>
CCPx
Timer2 Module
(Note 1)
8
8
10
10
10
CCP Module
Note 1: 8-bit timer is concatenated with 2-bit internal Q clock or 2 bits of the prescaler to
create 10-bit time-base.
(DCxB9:DCxB2)
(DCxB1:DCxB0)
Period = PR2 + 1
TMR2 = PR2 + 1, TMR2 forced to 0h
TMR2 = Duty Cycle
TMR2 = PR2 + 1, TMR2 forced to 0h
Duty Cycle =
DCxB9:DCxB0
1997 Microchip Technology Inc. DS31014A-page 14-9
Section 14. CCP
CCP
14
14.5.1 PWM Period
The PWM period is specified by writing to the PR2 register. The PWM period can be calculated
using the following formula:
PWM period = [(PR2) + 1] • 4 • TOSC • (TMR2 prescale value), specified in units of time
PWM frequency (FPWM) is defined as 1 / [PWM period].
When TMR2 is equal to PR2, the following three events occur on the next increment cycle:
TMR2 is cleared
The CCPx pin is set (exception: if PWM duty cycle = 0%, the CCPx pin will not be set)
The PWM duty cycle is latched from CCPRxL into CCPRxH
14.5.2 PWM Duty Cycle
The PWM duty cycle is specified by writing to the CCPRxL register and to the DCxB1:DCxB0
(CCPxCON<5:4>) bits. Up to 10-bit resolution is av ailab le: the CCPRxL contains the eight MSbs
and CCPxCON<5:4> contains the two LSbs. This 10-bit value is represented by DCxB9:DCxB0.
The following equation is used to calculate the PWM duty cycle:
PWM duty cycle = (DCxB9:DCxB0 bits value) • Tosc • (TMR2 prescale value), in units of time
The DCxB9:DCxB0 bits can be written to at any time, b ut the duty cycle value is not latched into
CCPRxH until after a match between PR2 and TMR2 occurs (which is the end of the current
period). In PWM mode, CCPRxH is a read-only register.
The CCPRxH register and a 2-bit internal latch are used to double buffer the PWM duty cycle.
This double buffering is essential for glitchless PWM operation.
When CCPRxH and 2-bit latch match the value of TMR2 concatenated with the internal 2-bit
Q clock (or two bits of the TMR2 prescaler), the CCPx pin is cleared. This is the end of the duty
cycle.
Maximum PWM resolution (bits) for a given PWM frequency:
Note: The Timer2 postscaler is not used in the determination of the PWM frequency. The
postscaler could be used to have a ser vo update rate at a different frequency than
the PWM output.
Note: If the PWM duty cycle value is longer than the PWM period, the CCPx pin will not
be cleared. This allows a duty cycle of 100%.
log( FPWM
log(2)
FOSC )bits
=
PICmicro MID-RANGE MCU FAMILY
DS31014A-page 14-10 1997 Microchip Technology Inc.
14.5.2.2 Minimum Resolution
The minimum resolution (in time) of each bit of the PWM duty cycle depends on the prescaler of
Timer2.
Table 14-4: Minimum Duty Cycle Bit Time
Example 14-2: PWM Period and Duty Cycle Calculation
At most, an 8-bit resolution duty cycle can be obtained from a 78.125 kHz frequency and a
20 MHz oscillator , i.e ., 0 DCxB9:DCxB0 255. An y value g reater than 255 will result in a 100%
duty cycle.
In order to achie ve higher resolution, the PWM frequency must be decreased. In order to achie v e
higher PWM frequency, the resolution must be decreased.
Table 14-5 lists example PWM frequencies and resolutions for Fosc = 20 MHz. The TMR2 pres-
caler and PR2 values are also shown.
Table 14-5: Example PWM Frequencies and Bit Resolutions at 20 MHz
Prescaler
Value T2CKPS1:T2CKPS0 Minimum Resolution
(Time)
10 0 T
OSC
40 1 T
CY
16 1 x 4 TCY
Desired PWM frequency is 78.125 kHz,
Fosc = 20 MHz
TMR2 prescale = 1
1/78.125 kHz= [(PR2) + 1] • 4 • 1/20 MHz • 1
12.8 µs = [(PR2) + 1] • 4 • 50 ns • 1
PR2 = 63
Find the maximum resolution of the duty cycle that can be used with a 78.125 kHz frequency
and 20 MHz oscillator:
1/78.125 kHz= 2PWM RESOLUTION • 1/20 MHz • 1
12.8 µs= 2
PWM RESOLUTION • 50 ns • 1
256 = 2PWM RESOLUTION
log(256) = (PWM Resolution) • log(2)
8.0 = PWM Resolution
PWM Frequency 1.22 kHz 4.88 kHz 19.53 kHz 78.12 kHz 156.3 kHz 208.3 kHz
Timer Prescaler
(1, 4, 16) 1641111
PR2 V alue 0xFF 0xFF 0xFF 0x3F 0x1F 0x17
Maximum
Resolution (bits) 10 10 10 8 7 5.5
1997 Microchip Technology Inc. DS31014A-page 14-11
Section 14. CCP
CCP
14
14.5.3 Set-up for PWM Operation
The following steps configure the CCP module for PWM operation:
1. Establish the PWM period by writing to the PR2 register.
2. Establish the PWM duty cycle by writing to the DCxB9:DCxB0 bits.
3. Make the CCPx pin an output by clearing the appropriate TRIS bit.
4. Establish the TMR2 prescale value and enable Timer2 by writing to T2CON.
5. Configure the CCP module for PWM operation.
14.5.4 Sleep Operation
When the device is placed in sleep, Timer2 will not increment, and the state of the module will
not change. If the CCP pin is driving a value, it will contin ue to driv e that value. When the device
wakes-up, it will continue from this state.
14.5.5 Effects of a Reset
The CCP module is off.
PICmicro MID-RANGE MCU FAMILY
DS31014A-page 14-12 1997 Microchip Technology Inc.
14.6 Initialization
The CCP module has three modes of operation. Example 14-3 shows the initialization of capture
mode, Example 14-4 sho ws the initialization of compare mode, and Example 14-5 shows the ini-
tialization of PWM mode.
Example 14-3: Capture Initialization
CLRF CCP1CON ; CCP Module is off
CLRF TMR1H ; Clear Timer1 High byte
CLRF TMR1L ; Clear Timer1 Low byte
CLRF INTCON ; Disable interrupts and clear T0IF
BSF STATUS, RP0 ; Bank1
BSF TRISC, CCP1 ; Make CCP pin input
CLRF PIE1 ; Disable peripheral interrupts
BCF STATUS, RP0 ; Bank0
CLRF PIR1 ; Clear peripheral interrupts Flags
MOVLW 0x06 ; Capture mode, every 4th rising edge
MOVWF CCP1CON ;
BSF T1CON, TMR1ON ; Timer1 starts to increment
;
; The CCP1 interrupt is disabled,
; do polling on the CCP Interrupt flag bit
;
Capture_Event
BTFSS PIR1, CCP1IF
GOTO Capture_Event
;
; Capture has occurred
;
BCF PIR1, CCP1IF ; This needs to be done before next compare
1997 Microchip Technology Inc. DS31014A-page 14-13
Section 14. CCP
CCP
14
Example 14-4: Compare Initialization
CLRF CCP1CON ; CCP Module is off
CLRF TMR1H ; Clear Timer1 High byte
CLRF TMR1L ; Clear Timer1 Low byte
CLRF INTCON ; Disable interrupts and clear T0IF
BSF STATUS, RP0 ; Bank1
BCF TRISC, CCP1 ; Make CCP pin output if controlling state of pin
CLRF PIE1 ; Disable peripheral interrupts
BCF STATUS, RP0 ; Bank0
CLRF PIR1 ; Clear peripheral interrupts Flags
MOVLW 0x08 ; Compare mode, set CCP1 pin on match
MOVWF CCP1CON ;
BSF T1CON, TMR1ON ; Timer1 starts to increment
;
; The CCP1 interrupt is disabled,
; do polling on the CCP Interrupt flag bit
;
Compare_Event
BTFSS PIR1, CCP1IF
GOTO Compare_Event
;
; Compare has occurred
;
BCF PIR1, CCP1IF ; This needs to be done before next compare
PICmicro MID-RANGE MCU FAMILY
DS31014A-page 14-14 1997 Microchip Technology Inc.
Example 14-5: PWM Initialization
CLRF CCP1CON ; CCP Module is off
CLRF TMR2 ; Clear Timer2
MOVLW 0x7F ;
MOVWF PR2 ;
MOVLW 0x1F ;
MOVWF CCPR1L ; Duty Cycle is 25% of PWM Period
CLRF INTCON ; Disable interrupts and clear T0IF
BSF STATUS, RP0 ; Bank1
BCF TRISC, PWM1 ; Make pin output
CLRF PIE1 ; Disable peripheral interrupts
BCF STATUS, RP0 ; Bank0
CLRF PIR1 ; Clear peripheral interrupts Flags
MOVLW 0x2C ; PWM mode, 2 LSbs of Duty cycle = 10
MOVWF CCP1CON ;
BSF T2CON, TMR2ON ; Timer2 starts to increment
;
; The CCP1 interrupt is disabled,
; do polling on the TMR2 Interrupt flag bit
;
PWM_Period_Match
BTFSS PIR1, TMR2IF
GOTO PWM_Period_Match
;
; Update this PWM period and the following PWM Duty cycle
;
BCF PIR1, TMR2IF
1997 Microchip Technology Inc. DS31014A-page 14-15
Section 14. CCP
CCP
14
14.7 Design Tips
Question 1:
What timers can I use for the capture and compare modes?
Answer 1:
The capture and compare modes are designed around Timer1, so no other timer can be used f or
these functions. This also means that if multiple CCP modules (in parts with more than one) are
being used for a capture or compare function, they will share the same timer.
Question 2:
What timers can I use with the PWM mode?
Answer 2:
The PWM mode is designed around Timer2, so no other timer can be used for this function. (It
is the only timer with a period register associated with it.) If multiple CCP modules (in parts with
more than one) are doing PWM they will share the same timer, meaning they will ha v e the same
PWM period and frequency.
Question 3:
Can I use one CCP module to do capture (or compare) AND PWM at the
same time, since they use different timers as their reference?
Answer 3:
The timers may be different, but other logic functions are shared. However you can switch from
one mode to the other. For a device with two CCP modules, you can also have CCP1 set up for
PWM and CCP2 set up for capture or compare (or vice versa) since they are two independent
modules.
Question 4:
How does a reset affect the CCP module?
Answer 4:
Any reset will turn the CCP module off. See the section on resets to see reset values.
Question 5:
I am setting up the CCP1CON module for “Compare Mode, trigger special
event” (1011) whic h resets TMR1. When a compare matc h occurs, will I have
both the TMR1 and the CCP1 interrupts pending (TMR1IF is set, CCP1IF is
set)?
Answer 5:
The CCP1IF flag will be set on the match condition. TMR1IF is set when Timer1 overflows, and
the special trigger reset of Timer1 is not considered an overflow. However, if both the CCPR1L
and CCPR1H registers are set at FFh, then an overflow occurs at the same time as the match,
which will then set both CCP1IF and TMR1IF.
Question 6:
How do I use Timer2 as a general purpose timer, with an interrupt flag on
rollover?
Answer 6:
Timer2 alwa ys resets to zero when it equals PR2 and flag bit TMR2IF alwa ys gets set at this time.
By putting FFh into PR2, you will get an interrupt on overflow at FFh, as you would with Timer0,
f or instance. Quite often it is desir able to ha ve an e v ent occur at a periodic rate, perhaps an inter-
rupt driv en e v ent. Normally an initial value w ould be placed into the timer so that the ov erflow will
occur at the desired time. This value would have to be placed back into the timer every time it
overflowed to mak e the interrupts occur at the same desired rate. The benefit of Timer2 is that a
value can be written to PR2 that will cause it to reset at your desired time inter val. This means
you do not ha ve the housek eeping chore of reloading the timer ev ery time it ov erflows, since PR2
maintains its value.
PICmicro MID-RANGE MCU FAMILY
DS31014A-page 14-16 1997 Microchip Technology Inc.
Question 7:
I am using a CCP module in PWM mode. The duty cycle being output is
almost always 100%, even when my program writes a value like 7Fh to the
duty cycle register, which should be 50%. What am I doing wrong?
Answer 7:
1. The value in CCPRxL is higher than PR2. This happens quite often when a user desires
a f ast PWM output frequency and will write a small v alue in the PR2. In this case, if a v alue
of 7Eh were written to PR2, then a value 7Fh in CCPRxL will result in 100% duty cycle.
2. If the TRIS bit corresponding to the CCP output pin you are using is configured as an input,
the PWM output cannot drive the pin. In this case the pin would float and duty cycle may
appear to be 0%, 100% or some other floating value.
Question 8:
I want to determine a signal frequency using the CCP module in capture
mode to find the period. I am currently resetting Timer1 on the first edge,
then using the value in the capture register on the second edge as the time
period. The problem is that my code to clear the timer does not occur until
almost twelve instructions after the first capture edge (interrupt latency
plus saving of register s in interrupt) so I cannot measure very fast frequen-
cies. Is there a better way to do this?
Answer 8:
You do not need to zero the counter to find the diff erence between two pulse edges . J ust take the
first captured value and put it into another set of registers. Then when the second capture event
occurs, just subtract the first event from the second. Assuming that your pulse edges are not so
f ar apart that the counter can wrap around past the last capture value, the answer will always be
correct. This is illustrated by the following example:
1. First captured value is FFFEh. Store this value in two registers.
2. The second capture value is 0001h (the counter has incremented three times).
3. 0001h - FFFEh = 0003, which is the same as if you had cleared Timer1 to zero and let it
count to 3. (Theoretically, except that there was a delay getting to the code that clears
Timer1, so actual values would differ).
The interrupt overhead is no w less important because the v alues are captured automatically. F or
even faster inputs do not enable interrupts and just test the flag bit in a loop. If you must also
capture very long time periods, such that the timer can wrap around past the previous capture
value, then consider using an auto-scaling technique that starts with a large prescale and
shorten the prescale as you converge on the exact frequency.
1997 Microchip Technology Inc. DS31014A-page 14-17
Section 14. CCP
CCP
14
14.8 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the CCP
modules are:
Title Application Note #
Using the CCP Modules AN594
Implementing Ultrasonic Ranging AN597
Air Flow Control Using Fuzzy Logic AN600
Adaptive Differential Pulse Code Modulation AN643
PICmicro MID-RANGE MCU FAMILY
DS31014A-page 14-18 1997 Microchip Technology Inc.
14.9 Revision History
Revision A
This is the initial released revision of the CCP module description.
1997 Microchip Technology Inc. DS31015A page 15-1
M
SSP
15
Section 15. Synchronous Serial Port (SSP)
HIGHLIGHTS
This section of the manual contains the following major topics:
15.1 Introduction..................................................................................................................15-2
15.2 Control Registers .........................................................................................................15-3
15.3 SPI Mode .....................................................................................................................15-6
15.4 SSP I2C Operation.....................................................................................................15-16
15.5 Initialization................................................................................................................15-26
15.6 Design Tips ................................................................................................................15-28
15.7 Related Application Notes..........................................................................................15-29
15.8 Revision History.........................................................................................................15-30
Note: Please refer to Appendix C.2 or the device data sheet to determine which devices
use this module.
I2C is a trademark of Philips Corporation.
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-2 1997 Microchip Technology Inc.
15.1 Introduction
The Synchronous Serial Por t (SSP) module is a serial interface useful for communicating with
other peripherals or microcontroller devices . These peripheral de vices ma y be serial EEPR OMs,
shift registers, display drivers, A/D converters, etc. The SSP module can operate in one of two
modes:
Serial Peripheral Interface (SPI™)
Inter-Integrated Circuit (I2C™)
- Slave mode
- I/O slope control, and Start and Stop bit detection to ease software implementation of
Master and Multi-master modes
SPI is a registered trademark of Motorola Corporation.
I2C is a trademark of Philips Corporation.
1997 Microchip Technology Inc. DS31015A-page 15-3
Section 15. SSP
SSP
15
15.2 Control Registers
Register 15-1: SSPSTAT: Synchronous Serial Port Status Register
R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0
SMP CKE D/A P S R/W UA BF
bit 7 bit 0
bit 7 SMP: SPI data input sample phase
SPI Master Mode
1 = Input data sampled at end of data output time
0 = Input data sampled at middle of data output time
SPI Slave Mode
SMP must be cleared when SPI is used in slave mode
bit 6 CKE: SPI Clock Edge Select (Figure 15-3, Figure 15-4, and Figure 15-5)
CKP = 0 (SSPCON<4>)
1 = Data transmitted on rising edge of SCK
0 = Data transmitted on falling edge of SCK
CKP = 1 (SSPCON<4>)
1 = Data transmitted on falling edge of SCK
0 = Data transmitted on rising edge of SCK
bit 5 D/A: Data/Address bit (I2C mode only)
1 = Indicates that the last byte received or transmitted was data
0 = Indicates that the last byte received or transmitted was address
bit 4 P: Stop bit
(I2C mode only. This bit is cleared when the SSP module is disabled)
1 = Indicates that a stop bit has been detected last (this bit is '0' on RESET)
0 = Stop bit was not detected last
bit 3 S: Start bit
(I2C mode only. This bit is cleared when the SSP module is disabled)
1 = Indicates that a start bit has been detected last (this bit is '0' on RESET)
0 = Start bit was not detected last
bit 2 R/W: Read/Write bit information (I2C mode only)
This bit holds the R/W bit inf ormation f ollowing the last address match. This bit is only valid from
the address match to the next start bit, stop bit, or not ACK bit.
1 = Read
0 = Write
bit 1 UA: Update Address (10-bit I2C mode only)
1 = Indicates that the user needs to update the address in the SSPADD register
0 = Address does not need to be updated
bit 0 BF: Buffer Full Status bit
Receive (SPI and I2C modes)
1 = Receive complete, SSPBUF is full
0 = Receive not complete, SSPBUF is empty
Transmit (I2C mode only)
1 = Transmit in progress, SSPBUF is full
0 = Transmit complete, SSPBUF is empty
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-4 1997 Microchip Technology Inc.
Register 15-2: SSPCON: Synchronous Serial Port Control Register
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
bit 7 bit 0
bit 7 WCOL: Write Collision Detect bit
1 = The SSPBUF register is written while it is still transmitting the previous word
(must be cleared in software)
0 = No collision
bit 6 SSPOV: Receive Overflow Indicator bit
In SPI mode:
1 = A new byte is received while the SSPBUF register is still holding the previous data. In case
of ov erflo w, the data in SSPSR is lost and the SSPBUF is no longer updated. Overflow can
only occur in slave mode. The user must read the SSPBUF, even if only transmitting data,
to avoid setting overflow. In master mode the overflow bit is not set since each new recep-
tion (and transmission) is initiated by writing to the SSPBUF register.
0 = No overflow
In I2C mode:
1 = A byte is received while the SSPBUF register is still holding the previous byte. SSPOV is a
“don‘t care” in transmit mode. SSPOV must be cleared in software in either mode.
0 = No overflow
bit 5 SSPEN: Synchronous Serial Port Enable bit
In both modes, when enabled, these pins must be properly configured as input or output.
In SPI mode:
1 = Enables serial port and configures SCK, SDO, SDI, and SS as the source of the
serial port pins
0 = Disables serial port and configures these pins as I/O port pins
In I2C mode:
1 = Enables the serial port and configures the SDA and SCL pins as the source of the
serial port pins
0 = Disables serial port and configures these pins as I/O port pins
bit 4 CKP: Clock Polarity Select bit
In SPI mode:
1 = Idle state for clock is a high level
0 = Idle state for clock is a low level
In I2C mode:
SCK release control
1 = Enable clock
0 = Holds clock low (clock stretch) (Used to ensure data setup time)
1997 Microchip Technology Inc. DS31015A-page 15-5
Section 15. SSP
SSP
15
bit 3:0 SSPM3:SSPM0: Synchronous Serial Port Mode Select bits
0000 = SPI master mode, clock = FOSC/4
0001 = SPI master mode, clock = FOSC/16
0010 = SPI master mode, clock = FOSC/64
0011 = SPI master mode, clock = TMR2 output/2
0100 = SPI slave mode, clock = SCK pin. SS pin control enabled.
0101 = SPI slave mode, clock = SCK pin. SS pin control disabled. SS can be used as I/O pin
0110 = I2C slave mode, 7-bit address
0111 = I2C slave mode, 10-bit address
1000 = Reserved
1001 = Reserved
1010 = Reserved
1011 = I2C firmware controlled master mode (slave idle)
1100 = Reserved
1101 = Reserved
1110 = I2C slave mode, 7-bit address with start and stop bit interrupts enabled
1111 = I2C slave mode, 10-bit address with start and stop bit interrupts enabled
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ’0’ - n = Value at POR reset
Register 15-2: SSPCON: Synchronous Serial Port Control Register (Cont’d)
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-6 1997 Microchip Technology Inc.
15.3 SPI Mode
The SPI mode allows 8-bits of data to be synchronously transmitted and received simulta-
neously. All four modes of SPI are suppor ted, as well as Microwire™ (sample edge) when the
SPI is in the master mode.
To accomplish communication, typically three pins are used:
Serial Data Out (SDO)
Serial Data In (SDI)
Serial Clock (SCK)
Additionally a fourth pin may be used when in a slave mode of operation:
Slave Select (SS)
15.3.1 Operation
When initializing the SPI, se veral options need to be specified. This is done by programming the
appropriate control bits in the SSPCON register (SSPCON<5:0>) and SSPSTAT<7:6>. These
control bits allow the following to be specified:
Master Mode (SCK is the clock output)
Slave Mode (SCK is the clock input)
Clock Polarity (Idle state of SCK)
Clock edge (output data on rising/falling edge of SCK)
Data Input Sample Phase
Clock Rate (Master mode only)
Slave Select Mode (Slave mode only)
Figure 15-1 shows the block diagram of the SSP module, when in SPI mode.
Figure 15-1: SSP Block Diagram (SPI Mode)
Read Write
Internal
data bus
SDI
SDO
SS
SCK
SSPSR reg
SSPBUF reg
SSPM3:SSPM0
bit0 shift clock
SS Control
Enable
Edge
Select
Clock Select
TMR2 output
TCY
Prescaler
4, 16, 64
TRIS bit of SCK pin
2
Edge
Select
2
4
1997 Microchip Technology Inc. DS31015A-page 15-7
Section 15. SSP
SSP
15
The SSP consists of a transmit/receiv e Shift Register (SSPSR) and a buffer register (SSPB UF).
The SSPSR shifts the data in and out of the device, MSb first. The SSPBUF holds the data that
was written to the SSPSR, until the received data is ready. Once the 8-bits of data have been
received, that byte is moved to the SSPBUF register. Then the buffer full detect bit, BF
(SSPSTAT<0>), and interr upt flag bit, SSPIF, are set. This double buffering of the received data
(SSPBUF) allows the next byte to start reception bef ore reading the data that was just received.
Any write to the SSPBUF register during transmission/reception of data will be ignored, and the
write collision detect bit, WCOL (SSPCON<7>), will be set. User software m ust clear the WCOL
bit so that it can be determined if the following write(s) to the SSPBUF register completed suc-
cessfully. When the application software is expecting to receive valid data, the SSPBUF should
be read before the next byte of data to transfer is written to the SSPBUF. Buffer full bit, BF
(SSPSTAT<0>), indicates when SSPBUF has been loaded with the received data (transmission
is complete). When the SSPBUF is read, the BF bit is cleared. This data may be irrelevant if the
SPI is only a transmitter. Generally the SSP Interrupt is used to deter mine when the transmis-
sion/reception has completed. The SSPBUF m ust be read and/or written. If the interrupt method
is not going to be used, then software polling can be done to ensure that a write collision does
not occur. Example 15-1 shows the loading of the SSPBUF (SSPSR) for data transmission. The
shaded instruction is only required if the received data is meaningful (some SPI applications are
transmit only).
Example 15-1: Loading the SSPBUF (SSPSR) Register
The SSPSR is not directly readable or writable, and can only be accessed from addressing the
SSPBUF register. Additionally, the SSP status register (SSPSTAT) indicates the various status
conditions.
BCF STATUS, RP1 ;Specify Bank1
BSF STATUS, RP0 ;
LOOP BTFSS SSPSTAT, BF ;Has data been received (transmit complete)?
GOTO LOOP ;No
BCF STATUS, RP0 ;Specify Bank0
MOVF SSPBUF, W ;W reg = contents of SSPBUF
MOVWF RXDATA ;Save in user RAM, if data is meaningful
MOVF TXDATA, W ;W reg = contents of TXDATA
MOVWF SSPBUF ;New data to xmit
Microwire is a trademark of National Semiconductor.
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-8 1997 Microchip Technology Inc.
15.3.2 Enabling SPI I/O
To enable the serial por t the SSP Enable bit, SSPEN (SSPCON<5>), must be set. To reset or
reconfigure SPI mode, clear the SSPEN bit which re-initializes the SSPCON register, and then
set the SSPEN bit. This configures the SDI, SDO, SCK, and SS pins as ser ial port pins. For the
pins to behave as the serial por t function, they must have their data direction bits (in the TRIS
register) appropriately programmed. That is:
SDI must have the TRIS bit set
SDO must have the TRIS bit cleared
SCK (Master mode) must have the TRIS bit cleared
SCK (Slave mode) must have the TRIS bit set
•SS
must have the TRIS bit set
Any serial port function that is not desired ma y be ov erridden by programming the corresponding
data direction (TRIS) register to the opposite value . An example would be in master mode where
you are only sending data (to a display driver), then both SDI and SS could be used as general
purpose outputs by clearing their corresponding TRIS register bits.
1997 Microchip Technology Inc. DS31015A-page 15-9
Section 15. SSP
SSP
15
15.3.3 Typical Connection
Figure 15-2 shows a typical connection between two microcontrollers. The master controller
(Processor 1) initiates the data transfer by sending the SCK signal. Data is shifted out of both
shift registers on their programmed cloc k edge, and latched on the edge of the cloc k specified by
the SMP bit. Both processors should be programmed to same Clock Polarity (CKP), then both
controllers would send and receive data at the same time. Whether the data is meaningful (or
dummy data) depends on the application software. This leads to three scenarios for data trans-
mission:
Master sends data Slave sends dummy data
Master sends data Slave sends data
Master sends dummy data Slave sends data
Figure 15-2: SPI Master/Slave Connection
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
MSb LSb
SDO
SDI
PROCESSOR 1
SCK
SPI Master SSPM3:SSPM0 = 00xxb
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
LSb
MSb
SDI
SDO
PROCESSOR 2
SCK
SPI Slave SSPM3:SSPM0 = 010xb
Serial Clock
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-10 1997 Microchip Technology Inc.
15.3.4 Master Operation
The master can initiate the data transfer at any time because it controls the SCK. The master
determines when the slave (Processor 2) is to broadcast data by the software protocol.
In master mode the data is transmitted/receiv ed as soon as the SSPBUF register is written to. If
the SPI is only going to receive, the SDO output could be disabled (programmed as an input).
The SSPSR register will continue to shift in the signal present on the SDI pin at the progr ammed
clock rate. As each byte is received, it will be loaded into the SSPBUF register as if a normal
received b yte (interrupts and status bits appropriately set). This could be useful in receiver appli-
cations as a “line activity monitor” mode.
The clock polarity is selected by appropriately programming bit CKP (SSPCON<4>). This then
would give waveforms for SPI communication as shown in Figure 15-3, Figure 15-4, and
Figure 15-5 where the MSb is transmitted first. In master mode, the SPI clock rate (bit rate) is
user programmable to be one of the following:
•F
OSC/4 (or TCY)
•F
OSC/16 (or 4 • TCY)
•F
OSC/64 (or 16 • TCY)
Timer2 output/2
This allows a maximum data rate of 5 Mbps (at 20 MHz).
Figure 15-3: SPI Mode Waveform, Master Mode
4 clock
modes
Input
Sample (SMP = 0)
Input
Sample (SMP = 1)
SDI (SMP = 0) bit7 bit0
SDO (CKE = 0) bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
bit7 bit0
SDI (SMP = 1)
SSPIF
Write to
SSPBUF
SSPSR to
SSPBUF
SDO (CKE = 1) bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
SCK (CKP = 0,
CKE = 0)
SCK (CKP = 0,
CKE = 1)
SCK (CKP = 1,
CKE = 0)
SCK (CKP = 1,
CKE = 1)
Next Q4 cycle
after Q2
1997 Microchip Technology Inc. DS31015A-page 15-11
Section 15. SSP
SSP
15
15.3.5 Slave Operation
In slav e mode , the data is transmitted and receiv ed as the e xternal clock pulses appear on SCK.
When the last bit is latched, the interrupt flag bit SSPIF is set.
The clock polarity is selected by appropriately programming bit CKP (SSPCON<4>). This then
would give waveforms for SPI communication as shown in Figure 15-3, Figure 15-4, and
Figure 15-5 where the MSb is transmitted first. When in sla ve mode the e xternal clock must meet
the minimum high and low times.
In sleep mode, the slave can transmit and receive data. When a byte is received, the device will
wake-up from sleep, if the interrupt is enabled.
Figure 15-4: SPI Mode Waveform (Slave Mode With CKE = 0)
SCK (CKP = 1,
SCK (CKP = 0,
Input
Sample (SMP = 0)
SDI bit7 bit0
SDO bit6 bit5 bit4 bit3 bit2 bit1 bit0
SSPIF
CKE = 0)
CKE = 0)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SS
optional
Next Q4 Cycle
after Q2
bit7
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-12 1997 Microchip Technology Inc.
15.3.6 Slave Select Mode
When in slave select mode, the SS pin allows multi-drop for multiple slaves with a single
master. The SPI must be in slave mode (SSPCON<3:0> = 04h) and the TRIS bit, for the
SS pin, must be set f or the slave select mode to be enabled. When the SS pin is lo w, trans-
mission and reception are enabled and the SDO pin is driven. When the SS pin goes high,
the SDO pin is no longer driven, even if in the middle of a transmitted byte, and becomes
a floating output. External pull-up/ pull-down resistors may be desirable, depending on the
application.
When the SPI is in Slave Mode with SS pin control enabled, (SSPCON<3:0> = 0100) the SPI
module will reset if the SS pin is set to VDD. If the SPI is used in Slave Mode with the CKE bit is
set, then the SS pin control must be enabled.
When the SPI module resets, the bit counter is f orced to 0. This can be done by either by forcing
the SS pin to a high level or clearing the SSPEN bit (Figure 15-6).
To emulate two-wire communication, the SDO pin can be connected to the SDI pin. When the
SPI needs to operate as a receiver the SDO pin can be configured as an input. This disables
transmissions from the SDO . The SDI can alwa ys be left as an input (SDI function) since it cannot
create a bus conflict.
Figure 15-5: SPI Mode Waveform (Slave Select Mode With CKE = 1)
SCK
(CKP = 1
SCK
(CKP = 0
Input
Sample
SDI bit7 bit0
SDO bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
SSPIF
Interrupt
(SMP = 0)
CKE = 1)
CKE = 1)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SS
Flag
not optional
Next Q4 cycle
after Q2
1997 Microchip Technology Inc. DS31015A-page 15-13
Section 15. SSP
SSP
15
Figure 15-6: Slave Synchronization Waveform
SCK
(CKP = 1
SCK
(CKP = 0
Input
Sample
SDI bit7
SDO bit7 bit6 bit7
SSPIF
Interrupt
(SMP = 0)
CKE = 0)
CKE = 0)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SS
Flag
bit0
bit7 bit0
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-14 1997 Microchip Technology Inc.
15.3.7 Sleep Operation
In master mode all module clocks are halted, and the transmission/reception will remain in that
state until the de vice wak es from sleep. After the device returns to normal mode, the module will
continue to transmit/receive data.
In slav e mode, the SPI transmit/receiv e shift register operates asynchronously to the de vice. This
allows the de vice to be placed in sleep mode, and data to be shifted into the SPI transmit/receiv e
shift register. When all 8-bits have been received, the SSP interrupt flag bit will be set and if
enabled will wake the device from sleep.
1997 Microchip Technology Inc. DS31015A-page 15-15
Section 15. SSP
SSP
15
15.3.8 Effects of a Reset
A reset disables the SSP module and terminates the current transfer.
Table 15-1: Registers Associated with SPI Operation
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on
POR,
BOR
Value on all
other resets
INTCON GIE PEIE T0IE INTE RBIE(2) T0IF INTF RBIF(2) 0000 000x 0000 000u
PIR SSPIF (1) 00
PIE SSPIE (1) 00
SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register xxxx xxxx uuuu uuuu
SSPCON WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
TRISA PORTA Data Direction Register --11 1111 --11 1111
TRISC PORTC Data Direction Control Register 1111 1111 1111 1111
SSPSTAT SMP CKE D/A P S R/W UA BF 0000 0000 0000 0000
Legend: x = unknown, u = unchanged, - = unimplemented read as '0'. Shaded cells are not used by the SSP in SPI
mode.
Note 1: The position of this bit is device dependent.
2: These bits may also be named GPIE and GPIF.
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-16 1997 Microchip Technology Inc.
15.4 SSP I2C Operation
The SSP module in I2C mode fully implements all slave functions, except general call support,
and provides interrupts on start and stop bits in hardware to facilitate software implementations
of the master functions. The SSP module implements the standard mode specifications as well
as 7-bit and 10-bit addressing. Appendix A gives an overview of the I2C bus specification.
Two pins are used for data transfer. These are the SCL pin, which is the clock, and the SD A pin,
which is the data. The user must configure these pins as inputs through the TRIS bits. The SSP
module functions are enabled by setting SSP Enable bit, SSPEN (SSPCON<5>).
A “glitch” filter is on the SCL and SDA pins when the pin is an input. This filter operates in both
the 100 KHz and 400 KHz modes. In the 100 KHz mode, when these pins are an output, there
is a slew rate control of the pin that is independent of device frequency.
Figure 15-7: SSP Block Diagram (I2C Mode)
Read Write
SSPSR reg
Match detect
SSPADD reg
Start and
Stop bit detect
SSPBUF reg
Internal
data bus
Address Match
Set, Reset
S, P bits
(SSPSTAT reg)
SCL
shift
clock
MSb LSb
SDA
1997 Microchip Technology Inc. DS31015A-page 15-17
Section 15. SSP
SSP
15
The SSP module has five registers for I2C operation. They are:
SSP Control Register (SSPCON)
SSP Status Register (SSPSTAT)
Serial Receive/Transmit Buffer (SSPBUF)
SSP Shift Register (SSPSR) - Not directly accessible
SSP Address Register (SSPADD)
The SSPCON register allows control of the I2C operation. Four mode selection bits
(SSPCON<3:0>) allow one of the following I2C modes to be selected:
•I
2C Slave mode (7-bit address)
•I
2C Slave mode (10-bit address)
•I
2C Firmware controlled Multi-Master mode (start and stop bit interrupts enabled)
•I
2C Firmware controlled Multi-Master mode (start and stop bit interrupts enabled)
•I
2C Firmware controlled Master mode, slave is idle
Bef ore selecting any I2C mode, the SCL and SD A pins must be prog rammed to inputs b y setting
the appropriate TRIS bits. Selecting an I2C mode, by setting the SSPEN bit, enables the SCL
and SDA pins to be used as the clock and data lines in I2C mode.
The SSPSTAT register gives the status of the data transfer. This infor mation includes detection
of a START or STOP bit, specifies if the received byte w as data or address, if the next byte is the
completion of 10-bit address, and if this will be a read or write data transfer.
The SSPBUF is the register to which transf er data is written to or read from. The SSPSR register
shifts the data in or out of the device. In receive operations, the SSPBUF and SSPSR create a
doubled buffered receiver. This allows reception of the next byte to begin before reading the last
byte of received data. When the complete byte is received, it is transferred to the SSPBUF reg-
ister and flag bit SSPIF is set. If another complete byte is received before the SSPBUF register
is read, a receiver overflow has occurred and the SSPOV bit (SSPCON<6>) is set and the byte
in the SSPSR is lost.
The SSPADD register holds the slave address. In 10-bit mode, the user needs to write the high
byte of the address (1111 0 A9 A8 0). Following the high byte address match, the low byte of
the address needs to be loaded (A7:A0).
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-18 1997 Microchip Technology Inc.
15.4.1 Slave Mode
In slav e mode, the SCL and SDA pins must be configured as inputs (TRIS set). The SSP module
will override the input state with the output data when required (slave-transmitter).
When an address is matched or the data transfer after an address match is received, the hard-
ware automatically will generate the acknowledge (ACK) pulse, and then load the SSPBUF reg-
ister with the received value currently in the SSPSR register.
There are cer tain conditions that will cause the SSP module not to give this ACK pulse. These
are if either (or both):
a) The buffer full bit, BF (SSPSTAT<0>), was set before the message completed.
b) The overflow bit, SSPOV (SSPCON<6>), was set before the message completed.
In this case, the SSPSR register v alue is not loaded into the SSPBUF, b ut the SSPIF and SSPO V
bits are set. Table 15-2 sho ws what happens when a data transf er byte is receiv ed, given the sta-
tus of bits BF and SSPO V. The shaded cells show the condition where user software did not prop-
erly clear the overflo w condition. Flag bit BF is cleared by reading the SSPB UF register while bit
SSPOV is cleared through software.
The SCL clock input m ust ha ve a minimum high and low time for proper operation. The high and
low times of the I2C specification as well as the requirement of the SSP module is shown in
Device Data Sheet electrical specifications parameters 100 and 101.
1997 Microchip Technology Inc. DS31015A-page 15-19
Section 15. SSP
SSP
15
15.4.1.1 Addressing
Once the SSP module has been enabled, it waits for a START condition to occur. Following the
START condition, the 8-bits are shifted into the SSPSR register. All incoming bits are sampled
with the rising edge of the clock (SCL) line. The value of register SSPSR<7:1> is compared to
the value of the SSPADD register . The address is compared on the falling edge of the eighth clock
(SCL) pulse. If the addresses match, and the BF and SSPOV bits are clear, the f ollo wing events
occur:
a) The SSPSR register value is loaded into the SSPBUF register on the falling edge of the
eight SCL pulse.
b) The buffer full bit, BF, is set on the falling edge of the eigth SCL pulse.
c) An ACK pulse is generated.
d) SSP interrupt flag bit, SSPIF, is set (interrupt is generated if enabled) - on the f alling edge
of the ninth SCL pulse.
In 10-bit address mode, two address bytes need to be received by the slave. The five Most
Significant bits (MSbs) of the first address byte specify if this is a 10-bit address. The R/W bit
(SSPSTAT<2>) must specify a write so the sla ve de vice will receive the second address b yte. F or
a 10-bit address the first byte w ould equal 1111 0 A9 A8 0’, where A9 and A8 are the two MSbs
of the address. The sequence of events for a 10-bit address is as follows, with steps 7- 9 for
slave-transmitter:
1. Receive first (high) byte of Address (the SSPIF, BF, and UA (SSPSTAT<1>) bits are set).
2. Update the SSPADD register with second (low) byte of Address (clears the UA bit and
releases the SCL line).
3. Read the SSPBUF register (clears the BF bit) and clear the SSPIF flag bit.
4. Receive second (low) byte of Address (the SSPIF, BF, and UA bits are set).
5. Update the SSPADD register with the high byte of Address. This will clear the UA bit and
releases SCL line.
6. Read the SSPBUF register (clears the BF bit) and clear the SSPIF flag bit.
7. Receive repeated START condition.
8. Receive first (high) byte of Address (the SSPIF and BF bits are set).
9. Read the SSPBUF register (clears the BF bit) and clear the SSPIF flag bit.
Table 15-2: Data Transfer Received Byte Actions
Note: Following the RESTART condition (step 7) in 10-bit mode, the user only needs to
match the first 7-bit address. The user does not update the SSPADD f or the second
half of the address.
Status Bits as Data
Transfer is Received
SSPSR SSPBUF Generate ACK
Pulse
Set bit SSPIF
(SSP Interrupt occurs
if enabled)
BF SSPOV
00 Yes Yes Yes
10 No No Yes
11 No No Yes
0 1 Yes No Yes
Note:Shaded cells show the conditions where the user software did not properly clear the overflow
condition.
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-20 1997 Microchip Technology Inc.
15.4.1.2 Reception
When the R/W bit of the address byte is clear and an address match occurs, the R/W bit of the
SSPSTAT register is cleared. The received address is loaded into the SSPBUF register.
When the address byte o v erflo w condition exists, then no acknowledge (ACK) pulse is given. An
overflow condition is defined as either the BF bit (SSPSTAT<0>) is set or the SSPOV bit
(SSPCON<6>) is set. So when a byte is received, with these conditions, and attempts to move
from the SSPSR register to the SSPBUF register, no acknowledge pulse is given.
An SSP interrupt is generated for each data transfer byte. The SSPIF flag bit must be cleared in
software. The SSPSTAT register is used to determine the status of the receive byte.
Figure 15-8: I2C Waveforms for Reception (7-bit Address)
P
9
8
7
6
5
D0
D1
D2
D3D4
D5
D6D7
S
A7 A6 A5 A4 A3 A2 A1SDA
SCL 123456789123456789123
4
Bus Master
terminates
transfer
Bit SSPOV is set because the SSPBUF register is still full.
Cleared in software
SSPBUF register is read
ACK Receiving Data
Receiving Data D0
D1
D2
D3D4
D5
D6D7
ACK
R/W=0
Receiving Address
SSPIF
BF (SSPSTAT<0>)
SSPOV (SSPCON<6>)
ACK
ACK is not sent.
1997 Microchip Technology Inc. DS31015A-page 15-21
Section 15. SSP
SSP
15
Figure 15-9: I2C Waveforms for Reception (10-bit Address)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
S1234 56 789 1 2345 67 89 1 2345 789 P
1 1 1 1 0 A9A8 A7 A6A5A4A3A2A1A0 D7D6D5D4D3 D1D0
Receive Data Byte
ACK
R/W = 0
ACK
Receive First Byte of Address
Cleared in software
Bus Master
terminates
transfer
D2
6
(PIR1<3>)
Receive Second Byte of Address
Cleared by hardware when
SSPADD is updated.
UA (SSPSTAT<1>)
Clock is held low until
update of SSPADD has
taken place
UA is set indicating that
the SSPADD needs to be
updated
UA is set indicating that
SSPADD needs to be
updated
SSPBUF is written with
contents of SSPSR Dummy read of SSPBUF
to clear BF flag
ACK
R/W = 1
Cleared in software
Dummy read of SSPBUF
to clear BF flag Read of SSPBUF
clears BF flag
Cleared by hardware when
SSPADD is updated.
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-22 1997 Microchip Technology Inc.
15.4.1.3 Transmission
When the R/W bit of the incoming address byte is set and an address match occurs , the R/W bit
of the SSPSTAT register is set. The received address is loaded into the SSPBUF register. The
ACK pulse will be sent on the ninth bit, and the SCL pin is held low. The transmit data must be
loaded into the SSPBUF register , which also loads the SSPSR register . Then the SCL pin should
be enabled by setting the CKP bit (SSPCON<4>). The master m ust monitor the SCL pin prior to
asserting another clock pulse . The sla v e devices may be holding off the master by stretching the
clock. The eight data bits are shifted out on the falling edge of the SCL input. This ensures that
the SDA signal is valid during the SCL high time (Figure 15-10).
An SSP interrupt is generated for each data transfer byte. The SSPIF flag bit must be cleared in
software, and the SSPSTAT register is used to determine the status of the byte transfer. The
SSPIF flag bit is set on the falling edge of the ninth clock pulse.
As a slave-transmitter, the ACK pulse from the master-receiver is latched on the rising edge of
the ninth SCL input pulse. If the SD A line was high (not ACK), then the data transfer is complete .
When the not A CK is latched by the sla v e, the sla v e logic is reset and the sla ve then monitors for
another occurrence of the START bit. If the SDA line was low (ACK), the transmit data must be
loaded into the SSPBUF register , which also loads the SSPSR register . Then the SCL pin should
be enabled by setting the CKP bit.
Figure 15-10: I2C Waveforms for Transmission (7-bit Address)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
CKP (SSPCON<4>)
A7 A6 A5 A4 A3 A2 A1 ACK D7 D6 D5 D4 D3 D2 D1 D0 ACKTransmitting DataR/W = 1Receiving Address
123456789 123456789 P
cleared in software
SSPBUF is written in software From SSP interrupt
service routine
Set bit after writing to SSPBUF
SData in
sampled SCL held low
while CPU
responds to SSPIF
(the SSPBUF must be written-to
before the CKP bit can be set)
R/W = 0
1997 Microchip Technology Inc. DS31015A-page 15-23
Section 15. SSP
SSP
15
Figure 15-11: I2C Waveforms for Transmission (10-bit Address)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
S123456789 123456789 12345 789 P
1 1 1 1 0 A9A8 A7 A6A5A4A3A2A1A0 1 1 1 1 0 A8
R/W=1
ACK
ACK
R/W = 0
ACK
Receive First Byte of Address
Cleared in software
Master sends NACK
A9
6
(PIR1<3>)
Receive Second Byte of Address
Cleared by hardware when
SSPADD is updated.
UA (SSPSTAT<1>)
Clock is held low until
update of SSPADD has
taken place
UA is set indicating that
the SSPADD needs to be
updated
UA is set indicating that
SSPADD needs to be
updated
Cleared by hardware when
SSPADD is updated.
SSPBUF is written with
contents of SSPSR Dummy read of SSPBUF
to clear BF flag
Receive First Byte of Address
12345 789
D7 D6 D5 D4 D3 D1
ACK
D2
6
Transmitting Data Byte
D0
Dummy read of SSPBUF
to clear BF flag
Sr
Cleared in software
Write of SSPBUF
initiates transmit
Cleared in software
Transmit is complete
CKP has to be set for clock to be released
Bus Master
terminates
transfer
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-24 1997 Microchip Technology Inc.
15.4.1.4 Clock Arbitration
Clock arbitr ation has the SCL pin to inhibit the master device from sending the next clock pulse.
The SSP module in I2C slave mode will hold the SCL pin low when the CPU needs to respond
to the SSP interrupt (SSPIF bit is set and the CKP bit is cleared). The data that needs to be trans-
mitted will need to be written to the SSPBUF register , and then the CKP bit will need to be set to
allow the master to generate the required clocks.
15.4.2 Master Mode (Firmware)
Master mode of operation is supported b y interrupt generation on the detection of the START and
STOP conditions. The STOP (P) and START (S) bits are cleared from a reset or when the SSP
module is disabled. Control of the I2C bus may be taken when the P bit is set, or the bus is idle
with both the S and P bits clear.
In master mode the SCL and SDA lines are manipulated by clearing the corresponding TRIS
bit(s). The output level is always low, irrespective of the value(s) in the PORT register. So when
transmitting data, a '1' data bit must have it’s TRIS bit set (input) and a '0' data bit must have it’s
TRIS bit cleared (output). The same scenario is true for the SCL line with the TRIS bit.
The following ev ents will cause SSP Interrupt Flag bit, SSPIF, to be set (SSP Interrupt if enabled):
START condition
STOP condition
Data transfer byte transmitted/received
Master mode of operation can be done with either the sla v e mode idle (SSPM3:SSPM0 = 1011)
or with the slav e active (SSPM3:SSP0 = 1110 or 1111). When the slave modes are enab led, the
software needs to differentiate the source(s) of the interrupt.
15.4.3 Multi-Master Mode (Firmware)
In multi-Master mode, the interrupt generation on the detection of the START and STOP condi-
tions allows the determination of when the bus is free. The STOP (P) and START (S) bits are
cleared from a reset or when the SSP module is disabled. Control of the I2C bus may be taken
when the P bit (SSPSTAT<4>) is set, or the bus is idle with both the S and P bits clear . When the
bus is busy, enabling the SSP Interrupt will generate the interrupt when the STOP condition
occurs.
In Multi-Master operation, the SDA line must be monitored to see if the signal level is the
e xpected output lev el. This check only needs to be done when a high lev el is output. If a high le vel
is expected and a low level is present, the device needs to release the SDA and SCL lines (set
the TRIS bits). There are two stages where this arbitration can be lost, they are:
Address transfer
Data transfer
When the slave logic is enabled, the slave continues to receive. If arbitration was lost during the
address transfer stage, communication to the device may be in progress. If addressed an ACK
pulse will be generated. If arbitration was lost during the data transf er stage , the de vice will need
to retransfer the data at a later time.
1997 Microchip Technology Inc. DS31015A-page 15-25
Section 15. SSP
SSP
15
15.4.4 Sleep Operation
While in sleep mode, the I2C module can receiv e addresses or data, and when an address match
or complete byte tr ansfer occurs w ake the processor from sleep (if the SSP interrupt is enab led).
15.4.5 Effect of a Reset
A reset disables the SSP module and terminates the current transfer.
Table 15-3: Registers Associated with I2C Operation
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on
POR,
BOR
Value on all
other resets
INTCON GIE PEIE T0IE INTE RBIE(2) T0IF INTF RBIF(2) 0000 000x 0000 000u
PIR SSPIF (1) 00
PIE SSPIE (1) 00
SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register xxxx xxxx uuuu uuuu
SSPADD Synchronous Serial Port (I2C mode) Address Register 0000 0000 0000 0000
SSPCON WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
SSPSTAT SMP CKE D/A P S R/W UA BF 0000 0000 0000 0000
Legend: x = unknown, u = unchanged, - = unimplemented read as '0'.
Shaded cells are not used by SSP in I2C mode.
Note 1: The positions of these bits are device dependent.
2: These bits may also be named GPIE and GPIF.
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-26 1997 Microchip Technology Inc.
15.5 Initialization
Example 15-2: SPI Master Mode Initialization
CLRF STATUS ; Bank 0
CLRF SSPSTAT ; SMP = 0, CKE = 0, and clear status bits
BSF SSPSTAT, CKE ; CKE = 1
MOVLW 0x31 ; Set up SPI port, Master mode, CLK/16,
MOVWF SSPCON ; Data xmit on falling edge (CKE=1 & CKP=1)
; Data sampled in middle (SMP=0 & Master mode)
BSF STATUS, RP0 ; Bank 1
BSF PIE, SSPIE ; Enable SSP interrupt
BCF STATUS, RP0 ; Bank 0
BSF INTCON, GIE ; Enable, enabled interrupts
MOVLW DataByte ; Data to be Transmitted
; Could move data from RAM location
MOVWF SSPBUF ; Start Transmission
1997 Microchip Technology Inc. DS31015A-page 15-27
Section 15. SSP
SSP
15
15.5.1 SSP Module / Basic SSP Module Compatibility
When upgrading from the Basic SSP module, the SSPSTAT register contains two additional
control bits. These bits are only used in SPI mode and are:
SMP, SPI data input sample phase
CKE, SPI Clock Edge Select
To be compatible with the SPI of the Basic SSP module, these bits m ust be appropriately config-
ured. If these bits are not at the states shown in Table 15-4, improper SPI communication may
occur.
Table 15-4: New Bit States for Compatibility
Basic SSP Module SSP Module
CKP CKP CKE SMP
1 100
0 000
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-28 1997 Microchip Technology Inc.
15.6 Design Tips
Question 1:
Using SPI mode, I do not seem able to talk to an SPI device.
Answer 1:
Ensure that you are using the correct SPI mode for that device. This SPI suppor ts all four SPI
modes so you should be able to get it to function. Check the clock polarity and the clock phase.
Question 2:
Using I
2
C mode, I do not seem able to make the master mode work.
Answer 2:
This SSP module does not hav e master mode fully automated in hardware , see Application Note
AN578 f or software which uses the SSP module to implement master mode. If you require a fully
automated hardware implementation of I2C Master Mode, please refer to the Microchip Line Card
for devices that have the Master SSP module.
Question 3:
Using I
2
C mode, I write data to the SSPBUF register, but the data did not
transmit.
Answer 3:
Ensure that you set the CKP bit to release the I2C clock.
Note: At the time of printing only the High-end family of devices (PIC17CXXX) have
devices with the Master SSP module implemented.
1997 Microchip Technology Inc. DS31015A-page 15-29
Section 15. SSP
SSP
15
15.7 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the SSP
Module are:
Title Application Note #
Use of the SSP Module in the I 2C Multi-Master Environment. AN578
Using Microchip 93 Series Serial EEPROMs with Microcontroller SPI Ports AN613
Software Implementation of I2C Bus Master AN554
Use of the SSP module in the Multi-master Environment AN578
Interfacing PIC16C64/74 to Microchip SPI Serial EEPROM AN647
Interfacing a Microchip PIC16C92x to Microchip SPI Serial EEPROM AN668
PICmicro MID-RANGE MCU FAMILY
DS31015A-page 15-30 1997 Microchip Technology Inc.
15.8 Revision History
Revision A
This is the initial released revision of the SSP module description.
1997 Microchip Technology Inc. DS31016A page 16-1
BSSP
16
M
Section 16. Basic Sychronous Serial Port (BSSP)
HIGHLIGHTS
This section of the manual contains the following major topics:
16.1 Introduction..................................................................................................................16-2
16.2 Control Registers .........................................................................................................16-3
16.3 SPI™ Mode..................................................................................................................16-6
16.4 SSP I2C Operation.....................................................................................................16-15
16.5 Initialization................................................................................................................16-23
16.6 Design Tips ................................................................................................................16-24
16.7 Related Application Notes..........................................................................................16-25
16.8 Revision History.........................................................................................................16-26
Note: Please refer to Appendix C.2 or the device data sheet to determine which devices
use this module.
SPI is a trademark of Motorola Corporation.
I2C is a trademark of Philips Corporation.
PICmicro MID-RANGE MCU FAMILY
DS31016A-page 16-2 1997 Microchip Technology Inc.
16.1 Introduction
The Basic Synchronous Serial P ort (BSSP) module is a serial interface useful f or communicating
with other peripheral or microcontroller devices. These peripheral devices may be Serial
EEPROMs, shift registers, display dr ivers, A/D conver ters, etc. The BSSP module can operate
in one of two modes:
Serial Peripheral Interface (SPI™)
Inter-Integrated Circuit (I2C™)
- Slave mode
- I/O slope control, Start and Stop bits to ease software implementation of Master and
Multi-master modes
I2C is a trademark of Philips Corporation.
1997 Microchip Technology Inc. DS31016A-page 16-3
Section 16. BSSP
BSSP
16
16.2 Control Registers
Register 16-1: SSPSTAT: Synchronous Serial Port Status Register
U-0 U-0 R-0 R-0 R-0 R-0 R-0 R-0
D/A P S R/W UA BF
bit 7 bit 0
bit 7:6 Unimplemented: Read as '0'
bit 5 D/A: Data/Address bit (I2C mode only)
1 = Indicates that the last byte received or transmitted was data
0 = Indicates that the last byte received or transmitted was address
bit 4 P: Stop bit
(I2C mode only. This bit is cleared when the SSP module is disabled)
1 = Indicates that a stop bit has been detected last (this bit is '0' on RESET)
0 = Stop bit was not detected last
bit 3 S: Start bit
(I2C mode only. This bit is cleared when the SSP module is disabled)
1 = Indicates that a start bit has been detected last (this bit is '0' on RESET)
0 = Start bit was not detected last
bit 2 R/W: Read/Write bit information (I2C mode only)
This bit holds the R/W bit inf ormation f ollowing the last address match. This bit is only valid from
the address match to the next start bit, stop bit, or not ACK bit.
1 = Read
0 = Write
bit 1 UA: Update Address (10-bit I2C mode only)
1 = Indicates that the user needs to update the address in the SSPADD register
0 = Address does not need to be updated
bit 0 BF: Buffer Full Status bit
Receive (SPI and I2C modes)
1 = Receive complete, SSPBUF is full
0 = Receive not complete, SSPBUF is empty
Transmit (I2C mode only)
1 = Transmit in progress, SSPBUF is full
0 = Transmit complete, SSPBUF is empty
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
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DS31016A-page 16-4 1997 Microchip Technology Inc.
Register 16-2: SSPCON: Synchronous Serial Port Control Register
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
bit 7 bit 0
bit 7 WCOL: Write Collision Detect bit
1 = The SSPBUF register is written while it is still transmitting the previous word
(must be cleared in software)
0 = No collision
bit 6 SSPOV: Receive Overflow Indicator bit
In SPI mode:
1 = A new byte is received while the SSPBUF register is still holding the previous data. In case
of overflow, the data in SSPSR is lost. Overflow can only occur in slave mode. The user
must read the SSPBUF, even if only transmitting data, to avoid setting overflow. In master
mode the overflow bit is not set since each new reception (and tr ansmission) is initiated by
writing to the SSPBUF register.
0 = No overflow
In I2C mode:
1 = A byte is received while the SSPBUF register is still holding the previous byte. SSPOV is a
“don‘t care” in transmit mode. SSPOV must be cleared in software in either mode.
0 = No overflow
bit 5 SSPEN: Synchronous Serial Port Enable bit
In both modes, when enabled, these pins must be properly configured as input or output.
In SPI mode:
1 = Enables serial port and configures SCK, SDO, SDI, and SS as the source of the
serial port pins
0 = Disables serial port and configures these pins as I/O port pins
In I2C mode:
1 = Enables the serial port and configures the SDA and SCL pins as the source of the
serial port pins
0 = Disables serial port and configures these pins as I/O port pins
bit 4 CKP: Clock Polarity Select bit
In SPI mode:
1 = Idle state for clock is a high level
0 = Idle state for clock is a low level
In I2C mode:
SCK release control
1 = Enable clock
0 = Holds clock low (clock stretch) (Used to ensure data setup time)
1997 Microchip Technology Inc. DS31016A-page 16-5
Section 16. BSSP
BSSP
16
bit 3:0 SSPM3:SSPM0: Synchronous Serial Port Mode Select bits
0000 = SPI master mode, clock = FOSC/4
0001 = SPI master mode, clock = FOSC/16
0010 = SPI master mode, clock = FOSC/64
0011 = SPI master mode, clock = TMR2 output/2
0100 = SPI slave mode, clock = SCK pin. SS pin control enabled.
0101 = SPI slave mode, clock = SCK pin. SS pin control disabled. SS can be used as I/O pin
0110 = I2C slave mode, 7-bit address
0111 = I2C slave mode, 10-bit address
1000 = Reserved
1001 = Reserved
1010 = Reserved
1011 = I2C Firmware controlled Master mode (slave idle)
1100 = Reserved
1101 = Reserved
1110 = I2C Firmware controlled Multi-Master mode,
7-bit address with start and stop bit interrupts enabled
1111 = I2C Firmware controlled Master mode,
10-bit address with start and stop bit interrupts enabled
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Register 16-2: SSPCON: Synchronous Serial Port Control Register (Cont’d)
PICmicro MID-RANGE MCU FAMILY
DS31016A-page 16-6 1997 Microchip Technology Inc.
16.3 SPI™ Mode
The SPI mode allows 8-bits of data to be synchronously transmitted and received simulta-
neously. To accomplish communication, typically three pins are used:
Serial Data Out (SDO)
Serial Data In (SDI)
Serial Clock (SCK)
Additionally a fourth pin may be used when in a slave mode of operation:
Slave Select (SS)
16.3.1 Operation
When initializing the SPI, se veral options need to be specified. This is done by programming the
appropriate control bits in the SSPCON register (SSPCON<5:0>). These control bits allow the
following to be specified:
Master Mode (SCK is the clock output)
Slave Mode (SCK is the clock input)
Clock Polarity (Output/Input data on the Rising/Falling edge of SCK)
Clock Rate (Master mode only)
Slave Select Mode (Slave mode only)
Figure 16-1 shows the block diagram of the SSP module, when in SPI mode.
Figure 16-1: SSP Block Diagram (SPI Mode)
Read Write
Internal
data bus
SDI
SDO
SS
SCK
SSPSR reg
SSPBUF reg
SSPM3:SSPM0
bit0 shift clock
SS Control
Enable
Edge
Select
Clock Select
TMR2 output
TCY
Prescaler
4, 16, 64
TRIS bit of SCK pin
2
Edge
Select
2
4
SPI is a trademark of Motorola Corporations.
1997 Microchip Technology Inc. DS31016A-page 16-7
Section 16. BSSP
BSSP
16
The SSP consists of a transmit/receiv e Shift Register (SSPSR) and a Buff er register (SSPB UF).
The SSPSR shifts the data in and out of the de vice, MSB first. The SSPBUF holds the data that
was previously written to the SSPSR, until the received data is ready. Once the 8-bits of data
hav e been received, that inf ormation is moved to the SSPB UF register . Then the b uffer full detect
bit, BF (SSPSTAT <0>), and interrupt flag bit, SSPIF, are set. This double b uffering of the received
data (SSPBUF) allows the ne xt b yte to start reception bef ore reading the data that was receiv ed.
Any write to the SSPBUF register during transmission/reception of data will be ignored, and the
write collision detect bit, WCOL (SSPCON<7>), will be set. User software m ust clear the WCOL
bit so that it can be determined if the following write(s) to the SSPBUF register completed suc-
cessfully. When the application software is expecting to receive valid data, the SSPBUF should
be read bef ore the ne xt b yte of data to transf er is written to the SSPBUF. Buffer full bit, BF (SSP-
STAT<0>), indicates when SSPBUF has been loaded with the received data (transmission is
complete). When the SSPBUF is read, the BF bit is cleared. This data ma y be irrelev ant if the SPI
is only a transmitter. Generally the SSP Interrupt is used to determine when the transmis-
sion/reception has completed. The SSPBUF can then be read (if data is meaningful) and/or the
SSPBUF (SSPSR) can be written. If the interrupt method is not going to be used, then software
polling can be done to ensure that a write collision does not occur . Example 16-1 shows the load-
ing of the SSPBUF (SSPSR) f or data tr ansmission. The shaded instruction is only required if the
received data is meaningful (some SPI applications are transmit only).
Example 16-1: Loading the SSPBUF (SSPSR) Register
The SSPSR is not directly readable or writable, and can only be accessed from addressing the
SSPBUF register. Additionally, the SSP status register (SSPSTAT) indicates the various status
conditions.
BCF STATUS, RP1 ;Specify Bank1
BSF STATUS, RP0 ;
LOOP BTFSS SSPSTAT, BF ;Has data been received (transmit complete)?
GOTO LOOP ;No
BCF STATUS, RP0 ;Specify Bank0
MOVF SSPBUF, W ;W reg = contents of SSPBUF
MOVWF RXDATA ;Save in user RAM, if data is meaningful
MOVF TXDATA, W ;W reg = contents of TXDATA
MOVWF SSPBUF ;New data to xmit
PICmicro MID-RANGE MCU FAMILY
DS31016A-page 16-8 1997 Microchip Technology Inc.
16.3.2 Enabling SPI I/O
To enable the serial port, SSP enable bit, SSPEN (SSPCON<5>), must be set. To reset or recon-
figure SPI mode, clear the SSPEN bit which re-initializ es the SSPCON register, and then set the
SSPEN bit. This configures the SDI, SDO, SCK, and SS pins as ser ial port pins. For the pins to
behave as the serial port function, they must have their data direction bits (in the TRIS register)
appropriately programmed. That is:
SDI must have the TRIS bit set
SDO must have the TRIS bit cleared
SCK (Master mode) must have the TRIS bit cleared
SCK (Slave mode) must have the TRIS bit set
•SS
must have the TRIS bit set
Any serial port function that is not desired ma y be ov erridden by programming the corresponding
data direction (TRIS) register to the opposite value . An example would be in master mode where
you are only sending data (to a display driver), then both SDI and SS could be used as general
purpose outputs by clearing their corresponding TRIS register bits.
1997 Microchip Technology Inc. DS31016A-page 16-9
Section 16. BSSP
BSSP
16
16.3.3 Typical Connection
Figure 16-2 shows a typical connection between two microcontrollers. The master controller
(Processor 1) initiates the data transfer by sending the SCK signal. Data is shifted out of both
shift registers on their programmed clock edge, and latched on the opposite edge of the clock.
Both processors should be programmed to same Clock Polarity (CKP), then both controllers
would send and receiv e data at the same time . Whether the data is meaningful (or dummy data)
depends on the application software. This leads to three scenarios for data transmission:
Master sends data Slave sends dummy data
Master sends data Slave sends data
Master sends dummy data Slave sends data
Figure 16-2: SPI Master/Slave Connection
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
MSb LSb
SDO
SDI
PROCESSOR 1
SCK
SPI Master (SSPM3:SSPM0 = 00xxb)
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
LSb
MSb
SDI
SDO
PROCESSOR 2
SCK
SPI Slave (SSPM3:SSPM0 = 010xb)
Serial Clock
PICmicro MID-RANGE MCU FAMILY
DS31016A-page 16-10 1997 Microchip Technology Inc.
16.3.4 Master Operation
The master can initiate the data transfer at any time because it controls the SCK. The master
determines when the slave (Processor 2) wishes to broadcast data by the software protocol.
In master mode the data is transmitted/receiv ed as soon as the SSPBUF register is written to. If
the SPI is only going to receive, the SDO output could be disabled (programmed as an input).
The SSPSR register will continue to shift in the signal present on the SDI pin at the progr ammed
clock rate. As each byte is received, it will be loaded into the SSPBUF register as if a normal
received b yte (interrupts and status bits appropriately set). This could be useful in receiver appli-
cations as a “line activity monitor” mode.
The clock polarity is selected by appropriately programming the CKP bit (SSPCON<4>). This
then would give waveforms for SPI communication as shown in Figure 16-5 and Figure 16-5
where the MSb is transmitted first. In master mode, the SPI clock r ate (bit rate) is user program-
mable to be one of the following:
•F
OSC/4 (or TCY)
•F
OSC/16 (or 4 • TCY)
•F
OSC/64 (or 16 • TCY)
Timer2 output/2
This allows a maximum data rate of 5 Mbps (at 20 MHz).
Figure 16-3: SPI Mode Waveform (Master Mode)
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
SSPIF
Interrupt flag
bit7
bit7 bit0
bit6 bit5 bit4 bit3 bit2 bit1 bit0
1997 Microchip Technology Inc. DS31016A-page 16-11
Section 16. BSSP
BSSP
16
16.3.5 Slave Operation
In slav e mode , the data is transmitted and receiv ed as the e xternal clock pulses appear on SCK.
When the last bit is latched the SSPIF interrupt flag bit is set.
The clock polarity is selected by appropriately programming the CKP bit (SSPCON<4>). This
then would give waveforms for SPI communication as shown in Figure 16-5 and Figure 16-5
where the MSb is transmitted first. When in slave mode the exter nal clock must meet the mini-
mum high and low times.
In sleep mode, the slave can transmit and receive data and wake the device from sleep if the
interrupt is enabled.
Figure 16-4: SPI Mode Waveform (Slave Mode w/o SS Control)
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
SSPIF
Interrupt flag
bit7
bit7 bit0
bit6 bit5 bit4 bit3 bit2 bit1 bit0
Next Q4 Cycle
after Q2
PICmicro MID-RANGE MCU FAMILY
DS31016A-page 16-12 1997 Microchip Technology Inc.
16.3.6 Slave Select Mode
The SS pin allows a synchronous slave mode. The SPI must be in slave mode
(SSPCON<3:0> = 04h) and the TRIS bit must be set the for the synchronous slave mode to be
enabled. When the SS pin is low, transmission and reception are enabled and the SDO pin is
driven. When the SS pin goes high, the SDO pin is no longer dr iven, even if in the middle of a
transmitted byte, and becomes a floating output. If the SS pin is taken low without resetting SPI
mode, the transmission will continue from the point at which it was taken high. To clear the bit
counter the Basic SSP module must be disab led and then re-enabled. External pull-up/pull-down
resistors may be desirable, depending on the application.
To emulate two-wire communication, the SDO pin can be connected to the SDI pin. When the
SPI needs to operate as a receiver the SDO pin can be configured as an input. This disables
transmissions from the SDO . The SDI can alwa ys be left as an input (SDI function) since it cannot
create a bus conflict.
Figure 16-5: SPI Mode Waveform (Slave Mode with ss Control)
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
SSPIF
bit7
bit7 bit0
bit6 bit5 bit4 bit3 bit2 bit1 bit0
SS
Next Q4 Cycle
after Q2
1997 Microchip Technology Inc. DS31016A-page 16-13
Section 16. BSSP
BSSP
16
Figure 16-6: Slave Synchronization Waveform
SCK
(CKP = 1)
SCK
(CKP = 0)
Input
Sample
SDI
SDO bit7 bit6 bit5
SSPIF
Interrupt
Write to
SSPBUF
SSPSR to
SSPBUF
SS
Flag
bit0
bit5 bit0
bit7
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DS31016A-page 16-14 1997 Microchip Technology Inc.
16.3.7 Sleep Operation
In master mode all module clocks are halted, and the transmission/reception will remain in that
state until the de vice wak es from sleep. After the device returns to normal mode, the module will
continue to transmit/receive data.
In slav e mode, the SPI transmit/receiv e shift register operates asynchronously to the de vice. This
allows the de vice to be placed in sleep mode, and data to be shifted into the SPI transmit/receiv e
shift register. When all 8-bits have been received, the SSP interrupt flag bit will be set and if
enabled will wake the device from sleep.
16.3.8 Effects of a Reset
A reset disables the SSP module and terminates the current transfer.
Table 16-1: Registers Associated with SPI Operation
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on
all other
resets
INTCON GIE PEIE T0IE INTE RBIE(2) T0IF INTF RBIF(2) 0000 000x 0000 000u
PIR SSPIF (1) 00
PIE SSPIE (1) 00
SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register xxxx xxxx uuuu uuuu
SSPCON WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
SSPSTAT D/A P S R/W UA BF --00 0000 --00 0000
Legend: x = unknown, u = unchanged, - = unimplemented read as '0'.
Shaded cells are not used by the SSP in SPI mode.
Note 1: The position of this bit is device dependent.
2: These bits can also be named GPIE and GPIF.
1997 Microchip Technology Inc. DS31016A-page 16-15
Section 16. BSSP
BSSP
16
16.4 SSP I2C Operation
The SSP module in I2C mode fully implements all sla ve functions, except General Call Support,
and provides interrupts on start and stop bits in hardware to facilitate software implementations
of the master functions. The SSP module implements the standard and fast mode specifications
as well as 7-bit and 10-bit addressing. Appendix A giv es an overview of the I2C bus specification.
Two pins are used for data transfer. These are the SCL pin, which is the clock, and the SD A pin,
which is the data. The user must configure these pins as inputs through the TRIS bits. The SSP
module functions are enabled by setting SSP Enable bit, SSPEN (SSPCON<5>).
A “glitch” filter is on the SCL and SDA pins when the pin is an input. This filter operates in both
the 100 KHz and 400 KHz modes. In the 100 KHz mode, when these pins are an output, there
is a slew rate control of the pin that is independent of device frequency.
Figure 16-7: SSP Block Diagram (I2C Mode)
Read Write
SSPSR reg
Match detect
SSPADD reg
Start and
Stop bit detect
SSPBUF reg
Internal
data bus
Addr Match
Set, Reset
S, P bits
(SSPSTAT reg)
SCL
shift
clock
MSb LSb
SDA
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DS31016A-page 16-16 1997 Microchip Technology Inc.
The SSP module has five registers for I2C operation. They are:
SSP Control Register (SSPCON)
SSP Status Register (SSPSTAT)
Serial Receive/Transmit Buffer (SSPBUF)
SSP Shift Register (SSPSR) - Not directly accessible
SSP Address Register (SSPADD)
The SSPCON register allows control of the I2C operation. Four mode selection bits
(SSPCON<3:0>) allow one of the following I2C modes to be selected:
•I
2C Slave mode (7-bit address)
•I
2C Slave mode (10-bit address)
•I
2C Firmware controlled Multi-Master mode, 7-bit address (start and stop bit interrupts
enabled)
•I
2C Firmware controlled Multi-Master mode, 10-bit address (start and stop bit interrupts
enabled)
•I
2C Firmware controlled Master mode, slave is idle
Bef ore selecting any I2C mode, the SCL and SD A pins must be prog rammed to inputs b y setting
the appropriate TRIS bits. Selecting an I2C mode, by setting the SSPEN bit, enables the SCL
and SDA pins to be used as the clock and data lines in I2C mode.
The SSPSTAT register gives the status of the data transfer. This infor mation includes detection
of a START or STOP bit, specifies if the received byte w as data or address, if the next byte is the
completion of 10-bit address, and if this will be a read or write data transfer. The SSPSTAT reg-
ister is read only.
The SSPBUF is the register to which transf er data is written to or read from. The SSPSR register
shifts the data in or out of the device. In receive operations, the SSPBUF and SSPSR create a
doubled buffered receiver. This allows reception of the next byte to begin before reading the last
byte of received data. When the complete byte is received, it is transferred to the SSPBUF reg-
ister and the SSPIF flag bit is set. If another complete byte is received before the SSPBUF reg-
ister is read, a receiver overflow has occurred and bit SSPOV (SSPCON<6>) is set.
The SSPADD register holds the slave address. In 10-bit mode, the user needs to write the high
byte of the address (1111 0 A9 A8 0). Following the high byte address match, the low byte of
the address needs to be loaded (A7:A0).
1997 Microchip Technology Inc. DS31016A-page 16-17
Section 16. BSSP
BSSP
16
16.4.1 Slave Mode
In slave mode, the SCL and SDA pins must be configured as inputs (TRIS bits set). The SSP
module will override the input state with the output data when required (slave-transmitter).
When an address is matched or the data transfer after an address match is received, the hard-
ware automatically will generate the acknowledge (ACK) pulse, and then load the SSPBUF reg-
ister with the received value currently in the SSPSR register.
There are cer tain conditions that will cause the SSP module not to give this ACK pulse. These
are if either (or both):
a) The buffer full bit, BF (SSPSTAT<0>), was set before the transfer was received.
b) The overflow bit, SSPOV (SSPCON<6>), was set before the transfer was received.
In this case, the SSPSR register v alue is not loaded into the SSPBUF, but bit SSPIF and SSPO V
bits are set. Table 16-2 sho ws what happens when a data transf er byte is receiv ed, given the sta-
tus of the BF and SSPOV bits. The shaded cells show the condition where user softw are did not
properly clear the overflow condition. The BF flag bit is cleared by reading the SSPBUF register
while the SSPOV bit is cleared through software.
The SCL clock input m ust ha ve a minimum high and low time for proper operation. The high and
low times of the I2C specification as well as the requirement of the SSP module are given in
parameter 100 and parameter 101 of the “Electrical Specifications” section.
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DS31016A-page 16-18 1997 Microchip Technology Inc.
16.4.1.1 Addressing
Once the SSP module has been enabled, it waits for a START condition to occur. Following the
START condition, the 8-bits are shifted into the SSPSR register. All incoming bits are sampled
with the rising edge of the clock (SCL) line. The value of register SSPSR<7:1> is compared to
the value of the SSPADD register . The address is compared on the falling edge of the eighth clock
(SCL) pulse. If the addresses match, and the BF and SSPOV bits are clear, the f ollo wing events
occur:
a) The SSPSR register value is loaded into the SSPBUF register on the falling edge of the
eight SCL pulse.
b) The buffer full bit, BF, is set on the falling edge of the eight SCL pulse.
c) An ACK pulse is generated.
d) SSP interrupt flag bit, SSPIF, is set (interrupt is generated if enabled) - on the f alling edge
of the ninth SCL pulse.
In 10-bit address mode, two address bytes need to be received by the slave. The five Most
Significant bits (MSbs) of the first address byte specify if this is a 10-bit address. The R/W bit
(SSPSTAT<2>) must specify a wr ite, so the slave device will receive the second address byte.
F or a 10-bit address the first byte would equal 1111 0 A9 A8 0’, where A9 and A8 are the two
MSbs of the address. The sequence of events for a 10-bit address is as follows, with steps 7- 9
for slave-transmitter:
1. Receive first (high) byte of Address (the SSPIF, BF, and UA (SSPSTAT<1>) bits are set).
2. Update the SSPADD register with second (low) byte of Address (clears the UA bit and
releases the SCL line).
3. Read the SSPBUF register (clears the BF bit) and clear the SSPIF flag bit.
4. Receive second (low) byte of Address (the SSPIF, BF, and UA bits are set).
5. Update the SSPADD register with the first (high) byte of Address. This will clear the UA bit
and release the SCL line.
6. Read the SSPBUF register (clears the BF bit) and clear the SSPIF flag bit.
7. Receive repeated START condition.
8. Receive first (high) byte of Address (the SSPIF and BF bits are set).
9. Read the SSPBUF register (clears the BF bit) and clear the SSPIF flag bit.
Table 16-2: Data Transfer Received Byte Actions
Note: Following the RESTART condition (step 7) in 10-bit mode, the user only needs to
match the first 7-bit address. The user does not update the SSPADD f or the second
half of the address.
Status bits as data
transfer is received
SSPSR SSPBUF Generate ACK
pulse
Set bit SSPIF
(SSP Interrupt occurs
if enabled)
BF SSPOV
00 Yes Yes Yes
10 No No Yes
11 No No Yes
0 1 Yes No Yes
Note:Shaded cells show the conditions where the user software did not properly clear the overflow con-
dition
1997 Microchip Technology Inc. DS31016A-page 16-19
Section 16. BSSP
BSSP
16
16.4.1.2 Reception
When the R/W bit of the address byte is clear and an address match occurs, the R/W bit of the
SSPSTAT register is cleared. The received address is loaded into the SSPBUF register.
When the address byte o v erflo w condition exists, then no acknowledge (ACK) pulse is given. An
overflow condition is defined as either the BF bit (SSPSTAT<0>) is set or the SSPOV bit
(SSPCON<6>) is set.
An SSP interrupt is generated for each data transfer byte. The SSPIF flag bit must be cleared in
software, and the SSPSTAT register is used to determine the status of the byte.
Figure 16-8: I2C Waveforms for Reception (7-bit Address)
P
9
8
7
6
5
D0
D1
D2
D3D4
D5
D6D7
S
A7 A6 A5 A4 A3 A2 A1SDA
SCL 123456789123456789123
4
Bus Master
terminates
transfer
Bit SSPOV is set because the SSPBUF register is still full.
Cleared in software
SSPBUF register is read
ACK Receiving Data
Receiving Data D0
D1
D2
D3D4
D5
D6D7
ACK
R/W=0
Receiving Address
SSPIF
BF (SSPSTAT<0>)
SSPOV (SSPCON<6>)
ACK
ACK is not sent.
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DS31016A-page 16-20 1997 Microchip Technology Inc.
16.4.1.3 Transmission
When the R/W bit of the incoming address byte is set and an address match occurs , the R/W bit
of the SSPSTAT register is set. The received address is loaded into the SSPBUF register. The
ACK pulse will be sent on the ninth bit, and the SCL pin is held low. The transmit data must be
loaded into the SSPBUF register , which also loads the SSPSR register . Then the SCL pin should
be enabled by setting the CKP bit (SSPCON<4>). The master m ust monitor the SCL pin prior to
asserting another clock pulse . The sla v e devices may be holding off the master by stretching the
clock. The eight data bits are shifted out on the falling edge of the SCL input. This ensures that
the SDA signal is valid during the SCL high time (Figure 16-9).
An SSP interrupt is generated for each data transfer byte. The SSPIF flag bit must be cleared in
software, and the SSPSTAT register is used to determine the status of the byte transfer. The
SSPIF flag bit is set on the falling edge of the ninth clock pulse.
As a slave-transmitter, the ACK pulse from the master-receiver is latched on the rising edge of
the ninth SCL input pulse. If the SD A line was high (not ACK), then the data transfer is complete .
When the not A CK is latched by the sla v e, the sla v e logic is reset and the sla ve then monitors for
another occurrence of the START bit. If the SDA line was low (ACK), the transmit data must be
loaded into the SSPBUF register , which also loads the SSPSR register . Then the SCL pin should
be enabled by setting the CKP bit.
Figure 16-9: I2C Waveforms for Transmission (7-bit Address)
16.4.1.4 Clock Arbitration
Clock arbitr ation has the SCL pin to inhibit the master device from sending the next clock pulse.
The SSP module in I2C slave mode will hold the SCL pin low when the CPU needs to respond
to the SSP interrupt (SSPIF bit is set and the CKP bit is cleared). The data that needs to be trans-
mitted will need to be written to the SSPBUF register , and then the CKP bit will need to be set to
allow the master to generate the required clocks.
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
CKP (SSPCON<4>)
A7 A6 A5 A4 A3 A2 A1 ACK D7 D6 D5 D4 D3 D2 D1 D0 ACKTransmitting DataR/W = 1Receiving Address
123456789 123456789 P
cleared in software
SSPBUF is written in software From SSP interrupt
service routine
Set bit after writing to SSPBUF
SData in
sampled SCL held low
while CPU
responds to SSPIF
1997 Microchip Technology Inc. DS31016A-page 16-21
Section 16. BSSP
BSSP
16
16.4.2 Master Mode (Firmware)
Master mode of operation is supported b y interrupt generation on the detection of the START and
STOP conditions. The STOP (P) and START (S) bits are cleared from a reset or when the SSP
module is disabled. Control of the I2C bus may be taken when the P bit is set, or the bus is idle
with both the S and P bits clear.
In master mode the SCL and SDA lines are manipulated by clearing the corresponding TRIS
bit(s). The output level is always low, irrespective of the value(s) in PORT. So when transmitting
data, a '1' data bit must have the TRIS bit set (input) and a '0' data bit must have the TRIS bit
cleared (output). The same scenario is true for the SCL line with the TRIS bit.
The following events will cause the SSPIF Interrupt Flag bit to be set (SSP Interrupt if enabled):
START condition
STOP condition
Data transfer byte transmitted/received
Master mode of operation can be done with either the sla v e mode idle (SSPM3:SSPM0 = 1011)
or with the slav e active (SSPM3:SSP0 = 1110 or 1111). When the slave modes are enab led, the
software needs to differentiate the source(s) of the interrupt.
16.4.3 Multi-Master Mode (Firmware)
In multi-master mode, the interrupt generation on the detection of the START and STOP condi-
tions allows the determination of when the bus is free. The STOP (P) and START (S) bits are
cleared from a reset or when the SSP module is disabled. Control of the I2C bus may be taken
when the P bit (SSPSTAT<4>) is set, or the bus is idle with both the S and P bits clear . When the
bus is busy, enabling the SSP Interrupt will generate the interrupt when the STOP condition
occurs.
In multi-master operation, the SDA line must be monitored to see if the signal level is the
e xpected output lev el. This check only needs to be done when a high lev el is output. If a high le vel
is expected and a low level is present, the device needs to release the SDA and SCL lines (set
the TRIS bits). There are two stages where this arbitration can be lost, they are:
Address Transfer
Data Transfer
When the slave logic is enabled, the slave continues to receive. If arbitration was lost during the
address transfer stage, communication to the device may be in progress. If addressed an ACK
pulse will be generated. If arbitration was lost during the data transf er stage , the de vice will need
to re-transfer the data at a later time.
PICmicro MID-RANGE MCU FAMILY
DS31016A-page 16-22 1997 Microchip Technology Inc.
16.4.4 Sleep Operation
While in sleep mode, the I2C module can receiv e addresses or data, and when an address match
or complete byte tr ansfer occurs w ake the processor from sleep (if the SSP interrupt is enab led).
16.4.5 Effect of a Reset
A reset disables the SSP module and terminates the current transfer.
Table 16-3: Registers Associated with I2C Operation
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on all
other resets
INTCON GIE PEIE T0IE INTE RBIE(2) T0IF INTF RBIF(2) 0000 000x 0000 000u
PIR SSPIF (1) 00
PIE SSPIE (1) 00
SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register xxxx xxxx uuuu uuuu
SSPADD Synchronous Serial Port (I2C mode) Address Register 0000 0000 0000 0000
SSPCON WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
SSPSTAT D/A P S R/W UA BF --00 0000 --00 0000
Legend: x = unknown, u = unchanged, - = unimplemented read as '0'.
Shaded cells are not used by SSP in I2C mode.
Note 1: The position of these bits is device dependent.
2: These bits can also be named GPIE and GPIF.
1997 Microchip Technology Inc. DS31016A-page 16-23
Section 16. BSSP
BSSP
16
16.5 Initialization
Example 16-2: SPI Master Mode Initialization
16.5.1 SSP Module / Basic SSP Module Compatibility
When changing from the SSP Module to the Basic SSP module, the SSPSTAT register contains
two additional control bits. These bits are:
SMP, SPI data input sample phase
CKE, SPI Clock Edge Select
To be compatible with the SPI of the Basic SSP module, these bits m ust be appropriately config-
ured. If these bits are not at the states shown in Table 16-4, improper SPI communication should
be expected. If the SSP module uses a different configuration then shown in Table 16-4, the
Basic SSP module can not be used to implement that mode. That mode may be implemented in
software.
Table 16-4: New Bit States for Compatibility
CLRF STATUS ; Bank 0
CLRF SSPSTAT ; Clear status bits
MOVLW 0x31 ; Set up SPI port, Master mode, CLK/16,
MOVWF SSPCON ; Data xmit on rising edge
; Data sampled in middle
BSF STATUS, RP0 ; Bank 1
BSF PIE1, SSPIE ; Enable SSP interrupt
BCF STATUS, RP0 ; Bank 0
BSF INTCON, GIE ; Enable, enabled interrupts
MOVLW DataByte ; Data to be Transmitted
; Could move data from RAM location
MOVWF SSPBUF ; Start Transmission
Basic SSP Module SSP Module
CKP CKP CKE SMP
1 100
0 000
PICmicro MID-RANGE MCU FAMILY
DS31016A-page 16-24 1997 Microchip Technology Inc.
16.6 Design Tips
Question 1:
Using SPI mode, I do not seem able to talk to an SPI device.
Answer 1:
Ensure that you are using the correct SPI mode f or that de vice . This SPI supports two of the four
SPI modes so ensure that the SPI de vice that you are trying to interface to is compatible with one
of these two modes. Check the clock polarity and the clock phase.
If the de vice is not compatible, switch to one of the Microchip devices that has the SSP module,
and that should solve this.
Question 2:
Using I
2
C mode, I do not seem able to make the master mode work.
Answer 2:
This SSP module does not hav e master mode fully automated in hardware , see Application Note
AN578 f or software which uses the SSP module to implement master mode. If you require a fully
automated Hardware implementation of I2C master mode, please refer to the Microchip Line
Card for devices that have the Master SSP module.
Question 3:
Using I
2
C mode, I write data to the SSPBUF register, but the data did not
transmit.
Answer 3:
Ensure that you set the CKP bit to release the I2C clock.
Note: At the time of printing only the High-end family of devices (PIC17CXXX) have
devices with the Master SSP module implemented.
1997 Microchip Technology Inc. DS31016A-page 16-25
Section 16. BSSP
BSSP
16
16.7 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to this section
are:
Title Application Note #
Use of the SSP Module in the I 2C Multi-Master Environment. AN578
Using Microchip 93 Series Serial EEPROMs with Microcontroller SPI Ports AN613
Software Implementation of I2C Bus Master AN554
Use of the SSP module in the Multi-Master Environment AN578
Interfacing PIC16C64/74 to Microchip SPI Serial EEPROM AN647
Interfacing a Microchip PIC16C92x to Microchip SPI Serial EEPROM AN668
PICmicro MID-RANGE MCU FAMILY
DS31016A-page 16-26 1997 Microchip Technology Inc.
16.8 Revision History
Revision A
This is the initial revision of the Basic SSP module description.
1997 Microchip Technology Inc. Preliminary DS31017A page 17-1
M
MSSP
17
Section 17. Master Synchronous Serial Port (MSSP)
HIGHLIGHTS
This section of the manual contains the following major topics:
17.1 Introduction..................................................................................................................17-2
17.2 Control Register...........................................................................................................17-4
17.3 SPI Mode .....................................................................................................................17-9
17.4 SSP I2C™ Operation .................................................................................................17-18
17.5 Connection Considerations for I2C Bus .....................................................................17-56
17.6 Initialization................................................................................................................17-57
17.7 Design Tips ................................................................................................................17-58
17.8 Related Application Notes..........................................................................................17-59
17.9 Revision History.........................................................................................................17-60
Note: At present NO Mid-Range MCU de vices are av ailab le with this module . Devices are
planned, but there is no schedule f or av ailability . Please ref er to Microchip’ s W eb site
or BBS for release of Product Br iefs. You will be able to find out the details and the
features for new devices.
This module is av ailable on Micr oc hip’s High End family (PIC17CXXX). Please
refer to Microchip’s Web site, BBS, Regional Sales Office, or Factory Repre-
sentatives.
I2C is a trademark of Philips Corporation.
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-2 Preliminary 1997 Microchip Technology Inc.
17.1 Introduction
The Master Synchronous Serial P ort (MSSP) module is a serial interface useful f or comm unicat-
ing with other peripheral or microcontroller devices. These peripheral devices may be serial
EEPROMs, shift registers, display dr ivers, A/D conver ters, etc. The MSSP module can operate
in one of two modes:
Serial Peripheral Interface (SPI™)
Inter-Integrated Circuit (I2C™)
- Full Master Mode
- Slave mode (with general address call)
Figure 17-1 shows a block diagram for the SPI mode, while Figure 17-2, and Figure 17-3 show
the block diagrams for the two different I2C modes of operation.
Figure 17-1: SPI Mode Block Diagram
Read Write
Internal
data bus
SSPSR reg
SSPBUF reg
SSPM3:SSPM0
bit0 shift clock
SS Control
Enable
Edge
Select
Clock Select
TMR2 output
TOSC
Prescaler
4, 16, 64
2
Edge
Select
2
4
Data to TX/RX in SSPSR
TRIS bit
2
SMP:CKE
SDI
SDO
SS
SCK
SPI is a trademark of Motorola Corporation.
I2C is a trademark of Philips Corporation.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-3
Section 17. MSSP
MSSP
17
Figure 17-2: I2C Slave Mode Block Diagram
Figure 17-3: I2C Master Mode Block Diagram
Read Write
SSPSR reg
Match detect
SSPADD reg
Start and
Stop bit detect
SSPBUF reg
Internal
data bus
Address Match or
Set, Reset
S, P bits
(SSPSTAT reg)
SCL
shift
clock
MSb LSb
SDA
General Call Detected
Read Write
SSPSR reg
Match detect
SSPADD reg
Start and Stop bit
detect / generate
SSPBUF reg
Internal
data bus
Address Match or
Set/Clear S bit
Clear/Set P bit
(SSPSTAT reg)
SCL
shift
clock
MSb LSb
SDA
Baud Rate Generator
7
SSPADD<6:0>
and
and Set SSPIF
General Call Detected
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-4 Preliminary 1997 Microchip Technology Inc.
17.2 Control Register
Register 17-1: SSPSTAT: SSP Status Register
R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0
SMP CKE D/A P S R/W UA BF
bit 7 bit 0
bit 7 SMP: Sample bit
SPI Master Mode
1 = Input data sampled at end of data output time
0 = Input data sampled at middle of data output time
SPI Slave Mode
SMP must be cleared when SPI is used in slave mode
In I2C master or slave mode:
1= Slew rate control disabled for standard speed mode (100 kHz and 1 MHz)
0= Slew rate control enabled for high speed mode (400 kHz)
bit 6 CKE: SPI Clock Edge Select
CKP = 0
1 = Data transmitted on rising edge of SCK
0 = Data transmitted on falling edge of SCK
CKP = 1
1 = Data transmitted on falling edge of SCK
0 = Data transmitted on rising edge of SCK
bit 5 D/A: Data/Address bit (I2C mode only)
1 = Indicates that the last byte received or transmitted was data
0 = Indicates that the last byte received or transmitted was address
bit 4 P: Stop bit
(I2C mode only. This bit is cleared when the SSP module is disabled, SSPEN is cleared)
1 = Indicates that a stop bit has been detected last (this bit is '0' on RESET)
0 = Stop bit was not detected last
bit 3 S: Start bit
(I2C mode only. This bit is cleared when the SSP module is disabled, SSPEN is cleared)
1 = Indicates that a start bit has been detected last (this bit is '0' on RESET)
0 = Start bit was not detected last
bit 2 R/W: Read/Write bit information (I2C mode only)
This bit holds the R/W bit inf ormation f ollowing the last address match. This bit is only valid from
the address match to the next start bit, stop bit, or not ACK bit.
In I2C slave mode:
1 = Read
0 = Write
In I2C master mode:
1 = Transmit is in progress
0 = Transmit is not in progress.
Or’ing this bit with SEN, RSEN, PEN, RCEN, or ACKEN will indicate if the SSP is
in IDLE mode.
bit 1 UA: Update Address (10-bit I2C mode only)
1 = Indicates that the user needs to update the address in the SSPADD register
0 = Address does not need to be updated
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-5
Section 17. MSSP
MSSP
17
bit 0 BF: Buffer Full Status bit
Receive (SPI and I2C modes)
1 = Receive complete, SSPBUF is full
0 = Receive not complete, SSPBUF is empty
Transmit (I2C mode only)
1 = Data Transmit in progress (does not include the ACK and stop bits), SSPBUF is full
0 = Data Transmit complete (does not include the ACK and stop bits), SSPBUF is empty
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Register 17-1: SSPSTAT: SSP Status Register (Cont’d)
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-6 Preliminary 1997 Microchip Technology Inc.
Register 17-2: SSPCON1: SSP Control Register1
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
bit 7 bit 0
bit 7 WCOL: Write Collision Detect bit
Master Mode:
1 = A write to the SSPBUF register was attempted while the I2C conditions were not valid for a
transmission to be started
0 = No collision
Slave Mode:
1 = The SSPBUF register is written while it is still transmitting the previous word
(must be cleared in software)
0 = No collision
bit 6 SSPOV: Receive Overflow Indicator bit
In SPI mode:
1 = A new byte is received while the SSPBUF register is still holding the previous data. In case
of overflow, the data in SSPSR is lost. Overflow can only occur in slave mode. In slave
mode, the user must read the SSPB UF, e v en if only transmitting data, to a v oid setting ov er-
flow . In master mode the ov erflow bit is not set since each ne w reception (and transmission)
is initiated by writing to the SSPBUF register.
0 = No overflow
In I2C mode:
1 = A byte is received while the SSPBUF register is still holding the previous byte. SSPOV is a
“don’t care” in transmit mode . SSPO V m ust be cleared in software in either mode . (must be
cleared in software)
0 = No overflow
bit 5 SSPEN: Synchronous Serial Port Enable bit
In both modes, when enabled, these pins must be properly configured as input or output.
In SPI mode:
1 = Enables serial port and configures SCK, SDO, SDI, and SS as the source of the serial
port pins
0 = Disables serial port and configures these pins as I/O port pins
In I2C mode:
1 = Enables the serial port and configures the SDA and SCL pins as the source of the
serial port pins
0 = Disables serial port and configures these pins as I/O port pins
bit 4 CKP: Clock Polarity Select bit
In SPI mode:
1 = Idle state for clock is a high level
0 = Idle state for clock is a low level
In I2C slave mode:
SCK release control
1 = Enable clock
0 = Holds clock low (clock stretch) (Used to ensure data setup time)
In I2C master mode
Unused in this mode
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-7
Section 17. MSSP
MSSP
17
bit 3 - 0 SSPM3:SSPM0: Synchronous Serial Port Mode Select bits
0000 = SPI master mode, clock = FOSC/4
0001 = SPI master mode, clock = FOSC/16
0010 = SPI master mode, clock = FOSC/64
0011 = SPI master mode, clock = TMR2 output/2
0100 = SPI slave mode, clock = SCK pin. SS pin control enabled.
0101 = SPI slave mode, clock = SCK pin. SS pin control disabled. SS can be used as I/O pin
0110 = I2C slave mode, 7-bit address
0111 = I2C slave mode, 10-bit address
1000 = I2C master mode, clock = FOSC / (4 * (SSPADD+1) )
1xx1 = Reserved
1x1x = Reserved
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Register 17-2: SSPCON1: SSP Control Register1 (Cont’d)
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-8 Preliminary 1997 Microchip Technology Inc.
Register 17-3: SSPCON2: SSP Control Register2
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
GCEN ACKSTAT ACKDT ACKEN RCEN PEN RSEN SEN
bit 7 bit 0
bit 7 GCEN: General Call Enable bit (In I2C slave mode only)
1 = Enable interrupt when a general call address (0000h) is received in the SSPSR
0 = General call address disabled
bit 6 ACKSTAT: Acknowledge Status bit (In I2C master mode only)
In master transmit mode:
1 = Acknowledge was not received from slave
0 = Acknowledge was received from slave
bit 5 ACKDT: Acknowledge Data bit (In I2C master mode only)
In master receive mode:
Value that will be transmitted when the user initiates an Ackno wledge sequence at the end of a
receive .
1 = Not Acknowledge
0 = Acknowledge
bit 4 ACKEN: Acknowledge Sequence Enable bit (In I2C master mode only)
In master receive mode:
1 = Initiate Acknowledge sequence on SDA and SCL pins, and transmit AKDT data bit.
Automatically cleared by hardware.
0 = Acknowledge sequence idle
Note: If the I2C module is not in the idle mode, this bit may not be set (no spooling), and
the SSPBUF may not be written (or writes to the SSPBUF are disabled).
bit 3 RCEN: Receive Enable bit (In I2C master mode only)
1 = Enables Receive mode for I2C
0 = Receive idle
Note: If the I2C module is not in the idle mode, this bit may not be set (no spooling), and
the SSPBUF may not be written (or writes to the SSPBUF are disabled).
bit 2 PEN: Stop Condition Enable bit (In I2C master mode only)
SCK release control
1 = Initiate Stop condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Stop condition idle
Note: If the I2C module is not in the idle mode, this bit may not be set (no spooling), and
the SSPBUF may not be written (or writes to the SSPBUF are disabled).
bit 1 RSEN: Repeated Start Condition Enabled bit (In I2C master mode only)
1 = Initiate Repeated Start condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Repeated Start condition idle.
Note: If the I2C module is not in the idle mode, this bit may not be set (no spooling), and
the SSPBUF may not be written (or writes to the SSPBUF are disabled).
bit 0 SEN: Start Condition Enabled bit (In I2C master mode only)
1 = Initiate Start condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Start condition idle
Note: If the I2C module is not in the idle mode, this bit may not be set (no spooling), and
the SSPBUF may not be written (or writes to the SSPBUF are disabled).
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-9
Section 17. MSSP
MSSP
17
17.3 SPI Mode
The SPI mode allows 8-bits of data to be synchronously transmitted and received simulta-
neously. All f our modes of SPI are supported. To accomplish communication, typically three pins
are used:
Serial Data Out (SDO)
Serial Data In (SDI)
Serial Clock (SCK)
Additionally a fourth pin may be used when in a slave mode of operation:
Slave Select (SS)
17.3.1 Operation
When initializing the SPI, se veral options need to be specified. This is done by programming the
appropriate control bits in the SSPCON1 register (SSPCON1<5:0>) and SSPSTAT<7:6>. These
control bits allow the following to be specified:
Master Mode (SCK is the clock output)
Slave Mode (SCK is the clock input)
Clock Polarity (Idle state of SCK)
Data input sample phase (middle or end of data output time)
Clock edge (output data on rising/falling edge of SCK)
Clock Rate (Master mode only)
Slave Select Mode (Slave mode only)
Figure 17-4 shows the block diagram of the SSP module, when in SPI mode.
Figure 17-4: SSP Block Diagram (SPI Mode)
Read Write
Internal
data bus
SSPSR reg
SSPBUF reg
SSPM3:SSPM0
bit0 shift
clock
SS Control
Enable
Edge
Select
Clock Select
TMR2 output
TOSC
Prescaler
4, 16, 64
2
Edge
Select
2
4
Data to TX/RX in SSPSR
TRIS bit
2
SMP:CKE
SDI
SDO
SS
SCK
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-10 Preliminary 1997 Microchip Technology Inc.
The SSP consists of a transmit/receiv e Shift Register (SSPSR) and a buffer register (SSPB UF).
The SSPSR shifts the data in and out of the device, MSb first. The SSPBUF holds the data that
was written to the SSPSR, until the received data is ready. Once the 8-bits of data have been
received, that byte is moved to the SSPBUF register. Then the buffer full detect bit, BF
(SSPSTAT<0>), and the interr upt flag bit, SSPIF, are set. This double buffering of the received
data (SSPBUF) allows the next byte to start reception before reading the data that was just
received. Any write to the SSPBUF register during transmission/reception of data will be ignored,
and the write collision detect bit, WCOL (SSPCON1<7>), will be set. User software must clear
the WCOL bit so that it can be deter mined if the following write(s) to the SSPBUF register com-
pleted successfully.
When the application software is expecting to receive valid data, the SSPBUF should be read
before the next byte of data to transfer is written to the SSPBUF. Buffer full bit, BF (SSPSTAT<0>),
indicates when SSPBUF has been loaded with the received data (transmission is complete).
When the SSPBUF is read, the BF bit is cleared. This data may be irrelevant if the SPI is only a
transmitter. Generally the SSP Interrupt is used to deter mine when the transmission/reception
has completed. The SSPB UF must be read and/or written. If the interrupt method is not going to
be used, then software polling can be done to ensure that a write collision does not occur.
Example 17-1 shows the loading of the SSPBUF (SSPSR) for data transmission.
Example 17-1: Loading the SSPBUF (SSPSR) Register
The SSPSR is not directly readable or writable, and can only be accessed by addressing the
SSPBUF register. Additionally, the SSP status register (SSPSTAT) indicates the various status
conditions.
17.3.2 Enabling SPI I/O
To enable the serial port, SSP Enable bit, SSPEN (SSPCON1<5>), must be set. To reset or
reconfigure SPI mode, clear the SSPEN bit, re-initializ e the SSPCON registers, and then set the
SSPEN bit. This configures the SDI, SDO, SCK, and SS pins as ser ial port pins. For the pins to
behav e as the serial port function, some must ha v e their data direction bits (in the TRIS register)
appropriately programmed. That is:
SDI is automatically controlled by the SPI module
SDO must have TRIS bit cleared
SCK (Master mode) must have TRIS bit cleared
SCK (Slave mode) must have TRIS bit set
•SS
must have TRIS bit set
Any serial port function that is not desired ma y be ov erridden by programming the corresponding
data direction (TRIS) register to the opposite value.
BCF STATUS, RP1 ;Specify Bank1
BSF STATUS, RP0 ;
LOOP BTFSS SSPSTAT, BF ;Has data been received (transmit complete)?
GOTO LOOP ;No
BCF STATUS, RP0 ;Specify Bank0
MOVF SSPBUF, W ;W reg = contents of SSPBUF
MOVWF RXDATA ;Save in user RAM, if data is meaningful
MOVF TXDATA, W ;W reg = contents of TXDATA
MOVWF SSPBUF ;New data to xmit
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-11
Section 17. MSSP
MSSP
17
17.3.3 Typical Connection
Figure 17-5 shows a typical connection between two microcontrollers. The master controller
(Processor 1) initiates the data transfer by sending the SCK signal. Data is shifted out of both
shift registers on their programmed clock edge, and latched on the opposite edge of the clock.
Both processors should be programmed to same Clock Polarity (CKP), then both controllers
would send and receiv e data at the same time . Whether the data is meaningful (or dummy data)
depends on the application software. This leads to three scenarios for data transmission:
Master sends data Slave sends dummy data
Master sends data Slave sends data
Master sends dummy data Slave sends data
Figure 17-5: SPI Master/Slave Connection
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
MSb LSb
SDO
SDI
PROCESSOR 1
SCK
SPI Master SSPM3:SSPM0 = 00xxb
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
LSb
MSb
SDI
SDO
PROCESSOR 2
SCK
SPI Slave SSPM3:SSPM0 = 010xb
Serial Clock
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-12 Preliminary 1997 Microchip Technology Inc.
17.3.4 Master Mode
The master can initiate the data transfer at any time because it controls the SCK. The master
determines when the slave (Processor 2, Figure 17-5) is to broadcast data by the software pro-
tocol.
In master mode the data is transmitted/receiv ed as soon as the SSPBUF register is written to. If
the SPI is only going to receive, the SDO output could be disabled (programmed as an input).
The SSPSR register will continue to shift in the signal present on the SDI pin at the progr ammed
clock rate. As each byte is received, it will be loaded into the SSPBUF register as if a normal
received b yte (interrupts and status bits appropriately set). This could be useful in receiver appli-
cations as a “line activity monitor” mode.
The clock polarity is selected by appropriately programming the CKP bit (SSPCON1<4>). This
then would give waveforms for SPI communication as shown in Figure 17-6, Figure 17-8, and
Figure 17-9 where the MSb is transmitted first. In master mode, the SPI clock rate (bit rate) is
user programmable to be one of the following:
•F
OSC/4 (or TCY)
•F
OSC/16 (or 4 • TCY)
•F
OSC/64 (or 16 • TCY)
Timer2 output/2
This allows a maximum data rate (at 20 MHz) of 8.25 Mbps.
Figure 17-6 Shows the wavefor ms for master mode. When the CKE bit is set, the SDO data is
valid before there is a clock edge on SCK. The change of the input sample is shown based on
the state of the SMP bit. The time when the SSPBUF is loaded with the received data is shown.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-13
Section 17. MSSP
MSSP
17
Figure 17-6: SPI Mode Waveform (Master Mode)
SCK
(CKP = 0
SCK
(CKP = 1
SCK
(CKP = 0
SCK
(CKP = 1
4 clock
modes
Input
Sample
Input
Sample
SDI bit7 bit0
SDO bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
bit7 bit0
SDI
SSPIF
(SMP = 1)
(SMP = 0)
(SMP = 1)
CKE = 1)
CKE = 0)
CKE = 1)
CKE = 0)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SDO bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
(CKE = 0)
(CKE = 1)
Next Q4 cycle
after Q2
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-14 Preliminary 1997 Microchip Technology Inc.
17.3.5 Slave Mode
In slav e mode , the data is transmitted and receiv ed as the e xternal clock pulses appear on SCK.
When the last bit is latched, the SSPIF interrupt flag bit is set.
While in slave mode the external clock is supplied by the external clock source on the SCK pin.
This external clock m ust meet the minimum high and low times as specified in the electrical spec-
ifications.
While in sleep mode, the slave can transmit/receive data. When a byte is receive the device will
wake-up from sleep.
17.3.6 Slave Select Synchronization
The SS pin allows a synchronous slave mode. The SPI must be in slave mode with SS pin
control enabled (SSPCON1<3:0> = 04h). The pin must not be driven low for the SS pin to
function as an input. The Data Latch must be high. When the SS pin is low, transmission
and reception are enabled and the SDO pin is driv en. When the SS pin goes high, the SDO
pin is no longer driven, even if in the middle of a transmitted byte, and becomes a floating
output. External pull-up/ pull-down resistors may be desirable, depending on the application.
When the SPI module resets, the bit counter is f orced to 0. This can be done by either by forcing
the SS pin to a high level or clearing the SSPEN bit.
To emulate two-wire communication, the SDO pin can be connected to the SDI pin. When the
SPI needs to operate as a receiver the SDO pin can be configured as an input. This disables
transmissions from the SDO . The SDI can alwa ys be left as an input (SDI function) since it cannot
create a bus conflict.
Note 1: When the SPI is in Slave Mode with SS pin control enabled, (SSPCON<3:0> =
0100) the SPI module will reset if the SS pin is set to VDD.
Note 2: If the SPI is used in Slave Mode with CKE is set, then the SS pin control must be
enabled.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-15
Section 17. MSSP
MSSP
17
Figure 17-7: Slave Synchronization Waveform
Figure 17-8: SPI Mode Waveform (Slave Mode with CKE = 0)
SCK
(CKP = 1
SCK
(CKP = 0
Input
Sample
SDI bit7
SDO bit7 bit6 bit7
SSPIF
Interrupt
(SMP = 0)
CKE = 0)
CKE = 0)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SS
Flag
bit0
bit7 bit0
Next Q4 cycle
after Q2
SCK
(CKP = 1
SCK
(CKP = 0
Input
Sample
SDI bit7 bit0
SDO bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
SSPIF
Interrupt
(SMP = 0)
CKE = 0)
CKE = 0)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SS
Flag
optional
Next Q4 cycle
after Q2
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-16 Preliminary 1997 Microchip Technology Inc.
Figure 17-9: SPI Mode Waveform (Slave Mode with CKE = 1)
SCK
(CKP = 1
SCK
(CKP = 0
Input
Sample
SDI bit7 bit0
SDO bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
SSPIF
Interrupt
(SMP = 0)
CKE = 1)
CKE = 1)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SS
Flag
not optional
Next Q4 cycle
after Q2
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-17
Section 17. MSSP
MSSP
17
17.3.7 Sleep Operation
In master mode all module clocks are halted, and the transmission/reception will remain in that
state until the de vice wak es from sleep. After the device returns to normal mode, the module will
continue to transmit/receive data.
In slav e mode, the SPI transmit/receiv e shift register operates asynchronously to the de vice. This
allows the de vice to be placed in sleep mode, and data to be shifted into the SPI transmit/receiv e
shift register. When all 8-bits have been received, the MSSP interrupt flag bit will be set and if
enabled will wake the device from sleep.
17.3.8 Effects of a Reset
A reset disables the MSSP module and terminates the current transfer.
Table 17-1: Registers Associated with SPI Operation
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on
POR,
BOR
Value on all
other resets
INTCON GIE PEIE T0IE INTE RBIE(2) T0IF INTF RBIF(2) 0000 0000 0000 0000
PIR SSPIF (1) 00
PIE SSPIE (1) 00
SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register xxxx xxxx uuuu uuuu
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
SSPSTAT SMP CKE D/A P S R/W UA BF 0000 0000 0000 0000
Legend: x = unknown, u = unchanged, - = unimplemented read as '0'.
Shaded cells are not used by the SSP in SPI mode.
Note 1: The position of this bit is device dependent.
2: These bits may also be named GPIE and GPIF.
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-18 Preliminary 1997 Microchip Technology Inc.
17.4 SSP I2C™ Operation
The MSSP module in I2C mode fully implements all master and slave functions (including gen-
eral call suppor t) and provides interrupts on star t and stop bits in hardware to deter mine a free
bus (multi-master function). The SSP module implements the standard mode specifications as
well as 7-bit and 10-bit addressing. Appendix A gives an overview of the I2C bus specification.
A “glitch” filter is on the SCL and SDA pins when the pin is an input. This filter operates in both
the 100 KHz and 400 KHz modes. In the 100 KHz mode, when these pins are an output, there
is a slew rate control of the pin that is independent of device frequency.
Figure 17-10: I2C Slave Mode Block Diagram
Figure 17-11: I2C Master Mode Block Diagram
Read Write
SSPSR reg
Match detect
SSPADD reg
Start and
Stop bit detect
SSPBUF reg
Internal
data bus
Address Match
Set, Reset
S, P bits
(SSPSTAT reg)
SCL
shift
clock
MSb LSb
SDA
Read Write
SSPSR reg
Match detect
SSPADD reg
Start and Stop bit
detect / generate
SSPBUF reg
Internal
data bus
Address Match
Set/Clear S bit
Clear/Set P bit
(SSPSTAT reg)
SCL
shift
clock
MSb LSb
SDA
Baud Rate Generator
7
SSPADD<6:0>
and
and Set SSPIF
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-19
Section 17. MSSP
MSSP
17
Two pins are used for data transfer. These are the SCL pin, which is the clock, and the SD A pin,
which is the data. Pins that are on the por t are automatically configured when the I2C mode is
enabled. The SSP module functions are enabled by setting SSP Enable bit, SSPEN
(SSPCON1<5>).
The SSP module has six registers for I2C operation. They are the:
SSP Control Register1 (SSPCON1)
SSP Control Register2 (SSPCON2)
SSP Status Register (SSPSTAT)
Serial Receive/Transmit Buffer (SSPBUF)
SSP Shift Register (SSPSR) - Not directly accessible
SSP Address Register (SSPADD)
The SSPCON1 register allows control of the I2C operation. Four mode selection bits
(SSPCON1<3:0>) allow one of the following I2C modes to be selected:
•I
2C Slave mode (7-bit address)
•I
2C Slave mode (10-bit address)
•I
2C Master mode, clock = OSC/4 (SSPADD +1)
Bef ore selecting any I2C mode, the SCL and SD A pins must be prog rammed to inputs b y setting
the appropriate TRIS bits. Selecting an I2C mode, by setting the SSPEN bit, enables the SCL
and SDA pins to be used as the clock and data lines in I2C mode.
The SSPSTAT register gives the status of the data transfer. This infor mation includes detection
of a START or STOP bit, specifies if the received byte w as data or address, if the next byte is the
completion of 10-bit address, and if this will be a read or write data transfer.
The SSPBUF is the register to which transf er data is written to or read from. The SSPSR register
shifts the data in or out of the device. In receive operations, the SSPBUF and SSPSR create a
double buffered receiver. This allows reception of the next byte to begin before reading the last
byte of received data. When the complete byte is received, it is transferred to the SSPBUF reg-
ister and flag bit SSPIF is set. If another complete byte is received before the SSPBUF register
is read, a receiver o v erflo w has occurred and the SSPOV bit (SSPCON1<6>) is set and the byte
in the SSPSR is lost.
The SSPADD register holds the slave address. In 10-bit mode, the user needs to write the high
byte of the address (1111 0 A9 A8 0). Following the high byte address match, the low byte of
the address needs to be loaded (A7:A0).
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-20 Preliminary 1997 Microchip Technology Inc.
17.4.1 Slave Mode
In slave mode, the SCL and SDA pins must be configured as inputs. The SSP module will over-
ride the input state with the output data when required (slave-transmitter).
When an address is matched or the data transfer after an address match is received, the hard-
ware automatically will generate the acknowledge (ACK) pulse, and then load the SSPBUF reg-
ister with the received value currently in the SSPSR register.
There are cer tain conditions that will cause the SSP module not to give this ACK pulse. These
are if either (or both):
a) The buffer full bit, BF (SSPSTAT<0>), was set before the transfer was received.
b) The overflow bit, SSPOV (SSPCON1<6>), was set before the transfer was received.
If the BF bit is set, the SSPSR register value is not loaded into the SSPBUF, but the SSPIF and
SSPO V bits are set. Table 17-2 sho ws what happens when a data transfer b yte is received, giv en
the status of the BF and SSPOV bits. The shaded cells show the condition where user software
did not properly clear the overflow condition. The BF flag bit is cleared by reading the SSPBUF
register while bit SSPOV is cleared through software.
The SCL clock input m ust ha ve a minimum high and low time for proper operation. The high and
low times of the I2C specification as well as the requirement of the SSP module is sho wn in timing
parameters 100 and 101 of the “Electrical Specifications” section.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-21
Section 17. MSSP
MSSP
17
17.4.1.1 Addressing
Once the SSP module has been enabled, it waits for a START condition to occur. Following the
START condition, the 8-bits are shifted into the SSPSR register. All incoming bits are sampled
with the rising edge of the clock (SCL) line. The value of register SSPSR<7:1> is compared to
the value of the SSPADD register . The address is compared on the falling edge of the eighth clock
(SCL) pulse. If the addresses match, and the BF and SSPOV bits are clear, the f ollo wing events
occur:
a) The SSPSR register value is loaded into the SSPBUF register on the falling edge of the
eighth SCL pulse.
b) The buffer full bit, BF, is set on the falling edge of the eighth SCL pulse.
c) An ACK pulse is generated.
d) SSP interrupt flag bit, SSPIF, is set (interrupt is generated if enabled) - on the f alling edge
of the ninth SCL pulse.
In 10-bit address mode, two address bytes need to be received by the slave. The five Most Sig-
nificant bits (MSbs) of the first address byte specify if this is a 10-bit address. The R/W bit
(SSPSTAT<2>) must specify a write so the sla ve de vice will receive the second address b yte. F or
a 10-bit address the first byte w ould equal 1111 0 A9 A8 0’, where A9 and A8 are the two MSbs
of the address. The sequence of events for a 10-bit address is as follows, with steps 7- 9 for
slave-transmitter:
1. Receive first (high) byte of Address (the SSPIF, BF, and UA (SSPSTAT<1>) bits are set).
2. Update the SSPADD register with second (low) byte of Address (clears the UA bit and
releases the SCL line).
3. Read the SSPBUF register (clears the BF bit) and clear flag bit SSPIF.
4. Receive second (low) byte of Address (the SSPIF, BF, and UA bits are set).
5. Update the SSPADD register with the first (high) byte of Address. This will clear the UA bit
and release the SCL line.
6. Read the SSPBUF register (clears the BF bit) and clear the SSPIF flag bit.
7. Receive repeated START condition.
8. Receive first (high) byte of Address (the SSPIF and BF bits are set).
9. Read the SSPBUF register (clears the BF bit) and clear the SSPIF flag bit.
Table 17-2: Data Transfer Received Byte Actions
Note: F ollowing the Repeated Start condition (step 7) in 10-bit mode, the user only needs
to match the first 7-bit address. The user does not update the SSPADD for the sec-
ond half of the address.
Status Bits as Data
Transfer is Received
SSPSR SSPBUF Generate ACK
Pulse
Set bit SSPIF
(SSP Interrupt occurs
if enabled)
BF SSPOV
00 Yes Yes Yes
10 No No Yes
11 No No Yes
0 1 Yes No Yes
Note: Shaded cells show the conditions where the user software did not properly clear the overflow
condition
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-22 Preliminary 1997 Microchip Technology Inc.
17.4.1.2 Slave Reception
When the R/W bit of the address byte is clear and an address match occurs, the R/W bit of the
SSPSTAT register is cleared. The received address is loaded into the SSPBUF register.
When the address byte o v erflo w condition exists, then no acknowledge (ACK) pulse is given. An
overflow condition is defined as either the BF bit (SSPSTAT<0>) is set or the SSPOV bit
(SSPCON1<6>) is set.
An SSP interrupt is generated for each data transfer byte. The SSPIF flag bit must be cleared in
software. The SSPSTAT register is used to determine the status of the received byte.
Note: The SSPBUF will be loaded if the SSPOV bit is set and the BF flag bit is cleared. If
a read of the SSPBUF was perfor med, but the user did not clear the state of the
SSPOV bit before the ne xt receive occurred. The ACK is not sent and the SSPBUF
is updated.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-23
Section 17. MSSP
MSSP
17
17.4.1.3 Slave Transmission
When the R/W bit of the incoming address byte is set and an address match occurs , the R/W bit
of the SSPSTAT register is set. The received address is loaded into the SSPBUF register. The
ACK pulse will be sent on the ninth bit, and the SCL pin is held low. The transmit data must be
loaded into the SSPBUF register , which also loads the SSPSR register . Then the SCL pin should
be enabled b y setting the CKP bit (SSPCON1<4>). The master should monitor the SCL pin prior
to asser ting another clock pulse. The slave devices may be holding off the master by stretching
the clock. The eight data bits are shifted out on the falling edge of the SCL input. This ensures
that the SDA signal is valid during the SCL high time (Figure 17-13).
An SSP interrupt is generated for each data transfer byte. The SSPIF flag bit must be cleared in
software, and the SSPSTAT register is used to determine the status of the byte transfer. The
SSPIF flag bit is set on the falling edge of the ninth clock pulse.
As a slave-transmitter, the ACK pulse from the master-receiver is latched on the rising edge of
the ninth SCL input pulse. If the SD A line was high (not ACK), then the data transfer is complete .
When the not A CK is latched by the sla v e, the sla v e logic is reset and the sla ve then monitors for
another occurrence of the START bit. If the SDA line was low (ACK), the transmit data must be
loaded into the SSPBUF register , which also loads the SSPSR register . Then the SCL pin should
be enabled by setting the CKP bit.
Figure 17-12: I2C Slave Mode Waveforms for Reception (7-bit Address)
Figure 17-13: I2C Slave Mode Waveforms for Transmission (7-bit Address)
P
9
8
7
6
5
D0
D1
D2
D3D4
D5
D6D7
S
A7 A6 A5 A4 A3 A2 A1SDA
SCL 123456789123456789123
4
Bus Master
terminates
transfer
Bit SSPOV is set because the SSPBUF register is still full.
Cleared in software
SSPBUF register is read
ACK Receiving Data
Receiving Data D0
D1
D2
D3D4
D5
D6D7
ACK
R/W=0
Receiving Address
SSPIF
BF (SSPSTAT<0>)
SSPOV (SSPCON1<6>)
ACK
ACK is not sent.
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
CKP (SSPCON1<4>)
A7 A6 A5 A4 A3 A2 A1 ACK D7 D6 D5 D4 D3 D2 D1 D0 ACKTransmitting DataR/W = 1Receiving Address
123456789 123456789 P
cleared in software
SSPBUF is written in software From SSP interrupt
service routine
Set bit after writing to SSPBUF
SData in
sampled SCL held low
while CPU
responds to SSPIF
(the SSPBUF must be written-to
before the CKP bit can be set)
R/W = 0
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-24 Preliminary 1997 Microchip Technology Inc.
Figure 17-14: I2C Slave Mode Waveform (Transmission 10-bit Address)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
S123456789 123456789 12345 789 P
1 1 1 1 0 A9A8 A7 A6A5A4A3A2A1A0 1 1 1 1 0 A8
R/W=1
ACK
ACK
R/W = 0
ACK
Receive First Byte of Address
Cleared in software
Master sends NACK
A9
6
(PIR1<3>)
Receive Second Byte of Address
Cleared by hardware when
SSPADD is updated.
UA (SSPSTAT<1>)
Clock is held low until
update of SSPADD has
taken place
UA is set indicating that
the SSPADD needs to be
updated
UA is set indicating that
SSPADD needs to be
updated
Cleared by hardware when
SSPADD is updated.
SSPBUF is written with
contents of SSPSR Dummy read of SSPBUF
to clear BF flag
Receive First Byte of Address
12345 789
D7 D6 D5 D4 D3 D1
ACK
D2
6
Transmitting Data Byte
D0
Dummy read of SSPBUF
to clear BF flag
Sr
Cleared in software
Write of SSPBUF
initiates transmit
Cleared in software
Transmit is complete
CKP has to be set for clock to be released
Bus Master
terminates
transfer
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-25
Section 17. MSSP
MSSP
17
Figure 17-15: I2C Slave Mode Waveform (Reception 10-bit Address)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
S1234 56 789 1 2345 67 89 12345 789 P
1 1 1 1 0 A9A8 A7 A6A5A4A3A2A1A0 D7D6D5D4D3 D1D0
Receive Data Byte
ACK
R/W = 0
ACK
Receive First Byte of Address
Cleared in software
Bus Master
terminates
transfer
D2
6
(PIR1<3>)
Receive Second Byte of Address
Cleared by hardware when
SSPADD is updated.
UA (SSPSTAT<1>)
Clock is held low until
update of SSPADD has
taken place
UA is set indicating that
the SSPADD needs to be
updated
UA is set indicating that
SSPADD needs to be
updated
SSPBUF is written with
contents of SSPSR Dummy read of SSPBUF
to clear BF flag
ACK
R/W = 1
Cleared in software
Dummy read of SSPBUF
to clear BF flag Read of SSPBUF
clears BF flag
Cleared by hardware when
SSPADD is updated.
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-26 Preliminary 1997 Microchip Technology Inc.
17.4.2 General Call Address Support
The addressing procedure for the I2C bus is such that the first byte after the START condition
usually determines which device will be the slave addressed by the master . The exception is the
general call address which can address all devices. When this address is used, all devices
should, in theory, respond with an acknowledge.
The general call address is one of eight addresses reserved f or specific purposes by the I 2C pro-
tocol. It consists of all 0’s with R/W = 0.
The general call address is recognized when the General Call Enable bit (GCEN) is enabled
(SSPCON2<7> set). Following a start-bit detect, 8-bits are shifted into SSPSR and the address
is compared against SSPADD, and is also compared to the general call address, fixed in hard-
ware.
If the general call address matches, the SSPSR is transferred to the SSPBUF, the BF flag bit is
set (eight bit), and on the f alling edge of the ninth bit (ACK bit) the SSPIF interrupt flag bit is set.
When the interrupt is serviced. The source for the interrupt can be checked by reading the con-
tents of the SSPBUF to determine if the address was device specific or a general call address.
In 10-bit mode, the SSPADD is required to be updated for the second half of the address to
match, and the UA bit is set (SSPSTAT<1>). If the general call address is sampled when the
GCEN bit is set while the slav e is configured in 10-bit address mode , then the second half of the
address is not necessar y, the UA bit will not be set, and the slave will begin receiving data after
the acknowledge (Figure 17-16).
Figure 17-16: Slave Mode General Call Address Sequence (7 or 10-bit Address Mode)
SDA
SCL S
SSPIF
BF (SSPSTAT<0>)
SSPOV (SSPCON1<6>)
Cleared in software
SSPBUF is read
R/W = 0ACK
General Call Address
Address is compared to General Call Address
GCEN (SSPCON2<7>)
Receiving data ACK
123456789123456789
D7 D6 D5 D4 D3 D2 D1 D0
after ACK, set interrupt
'0'
'1'
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-27
Section 17. MSSP
MSSP
17
17.4.3 Sleep Operation
While in sleep mode, the I2C module can receiv e addresses or data, and when an address match
or complete byte transfer occurs wake the processor from sleep (if the MSSP interrupt is
enabled).
17.4.4 Effect of a Reset
A reset disables the MSSP module and terminates the current transfer.
Table 17-3: Registers Associated with I2C Operation
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on
POR,
BOR
V alue on all
other resets
INTCON GIE PEIE T0IE INTE RBIE(2) T0IF INTF RBIF(2) 0000 0000 0000 0000
PIR SSPIF, BCLIF (1) 0, 0 0, 0
PIE SSPIE, BCLIF (1) 0, 0 0, 0
SSPADD Synchronous Serial Port (I2C mode)
Address Register (slave mode)/Baud Rate Generator (master mode) 0000 0000 0000 0000
SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register xxxx xxxx uuuu uuuu
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
SSPCON2 GCEN ACKSTAT ACKDT ACKEN RCEN PEN RSEN SEN 0000 0000 0000 0000
SSPSTAT SMP CKE D/A P S R/W UA BF 0000 0000 0000 0000
Legend: x = unknown, u = unchanged, - = unimplemented read as '0'.
Shaded cells are not used by the SSP in I2C mode.
Note 1: The position of these bits is device dependent.
2: These bits may also be named GPIE and GPIF.
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DS31017A-page 17-28 Preliminary 1997 Microchip Technology Inc.
17.4.5 Master Mode
Master mode of operation is supported b y interrupt generation on the detection of the START and
STOP conditions. The STOP (P) and START (S) bits are cleared from a reset or when the SSP
module is disabled. Control of the I2C bus may be taken when the P bit is set, or the bus is idle
with both the S and P bits clear.
In master mode the SCL and SDA lines are manipulated by the SSP hardware.
The following ev ents will cause SSP Interrupt Flag bit, SSPIF, to be set (SSP Interrupt if enabled):
START condition
STOP condition
Data transfer byte transmitted/received
Ackno wledge Transmit
Repeated Start
Figure 17-17: SSP Block Diagram (I2C Master Mode)
Read Write
SSPSR
Start bit, Stop bit,
Start bit detect
SSPBUF
Internal
data bus
Set/Reset, S, P, WCOL (SSPSTAT)
shift
clock
MSb LSb
SDA
Acknowledge
Generate
Stop bit detect
Write collision detect
Clock Arbitration
State counter for
end of XMIT/RCV
SCL
SCL in
Bus Collision
SDA in
Receive Enable
clock cntl
clock arbitrate/WCOL detect
(hold off clock source)
SSPADD<6:0>
Baud
Set SSPIF, BCLIF
Reset ACKSTAT, PEN (SSPCON2)
rate
generator
SSPM3:SSPM0
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-29
Section 17. MSSP
MSSP
17
17.4.6 Multi-Master Mode
In multi-master mode, the interrupt generation on the detection of the START and STOP condi-
tions allows the determination of when the bus is free. The STOP (P) and START (S) bits are
cleared from a reset or when the SSP module is disabled. Control of the I2C bus may be taken
when the P bit (SSPSTAT<4>) is set, or the bus is idle with both the S and P bits clear . When the
bus is busy, enabling the SSP Interrupt will generate the interrupt when the STOP condition
occurs.
In multi-master operation, the SD A line must be monitored, f or arbitration, to see if the signal lev el
is the expected output level. This check is performed in hardware, with the result placed in the
BCLIF bit.
The states where arbitration can be lost are:
Address Transfer
Data Transfer
A Start Condition
A Repeated Start Condition
An Acknowledge Condition
17.4.7 I2C Master Mode Support
Master Mode is enabled b y setting and clearing the appropriate SSPM bits in SSPCON1 and by
setting the SSPEN bit. Once master mode is enabled, the user has six options.
1. Assert a start condition on SDA and SCL.
2. Assert a Repeated Start condition on SDA and SCL.
3. Write to the SSPBUF register initiating transmission of data/address.
4. Generate a stop Condition on SDA and SCL.
5. Configure the I2C port to receive data.
6. Generate an acknowledge condition at the end of a received byte of data.
Note: The SSP Module when configured in I2C Master Mode does not allow queueing of
e vents. For instance: The user is not allowed to initiate a start condition, and imme-
diately write the SSPBUF register to imitate transmission before the START condi-
tion is complete. In this case the SSPBUF will not be written to, and the WCOL bit
will be set, indicating that a write to the SSPBUF did not occur.
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-30 Preliminary 1997 Microchip Technology Inc.
17.4.7.1 I2C Master Mode Operation
The master de vice generates all of the serial clock pulses and the STAR T and STOP conditions.
A transfer is ended with a STOP condition or with a repeated START condition. Since the
repeated START condition is also the beginning of the ne xt serial transf er, the I2C bus will not be
released.
In Master transmitter mode serial data is output through SD A, while SCL outputs the serial clock.
The first byte transmitted contains the slave address of the receiving device, (7 bits) and the
Read/Write (R/W) bit. In this case the R/W bit will be logic '0'. Serial data is transmitted 8 bits at
a time. After each byte is transmitted, an acknowledge bit is received. START and STOP condi-
tions are output to indicate the beginning and the end of a serial transfer.
In Master receive mode the first byte transmitted contains the slave address of the transmitting
device (7 bits) and the R/W bit. In this case the R/W bit will be logic ‘1‘. Thus the first byte trans-
mitted is a 7-bit slave address followed by a '1' to indicate receive bit. Serial data is received via
SDA while SCL outputs the serial clock. Ser ial data is received 8 bits at a time. After each byte
is received, an acknowledge bit is transmitted. START and STOP conditions indicate the begin-
ning and end of transmission.
The baud rate generator used f or SPI mode oper ation is used to set the SCL cloc k frequency f or
either 100 kHz, 400 kHz, or 1 MHz I2C operation. The baud rate generator reload value is con-
tained in the lower 7 bits of the SSPADD register. The baud rate generator will automatically
begin counting on a write to the SSPBUF. Once the given operation is complete (i.e., transmis-
sion of the last data bit is f ollowed b y A CK) the internal clock will automatically stop counting and
the SCL pin will remain in its last state.
A typical transmit sequence would go as follows:
a) The user generates a Start Condition by setting the START enable bit, SEN
(SSPCON2<0>).
b) SSPIF is set. The SSP module will w ait the required start time before any other oper ation
takes place.
c) The user loads the SSPBUF with the address to transmit.
d) Address is shifted out the SDA pin until all 8 bits are transmitted.
e) The SSP Module shifts in the ACK bit from the slave device, and writes its value into the
SSPCON2 register (SSPCON2<6>).
f) The SSP module generates an interrupt at the end of the ninth clock cycle by setting the
SSPIF bit.
g) The user loads the SSPBUF with eight bits of data.
h) DATA is shifted out the SDA pin until all 8 bits are transmitted.
i) The SSP Module shifts in the ACK bit from the slave device, and writes its value into the
SSPCON2 register (SSPCON2<6>).
j) The SSP module generates an interrupt at the end of the ninth clock cycle by setting the
SSPIF bit.
k) The user generates a STOP condition by setting the STOP enable bit, PEN
(SSPCON2<2>).
l) Interrupt is generated once the stop condition is complete.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-31
Section 17. MSSP
MSSP
17
17.4.8 Baud Rate Generator
In I2C master mode, the reload value for the BRG is located in the lower 7 bits of the SSPADD
register (Figure 17-18). When the BRG is loaded with this value, the BRG counts down to 0 and
stops until another reload has taken place. In I2C master mode, the BRG is reloaded automati-
cally. If Clock Arbitr ation is taking place f or instance , the BRG will be reloaded when the SCL pin
is sampled high (Figure 17-19).
Figure 17-18: Baud Rate Generator Block Diagram
Figure 17-19: Baud Rate Generator Timing With Clock Arbitration
SSPM3:SSPM0
BRG Down Counter
CLKOUT Fosc/4
SSPADD<6:0>
SSPM3:SSPM0
SCL Reload
Control Reload
SDA
SCL
SCL de-asserted but slave holds
DX-1DX
BRG
SCL is sampled high, reload takes
place, and BRG starts its count.
03h 02h 01h 00h (hold off) 03h 02h
reload
BRG
value
SCL low (clock arbitration) SCL allowed to transition high
BRG counts
down BRG counts
down
BRG counts
down
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-32 Preliminary 1997 Microchip Technology Inc.
17.4.9 I2C Master Mode Start Condition Timing
To initiate a START condition the user sets the star t condition enable bit, SEN (SSPCON2<0>).
If the SD A and SCL pins are sampled high, the baud rate generator is re-loaded with the contents
of SSPADD<6:0>, and star ts its count. If SCL and SDA are both sampled high when the baud
rate generator times out (TBRG), the SDA pin is driven low. The action of the SDA being dr iven
low while SCL is high is the STAR T condition, and causes the S bit (SSPSTAT<3>) to be set. F ol-
lowing this , the baud rate generator is reloaded with the contents of SSPADD<6:0> and resumes
its count. When the baud rate generator times out (TBRG) the SEN bit (SSPCON2<0>) will be
automatically cleared by hardware, the baud rate generator is suspended leaving the SDA line
held low, and the START condition is complete.
17.4.9.1 WCOL Status Flag
If the user writes the SSPBUF when an START sequence is in progress, then WCOL is set and
the contents of the buffer are unchanged (the write doesn’t occur).
Figure 17-20: First Start Bit Timing
Note: If at the beginning of START condition the SDA and SCL pins are already sampled
low, or if during the START condition the SCL line is sampled low before the SDA
line is driven low, a bus collision occurs, the Bus Collision Interrupt Flag,BCLIF, is
set, the START condition is aborted, and the I2C module is reset into its IDLE state.
Note: Because queueing of e v ents is not allo wed, writing to the low er 5 bits of SSPCON2
is disabled until the START condition is complete.
SDA
SCL
S
TBRG
1st Bit 2nd Bit
TBRG
SDA = 1, At completion of start bit,
SCL = 1
Write to SSPBUF occurs here
TBRG
Hardware clears SEN bit
TBRG
Write to SEN bit occurs here. Set S bit (SSPSTAT<3>)
and sets SSPIF bit
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-33
Section 17. MSSP
MSSP
17
Figure 17-21: Start Condition Flowchart
Idle Mode
SEN (SSPCON2<0> = 1)
Bus collision detected,
Set BCLIF, SDA = 1?
Load BRG with
Yes
BRG
Rollover?
Force SDA = 0,
Load BRG with
SSPADD<6:0>,
No
Yes
Force SCL = 0,
Clear SEN.
Set S bit
SSPADD<6:0>
SCL = 1?
SDA = 0? No
Yes
BRG
rollover?
No
Clear SEN
Start Condition Done,
No
Yes
Reset BRG
SCL= 0?
No
Yes
SCL = 0?
No
Yes
Reset BRG
Release SCL,
SSPEN = 1,
SSPCON1<3:0> = 1000
Set SSPIF
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-34 Preliminary 1997 Microchip Technology Inc.
17.4.10 I2C Master Mode Repeated Start Condition Timing
A Repeated Start condition occurs when the RSEN bit (SSPCON2<1>) is programmed high and
the I2C logic module is in the idle state. When the RSEN bit is set, the SCL pin is asserted low.
When the SCL pin is sampled low, the baud rate generator is loaded with the contents of
SSPADD<5:0>, and begins counting. The SDA pin is released (brought high) for one baud rate
generator count (TBRG). When the baud rate generator times out, if SDA is sampled high, the
SCL pin will be de-asserted (brought high). When SCL is sampled high the baud rate generator
is re-loaded with the contents of SSPADD<6:0> and begins counting. SDA and SCL must be
sampled high for one TBRG. This action is then followed by assertion of the SDA pin (SDA = 0)
for one TBRG while SCL is high. Following this, the RSEN bit (SSPCON2<1>) will be automati-
cally cleared, and the baud rate generator is not reloaded, lea ving the SD A pin held low. As soon
as a star t condition is detected on the SDA and SCL pins, the S bit (SSPSTAT<3>) will be set.
The SSPIF bit will not be set until the baud rate generator has timed-out.
Immediately following the SSPIF bit getting set, the user may write the SSPBUF with the 7-bit
address in 7-bit mode, or the default first address in 10-bit mode. After the first eight bits are
transmitted and an ACK is received, the user may then transmit an additional eight bits of
address (10-bit mode) or eight bits of data (7-bit mode).
Note 1: If RSEN is programmed while any other event is in progress, it will not take effect.
Note 2: A bus collision during the Repeated Start condition occurs if:
• SDA is sampled low when SCL goes from low to high.
• SCL goes low before SDA is asserted low. This may indicates that another
master is attempting to transmit a data ‘1’.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-35
Section 17. MSSP
MSSP
17
17.4.10.1 WCOL Status Flag
If the user writes the SSPBUF when a Repeated Star t sequence is in progress, then WCOL is
set and the contents of the buffer are unchanged (the write doesn’t occur).
Figure 17-22: Repeat Start Condition Waveform
Note: Because queueing of e v ents is not allo wed, writing of the low er 5 bits of SSPCON2
is disabled until the Repeated Start condition is complete.
SDA
SCL
Sr = Repeated Start
Write to SSPCON2
Write to SSPBUF occurs here.
Falling edge of ninth clock
End of Xmit
At completion of start bit,
hardware clear RSEN bit
1st Bit
Set S (SSPSTAT<3>)
TBRG
TBRG
SDA = 1,
SDA = 1,
SCL(no change) SCL = 1
occurs here.
TBRG TBRG TBRG
and set SSPIF
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-36 Preliminary 1997 Microchip Technology Inc.
Figure 17-23: Repeated Start Condition Flowchart (part 1 of 2)
Idle Mode,
SSPEN = 1,
Force SCL = 0
SCL = 0?
Release SDA,
Load BRG with
SCL = 1? No
Yes
No
Yes
BRG
No
Yes
Release SCL
SSPCON1<3:0> = 1000
rollover?
SSPADD<6:0>
Load BRG with
SSPADD<6:0>
(Clock Arbitration)
A
B
C
SDA = 1?
No
Yes
Start
RSEN = 1
Bus Collision,
Set BCLIF,
Release SDA,
Clear RSEN
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-37
Section 17. MSSP
MSSP
17
Figure 17-24: Repeated Start Condition Flowchart (part 2 of 2)
Force SDA = 0,
Load BRG with
SSPADD<6:0>
Yes
Repeated Start
Clear RSEN,
Yes
BRG
rollover?
BRG
rollover?
Yes
SDA = 0?
No SCL = 1? No
B
Set S
CA
No
No
Yes
Force SCL = 0,
Reset BRG
Set SSPIF.
SCL = '0'?
Reset BRG
No
Yes
condition done,
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-38 Preliminary 1997 Microchip Technology Inc.
17.4.11 I2C Master Mode Transmission
Transmission of a data byte , a 7-bit address, or the either half of a 10-bit address is accomplished
by simply writing a value to SSPBUF register. This action will set the buffer full flag bit, BF, and
allow the baud rate generator to begin counting and start the next transmission. Each bit of
address/data will be shifted out onto the SDA pin after the falling edge of SCL is asserted (see
data hold time specification parameters 106). SCL is held low for one baud rate generator roll
ov er count (TBRG). Data should be v alid before SCL is released high (see Data setup time spec-
ification parameters 107). When the SCL pin is released high, it is held that way for TBRG, the
data on the SD A pin must remain stable f or that duration and some hold time after the ne xt f alling
edge of SCL. After the eighth bit is shifted out (the falling edge of the eighth clock), the BF flag
is cleared and the master releases SDA allowing the slave device being addressed to respond
with an A CK bit during the ninth bit time, if an address match occurs or if data was received prop-
erly. The status of ACK is written into the A CKDT bit on the falling edge of the ninth clock. If the
master receives an ac kno wledge, the ac knowledge status bit, A CKS TAT, is cleared. If not, the bit
is set. After the ninth clock the SSPIF bit is set, and the master clock (baud rate generator) is
suspended until the next data byte is loaded into the SSPBUF leaving SCL low and SDA
unchanged (Figure 17-26).
After the write to the SSPBUF, each bit of address will be shifted out on the falling edge of SCL
until all se ven address bits and the R/W bit are completed. On the f alling edge of the eighth clock
the master will de-assert the SD A pin allowing the sla v e to respond with an ackno wledge. On the
falling edge of the ninth clock the master will sample the SDA pin to see if the address was rec-
ognized by a slave. The status of the ACK bit is loaded into the ACKSTAT status bit
(SSPCON2<6>). Following the falling edge of the ninth clock transmission of the address, the
SSPIF is set, the BF flag is cleared, and the baud rate generator is turned off until another write
to the SSPBUF takes place, holding SCL low and allowing SDA to float.
17.4.11.1 BF Status Flag
In transmit mode, the BF bit (SSPSTAT<0>) is set when the CPU writes to SSPBUF and is
cleared when all 8 bits are shifted out.
17.4.11.2 WCOL Status Flag
If the user writes the SSPBUF when a transmit is already in progress (i.e . SSPSR is still shifting
out a data byte), then WCOL is set and the contents of the buffer are unchanged (the write
doesn’t occur).
WCOL must be cleared in software.
17.4.11.3 ACKSTAT Status Flag
In transmit mode, the ACKSTAT bit (SSPCON2<6>) is cleared when the slave has sent an
acknowledge (ACK = 0), and is set when the slave does not acknowledge (ACK = 1). A slave
sends an ackno wledge when it has recognized its address (including a general call), or when the
slave has properly received its data.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-39
Section 17. MSSP
MSSP
17
Figure 17-25: Master Transmit Flowchart
Idle Mode
Num_Clocks = 0,
Release SDA so
slave can drive ACK,
Num_Clocks
Load BRG with
SDA = Current Data bit
Yes
BRG
rollover?
No
BRG
No
Yes
Force SCL = 0
= 8?
Yes
No
Yes
BRG
rollover? No
Force SCL = 1,
Stop BRG
SCL = 1?
Load BRG with
count high time
Rollover? No
Read SDA and place into
ACKSTAT bit (SSPCON2<6>)
Force SCL = 0,
SCL = 1?
SDA =
Data bit?
No
Yes
Yes
rollover?
No
Yes
Stop BRG,
Force SCL = 1
(Clock Arbitration)
(Clock Arbitration)
Num_Clocks
= Num_Clocks + 1
Bus collision detected
Set BCLIF, hold prescale off,
Yes
No
BF = 1
Force BF = 0
SSPADD<6:0>,
start BRG count,
Load BRG with
SSPADD<6:0>,
start BRG count
SSPADD<6:0>,
Load BRG with
count SCL high time
SSPADD<6:0>,
SDA =
Data bit?
Yes
No
Clear XMIT enable
SCL = 0? No
Yes
Reset BRG
Write SSPBUF
Set SSPIF
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-40 Preliminary 1997 Microchip Technology Inc.
Figure 17-26: I2C Master Mode Waveform (Transmission, 7 or 10-bit Address)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
SEN
A7 A6 A5 A4 A3 A2 A1 ACK = 0 D7D6D5D4D3D2D1D0
ACK
Transmitting Data or Second Half
R/W = 0Transmit Address to Slave
123456789 123456789 P
cleared in software service routine
SSPBUF is written in software
From SSP interrupt
After start condition SEN cleared by hardware.
S
SSPBUF written with 7 bit address and R/W
start transmit
SCL held low
while CPU
responds to SSPIF
SEN = 0
of 10-bit Address
Write SSPCON2<0> SEN = 1
START condition begins From slave clear ACKSTAT bit SSPCON2<6>
ACKSTAT in
SSPCON2 = 1
cleared in software
SSPBUF written
PEN
Cleared in software
R/W
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-41
Section 17. MSSP
MSSP
17
17.4.12 I2C Master Mode Reception
Master mode reception is enabled by programming the receive enable bit, RCEN
(SSPCON2<3>).
The baud rate generator begins counting, and on each rollo ver, the state of the SCL pin changes
(high to low/low to high), and data is shifted into the SSPSR. After the falling edge of the eighth
clock, the receiv e enable flag is automatically cleared, the contents of the SSPSR are loaded into
the SSPBUF, the BF flag bit is set, the SSPIF flag bit is set, and the baud rate generator is sus-
pended from counting, holding SCL low. The SSP is now in IDLE state, awaiting the next com-
mand. When the b uffer is read by the CPU , the BF flag bit is automatically cleared. The user can
then send an acknowledge bit at the end of reception, by setting the acknowledge sequence
enable bit, ACKEN (SSPCON2<4>).
17.4.12.1 BF Status Flag
In receive oper ation, the BF bit is set when an address or data b yte is loaded into SSPBUF from
SSPSR. It is cleared when the SSPBUF register is read.
17.4.12.2 SSPOV Status Flag
In receive operation, the SSPOV bit is set when 8 bits are received into the SSPSR, and the BF
flag bit is already set from a previous reception.
17.4.12.3 WCOL Status Flag
If the user writes the SSPBUF when a receive is already in progress (i.e. SSPSR is still shifting
in a data byte), then the WCOL bit is set and the contents of the buff er are unchanged (the write
doesn’t occur).
Note: The SSP Module must be in an IDLE STATE before the RCEN bit is set, or the
RCEN bit will be disregarded.
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-42 Preliminary 1997 Microchip Technology Inc.
Figure 17-27: Master Receiver Flowchart
Idle mode
Num_Clocks = 0,
Release SDA
Force SCL=0,
Yes
No
BRG
rollover?
Release SCL
Yes
No
SCL = 1?
Load BRG with
Yes
No
BRG
rollover?
(Clock Arbitration)
Load BRG w/
start count
SSPADD<6:0>,
start count.
Sample SDA,
Shift data into SSPSR
Num_Clocks
= Num_Clocks + 1
Yes
Num_Clocks
= 8?
No
Force SCL = 0,
Set SSPIF,
Set BF.
Move contents of SSPSR
into SSPBUF,
Clear RCEN.
RCEN = 1
SSPADD<6:0>,
SCL = 0?
Yes
No
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-43
Section 17. MSSP
MSSP
17
Figure 17-28: I2C Master Mode Waveform (Reception 7-Bit Address)
P
9
87
6
5
D0
D1
D2
D3D4
D5
D6D7
S
A7 A6 A5 A4 A3 A2 A1
SDA
SCL 12345678912345678 9 1234
Bus Master
terminates
transfer
ACK Receiving Data from Slave
Receiving Data from Slave D0
D1
D2
D3D4
D5
D6D7
ACK
R/W = 1
Transmit Address to Slave
SSPIF
BF
ACK is not sent
Write to SSPCON2<0> (SEN = 1)
Write to SSPBUF occurs here ACK from Slave
Master configured as a receiver
by programming SSPCON2<3>, (RCEN = 1) PEN bit = 1
written here
Data shifted in on falling edge of CLK
Cleared in software
Start XMIT
SEN = 0
SSPOV
SDA = 0, SCL = 1
while CPU
(SSPSTAT<0>)
ACK
Last bit is shifted into SSPSR and
contents are unloaded into SSPBUF
Cleared in software
Cleared in software
Set SSPIF interrupt
at end of receive
Set P bit
(SSPSTAT<4>)
and SSPIF
Cleared in
software
ACK from Master
Set SSPIF at end
Set SSPIF interrupt
at end of acknowledge
sequence
Set SSPIF interrupt
at end of acknow-
ledge sequence
of receive
Set ACKEN start acknowledge sequence
SSPOV is set because
SSPBUF is still full
SDA = ACKDT = 1
RCEN cleared
automatically
RCEN = 1 start
next receive
Write to SSPCON2<4>
to start acknowledge sequence
SDA = ACKDT (SSPCON2<5>) = 0
RCEN cleared
automatically
responds to SSPIF
ACKEN
Begin Start Condition
Cleared in software
SDA = ACKDT = 0
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-44 Preliminary 1997 Microchip Technology Inc.
17.4.13 Acknowledge Sequence Timing
An ackno wledge sequence is enab led b y setting the acknowledge sequence enab le bit, ACKEN
(SSPCON2<4>). When this bit is set, the SCL pin is pulled lo w and the contents of the acknowl-
edge data bit is presented on the SDA pin. If the user wishes to generate an acknowledge, then
the ACKDT bit should be cleared. If not, the user should set the ACKDT bit before star ting an
ackno wledge sequence. The baud rate generator then counts f or one rollov er period (TBRG), and
the SCL pin is de-asser ted (pulled high). When the SCL pin is sampled high (clock arbitration),
the baud rate generator counts for TBRG. The SCL pin is then pulled low. Following this, the
ACKEN bit is automatically cleared, the baud rate generator is turned off, and the SSP module
then goes into IDLE mode (Figure 17-29).
17.4.13.1 WCOL Status Flag
If the user writes the SSPBUF when an ackno wledge sequence is in progress, then WCOL is set
and the contents of the buffer are unchanged (the write doesn’t occur).
Figure 17-29: Acknowledge Sequence Waveform
Note: TBRG= one baud rate generator period.
SDA
SCL
Set SSPIF at the end
Acknowledge sequence starts here,
Write to SSPCON2 ACKEN automatically cleared
Cleared in
TBRG TBRG
of receive
ACK
8
ACKEN = 1, ACKDT = 0
D0
9
SSPIF
software Set SSPIF at the end
of acknowledge sequence
Cleared in
software
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-45
Section 17. MSSP
MSSP
17
Figure 17-30: Acknowledge Flowchart
Idle mode
Force SCL = 0
Yes
No SCL = 0?
Drive ACKDT bit
Yes
No BRG
rollover?
(SSPCON2<5>)
onto SDA pin,
Load BRG with
SSPADD<6:0>,
start count.
Force SCL = 1
Yes
No SCL = 1?
No ACKDT = 1?
Load BRG with
No
BRG
rollover?
SSPADD <6:0>,
start count.
No
SDA = 1?
Bus collision detected,
Set BCLIF,
Yes
Force SCL = 0,
(Clock Arbitration)
Clear ACKEN
No
SCL = 0? Reset BRG Clear ACKEN
Set ACKEN
Release SCL,
Yes
Yes
Yes
Set SSPIF
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-46 Preliminary 1997 Microchip Technology Inc.
17.4.14 Stop Condition Timing
A stop bit is asserted on the SDA pin at the end of a receive/transmit by setting the Stop
sequence enable bit, PEN (SSPCON2<2>). At the end of a receive/tr ansmit the SCL line is held
low after the falling edge of the ninth clock. When the PEN bit is set, the master will asser t the
SD A line low. When the SDA line is sampled low, the baud rate generator is reloaded and counts
down to 0. When the baud rate generator times out, the SCL pin will be brought high, and one
TBRG (baud rate generator rollover count) later, the SDA pin will be de-asserted. When the SDA
pin is sampled high while SCL is high the P bit (SSPSTAT<4>) is set. A TBRG later, the PEN bit
is cleared and the SSPIF bit is set (Figure 17-31).
Whene ver the firmw are decides to tak e control of the bus, it will first determine if the bus is busy
by checking the S and P bits in the SSPSTAT register. If the bus is busy, then the CPU can be
interrupted (notified) when a Stop bit is detected (i.e. bus is free).
17.4.14.1 WCOL Status Flag
If the user writes the SSPBUF when a STOP sequence is in progress, then the WCOL bit is set
and the contents of the buffer are unchanged (the write doesn’t occur).
Figure 17-31: Stop Condition Receive or Transmit Mode
SCL
SDA
SDA asserted low before rising edge of clock
Write to SSPCON2
Set PEN
Falling edge of
SCL = 1 for TBRG, followed by SDA = 1 for TBRG
9th clock
SCL brought high after TBRG
Note: TBRG = one baud rate generator period.
TBRG TBRG
after SDA sampled high. P bit (SSPSTAT<4>) is set
TBRG
to setup stop condition.
ACK P
TBRG
PEN bit (SSPCON2<2>) is cleared by
hardware and the SSPIF bit is set
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-47
Section 17. MSSP
MSSP
17
Figure 17-32: Stop Condition Flowchart
Idle Mode,
SSPEN = 1,
Force SDA = 0
SCL doesn’t change
SDA = 0?
De-assert SCL,
SCL = 1
SCL = 1? No
Yes
Start BRG
No
Yes
BRG
SDA going from
0 to 1 while SCL = 1,
No
Yes
Set SSPIF,
Release SDA,
Start BRG
Stop Condition done
SSPCON1<3:0> = 1000
rollover?
No
BRG
rollover?
Yes
P bit Set? No
Yes
Bus Collision detected,
Set BCLIF,
Clear PEN
Start BRG
No
Yes
BRG
rollover?
(Clock Arbitration)
PEN = 1
PEN Cleared
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-48 Preliminary 1997 Microchip Technology Inc.
17.4.15 Clock Arbitration
Clock arbitration occurs when the master, dur ing any receive, transmit, or Repeated Star t/stop
condition de-asserts the SCL pin (SCL allow ed to float high). When the SCL pin is allo wed to float
high, the baud rate generator (BRG) is suspended from counting until the SCL pin is actually
sampled high. When the SCL pin is sampled high, the baud rate generator is reloaded with the
contents of SSPADD<6:0> and begins counting. This ensures that the SCL high time will alwa ys
be at least one BRG rollover count in the event that the clock is held low by an exter nal device
(Figure 17-33).
Figure 17-33: Clock Arbitration Timing in Master Transmit Mode
17.4.16 Sleep Operation
While in sleep mode, the I2C module can receiv e addresses or data, and when an address match
or complete byte transfer occurs wake the processor from sleep (if the MSSP interrupt is
enabled).
17.4.17 Effect of a Reset
A reset disables the MSSP module and terminates the current transfer.
SCL
SDA
BRG overflow,
Release SCL,
If SCL = 1 Load BRG with
SSPADD<6:0>, and start count BRG overflow occurs,
Release SCL, Slave device holds SCL low. SCL = 1 BRG starts counting
clock high interval.
SCL line sampled once every machine cycle (Tosc 4).
Hold off BRG until SCL is sampled high.
TBRG TBRG TBRG
to measure high time interval
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-49
Section 17. MSSP
MSSP
17
17.4.18 Multi -Master Communication, Bus Collision, and Bus Arbitration
Multi-Master mode support is achie ved by b us arbitration. When the master outputs address/data
bits onto the SDA pin, arbitration takes place when the master outputs a '1' on SDA by letting
SDA float high and another master asserts a '0'. When the SCL pin floats high, data should be
stable . If the e xpected data on SD A is a '1' and the data sampled on the SDA pin = '0', then a bus
collision has taken place. The master will set the Bus Collision Interrupt Flag, BCLIF and reset
the I2C port to its IDLE state. (Figure 17-34).
If a transmit was in progress when the bus collision occurred, the transmission is halted, the BF
flag is cleared, the SD A and SCL lines are de-asserted, and the SSPBUF can be written to. When
the user ser vices the bus collision interrupt ser vice routine, and if the I2C bus is free, the user
can resume communication by asserting a START condition.
If a START, Repeated Start, ST OP, or Ac kno wledge condition w as in progress when the b us col-
lision occurred, the condition is aborted, the SD A and SCL lines are de-asserted, and the respec-
tive control bits in the SSPCON2 register are cleared. When the user ser vices the bus collision
interrupt service routine, and if the I2C b us is free, the user can resume communication by assert-
ing a START condition.
The Master will continue to monitor the SDA and SCL pins, and if a STOP condition occurs, the
SSPIF bit will be set.
A write to the SSPBUF will start the transmission of data at the first data bit, regardless of where
the transmitter left off when bus collision occurred.
In multi-master mode, the interrupt generation on the detection of start and stop conditions allows
the determination of when the bus is free. Control of the I2C bus can be taken when the P bit is
set in the SSPSTAT register, or the bus is idle and the S and P bits are cleared.
Figure 17-34: Bus Collision Timing for Transmit and Acknowledge
SDA
SCL
BCLIF
SDA released
SDA line pulled low
by another source Sample SDA. While SCL is high
data doesn’t match what is driven
Bus collision has occurred.
Set bus collision
interrupt (BCLIF).
by the master.
by master
Data changes
while SCL = 0
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-50 Preliminary 1997 Microchip Technology Inc.
17.4.18.1 Bus Collision During a START Condition
During a START condition, a bus collision occurs if:
a) SDA or SCL are sampled low at the beginning of the START condition (Figure 17-35).
b) SCL is sampled low before SDA is asserted low (Figure 17-36).
During a START condition both the SDA and the SCL pins are monitored.
If: the SDA pin is already low
or the SCL pin is already low,
then:
the START condition is aborted,
and the BCLIF flag is set,
and the SSP module is reset to its IDLE state (Figure 17-35).
The START condition begins with the SD A and SCL pins de-asserted. When the SD A pin is sam-
pled high, the baud rate generator is loaded from SSPADD<6:0> and counts down to 0. If the
SCL pin is sampled low while SDA is high, a bus collision occurs, because it is assumed that
another master is attempting to drive a data '1' during the START condition.
If the SDA pin is sampled low during this count, the BRG is reset and the SDA line is asser ted
early (Figure 17-37). If however a '1' is sampled on the SDA pin, the SDA pin is asserted low at
the end of the BRG count. The baud rate generator is then reloaded and counts down to 0, and
during this time, if the SCL pins is sampled as '0', a bus collision does not occur. At the end of
the BRG count the SCL pin is asserted low.
Note: The reason that bus collision is not a f actor during a START condition is that no tw o
bus masters can assert a STAR T condition at the e xact same time. Theref ore, one
master will alwa ys assert SD A before the other. This condition does not cause a b us
collision because the two masters must be allo w ed to arbitr ate the first address fol-
lowing the START condition, and if the address is the same, arbitration must be
allowed to continue into the data portion, Repeated Start, or STOP conditions.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-51
Section 17. MSSP
MSSP
17
Figure 17-35: Bus Collision During Start Condition (SDA only)
Figure 17-36: Bus Collision During Start Condition (SCL = 0)
SDA
SCL
SEN
SDA sampled low before
SDA goes low before the SEN bit is set.
S bit and SSPIF set because
SSP module reset into idle state.
SEN cleared automatically because of bus collision.
S bit and SSPIF set because
Set SEN, enable start
condition if SDA = 1, SCL=1
SDA = 0, SCL = 1
BCLIF
S
SSPIF
SDA = 0, SCL = 1 SSPIF and BCLIF are
cleared in software.
SSPIF and BCLIF are
cleared in software.
. Set BCLIF,
Set BCLIF.
START condition.
SDA
SCL
SEN Bus collision occurs, Set BCLIF.
SCL = 0 before SDA = 0,
Set SEN, enable start
sequence if SDA = 1, SCL = 1
TBRG TBRG
SDA = 0, SCL = 1
BCLIF
S
SSPIF
Interrupts cleared
in software.
Bus collision occurs, Set BCLIF.
SCL = 0 before BRG time out,
'0' '0'
'0''0'
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-52 Preliminary 1997 Microchip Technology Inc.
Figure 17-37: BRG Reset Due to SDA Arbitration During Start Condition
SDA
SCL
SEN
Set S
Set SEN, enable start
sequence if SDA = 1, SCL = 1
Less than TBRG TBRG
SDA = 0, SCL = 1
BCLIF
S
SSPIF
S
Interrupts cleared
in software.
Set SSPIF
SDA = 0, SCL = 1
SDA pulled low by other master.
Reset BRG and assert SDA
SCL pulled low after BRG
Timeout
Set SSPIF
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-53
Section 17. MSSP
MSSP
17
17.4.18.2 Bus Collision During a Repeated Start Condition
During a Repeated Start condition, a bus collision occurs if:
a) A low level is sampled on SDA when SCL goes from low level to high level.
b) SCL goes low before SD A is asserted low, indicating that another master is attempting to
transmit a data ’1’.
When the user de-asserts SDA and the pin is allowed to float high, the BRG is loaded with
SSPADD<6:0>, and counts down to zero. The SCL pin is then de-asser ted, and when sampled
high, the SDA pin is sampled. If SDA is low, a bus collision has occurred (i.e. another master,
Figure 17-38, is attempting to transmit a data ’0’). If , howe ver , SD A is sampled high then the BRG
is reloaded and begins counting. If SDA goes from high to lo w before the BRG times out, no bus
collision occurs, because no two masters can assert SDA at exactly the same time.
If , how e v er, SCL goes from high to low bef ore the BRG times out and SDA has not already been
asserted, then a bus collision occurs . In this case, another master is attempting to transmit a data
’1’ during the Repeated Start condition, Figure 17-39.
If at the end of the BRG time out both SCL and SDA are still high, the SD A pin is driven low, the
BRG is reloaded, and begins counting. At the end of the count, regardless of the status of the
SCL pin, the SCL pin is driven low and the Repeated Start condition is complete.
Figure 17-38: Bus Collision During a Repeated Start Condition (Case 1)
SDA
SCL
RSEN
BCLIF
S
SSPIF
Sample SDA when SCL goes high.
If SDA = 0, set BCLIF and release SDA and SCL
Cleared in software
'0'
'0'
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-54 Preliminary 1997 Microchip Technology Inc.
Figure 17-39: Bus Collision During Repeated Start Condition (Case 2)
SDA
SCL
BCLIF
RSEN
S
SSPIF
Interrupt cleared
in software
SCL goes low before SDA,
Set BCLIF. Release SDA and SCL
TBRG TBRG
'0'
'0'
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-55
Section 17. MSSP
MSSP
17
17.4.18.3 Bus Collision During a STOP Condition
Bus collision occurs during a STOP condition if:
a) After the SDA pin has been de-asser ted and allowed to float high, SDA is sampled low
after the BRG has timed out.
b) After the SCL pin is de-asserted, SCL is sampled low before SDA goes high.
The STOP condition begins with SDA asser ted low. When SDA is sampled low, the SCL pin is
allow to float. When the pin is sampled high (cloc k arbitr ation), the baud rate gener ator is loaded
with SSPADD<6:0> and counts down to 0. After the BRG times out SDA is sampled. If SDA is
sampled low, a bus collision has occurred. This is due to another master attempting to drive a
data '0' (Figure 17-40). If the SCL pin is sampled low before SDA is allowed to float high, a bus
collision occurs. This is another case of another master attempting to drive a data '0'
(Figure 17-41).
Figure 17-40: Bus Collision During a STOP Condition (Case 1)
Figure 17-41: Bus Collision During a STOP Condition (Case 2)
SDA
SCL
BCLIF
PEN
P
SSPIF
TBRG TBRG TBRG
SDA asserted low
SDA sampled
low after TBRG,
Set BCLIF
'0'
'0'
SDA
SCL
BCLIF
PEN
P
SSPIF
TBRG TBRG TBRG
Assert SDA SCL goes low before SDA goes high
Set BCLIF
'0'
'0'
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-56 Preliminary 1997 Microchip Technology Inc.
17.5 Connection Considerations for I2C Bus
F or standard-mode I2C bus devices, the values of resistors
R
P
and
R
S
in Figure 17-42 depends
on the following parameters:
Supply voltage
Bus capacitance
Number of connected devices (input current + leakage current)
The supply voltage limits the minimum value of resistor
R
P
due to the specified minimum sink
current of 3 mA at VOLMAX = 0.4V f or the specified output stages. For e xample, with a supply v olt-
age of VDD = 5V+10% and VOLMAX = 0.4V at 3 mA, RPMIN = (5.5-0.4)/0.003 = 1.7 kΩ. VDD as a
function of
R
P
is shown in Figure 17-42. The desired noise margin of 0.1VDD for the low level,
limits the maximum v alue of
R
S
. Series resistors are optional, and used to improv e ESD suscep-
tibility.
The bus capacitance is the total capacitance of wire , connections, and pins. This capacitance lim-
its the maximum value of
R
P
due to the specified rise time (Figure 17-42).
The SMP bit is the slew r ate control enabled bit. This bit is in the SSPSTAT register, and controls
the slew rate of the I/O pins when in I2C mode (master or slave).
Figure 17-42: Sample Device Configuration for I2C Bus
RPRP
VDD + 10%
SDA
SCL
NOTE: I2C devices with input levels related to VDD must have one common supply
line to which the pull up resistor is also connected.
DEVICE
CB = 10 - 400 pF
RSRS
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-57
Section 17. MSSP
MSSP
17
17.6 Initialization
Example 17-2: SPI Master Mode Initialization
17.6.1 Master SSP Module / Basic SSP Module Compatibility
When changing from the SPI in the Basic SSP module, the SSPSTAT register contains two addi-
tional control bits. These bits are:
SMP, SPI data input sample phase
CKE, SPI Clock Edge Select
To be compatible with the SPI of the Master SSP module, these bits m ust be appropriately con-
figured. If these bits are not at the states shown in Table 17-4, improper SPI communication ma y
occur.
Table 17-4: New bit States for Compatibility
CLRF STATUS ; Bank 0
CLRF SSPSTAT ; SMP = 0, CKE = 0, and clear status bits
BSF SSPSTAT, CKE ; CKE = 1
MOVLW 0x31 ; Set up SPI port, Master mode, CLK/16,
MOVWF SSPCON ; Data xmit on falling edge (CKE=1 & CKP=1)
; Data sampled in middle (SMP=0 & Master mode)
BSF STATUS, RP0 ; Bank 1
BSF PIE, SSPIE ; Enable SSP interrupt
BCF STATUS, RP0 ; Bank 0
BSF INTCON, GIE ; Enable, enabled interrupts
MOVLW DataByte ; Data to be Transmitted
; Could move data from RAM location
MOVWF SSPBUF ; Start Transmission
Basic SSP Module Master SSP Module
CKP CKP CKE SMP
1 100
0 000
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-58 Preliminary 1997 Microchip Technology Inc.
17.7 Design Tips
Question 1:
Using SPI mode, I do not seem able to talk to an SPI device.
Answer 1:
Ensure that you are using the correct SPI mode f or that device. This SPI supports all 4 SPI modes
so you should be able to get it to function. Check the clock polarity and the clock phase.
Question 2:
Using I
2
C mode, I write data to the SSPBUF register, but the data did not
transmit.
Answer 2:
Ensure that you set the CKP bit to release the I2C clock.
1997 Microchip Technology Inc. Preliminary DS31017A-page 17-59
Section 17. MSSP
MSSP
17
17.8 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the Master
SSP module are:
Title Application Note #
Use of the SSP Module in the I 2C Multi-Master Environment. AN578
Using Microchip 93 Series Serial EEPROMs with Microcontroller SPI Ports AN613
Interfacing PIC16C64/74 to Microchip SPI Serial EEPROM AN647
Interfacing a Microchip PIC16C92x to Microchip SPI Serial EEPROM AN668
PICmicro MID-RANGE MCU FAMILY
DS31017A-page 17-60 1997 Microchip Technology Inc.
17.9 Revision History
Revision A
This is the initial released revision of the Master SSP module description.
1997 Microchip Technology Inc. DS31018A page 18-1
M
USART
18
Section 18. USART
HIGHLIGHTS
This section of the manual contains the following major topics:
18.1 Introduction..................................................................................................................18-2
18.2 Control Registers .........................................................................................................18-3
18.3 USART Baud Rate Generator (BRG)...........................................................................18-5
18.4 USART Asynchronous Mode.......................................................................................18-8
18.5 USART Synchronous Master Mode...........................................................................18-15
18.6 USART Synchronous Slave Mode.............................................................................18-19
18.7 Initialization................................................................................................................18-21
18.8 Design Tips ................................................................................................................18-22
18.9 Related Application Notes..........................................................................................18-23
18.10 Revision History.........................................................................................................18-24
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-2 1997 Microchip Technology Inc.
18.1 Introduction
The Universal Synchronous Asynchronous Receiver Transmitter (USART) module is one of the
two serial I/O modules (other is the SSP module). The USART is also known as a Serial Com-
munications Interface or SCI. The USART can be configured as a full duplex asynchronous sys-
tem that can communicate with peripheral devices such as CRT terminals and personal
computers, or it can be configured as a half duplex synchronous system that can communicate
with peripheral devices such as A/D or D/A integrated circuits, Serial EEPROMs etc.
The USART can be configured in the following modes:
Asynchronous (full duplex)
Synchronous - Master (half duplex)
Synchronous - Slave (half duplex)
The SPEN bit (RCSTA<7>), and the TRIS bits, hav e to be set in order to configure the TX/CK and
RX/DT pins for the USART.
1997 Microchip Technology Inc. DS31018A-page 18-3
Section 18. USART
USART
18
18.2 Control Registers
Register 18-1: TXSTA: Transmit Status and Control Register
R/W-0 R/W-0 R/W-0 R/W-0 U-0 R/W-0 R-1 R/W-0
CSRC TX9 TXEN SYNC BRGH TRMT TX9D
bit 7 bit 0
bit 7 CSRC: Clock Source Select bit
Asynchronous mode
Don’t care
Synchronous mode
1 = Master mode (Clock generated internally from BRG)
0 = Slave mode (Clock from external source)
bit 6 TX9: 9-bit Transmit Enable bit
1 = Selects 9-bit transmission
0 = Selects 8-bit transmission
bit 5 TXEN: Transmit Enable bit
1 = Transmit enabled
0 = Transmit disabled
Note: SREN/CREN overrides TXEN in SYNC mode.
bit 4 SYNC: USART Mode Select bit
1 = Synchronous mode
0 = Asynchronous mode
bit 3 Unimplemented: Read as '0'
bit 2 BRGH: High Baud Rate Select bit
Asynchronous mode
1 = High speed
0 = Low speed
Synchronous mode
Unused in this mode
bit 1 TRMT: Transmit Shift Register Status bit
1 = TSR empty
0 = TSR full
bit 0 TX9D: 9th bit of transmit data. Can be parity bit.
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-4 1997 Microchip Technology Inc.
Register 18-2: RCSTA: Receive Status and Control Register
R/W-0 R/W-0 R/W-0 R/W-0 U-0 R-0 R-0 R-0
SPEN RX9 SREN CREN FERR OERR RX9D
bit 7 bit 0
bit 7 SPEN: Serial Port Enable bit
1 = Serial port enabled (Configures RX/DT and TX/CK pins as serial port pins)
0 = Serial port disabled
bit 6 RX9: 9-bit Receive Enable bit
1 = Selects 9-bit reception
0 = Selects 8-bit reception
bit 5 SREN: Single Receive Enable bit
Asynchronous mode
Don’t care
Synchronous mode - master
1 = Enables single receive
0 = Disables single receive
This bit is cleared after reception is complete.
Synchronous mode - slave
Unused in this mode
bit 4 CREN: Continuous Receive Enable bit
Asynchronous mode
1 = Enables continuous receive
0 = Disables continuous receive
Synchronous mode
1 = Enables continuous receive until enable bit CREN is cleared (CREN overrides SREN)
0 = Disables continuous receive
bit 3 Unimplemented: Read as '0'
bit 2 FERR: Framing Error bit
1 = Framing error (Can be updated by reading RCREG register and receive next valid byte)
0 = No framing error
bit 1 OERR: Overrun Error bit
1 = Overrun error (Can be cleared by clearing bit CREN)
0 = No overrun error
bit 0 RX9D: 9th bit of received data, can be parity bit.
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
1997 Microchip Technology Inc. DS31018A-page 18-5
Section 18. USART
USART
18
18.3 USART Baud Rate Generator (BRG)
The BRG suppor ts both the Asynchronous and Synchronous modes of the USART. It is a dedi-
cated 8-bit baud rate generator. The SPBRG register controls the period of a free running 8-bit
timer . In asynchronous mode bit BRGH (TXSTA<2>) also controls the baud rate. In synchronous
mode bit BRGH is ignored. Table 18-1 shows the formula for computation of the baud rate for
different USART modes which only apply in master mode (internal clock).
Given the desired baud rate and Fosc, the nearest integer value for the SPBRG register can be
calculated using the f ormula in Table 18-1, where X equals the value in the SPBRG register (0 to
255). From this, the error in baud rate can be determined.
Table 18-1: Baud Rate Formula
Example 18-1 shows the calculation of the baud rate error for the following conditions:
FOSC = 16 MHz
Desired Baud Rate = 9600
BRGH = 0
SYNC = 0
Example 18-1: Calculating Baud Rate Error
It ma y be adv antageous to use the high baud r ate (BRGH = 1) even for slo w er baud cloc ks . This
is because the FOSC / (16(X + 1)) equation can reduce the baud rate error in some cases.
Writing a new value to the SPBRG register causes the BRG timer to be reset (or cleared). This
ensures the BRG does not wait for a timer overflow before outputting the new baud rate.
Table 18-2: Registers Associated with Baud Rate Generator
SYNC BRGH = 0 (Low Speed) BRGH = 1 (High Speed)
0
1(Asynchronous) Baud Rate = FOSC/(64(X+1))
(Synchronous) Baud Rate = FOSC/(4(X+1)) Baud Rate= FOSC/(16(X+1))
NA
X = value in SPBRG (0 to 255)
Desired Baud rate = Fosc / (64 (X + 1))
9600 = 16000000 / (64 (X + 1))
X=25.042 = 25
Calculated Baud Rate = 16000000 / (64 (25 + 1))
= 9615
Error = (Calculated Baud Rate - Desired Baud Rate)
Desired Baud Rate
= (9615 - 9600) / 9600
= 0.16%
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on all
other resets
TXSTA CSRC TX9 TXEN SYNC BRGH TRMT TX9D 0000 -010 0000 -010
RCSTA SPEN RX9 SREN CREN FERR OERR RX9D 0000 -00x 0000 -00x
SPBRG Baud Rate Generator Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented read as '0'. Shaded cells are not used by the BRG.
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-6 1997 Microchip Technology Inc.
Table 18-3: Baud Rates for Synchronous Mode
BAUD
RATE
(Kbps)
FOSC = 20 MHz SPBRG
value
(decimal)
16 MHz SPBRG
value
(decimal)
10 MHz SPBRG
value
(decimal)
7.15909 MHz SPBRG
value
(decimal)
KBAUD %
ERROR KBAUD %
ERROR KBAUD %
ERROR KBAUD %
ERROR
0.3 NA - - NA - - NA - - NA - -
1.2 NA - - NA - - NA - - NA - -
2.4 NA - - NA - - NA - - NA - -
9.6 NA - - NA - - 9.766 +1.73 255 9.622 +0.23 185
19.2 19.53 +1.73 255 19.23 +0.16 207 19.23 +0.16 129 19.24 +0.23 92
76.8 76.92 +0.16 64 76.92 +0.16 51 75.76 -1.36 32 77.82 +1.32 22
96 96.15 +0.16 51 95.24 -0.79 41 96.15 +0.16 25 94.20 -1.88 18
300 294.1 -1.96 16 307.69 +2.56 12 312.5 +4.17 7 298.3 -0.57 5
500 500 0 9 500 0 7 500 0 4 NA - -
HIGH 5000 - 0 4000 - 0 2500 - 0 1789.8 - 0
LOW 19.53 - 255 15.625 - 255 9.766 - 255 6.991 - 255
BAUD
RATE
(Kbps)
FOSC = 5.0688 MHz 4 MHz SPBRG
value
(decimal)
3.579545 MHz SPBRG
value
(decimal)
1 MHz SPBRG
value
(decimal)
32.768 kHz SPBRG
value
(decimal)
KBAUD %
ERROR
SPBRG
value
(decimal) KBAUD %
ERROR KBAUD %
ERROR KBAUD %
ERROR KBAUD %
ERROR
0.3 NA - - NA - - NA - - NA - - 0.303 +1.14 26
1.2 NA - - NA - - NA - - 1.202 +0.16 207 1.170 -2.48 6
2.4 NA - - NA - - NA - - 2.404 +0.16 103 NA - -
9.6 9.6 0 131 9.615 +0.16 103 9.622 +0.23 92 9.615 +0.16 25 NA - -
19.2 19.2 0 65 19.231 +0.16 51 19.04 -0.83 46 19.24 +0.16 12 NA - -
76.8 79.2 +3.13 15 76.923 +0.16 12 74.57 -2.90 11 83.34 +8.51 2 NA - -
96 97.48 +1.54 12 1000 +4.17 9 99.43 +3.57 8 NA - - NA - -
300 316.8 +5.60 3 NA - - 298.3 -0.57 2 NA - - NA - -
500 NA - - NA - - NA - - NA - - NA - -
HIGH 1267 - 0 100 - 0 894.9 - 0 250 - 0 8.192 - 0
LOW 4.950 - 255 3.906 - 255 3.496 - 255 0.9766 - 255 0.032 - 255
1997 Microchip Technology Inc. DS31018A-page 18-7
Section 18. USART
USART
18
Table 18-4: Baud Rates for Asynchronous Mode (BRGH = 0)
Table 18-5: Baud Rates for Asynchronous Mode (BRGH = 1)
BAUD
RATE
(Kbps)
FOSC = 20 MHz SPBRG
value
(decimal)
16 MHz SPBRG
value
(decimal)
10 MHz SPBRG
value
(decimal)
7.15909 MHz SPBRG
value
(decimal)KBAUD %
ERROR KBAUD %
ERROR KBAUD %
ERROR KBAUD %
ERROR
0.3 NA - - NA - - NA - - NA - -
1.2 1.221 +1.73 255 1.202 +0.16 207 1.202 +0.16 129 1.203 +0.23 92
2.4 2.404 +0.16 129 2.404 +0.16 103 2.404 +0.16 64 2.380 -0.83 46
9.6 9.469 -1.36 32 9.615 +0.16 25 9.766 +1.73 15 9.322 -2.90 11
19.2 19.53 +1.73 15 19.23 +0.16 12 19.53 +1.73 7 18.64 -2.90 5
76.8 78.13 +1.73 3 83.33 +8.51 2 78.13 +1.73 1 NA - -
96 104.2 +8.51 2 NA - - NA - - NA - -
300 312.5 +4.17 0 NA - - NA - - NA - -
500 NA - - NA - - NA - - NA - -
HIGH 312.5 - 0 250 - 0 156.3 - 0 111.9 - 0
LOW 1.221 - 255 0.977 - 255 0.6104 - 255 0.437 - 255
BAUD
RATE
(Kbps)
FOSC = 5.0688 MHz 4 MHz SPBRG
value
(decimal)
3.579545 MHz SPBRG
value
(decimal)
1 MHz SPBRG
value
(decimal)
32.768 kHz SPBRG
value
(decimal)
KBAUD %
ERROR
SPBRG
value
(decimal) KBAUD
%
ERROR KBAUD
%
ERROR KBAUD
%
ERROR KBAUD
%
ERROR
0.3 0.31 +3.13 255 0.3005 -0.17 207 0.301 +0.23 185 0.300 +0.16 51 0.256 -14.67 1
1.2 1.2 0 65 1.202 +1.67 51 1.190 -0.83 46 1.202 +0.16 12 NA - -
2.4 2.4 0 32 2.404 +1.67 25 2.432 +1.32 22 2.232 -6.99 6 NA - -
9.6 9.9 +3.13 7 NA - - 9.322 -2.90 5 NA - - NA - -
19.2 19.8 +3.13 3 NA - - 18.64 -2.90 2 NA - - NA - -
76.8 79.2 +3.13 0 NA - - NA - - NA - - NA - -
96 NA - - NA - - NA - - NA - - NA - -
300 NA - - NA - - NA - - NA - - NA - -
500 NA - - NA - - NA - - NA - - NA - -
HIGH 79.2 - 0 62.500 - 0 55.93 - 0 15.63 - 0 0.512 - 0
LOW 0.3094 - 255 3.906 - 255 0.2185 - 255 0.0610 - 255 0.0020 - 255
BAUD
RATE
(Kbps)
FOSC = 20 MHz SPBRG
value
(decimal)
16 MHz SPBRG
value
(decimal)
10 MHz SPBRG
value
(decimal)
7.15909 MHz SPBRG
value
(decimal)KBAUD %
ERROR KBAUD %
ERROR KBAUD %
ERROR KBAUD %
ERROR
9.6 9.615 +0.16 129 9.615 +0.16 103 9.615 +0.16 64 9.520 -0.83 46
19.2 19.230 +0.16 64 19.230 +0.16 51 18.939 -1.36 32 19.454 +1.32 22
38.4 37.878 -1.36 32 38.461 +0.16 25 39.062 +1.7 15 37.286 -2.90 11
57.6 56.818 -1.36 21 58.823 +2.12 16 56.818 -1.36 10 55.930 -2.90 7
115.2 113.636 -1.36 10 111.111 -3.55 8 125 +8.51 4 111.860 -2.90 3
250 250 0 4 250 0 3 NA - - NA - -
625 625 0 1 NA - - 625 0 0 NA - -
1250 1250 0 0 NA - - NA - - NA - -
BAUD
RATE
(Kbps)
FOSC = 5.0688 MHz 4 MHz SPBRG
value
(decimal)
3.579545 MHz SPBRG
value
(decimal)
1 MHz SPBRG
value
(decimal)
32.768 kHz SPBRG
value
(decimal)
KBAUD %
ERROR
SPBRG
value
(decimal) KBAUD
%
ERROR KBAUD
%
ERROR KBAUD
%
ERROR KBAUD
%
ERROR
9.6 9.6 0 32 NA - - 9.727 +1.32 22 8.928 -6.99 6 NA - -
19.2 18.645 -2.94 16 1.202 +0.17 207 18.643 -2.90 11 20.833 +8.51 2 NA - -
38.4 39.6 +3.12 7 2.403 +0.13 103 37.286 -2.90 5 31.25 -18.61 1 NA - -
57.6 52.8 -8.33 5 9.615 +0.16 25 55.930 -2.90 3 62.5 +8.51 0 NA - -
115.2 105.6 -8.33 2 19.231 +0.16 12 111.860 -2.90 1 NA - - NA - -
250 NA - - NA - - 223.721 -10.51 0 NA - - NA - -
625 NA - - NA - - NA - - NA - - NA - -
1250 NA - - NA - - NA - - NA - - NA - -
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-8 1997 Microchip Technology Inc.
18.4 USART Asynchronous Mode
In this mode, the USART uses standard nonreturn-to-zero (NRZ) format (one star t bit, eight or
nine data bits and one stop bit). The most common data format is 8-bits. An on-chip dedicated
8-bit baud rate generator can be used to deriv e standard baud rate frequencies from the oscilla-
tor. The USART transmits and receives the LSb first. The USART’s transmitter and receiver are
functionally independent but use the same data format and baud rate. The baud rate generator
produces a clock either x16 or x64 of the bit shift r ate , depending on the BRGH bit (TXSTA<2>).
P arity is not supported by the hardw are, b ut can be implemented in software (stored as the ninth
data bit). Asynchronous mode is stopped during SLEEP.
Asynchronous mode is selected by clearing the SYNC bit (TXSTA<4>).
The USART Asynchronous module consists of the following important elements:
Baud Rate Generator
Sampling Circuit
Asynchronous Transmitter
Asynchronous Receiver
18.4.1 USART Asynchronous Transmitter
The USAR T transmitter bloc k diagram is sho wn in Figure 18-1. The heart of the transmitter is the
transmit (serial) shift register (TSR). The shift register obtains its data from the read/write transmit
buffer, TXREG. The TXREG register is loaded with data in software. The TSR register is not
loaded until the ST OP bit has been tr ansmitted from the previous load. As soon as the STOP bit
is transmitted, the TSR is loaded with new data from the TXREG register (if availab le). Once the
TXREG register transfers the data to the TSR register (occurs in one TCY), the TXREG register
is empty and the TXIF flag bit is set. This interr upt can be enabled/disabled by setting/clear ing
the TXIE enable bit. The TXIF flag bit will be set regardless of the state of the TXIE enable bit and
cannot be cleared in software . It will reset only when ne w data is loaded into the TXREG register .
While the TXIF flag bit indicated the status of the TXREG register, the TRMT bit (TXSTA<1>)
shows the status of the TSR register. The TRMT status bit is a read only bit which is set when
the TSR register is empty. No interr upt logic is tied to this bit, so the user has to poll this bit in
order to determine if the TSR register is empty.
Transmission is enabled b y setting the TXEN enab le bit (TXSTA<5>). The actual tr ansmission will
not occur until the TXREG register has been loaded with data and the baud rate generator (BRG)
has produced a shift clock (Figure 18-1). The transmission can also be star ted by first loading
the TXREG register and then setting the TXEN enable bit. Nor mally when transmission is first
started, the TSR register is empty, so a transfer to the TXREG register will result in an immediate
transfer to TSR resulting in an empty TXREG. A back-to-back transfer is thus possible
(Figure 18-3). Clearing the TXEN enable bit during a transmission will cause the transmission to
be aborted and will reset the transmitter. As a result the TX/CK pin will revert to hi-impedance.
In order to select 9-bit transmission, transmit bit, TX9 (TXSTA<6>), should be set and the ninth
bit should be written to the TX9D bit (TXSTA<0>). The ninth bit must be written before writing the
8-bit data to the TXREG register. This is because a data wr ite to the TXREG register can result
in an immediate transf er of the data to the TSR register (if the TSR is empty). In such a case, an
incorrect ninth data bit maybe loaded in the TSR register.
Note 1: The TSR register is not mapped in data memory so it is not available to the user.
Note 2: When the TXEN bit is set, the TXIF flag bit will also be set since the transmit buffer
is not yet full (still can move transmit data to the TXREG register).
1997 Microchip Technology Inc. DS31018A-page 18-9
Section 18. USART
USART
18
Figure 18-1: USART Transmit Block Diagram
Steps to follow when setting up a Asynchronous Transmission:
1. Initialize the SPBRG register for the appropriate baud rate. If a high speed baud rate is
desired, set the BRGH bit. (Subsection 18.3 “USART Baud Rate Generator (BRG)” )
2. Enable the asynchronous serial port by clearing the SYNC bit and setting the SPEN bit.
3. If interrupts are desired, then set the TXIE, GIE and PEIE bits.
4. If 9-bit transmission is desired, then set the TX9 bit.
5. Enable the transmission by setting the TXEN bit, which will also set the TXIF bit.
6. If 9-bit transmission is selected, the ninth bit should be loaded in the TX9D bit.
7. Load data to the TXREG register (starts transmission).
Figure 18-2: Asynchronous Master Transmission
TXIF
TXIE
Interrupt
TXEN Baud Rate CLK
SPBRG
Baud Rate Generator TX9D
MSb LSb
Data Bus
TXREG register
TSR register
(8) 0
TX9
TRMT SPEN
TX/CK pin
Pin Buffer
and Control
8
• • •
8
WORD 1 Stop Bit
WORD 1
Transmit Shift Reg
Start Bit Bit 0 Bit 1 Bit 7/8
Write to TXREG Word 1
BRG output
(shift clock)
TX/CK pin
TXIF bit
(Transmit buffer
reg. empty flag)
TRMT bit
(Transmit shift
reg. empty flag)
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-10 1997 Microchip Technology Inc.
Figure 18-3: Asynchronous Master Transmission (Back to Back)
Table 18-6: Registers Associated with Asynchronous Transmission
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on
all other
Resets
PIR TXIF (1) 00
RCSTA SPEN RX9 SREN CREN FERR OERR RX9D 0000 -00x 0000 -00x
TXREG TX7 TX6 TX5 TX4 TX3 TX2 TX1 TX0 0000 0000 0000 0000
PIE TXIE (1) 00
TXSTA CSRC TX9 TXEN SYNC BRGH TRMT TX9D 0000 -010 0000 -010
SPBRG Baud Rate Generator Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented locations read as '0'.
Shaded cells are not used for Asynchronous Transmission.
Note 1: The position of this bit is device dependent.
Transmit Shift Reg.
Write to TXREG
BRG output
(shift clock)
TX/CK pin
TXIF bit
(interrupt reg. flag)
TRMT bit
(Transmit shift
reg. empty flag)
Word 1 Word 2
WORD 1 WORD 2
Start Bit Stop Bit Start Bit
Transmit Shift Reg.
WORD 1 WORD 2
Bit 0 Bit 1 Bit 7/8 Bit 0
Note: This timing diagram shows two consecutive transmissions.
1997 Microchip Technology Inc. DS31018A-page 18-11
Section 18. USART
USART
18
18.4.2 USART Asynchronous Receiver
The receiver block diagram is shown in Figure 18-4. The data is received on the RX/DT pin and
drives the data recov ery bloc k. The data recov ery bloc k is actually a high speed shifter operating
at x16 times the baud rate, whereas the main receive ser ial shifter operates at the bit rate or at
FOSC.
Once Asynchronous mode is selected, reception is enabled by setting the CREN bit
(RCSTA<4>).
The heart of the receiv er is the receive (serial) shift register (RSR). After sampling the RX/TX pin
for the STOP bit, the receiv ed data in the RSR is transferred to the RCREG register (if it is empty).
If the transfer is complete, the RCIF flag bit is set. The actual interrupt can be enabled/disabled
by setting/clearing the RCIE enable bit. The RCIF flag bit is a read only bit which is cleared by
the hardware. It is cleared when the RCREG register has been read and is empty. The RCREG
is a double buffered register, i.e. it is a two deep FIFO. It is possible for two bytes of data to be
received and tr ansf erred to the RCREG FIFO and a third b yte begin shifting to the RSR register.
On the detection of the STOP bit of the third byte, if the RCREG register is still full then overrun
error bit, OERR (RCSTA<1>), will be set. The word in the RSR will be lost. The RCREG register
can be read twice to retrieve the two bytes in the FIFO. The OERR bit has to be cleared in soft-
ware. This is done by resetting the receive logic (the CREN bit is cleared and then set). If the
OERR bit is set, transfers from the RSR register to the RCREG register are inhibited, so it is
essential to clear the OERR bit if it is set. Framing error bit, FERR (RCSTA<2>), is set if a stop
bit is detected as a low le vel. The FERR bit and the 9th receive bit are b uffered the same way as
the receive data. Reading the RCREG will load the RX9D and FERR bits with new v alues , there-
fore it is essential for the user to read the RCSTA register before reading the next RCREG reg-
ister in order not to lose the old (previous) information in the FERR and RX9D bits.
Figure 18-4: USART Receive Block Diagram
x64 Baud Rate CLK
SPBRG
Baud Rate Generator
RX/DT
Pin Buffer
and Control
SPEN
Data
Recovery
CREN OERR FERR
RSR register
MSb LSb
RX9D RCREG register FIFO
Interrupt RCIF
RCIE
Data Bus
8
Stop Start
(8) 710
RX9
• • •
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-12 1997 Microchip Technology Inc.
Steps to follow when setting up an Asynchronous Reception:
1. Initialize the SPBRG register for the appropriate baud rate. If a high speed baud rate is
desired, set bit BRGH. (Subsection 18.3 “USART Baud Rate Generator (BRG)” ).
2. Enable the asynchronous serial port by clearing the SYNC bit, and setting the SPEN bit.
3. If interrupts are desired, then set the RCIE, GIE and PEIE bits.
4. If 9-bit reception is desired, then set the RX9 bit.
5. Enable the reception by setting the CREN bit.
6. The RCIF flag bit will be set when reception is complete and an interrupt will be generated
if the RCIE bit was set.
7. Read the RCSTA register to get the ninth bit (if enabled) and determine if any error
occurred during reception.
8. Read the 8-bit received data by reading the RCREG register.
9. If any error occurred, clear the error by clearing the CREN bit.
Figure 18-5: Asynchronous Reception
Start
bit bit7/8
bit1bit0 bit7/8 bit0Stop
bit
Start
bit Start
bit
bit7/8 Stop
bit
RX (pin)
reg
Rcv buffer reg
Rcv shift
Read Rcv
buffer reg
RCREG
RCIF
(interrupt flag)
OERR bit
CREN
WORD 1
RCREG WORD 2
RCREG
Stop
bit
Note: This timing diagram shows three words appearing on the RX input. The RCREG (receive buffer) is read after the third word,
causing the OERR (overrun) bit to be set.
1997 Microchip Technology Inc. DS31018A-page 18-13
Section 18. USART
USART
18
18.4.3 Sampling
The data on the RX/DT pin is sampled three times by a majority detect circuit to determine if a
high or a low level is present at the RX pin. Figure 18-6 shows the waveform for the sampling
circuit. The sampling operates the same regardless of the state of the BRGH bit, only the source
of the x16 clock is different.
Figure 18-6: RX Pin Sampling Scheme, BRGH = 0 or BRGH = 1
18.4.3.1 Device Exceptions
All new de vices will use the sampling scheme shown in Figure 18-6. De vices that have an e xcep-
tion to the above sampling scheme are:
PIC16C63
PIC16C65
PIC16C65A
PIC16C73
PIC16C73A
PIC16C74
PIC16C74A
These devices have a sampling circuitry that works as follows. If the BRGH bit (TXSTA<2>) is
clear (i.e., at the low baud rates), the sampling is done on the seventh, eighth and ninth falling
edges of a x16 clock (Figure 18-7). If bit BRGH is set (i.e., at the high baud rates), the sampling
is done on the 3 clock edges preceding the second rising edge after the first f alling edge of a x4
clock (Figure 18-8 and Figure 18-9).
Figure 18-7: RX Pin Sampling Scheme (BRGH = 0)
RX
baud CLK
x16 CLK
Start bit Bit0
Samples
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3
Baud CLK for all but start bit
(RX/DT pin)
RX
baud CLK
x16 CLK
Start bit Bit0
Samples
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3
Baud CLK for all but start bit
(RX/DT pin)
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-14 1997 Microchip Technology Inc.
Figure 18-8: RX Pin Sampling Scheme (BRGH = 1)
Figure 18-9: RX Pin Sampling Scheme (BRGH = 1)
Table 18-7: Registers Associated with Asynchronous Reception
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on
all other
Resets
PIR RCIF (1) 00
RCSTA SPEN RX9 SREN CREN FERR OERR RX9D 0000 -00x 0000 -00x
RCREG RX7 RX6 RX5 RX4 RX3 RX2 RX1 RX0 0000 0000 0000 0000
PIE RCIE (1) 00
TXSTA CSRC TX9 TXEN SYNC BRGH TRMT TX9D 0000 -010 0000 -010
SPBRG Baud Rate Generator Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented locations read as '0'.
Shaded cells are not used for Asynchronous Reception.
Note 1: The position of this bit is device dependent.
RX pin
baud clk
x4 clk
Q2, Q4 clk
Start Bit bit0 bit1
First falling edge after RX pin goes low
Second rising edge
Samples Samples Samples
1234123412
RX pin
baud clk
x4 clk
Q2, Q4 clk
Start Bit bit0
First falling edge after RX pin goes low
Second rising edge
Samples
1234
Baud clk for all but start bit
1997 Microchip Technology Inc. DS31018A-page 18-15
Section 18. USART
USART
18
18.5 USART Synchronous Master Mode
In Synchronous Master mode, the data is transmitted in a half-duplex manner, i.e. transmission
and reception do not occur at the same time. When transmitting data, the reception is inhibited
and vice versa. Synchronous mode is entered by setting the SYNC bit (TXSTA<4>). In addition,
the SPEN enable bit (RCSTA<7>) is set in order to configure the TX/CK and RX/DT I/O pins to
CK (clock) and DT (data) lines respectiv ely. The Master mode indicates that the processor trans-
mits the master clock on the CK line. The Master mode is entered by setting the CSRC bit
(TXSTA<7>).
18.5.1 USART Synchronous Master Transmission
The USAR T transmitter bloc k diagram is sho wn in Figure 18-1. The heart of the transmitter is the
transmit (serial) shift register (TSR). The shift register obtains its data from the read/write transmit
buffer register TXREG. The TXREG register is loaded with data in software. The TSR register is
not loaded until the last bit has been transmitted from the previous load. As soon as the last bit
is transmitted, the TSR is loaded with new data from the TXREG (if availab le). Once the TXREG
register transfers the data to the TSR register (occurs in one Tcycle), the TXREG is empty and
the TXIF interrupt flag bit is set. The interrupt can be enabled/disab led b y setting/clearing enable
the TXIE bit. The TXIF flag bit will be set regardless of the state of the TXIE enab le bit and cannot
be cleared in software . It will reset only when new data is loaded into the TXREG register. While
the TXIF flag bit indicates the status of the TXREG register , the TRMT bit (TXSTA<1>) shows the
status of the TSR register. The TRMT bit is a read only bit which is set when the TSR is empty.
No interrupt logic is tied to this bit, so the user has to poll this bit in order to determine if the TSR
register is empty. The TSR is not mapped in data memory so it is not available to the user.
Transmission is enabled by setting the TXEN bit (TXSTA<5>). The actual transmission will not
occur until the TXREG register has been loaded with data. The first data bit will be shifted out on
the ne xt availab le rising edge of the cloc k on the CK line. Data out is stable at the falling edge of
the synchronous clock (Figure 18-10). The transmission can also be started by first loading the
TXREG register and then setting the TXEN bit. This is advantageous when slow baud rates are
selected, since the BRG is kept in reset when the TXEN, CREN, and SREN bits are clear . Setting
the TXEN bit will start the BRG, creating a shift clock immediately. Normally when transmission
is first started, the TSR register is empty, so a transfer to the TXREG register will result in an
immediate transfer to TSR resulting in an empty TXREG. Back-to-back transfers are possible.
Clearing the TXEN bit during a transmission will cause the transmission to be abor ted and will
reset the transmitter. The DT and CK pins will rever t to hi-impedance. If either of the CREN or
SREN bits are set during a transmission, the transmission is aborted and the DT pin re v erts to a
hi-impedance state (f or a reception). The CK pin will remain an output if the CSRC bit is set (inter-
nal clock). The transmitter logic is not reset although it is disconnected from the pins. In order to
reset the transmitter, the user has to clear the TXEN bit. If the SREN bit is set (to interrupt an
on-going transmission and receive a single word), then after the single word is received, the
SREN bit will be cleared and the serial port will revert back to transmitting since the TXEN bit is
still set. The DT line will immediately switch from hi-impedance receiv e mode to transmit and start
driving. To avoid this the TXEN bit should be cleared.
In order to select 9-bit transmission, the TX9 bit (TXSTA<6>) should be set and the ninth bit
should be written to the TX9D bit (TXSTA<0>). The ninth bit must be written before writing the
8-bit data to the TXREG register. This is because a data write to the TXREG can result in an
immediate transfer of the data to the TSR register (if the TSR is empty). If the TSR was empty
and the TXREG was written before writing the “ne w” value to the TX9D bit, the “present” v alue of
of the TX9D bit is loaded.
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-16 1997 Microchip Technology Inc.
Steps to follow when setting up a Synchronous Master Transmission:
1. Initialize the SPBRG register for the appropriate baud rate (Subsection 18.3 “USART
Baud Rate Generator (BRG)” ).
2. Enable the synchronous master serial port by setting the SYNC, SPEN, and CSRC bits.
3. If interrupts are desired, then set the TXIE bit.
4. If 9-bit transmission is desired, then set the TX9 bit.
5. Enable the transmission by setting the TXEN bit.
6. If 9-bit transmission is selected, the ninth bit should be loaded in the TX9D bit.
7. Start transmission by loading data to the TXREG register.
Table 18-8: Registers Associated with Synchronous Master Transmission
Figure 18-10: Synchronous Transmission
Figure 18-11: Synchronous Transmission (Through TXEN)
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on all
other Resets
PIR TXIF (1) 00
RCSTA SPEN RX9 SREN CREN FERR OERR RX9D 0000 -00x 0000 -00x
TXREG TX7 TX6 TX5 TX4 TX3 TX2 TX1 TX0 0000 0000 0000 0000
PIE TXIE (1) 00
TXSTA CSRC TX9 TXEN SYNC BRGH TRMT TX9D 0000 -010 0000 -010
SPBRG Baud Rate Generator Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented, read as '0'.
Shaded cells are not used for Synchronous Master Transmission.
Note 1: The position of this bit is device dependent.
Bit 0 Bit 1 Bit 7
WORD 1
Q1Q2 Q3Q4 Q1 Q2Q3 Q4Q1 Q2Q3 Q4Q1 Q2Q3 Q4Q1 Q2 Q3Q4 Q3Q4 Q1Q2 Q3Q4 Q1Q2 Q3Q4 Q1Q2 Q3 Q4Q1 Q2Q3 Q4Q1 Q2Q3 Q4Q1 Q2Q3 Q4
Bit 2 Bit 0 Bit 1 Bit 7
RX/DT pin
TX/CK pin
Write to
TXREG reg
TXIF bit
(Interrupt flag)
TRMT
TXEN bit '1' '1'
Note: Sync master mode; SPBRG = '0'. Continuous transmission of two 8-bit words.
WORD 2
TRMT bit
Write word1 Write word2
RX/DT pin
TX/CK pin
Write to
TXREG reg
TXIF bit
TRMT bit
bit0 bit1 bit2 bit6 bit7
1997 Microchip Technology Inc. DS31018A-page 18-17
Section 18. USART
USART
18
18.5.2 USART Synchronous Master Reception
Once Synchronous mode is selected, reception is enabled by setting either of the SREN
(RCSTA<5>) or CREN (RCSTA<4>) bits. Data is sampled on the RX/DT pin on the falling edge
of the clock. If the SREN bit is set, then only a single word is receiv ed. If the CREN bit is set, the
reception is continuous until the CREN bit is cleared. If both bits are set then the CREN bit takes
precedence. After clocking the last serial data bit, the received data in the Receiv e Shift Register
(RSR) is transferred to the RCREG register (if it is empty). When the transfer is complete, the
RCIF interrupt flag bit is set. The actual interrupt can be enabled/disabled b y setting/clearing the
RCIE enable bit. The RCIF flag bit is a read only bit which is cleared by the hardw are. In this case
it is cleared when the RCREG register has been read and is empty. The RCREG is a double b uff-
ered register, i.e. it is a two deep FIFO. It is possible for two bytes of data to be received and
transferred to the RCREG FIFO and a third byte to begin shifting into the RSR register. On the
clocking of the last bit of the third byte, if the RCREG register is still full then overrun error bit,
OERR (RCSTA<1>), is set and the word in the RSR is lost. The RCREG register can be read
twice to retriev e the two b ytes in the FIFO. The OERR bit has to be cleared in software (by clear-
ing the CREN bit). If the OERR bit is set, transfers from the RSR to the RCREG are inhibited, so
it is essential to clear the OERR bit if it is set. The 9th receiv e bit is buffered the same way as the
receive data. Reading the RCREG register will load the RX9D bit with a new value, therefore it
is essential for the user to read the RCSTA register before reading RCREG in order not to lose
the old (previous) information in the RX9D bit.
Steps to follow when setting up a Synchronous Master Reception:
1. Initialize the SPBRG register for the appropriate baud rate. (Subsection 18.3 “USART
Baud Rate Generator (BRG)” )
2. Enable the synchronous master serial port by setting the SYNC, SPEN, and CSRC bits.
3. Ensure that the CREN and SREN bits are clear.
4. If interrupts are desired, then set the RCIE bit.
5. If 9-bit reception is desired, then set the RX9 bit.
6. If a single reception is required, set the SREN bit. For continuous reception set the CREN
bit.
7. The RCIF bit will be set when reception is complete and an interrupt will be generated if
the RCIE bit was set.
8. Read the RCSTA register to get the ninth bit (if enabled) and determine if any error
occurred during reception.
9. Read the 8-bit received data by reading the RCREG register.
10. If any error occurred, clear the error by clearing the CREN bit.
Table 18-9: Registers Associated with Synchronous Master Reception
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on all
other Resets
PIR RCIF (1) 00
RCSTA SPEN RX9 SREN CREN FERR OERR RX9D 0000 -00x 0000 -00x
RCREG RX7 RX6 RX5 RX4 RX3 RX2 RX1 RX0 0000 0000 0000 0000
PIE RCIE (1) 00
TXSTA CSRC TX9 TXEN SYNC BRGH TRMT TX9D 0000 -010 0000 -010
SPBRG Baud Rate Generator Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented read as '0'.
Shaded cells are not used for Synchronous Master Reception.
Note 1: The position of this bit is device dependent.
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-18 1997 Microchip Technology Inc.
Figure 18-12: Synchronous Reception (Master Mode, SREN)
CREN bit
DT pin
CK pin
Write to
SREN bit
SREN bit
RCIF bit
(interrupt)
Read
RXREG Note: Timing diagram demonstrates SYNC master mode with SREN = '1' and BRG = '0'.
Q3Q4 Q1Q2Q3 Q4Q1Q2Q3 Q4Q2 Q1Q2 Q3Q4Q1Q2 Q3Q4 Q1Q2Q3 Q4Q1 Q2Q3Q4 Q1 Q2Q3Q4Q1Q2 Q3Q4 Q1Q2 Q3Q4
'0'
bit0 bit1 bit2 bit3 bit4 bit5 bit6 bit7
Q1Q2Q3Q4
1997 Microchip Technology Inc. DS31018A-page 18-19
Section 18. USART
USART
18
18.6 USART Synchronous Slave Mode
Synchronous slave mode differs from the Master mode in the fact that the shift clock is supplied
e xternally at the TX/CK pin (instead of being supplied internally in master mode). This allows the
device to transfer or receive data while in SLEEP mode. Slave mode is entered by clearing the
CSRC bit (TXSTA<7>).
18.6.1 USART Synchronous Slave Transmit
The operation of the synchronous master and sla ve modes are identical e xcept in the case of the
SLEEP mode.
If two words are written to the TXREG and then the SLEEP instr uction is executed, the following
will occur:
a) The first word will immediately transfer to the TSR register and transmit.
b) The second word will remain in TXREG register.
c) The TXIF flag bit will not be set.
d) When the first word has been shifted out of TSR, the TXREG register will transf er the sec-
ond word to the TSR and the TXIF flag bit will now be set.
e) If the TXIE enable bit is set, the interrupt will wake the chip from SLEEP and if the global
interrupt is enabled, the program will branch to the interrupt vector (0004h).
Steps to follow when setting up a Synchronous Slave Transmission:
1. Enable the synchronous sla ve serial port by setting the SYNC and SPEN bits and clearing
the CSRC bit.
2. Clear the CREN and SREN bits.
3. If interrupts are desired, then set the TXIE enable bit.
4. If 9-bit transmission is desired, then set the TX9 bit.
5. Enable the transmission by setting the TXEN enable bit.
6. If 9-bit transmission is selected, the ninth bit should be loaded into the TX9D bit.
7. Start transmission by loading data to the TXREG register.
Table 18-10: Registers Associated with Synchronous Slave Transmission
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on all
other Resets
PIR TXIF (1) 00
RCSTA SPEN RX9 SREN CREN FERR OERR RX9D 0000 -00x 0000 -00x
TXREG TX7 TX6 TX5 TX4 TX3 TX2 TX1 TX0 0000 0000 0000 0000
PIE TXIE (1) 00
TXSTA CSRC TX9 TXEN SYNC BRGH TRMT TX9D 0000 -010 0000 -010
SPBRG Baud Rate Generator Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented read as '0'.
Shaded cells are not used for Synchronous Slave Transmission.
Note 1: The position of this bit is device dependent.
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-20 1997 Microchip Technology Inc.
18.6.2 USART Synchronous Slave Reception
The operation of the synchronous master and sla ve modes is identical except in the case of the
SLEEP mode. Also, bit SREN is a don't care in slave mode.
If receive is enab led, b y setting the CREN bit, prior to the SLEEP instruction, then a word ma y be
received during SLEEP. On completely receiving the w ord, the RSR register will transf er the data
to the RCREG register and if the RCIE enable bit bit is set, the interrupt generated will w ake the
chip from SLEEP. If the global interrupt is enab led, the program will branch to the interrupt v ector
(0004h).
Steps to follow when setting up a Synchronous Slave Reception:
1. Enable the synchronous master serial port b y setting the SYNC and SPEN bits and clear-
ing the CSRC bit.
2. If interrupts are desired, then set the RCIE enable bit.
3. If 9-bit reception is desired, then set the RX9 bit.
4. To enable reception, set the CREN enable bit.
5. The RCIF bit will be set when reception is complete and an interrupt will be generated, if
the RCIE bit was set.
6. Read the RCSTA register to get the ninth bit (if enabled) and determine if any error
occurred during reception.
7. Read the 8-bit received data by reading the RCREG register.
8. If any error occurred, clear the error by clearing the CREN bit.
Table 18-11: Registers Associated with Synchronous Slave Reception
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on:
POR,
BOR
Value on all
other Resets
PIR RCIF (1) 00
RCSTA SPEN RX9 SREN CREN FERR OERR RX9D 0000 -00x 0000 -00x
RCREG RX7 RX6 RX5 RX4 RX3 RX2 RX1 RX0 0000 0000 0000 0000
PIE RCIE (1) 00
TXSTA CSRC TX9 TXEN SYNC BRGH TRMT TX9D 0000 -010 0000 -010
SPBRG Baud Rate Generator Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented read as '0'.
Shaded cells are not used for Synchronous Slave Reception.
Note 1: The position of this bit is device dependent.
1997 Microchip Technology Inc. DS31018A-page 18-21
Section 18. USART
USART
18
18.7 Initialization
Example 18-2 is an initialization routine for asynchronous Transmitter/Receiver mode.
Example 18-3 is f or the synchronous mode. In both e xamples the data is 8-bits , and the v alue to
load into the SPBRG register is dependent on the desired baud rate and the device frequency.
Example 18-2: Asynchronous Transmitter/Receiver
Example 18-3: Synchronous Transmitter/Receiver
BSF STATUS,RP0 ; Go to Bank1
MOVLW <baudrate> ; Set Baud rate
MOVWF SPBRG
MOVLW 0x40 ; 8-bit transmit, transmitter enabled,
MOVWF TXSTA ; asynchronous mode, low speed mode
BSF PIE1,TXIE ; Enable transmit interrupts
BSF PIE1,RCIE ; Enable receive interrupts
BCF STATUS,RP0 ; Go to Bank 0
MOVLW 0x90 ; 8-bit receive, receiver enabled,
MOVWF RCSTA ; serial port enabled
BSF STATUS,RP0 ; Go to Bank 1
MOVLW <baudrate> ; Set Baud Rate
MOVWF SPBRG
MOVLW 0xB0 ; Synchronous Master,8-bit transmit,
MOVWF TXSTA ; transmitter enabled, low speed mode
BSF PIE1,TXIE ; Enable transmit interrupts
BSF PIE1,RCIE ; Enable receive interrupts
BCF STATUS,RP0 ; Go to Bank 0
MOVLW 0x90 ; 8-bit receive, receiver enabled,
MOVWF RCSTA ; continuous receive, serial port enabled
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-22 1997 Microchip Technology Inc.
18.8 Design Tips
Question 1:
Using the Asynchronous mode I am getting a lot of transmission errors.
Answer 1:
The most common reasons are
1. You are using the high speed mode (BRGH is set) on one of the devices which has an
errata for this mode (PIC16C65/65A/73/73A/74/74A).
2. You have incorrectly calculated the value to load in to the SPBRG register
3. The sum of the baud errors for the transmitter and receiver is too high.
1997 Microchip Technology Inc. DS31018A-page 18-23
Section 18. USART
USART
18
18.9 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to this section
are:
Title Application Note #
Serial Port Utilities AN547
Servo Control of a DC Brushless Motor AN543
PICmicro MID-RANGE MCU FAMILY
DS31018A-page 18-24 1997 Microchip Technology Inc.
18.10 Revision History
Revision A
This is the initial released revision of the USART module description.
1997 Microchip Technology Inc. DS31019A page 19-1
M
Voltage
Reference
19
Section 19. Voltage Reference
HIGHLIGHTS
This section of the manual contains the following major topics:
19.1 Introduction..................................................................................................................19-2
19.2 Control Register...........................................................................................................19-3
19.3 Configuring the Voltage Reference ..............................................................................19-4
19.4 Voltage Reference Accuracy/Error...............................................................................19-5
19.5 Operation During Sleep ...............................................................................................19-5
19.6 Effects of a Reset.........................................................................................................19-5
19.7 Connection Considerations..........................................................................................19-6
19.8 Initialization..................................................................................................................19-7
19.9 Design Tips ..................................................................................................................19-8
19.10 Related Application Notes............................................................................................19-9
19.11 Revision History.........................................................................................................19-10
PICmicro MID-RANGE MCU FAMILY
DS31019A-page 19-2 1997 Microchip Technology Inc.
19.1 Introduction
The Voltage Reference module is typically used in conjunction with the Comparator module. The
comparator module’s inputs do not require very large drive, and therefore the drive capability of
the Voltage Reference is limited.
The Voltage Reference is a 16-tap resistor ladder network that provides a selectab le v oltage ref-
erence. The resistor ladder is segmented to provide two ranges of VREF values and has a
power-do wn function to conserve pow er when the ref erence is not being used. The VRCON reg-
ister controls the operation of the ref erence as sho wn in Figure 19-1. The block diagr am is given
in Figure 19-1. Within each range, the 16 steps are monotonic (i.e. each increasing code will
result in an increasing output).
Figure 19-1: Voltage Reference Block Diagram
Table 19-1: Typical Voltage Reference with VDD = 5.0V
VR3:VR0 VREF
VRR = 1 VRR = 0
0000 0.00 V 1.25 V
0001 0.21 V 1.41 V
0010 0.42 V 1.56 V
0011 0.63 V 1.72 V
0100 0.83 V 1.88 V
0101 1.04 V 2.03 V
0110 1.25 V 2.19 V
0111 1.46 V 2.34 V
1000 1.67 V 2.50 V
1001 1.88 V 2.66 V
1010 2.08 V 2.81 V
1011 2.29 V 2.97 V
1100 2.50 V 3.13 V
1101 2.71 V 3.28 V
1110 2.92 V 3.44 V
1111 3.13 V 3.59 V
Note 1: See parameter D312 in the Electrical Specifications section of the device data sheet.
VRR
8R(1)
VR3
VR0 (F rom VRCON<3:0>)
16-1 Analog MUX
8R(1) R(1) R(1) R(1) R(1)
VREN
VREF
16 Stages
1997 Microchip Technology Inc. DS31019A-page 19-3
Section 19. Voltage Reference
Voltage
Reference
19
19.2 Control Register
Register 19-1: VRCON Register
R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0
VREN VROE VRR VR3 VR2 VR1 VR0
bit 7 bit 0
bit 7 VREN: VREF Enable
1 = VREF circuit powered on
0 = VREF circuit powered down
bit 6 VROE: VREF Output Enable
1 = VREF is internally connected to Comparator module’s VREF. This voltage level is also
output on the VREF pin
0 = VREF is not connected to the comparator module. This voltage is disconnected from the
VREF pin
bit 5 VRR: VREF Range selection
1 = 0V to 0.75 VDD, with VDD/24 step size
0 = 0.25 VDD to 0.75 VDD, with VDD/32 step size
bit 4 Unimplemented: Read as '0'
bit 3:0 VR3:VR0: VREF value selection 0 VR3:VR0 15
When VRR = 1:
VREF = (VR<3:0>/ 24) VDD
When VRR = 0:
VREF = 1/4 * VDD + (VR3:VR0/ 32) VDD
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31019A-page 19-4 1997 Microchip Technology Inc.
19.3 Configuring the Voltage Reference
The Voltage Reference can output 16 distinct voltage levels for each range.
The equations used to calculate the output of the Voltage Reference are as follows:
if VRR = 1: VREF = (VR3:VR0/24) x VDD
if VRR = 0: VREF = (VDD x 1/4) + (VR3:VR0/32) x VDD
The settling time of the Voltage Reference must be considered when changing the VREF output.
Example 19-1 shows an e xample of how to configure the V oltage Ref erence for an output v oltage
of 1.25V with VDD = 5.0V.
Generally the VREF and VDD of the system will be known and y ou need to determine the value to
load into VR3:VR0. Equation 19-1 shows how to calculate the VR3:VR0 value. There will be
some error since VR3:VR0 can only be an integer, and the V REF and VDD lev els must be chosen
so that the result is not greater then 15.
Equation 19-1: Calculating VR3:VR0
V
REF
V
DD
X 24
VR3:VR0 =
When VRR = 1
V
REF
- V
DD
/4
V
DD
X 32
VR3:VR0 =
When VRR = 0
1997 Microchip Technology Inc. DS31019A-page 19-5
Section 19. Voltage Reference
Voltage
Reference
19
19.4 Voltage Reference Accuracy/Error
The full range of VSS to VDD cannot be realized due to the construction of the module. The tran-
sistors on the top and bottom of the resistor ladder network (Figure 19-1) keep VREF from
approaching VSS or VDD. The Voltage Reference is VDD derived and therefore, the VREF output
changes with fluctuations in VDD. The absolute accuracy of the Voltage Reference can be found
in the Device Data Sheets electrical specification parameter D311.
19.5 Operation During Sleep
When the device wakes up from sleep through an interrupt or a Watchdog Timer time-out, the
contents of the VRCON register are not affected. To minimize current consumption in SLEEP
mode, the Voltage Reference should be disabled.
19.6 Effects of a Reset
A de vice reset disables the Voltage Reference by clearing the VREN bit (VRCON<7>). This reset
also disconnects the reference from the VREF pin by clearing the VROE bit (VRCON<6>) and
selects the high voltage r ange b y clearing the VRR bit (VRCON<5>). The V REF value select bits,
VRCON<3:0>, are also cleared.
PICmicro MID-RANGE MCU FAMILY
DS31019A-page 19-6 1997 Microchip Technology Inc.
19.7 Connection Considerations
The Voltage Ref erence Module oper ates independently of the comparator module . The output of
the reference generator may be connected to the VREF pin if the corresponding TRIS bit is set
and the VROE bit (VRCON<6>) is set. Enabling the Voltage Reference output onto the VREF pin
with an input signal present will increase current consumption. Configuring the VREF as a digital
output with VREF enabled will also increase current consumption.
The VREF pin can be used as a simple D/A output with limited drive capability. Due to the limited
drive capability, a buffer m ust be used in conjunction with the Voltage Reference output f or e xter-
nal connections to VREF. Figure 19-2 shows an example buffering technique.
Figure 19-2: Voltage Reference Output Buffer Example
VREF Output
+
VREF ModuleR(1) ANx
Note 1: R is the V oltage Reference Output Impedance and is dependent upon the
Voltage Reference Configuration VRCON<3:0> and VRCON<5>.
PIC16CXXX
1997 Microchip Technology Inc. DS31019A-page 19-7
Section 19. Voltage Reference
Voltage
Reference
19
19.8 Initialization
Example 19-1 shows the steps to configure the voltage reference module.
Example 19-1: Voltage Reference Configuration
MOVLW 0x02 ; 4 Inputs Muxed to 2 comparators
MOVWF CMCON ;
BSF STATUS,RP0 ; go to Bank1
MOVLW 0x07 ; RA3:RA0 are outputs
MOVWF TRISA ; outputs
MOVLW 0xA6 ; enable VREF
MOVWF VRCON ; low range set VR3:VR0 = 6
BCF STATUS,RP0 ; go to Bank0
CALL DELAY10 ; 10 µs delay
PICmicro MID-RANGE MCU FAMILY
DS31019A-page 19-8 1997 Microchip Technology Inc.
19.9 Design Tips
Question 1:
My V
REF
is not what I expect.
Answer 1:
Any v ariation of the device VDD will translate directly onto the VREF pin. Also ensure that y ou have
correctly calculated (specified) the VDD divider which generates the VREF.
Question 2:
I am connecting V
REF
into a low impedance circuit, and the V
REF
is not at
the expected level.
Answer 2:
The Voltage Reference module is not intended to drive large loads. A buffer must be used
between the PICmicro’s VREF pin and the load.
1997 Microchip Technology Inc. DS31019A-page 19-9
Section 19. Voltage Reference
Voltage
Reference
19
19.10 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to Voltage Ref-
erence are:
Title Application Note #
Resistance and Capacitance Meter using a PIC16C622 AN611
PICmicro MID-RANGE MCU FAMILY
DS31019A-page 19-10 1997 Microchip Technology Inc.
19.11 Revision History
Revision A
This is the initial released revision of the Voltage Reference description.
1997 Microchip Technology Inc. DS31020A page 20-1
M
Comparator
20
Section 20. Comparator
HIGHLIGHTS
This section of the manual contains the following major topics:
20.1 Introduction..................................................................................................................20-2
20.2 Control Register...........................................................................................................20-3
20.3 Comparator Configuration............................................................................................20-4
20.4 Comparator Operation .................................................................................................20-6
20.5 Comparator Reference.................................................................................................20-6
20.6 Comparator Response Time........................................................................................20-8
20.7 Comparator Outputs ....................................................................................................20-8
20.8 Comparator Interrupts..................................................................................................20-9
20.9 Comparator Operation During SLEEP.........................................................................20-9
20.10 Effects of a RESET......................................................................................................20-9
20.11 Analog Input Connection Considerations...................................................................20-10
20.12 Initialization................................................................................................................20-11
20.13 Design Tips................................................................................................................20-12
20.14 Related Application Notes..........................................................................................20-13
20.15 Revision History.........................................................................................................20-14
PICmicro MID-RANGE MCU FAMILY
DS31020A-page 20-2 1997 Microchip Technology Inc.
20.1 Introduction
The comparator module contains two analog comparators. The inputs to the comparators are
multiple x ed with the I/O pins. The on-chip Voltage Reference (see the “Volta ge Reference” sec-
tion) can also be an input to the comparators.
The CMCON register, shown in Figure 20-1, controls the comparator input and output multiple x-
ers. A block diagram of the comparator is shown in Figure 20-1.
1997 Microchip Technology Inc. DS31020A-page 20-3
Section 20. Comparator
Comparator
20
20.2 Control Register
Register 20-1: CMCON Register
R-0 R-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0
C2OUT C1OUT CIS CM2 CM1 CM0
bit 7 bit 0
bit 7 C2OUT: Comparator2 Output Indicator bit
1 = C2 VIN+ > C2 VIN
0 = C2 VIN+ < C2 VIN
bit 6 C1OUT: Comparator1 Output Indicator bit
1 = C1 VIN+ > C1 VIN
0 = C1 VIN+ < C1 VIN
bit 5:4 Unimplemented: Read as '0'
bit 3 CIS: Comparator Input Switch bit
When CM2:CM0: = 001:
1 = C1 VIN– connects to AN3
0 = C1 VIN– connects to AN0
When CM2:CM0 = 010:
1 = C1 VIN– connects to AN3
C2 VIN– connects to AN2
0 = C1 VIN– connects to AN0
C2 VIN– connects to AN1
bit 2:0 CM2:CM0: Comparator Mode Select bits
See Figure 20-1.
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31020A-page 20-4 1997 Microchip Technology Inc.
20.3 Comparator Configuration
There are eight modes of operation for the comparators. The CMCON register is used to select
the mode. Figure 20-1 shows the eight possible modes. The TRIS register controls the data
direction of the comparator I/O pins f or each mode. If the comparator mode is changed, the com-
parator output level may not be valid for the new mode for the delay specified in the electr ical
specifications of the device.
Note: Comparator interrupts should be disabled during a comparator mode change, oth-
erwise a false interrupt may occur.
1997 Microchip Technology Inc. DS31020A-page 20-5
Section 20. Comparator
Comparator
20
Figure 20-1: Comparator I/O Operating Modes
C1
RA0/AN0 VIN-
VIN+
RA3/AN3 Off (Read as '0')
Comparators Reset (POR Default Value)
A
A
CM2:CM0 = 000
C2
RA1/AN1 VIN-
VIN+
RA2/AN2 Off (Read as '0')
A
A
C1
RA0/AN0 VIN-
VIN+
RA3/AN3 C1OUT
Two Independent Comparators
A
A
CM2:CM0 = 100
C2
RA1/AN1 VIN-
VIN+
RA2/AN2 C2OUT
A
A
C1
RA0/AN0 VIN-
VIN+
RA3/AN3 C1OUT
Two Common Reference Comparators
A
D
CM2:CM0 = 011
C2
RA1/AN1 VIN-
VIN+
RA2/AN2 C2OUT
A
A
C1
RA0/AN0 VIN-
VIN+
RA3/AN3 Off (Read as '0')
One Independent Comparator
D
D
CM2:CM0 = 101
C2
RA1/AN1 VIN-
VIN+
RA2/AN2 C2OUT
A
A
C1
RA0/AN0 VIN-
VIN+
RA3/AN3 Off (Read as '0')
Comparators Off
D
D
CM2:CM0 = 111
C2
RA1/AN1 VIN-
VIN+
RA2/AN2 Off (Read as '0')
D
D
C1
RA0/AN0 VIN-
VIN+
RA3/AN3 C1OUT
Four Inputs Multiplexed to Two Comparators
A
A
CM2:CM0 = 010
C2
RA1/AN1 VIN-
VIN+
RA2/AN2 C2OUT
A
A
From VREF Module
CIS = 0
CIS = 1
CIS = 0
CIS = 1
C1
RA0/AN0 VIN-
VIN+
RA3/AN3 C1OUT
Two Common Reference Comparators with Outputs
A
D
CM2:CM0 = 110
C2
RA1/AN1 VIN-
VIN+
RA2/AN2 C2OUT
A
A
RA4 Open Drain
C1
RA0/AN0 VIN-
VIN+
RA3/AN3 C1OUT
Three Inputs Multiplexed to Two Comparators
A
A
CM2:CM0 = 001
C2
RA1/AN1 VIN-
VIN+
RA2/AN2 C2OUT
A
A
CIS = 0
CIS = 1
A = Analog Input, port reads as zeros always.
D = Digital Input.
CIS (CMCON<3>) is the Comparator Input Switch.
PICmicro MID-RANGE MCU FAMILY
DS31020A-page 20-6 1997 Microchip Technology Inc.
20.4 Comparator Operation
A single comparator is shown in Figure 20-2 along with the relationship betw een the analog input
levels and the digital output. When the analog input at VIN+ is less than the analog input VIN–,
the output of the comparator is a digital low level. When the analog input at VIN+ is greater than
the analog input VIN–, the output of the comparator is a digital high level. The shaded areas of
the output of the comparator in Figure 20-2 represent the uncertainty due to input offsets and
response time.
20.5 Comparator Reference
An external or internal reference signal may be used depending on the comparator operating
mode. The analog signal that is present at VIN– is compared to the signal at VIN+, and the digital
output of the comparator is adjusted accordingly (Figure 20-2).
Figure 20-2: Single Comparator
+
VIN+
VINOutput
VIN–
VIN+
Output
1997 Microchip Technology Inc. DS31020A-page 20-7
Section 20. Comparator
Comparator
20
20.5.1 External Reference Signal
When exter nal voltage references are used, the comparator module can be configured to have
the comparators operate from the same or diff erent reference sources . The ref erence signal must
be between VSS and VDD, and can be applied to either pin of the comparator(s).
20.5.2 Internal Reference Signal
The comparator module also allows the selection of an internally generated v oltage reference f or
the comparators. The “Voltage Reference” section contains a detailed description of the V oltage
Ref erence Module that provides this signal. The internal ref erence signal is used when the com-
parators are in mode CM2:CM0 = 010 (Figure 20-1). In this mode, the internal v oltage ref erence
is applied to the VIN+ input of both comparators.
The internal voltage ref erence may be used in any comparator mode. When used in this fashion
the I/O/VREF pin may be used for I/O. The voltage reference is connected to the VREF pin.
PICmicro MID-RANGE MCU FAMILY
DS31020A-page 20-8 1997 Microchip Technology Inc.
20.6 Comparator Response Time
Response time is the minimum time, after selecting a new reference voltage or input source,
before the comparator output is guaranteed to have a valid level. If the internal reference is
changed, the maximum settling time of the internal voltage reference must be considered when
using the comparator outputs. Otherwise the maximum response time of the comparators should
be used.
20.7 Comparator Outputs
The comparator outputs are read through the CMCON register. These bits are read only. The
comparator outputs ma y also be directly output to the I/O pins. When CM2:CM0 = 110, m ultiplex-
ors in the output path of the I/O pins will s witch and the output of each pin will be the unsynchro-
nized output of the comparator. The uncertainty of each of the comparators is related to the input
offset voltage and the response time given in the specifications. Figure 20-3 shows the compar-
ator output block diagram.
The TRIS bits will still function as the output enab le/disab le f or the I/O pins while in this mode.
Figure 20-3: Comparator Output Block Diagram
Note 1: When reading the Por t register, all pins configured as analog inputs will read as a
‘0’. Pins configured as digital inputs will convert an analog input according to the
Schmitt Trigger input specification.
Note 2: Analog lev els on an y pin that is defined as a digital input ma y cause the input b uff er
to consume more current than is specified.
DQ
EN
To I/O pin
Bus
Data
RD CMCON
Set
MULTIPLEX
CMIF
bit
-+
DQ
EN
CL
Port Pins
RD CMCON
RESET
From
Other
Comparator
1997 Microchip Technology Inc. DS31020A-page 20-9
Section 20. Comparator
Comparator
20
20.8 Comparator Interrupts
The comparator interrupt flag is set whenev er the compar ators v alue changes relativ e to the last
value loaded into CMxOUT bits. Software will need to maintain information about the status of
the output bits, as read from CMCON<7:6>, to determine the actual change that has occurred.
The CMIF bit, is the comparator interrupt flag. The CMIF bit must be cleared. Since it is also pos-
sible to set this bit, a simulated interrupt may be initiated.
The CMIE bit and the PEIE bit (INTCON<6>) must be set to enab le the interrupt. In addition, the
GIE bit must also be set. If any of these bits are clear, the interr upt is not enabled, though the
CMIF bit will still be set if an interrupt condition occurs.
The user, in the interrupt service routine, can clear the interrupt in the following manner:
a) Any read or write of the CMCON register. This will load the CMCON register with the new
value with the CMxOUT bits.
b) Clear the CMIF flag bit.
An interrupt condition will continue to set the CMIF flag bit. Reading CMCON will end the interrupt
condition, and allow the CMIF flag bit to be cleared.
20.9 Comparator Operation During SLEEP
When a comparator is active and the device is placed in SLEEP mode, the comparator remains
active and the interrupt is functional if enab led. This interrupt will wake up the de vice from SLEEP
mode when enabled. While the comparator is powered-up, each comparator that is operational
will consume additional current as shown in the comparator specifications. To minimize power
consumption while in SLEEP mode, turn off the comparators, CM2:CM0 = 111, before entering
sleep. If the device wakes-up from sleep, the contents of the CMCON register are not affected.
20.10 Effects of a RESET
A device reset forces the CMCON register to its reset state. This forces the comparator module
to be in the comparator reset mode, CM2:CM0 = 000. This ensures that all potential inputs are
analog inputs. Device current is minimized when analog inputs are present at reset time. The
comparators will be powered-down during the reset interval.
PICmicro MID-RANGE MCU FAMILY
DS31020A-page 20-10 1997 Microchip Technology Inc.
20.11 Analog Input Connection Considerations
A simplified circuit for an analog input is shown in Figure 20-4. Since the analog pins are con-
nected to a digital output, they have reverse biased diodes to VDD and VSS. The analog input
therefore, must be between VSS and VDD. If the input voltage deviates from this range by more
than 0.6V in either direction, one of the diodes is forward biased and a latch-up may occur. A
maximum source impedance of 10 k is recommended for the analog sources.
Figure 20-4: Analog Input Model
Table 20-1: Registers Associated with Comparator Module
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on
POR,
BOR
Value on
All Other
Resets
CMCON C2OUT C1OUT CIS CM2 CM1 CM0 00-- 0000 00-- 0000
VRCON VREN VROE VRR VR3 VR2 VR1 VR0 000- 0000 000- 0000
INTCON GIE PEIE T0IE INTE RBIE(2) T0IF INTF RBIF(2) 0000 000x 0000 000x
PIR CMIF (1) 00
PIE CMIE (1) 00
Legend: x = unknown, - = unimplemented locations read as '0'.
Shaded cells are not used for Comparator Module.
Note 1: The position of this bit is device dependent.
2: These bits can also be named GPIE and GPIF.
VAIN
RS
AIN CPIN
5 pF
VDD
VT = 0.6V
VT = 0.6V
RC < 10k
ILEAKAGE
±500 nA
VSS
Legend
CPIN = Input Capacitance
VT= Threshold Voltage
ILEAKAGE = Leakage Current at the pin due to various junctions
RIC = Interconnect Resistance
RS= Source Impedance
VA= Analog Voltage
1997 Microchip Technology Inc. DS31020A-page 20-11
Section 20. Comparator
Comparator
20
20.12 Initialization
The code in Example 20-1 depicts example steps required to configure the comparator module
of the PIC16C62X de vices. RA3 and RA4 are configured as digital output. RA0 and RA1 are con-
figured as the V- inputs and RA2 as the V+ input to both comparators.
Example 20-1: Initializing Comparator Module (PIC16C62X)
FLAG_REG EQU 0X20
;
CLRF FLAG_REG ; Init flag register
CLRF PORTA ; Init PORTA
ANDLW 0xC0 ; Mask comparator bits
IORWF FLAG_REG,F ; Store bits in flag register
MOVLW 0x03 ; Init comparator mode
MOVWF CMCON ; CM<2:0> = 011
BSF STATUS,RP0 ; Select Bank1
MOVLW 0x07 ; Initialize data direction
MOVWF TRISA ; Set RA<2:0> as inputs, RA<4:3> as outputs,
; TRISA<7:5> always read ‘0’
BCF STATUS,RP0 ; Select Bank0
CALL DELAY 10 ; 10µs delay
MOVF CMCON,F ; Read CMCON to end change condition
BCF PIR1,CMIF ; Clear pending interrupts
BSF STATUS,RP0 ; Select Bank1
BSF PIE1,CMIE ; Enable comparator interrupts
BCF STATUS,RP0 ; Select Bank0
BSF INTCON,PEIE ; Enable peripheral interrupts
BSF INTCON,GIE ; Global interrupt enable
PICmicro MID-RANGE MCU FAMILY
DS31020A-page 20-12 1997 Microchip Technology Inc.
20.13 Design Tips
Question 1:
My program appears to lock up.
Answer 1:
You may be getting stuck in an infinite loop with the comparator interrupt service routine if you
did not follow the proper sequence to clear the CMIF flag bit. First you must read the CMCON
register, and then you can clear the CMIF flag bit.
1997 Microchip Technology Inc. DS31020A-page 20-13
Section 20. Comparator
Comparator
20
20.14 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the compar-
ator module are:
Title Application Note #
Resistance and Capacitance Meter using a PIC16C622 AN611
PICmicro MID-RANGE MCU FAMILY
DS31020A-page 20-14 1997 Microchip Technology Inc.
20.15 Revision History
Revision A
This is the initial released revision of the Comparator module description.
1997 Microchip Technology Inc. DS31021A page 21-1
8-bit A/D
Convertor
21
M
Section 21. 8-bit A/D Converter
HIGHLIGHTS
This section of the manual contains the following major topics:
21.1 Introduction..................................................................................................................21-2
21.2 Control Registers .........................................................................................................21-3
21.3 Operation .....................................................................................................................21-5
21.4 A/D Acquisition Requirements .....................................................................................21-6
21.5 Selecting the A/D Conversion Clock ............................................................................21-8
21.6 Configuring Analog Port Pins.......................................................................................21-9
21.7 A/D Conversions........................................................................................................21-10
21.8 A/D Operation During Sleep ......................................................................................21-12
21.9 A/D Accuracy/Error ....................................................................................................21-13
21.10 Effects of a RESET....................................................................................................21-13
21.11 Use of the CCP Trigger..............................................................................................21-14
21.12 Connection Considerations........................................................................................21-14
21.13 Transfer Function .......................................................................................................21-14
21.14 Initialization................................................................................................................21-15
21.15 Design Tips................................................................................................................21-16
21.16 Related Application Notes..........................................................................................21-17
21.17 Revision History.........................................................................................................21-18
Note: Please ref er to Appendix C.3 or device Data Sheet to determine which de vices use
this module.
PICmicro MID-RANGE MCU FAMILY
DS31021A-page 21-2 1997 Microchip Technology Inc.
21.1 Introduction
The analog-to-digital (A/D) converter module has up to eight analog inputs.
The A/D allows con v ersion of an analog input signal to a corresponding 8-bit digital number. The
output of the sample and hold is the input into the converter, which generates the result via suc-
cessive appro ximation. The analog ref erence v oltage is software selectab le to either the de vice’ s
positive supply voltage (VDD) or the voltage level on the VREF pin. The A/D converter has a
unique feature of being able to operate while the device is in SLEEP mode.
The A/D module has three registers. These registers are:
A/D Result Register (ADRES)
A/D Control Register0 (ADCON0)
A/D Control Register1 (ADCON1)
The ADCON0 register, shown in Figure 21-1, controls the operation of the A/D module. The
ADCON1 register, shown in Figure 21-2, configures the functions of the por t pins. The I/O pins
can be configured as analog inputs (one I/O can also be a voltage reference) or as digital I/O.
The block diagram of the A/D module is shown in Figure 21-1.
Figure 21-1: 8-bit A/D Block Diagram
(Input voltage)
VAIN
VREF
(Reference
voltage)
VDD (1)
PCFG2:PCFG0
CHS2:CHS0
000 or
010 or
100
001 or
011 or
101
AN7
AN6
AN5
AN4
AN3/VREF
AN2
AN1
AN0
111
110
101
100
011
010
001
000
8-bit A/D
Converter
Note: On some devices this is a separate pin called AVDD. This allows the A/D VDD to be connected to a precise voltage source.
1997 Microchip Technology Inc. DS31021A-page 21-3
Section 21. 8-bit A/D Converter
8-bit A/D
Converter
21
21.2 Control Registers
Register 21-1: ADCON0 Register
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE Resv ADON
bit 7 bit 0
bit 7:6 ADCS1:ADCS0: A/D Conversion Clock Select bits
00 = FOSC/2
01 = FOSC/8
10 = FOSC/32
11 = FRC (clock derived from the internal A/D RC oscillator)
bit 5:3 CHS2:CHS0: Analog Channel Select bits
000 = channel 0, (AN0)
001 = channel 1, (AN1)
010 = channel 2, (AN2)
011 = channel 3, (AN3)
100 = channel 4, (AN4)
101 = channel 5, (AN5)
110 = channel 6, (AN6)
111 = channel 7, (AN7)
Note: For devices that do not implement the full 8 A/D channels, the unimplemented selec-
tions are reserved. Do not select any unimplemented channels.
bit 2 GO/DONE: A/D Conversion Status bit
When ADON = 1
1 = A/D conversion in progress
(Setting this bit starts the A/D conversion. This bit is automatically cleared
by hardware when the A/D conversion is complete)
0 = A/D conversion not in progress
bit 1 Reserved: Always maintain this bit cleared.
bit 0 ADON: A/D On bit
1 = A/D converter module is operating
0 = A/D converter module is shutoff and consumes no operating current
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31021A-page 21-4 1997 Microchip Technology Inc.
Register 21-2: ADCON1 Register
U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0
PCFG2 PCFG1 PCFG0
bit 7 bit 0
bit 7:3 Unimplemented: Read as '0'
bit 2:0 PCFG2:PCFG0: A/D Port Configuration Control bits
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
A = Analog input D = Digital I/O
Note: When AN3 is selected as VREF, the A/D reference is the voltage on the AN3
pin. When AN3 is selected as an analog input (A), then the voltage reference
for the A/D is the device VDD.
PCFG2:PCFG0 AN7 AN6 AN5 AN4 AN3 AN2 AN1 AN0
000 AA A A A AAA
001 AA A A V
REF AAA
010 DD D A A A AA
011 DD A A V
REF AAA
100 DD D D A DAA
101 DD D D V
REF DAA
11x DD D D D DDD
Note 1: On any device reset, the Port pins multiplexed with analog functions (ANx) are
forced to be an analog input.
1997 Microchip Technology Inc. DS31021A-page 21-5
Section 21. 8-bit A/D Converter
8-bit A/D
Converter
21
21.3 Operation
When the A/D conversion is complete, the result is loaded into the ADRES register, the
GO/DONE bit (ADCON0<2>) is cleared, and A/D interrupt flag bit, ADIF, is set.
After the A/D module has been configured as desired, the selected channel must be acquired
bef ore the con v ersion is started. The analog input channels must hav e their corresponding TRIS
bits selected as an input. To determine acquisition time, see Subsection 21.4 “A/D Acquisition
Requirements. After this acquisition time has elapsed the A/D con version can be started. The
following steps should be followed for doing an A/D conversion:
1. Configure the A/D module:
Configure analog pins / voltage reference / and digital I/O (ADCON1)
Select A/D input channel (ADCON0)
Select A/D conversion clock (ADCON0)
Turn on A/D module (ADCON0)
2. Configure A/D interrupt (if desired):
Clear the ADIF bit
Set the ADIE bit
Set the GIE bit
3. Wait the required acquisition time.
4. Start conversion:
Set the GO/DONE bit (ADCON0)
5. Wait for A/D conversion to complete, by either:
Polling for the GO/DONE bit to be cleared
OR
Waiting for the A/D interrupt
6. Read A/D Result register (ADRES), clear the ADIF bit, if required.
7. F or ne xt con version, go to step 1 or step 2 as required. The A/D conv ersion time per bit is
defined as TAD. A minimum wait of 2TAD is required before next acquisition starts.
Figure 21-2 shows the con version sequence , and the terms that are used. Acquisition time is the
time that the A/D module’s holding capacitor is connected to the external voltage level. Then
there is the conv ersion time of 10 TAD, which is started when the GO bit is set. The sum of these
two times is the sampling time. There is a minimum acquisition time to ensure that the holding
capacitor is charged to a level that will give the desired accuracy for the A/D conversion.
Figure 21-2: A/D Conversion Sequence
Acquisition Time Con version Time
A/D Sample Time
When A/D holding capacitor start to charge.
After A/D conversion, or new A/D channel is selected.
When A/D conversion is started (setting the GO bit).
Holding capacitor is disconnected from the analog input before
the conversion is started.
A/D conversion complete,
result is loaded in ADRES register.
Holding capacitor begins acquiring
voltage level on selected channel.
ADIF bit is set.
PICmicro MID-RANGE MCU FAMILY
DS31021A-page 21-6 1997 Microchip Technology Inc.
21.4 A/D Acquisition Requirements
F or the A/D converter to meet its specified accuracy, the charge holding capacitor (
C
HOLD
) must
be allowed to fully charge to the input channel voltage level. The analog input model is shown in
Figure 21-3. The source impedance (
R
S
) and the internal sampling switch (
R
SS
) impedance
directly affect the time required to charge the capacitor CHOLD. The sampling switch (
R
SS
) imped-
ance varies over the device voltage (VDD) (Figure 21-3). The maximum recommended imped-
ance for analog sources is 10 k. After the analog input channel is selected (changed) the
acquisition must be done before the conversion can be started.
To calculate the minimum acquisition time, Equation 21-1 may be used. This equation assumes
that 1/2 LSb error is used (512 steps f or the A/D). The 1/2 LSb error is the maxim um error allowed
for the A/D to meet its specified resolution.
Equation 21-1: Acquisition Time
Equation 21-2: A/D Minimum Charging Time
Example 21-1 shows the calculation of the minimum required acquisition time T ACQ. This calcu-
lation is based on the following system assumptions.
Rs = 10 k
Conversion Error 1/2 LSb
VDD = 5V Rss = 7 k (see graph in Figure 21-3)
Temperature = 50°C (system max.)
VHOLD = 0V @ time = 0
Example 21-1: Calculating the Minimum Required Acquisition Time
TACQ =Amplifier Settling Time +
Holding Capacitor Charging Time +
Temperature Coefficient
=TAMP + TC + TCOFF
VHOLD = (VREF - (VREF/512)) • (1 - e(-Tc/CHOLD(RIC + RSS + RS)))
or
Tc = -(51.2 pF)(1 k + RSS + RS) ln(1/511)
TACQ =TAMP + TC + TCOFF
TACQ =5 µs + Tc + [(Temp - 25°C)(0.05 µs/°C)]
TC =-CHOLD (RIC + RSS + RS) ln(1/512)
-51.2 pF (1 k + 7 k + 10 k) ln(0.0020)
-51.2 pF (18 k) ln(0.0020)
-0.921 µs (-6.2146)
5.724 µs
TACQ =5 µs + 5.724 µs + [(50°C - 25°C)(0.05 µs/°C)]
10.724 µs + 1.25 µs
11.974 µs
1997 Microchip Technology Inc. DS31021A-page 21-7
Section 21. 8-bit A/D Converter
8-bit A/D
Converter
21
Figure 21-3: Analog Input Model
Note 1: The reference voltage (VREF) has no effect on the equation, since it cancels itself
out.
Note 2: The charge holding capacitor (CHOLD) is not discharged after each conversion.
Note 3: The maximum recommended impedance for analog sources is 10 k. This is
required to meet the pin leakage specification.
Note 4: After a conv ersion has completed, a 2.0 TAD dela y must complete before acquisition
can begin again. During this time the holding capacitor is not connected to the
selected A/D input channel.
CPIN
VAIN
Rs ANx
5 pF
VDD
VT = 0.6V
VT = 0.6V I leakage
RIC 1k
Sampling
Switch
SS RSS
CHOLD = 51.2 pF
VSS
6V
Sampling Switch
5V
4V
3V
2V
5 6 7 8 9 10 11
( k )
VDD
± 500 nA
Legend CPIN
VT
I LEAKAGE
RIC
SS
CHOLD
= input capacitance
= threshold voltage
= leakage current at the pin due to
= interconnect resistance
= sampling switch
= sample/hold capacitance (from DAC)
various junctions
= Analog input voltageVAIN
PICmicro MID-RANGE MCU FAMILY
DS31021A-page 21-8 1997 Microchip Technology Inc.
21.5 Selecting the A/D Conversion Clock
The A/D conv ersion time per bit is defined as TAD. The A/D con v ersion requires 9.5 TAD per 8-bit
conversion. The source of the A/D conversion clock is software selected. The four possible
options for TAD are:
•2T
OSC
•8TOSC
32TOSC
Internal RC oscillator
For correct A/D conversions, the A/D conversion clock (TAD) must be selected to ensure a mini-
mum TAD time of 1.6 µs f or all devices , as shown in parameter 130 of the de vices electrical spec-
ifications.
Table 21-1 and Table 21-2 show the resultant TAD times der ived from the device operating fre-
quencies and the A/D clock source selected.
Table 21-1: TAD vs. Device Operating Frequencies (for Standard, C, Devices)
Table 21-2: TAD vs. Device Operating Frequencies (for Extended, LC, Devices)
AD Clock Source (TAD) Device Frequency
Operation ADCS1:ADCS0 20 MHz 5 MHz 1.25 MHz 333.33 kHz
2TOSC 00 100 ns(2) 400 ns(2) 1.6 µs6 µs
8TOSC 01 400 ns(2) 1.6 µs 6.4 µs 24 µs(3)
32TOSC 10 1.6 µs 6.4 µs 25.6 µs(3) 96 µs(3)
RC 11 2 - 6 µs(1,4) 2 - 6 µs(1,4) 2 - 6 µs(1,4) 2 - 6 µs(1)
Legend: Shaded cells are outside of recommended range.
Note 1: The RC source has a typical TAD time of 4 µs.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion, or the A/D
accuracy may be out of specification.
AD Clock Source (TAD) Device Frequency
Operation ADCS1:ADCS0 4 MHz 2 MHz 1.25 MHz 333.33 kHz
2TOSC 00 500 ns(2) 1.0 µs(2) 1.6 µs(2) 6 µs
8TOSC 01 2.0 µs(2) 4.0 µs 6.4 µs 24 µs(3)
32TOSC 10 8.0 µs 16.0 µs 25.6 µs(3) 96 µs(3)
RC 11 3 - 9 µs(1,4) 3 - 9 µs(1,4) 3 - 9 µs(1,4) 3 - 9 µs(1)
Legend: Shaded cells are outside of recommended range.
Note 1: The RC source has a typical TAD time of 6 µs.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion, or the A/D
accuracy may be out of specification.
1997 Microchip Technology Inc. DS31021A-page 21-9
Section 21. 8-bit A/D Converter
8-bit A/D
Converter
21
21.6 Configuring Analog Port Pins
ADCON1 and the corresponding TRIS registers control the operation of the A/D por t pins. The
por t pins that are desired as analog inputs must have their corresponding TRIS bits set (input).
If the TRIS bit is cleared (output), the digital output level (VOH or VOL) will be converted.
The A/D operation is independent of the state of the CHS2:CHS0 bits and the TRIS bits.
Note 1: When reading the port register, all pins configured as analog input channels will
read as cleared (a low le vel). Pins configured as digital inputs , will convert an analog
input. Analog levels on a digitally configured input will not affect the conversion
accuracy.
Note 2: Analog levels on any pin that is defined as a digital input (including the AN7:AN0
pins), ma y cause the input buff er to consume current that is out of the devices spec-
ification.
PICmicro MID-RANGE MCU FAMILY
DS31021A-page 21-10 1997 Microchip Technology Inc.
21.7 A/D Conversions
Example 21-2 show how to perform an A/D conversion. The I/O pins are configured as analog
inputs. The analog ref erence (VREF) is the device VDD. The A/D interrupt is enab led, and the A/D
conversion clock is FRC. The conversion is performed on the AN0 channel.
Clearing the GO/DONE bit during a conversion will abort the current conversion. The ADRES
register will NOT be updated with the partially completed A/D conversion sample. That is, the
ADRES register will continue to contain the value of the last completed conversion (or the last
value written to the ADRES register). After the A/D con version is aborted, a 2TAD wait is required
bef ore the next acquisition is started. After this 2TAD wait, an acquisition is automatically started
on the selected channel.
Example 21-2: Doing an A/D Conversion
Figure 21-4: A/D Conversion TAD Cycles
Note: The GO/DONE bit should NOT be set in the same instruction that turns on the A/D,
due to the required acquition time requirement.
BSF STATUS, RP0 ; Select Bank1
CLRF ADCON1 ; Configure A/D inputs
BSF PIE1, ADIE ; Enable A/D interrupts
BCF STATUS, RP0 ; Select Bank0
MOVLW 0xC1 ; RC Clock, A/D is on, Channel 0 is selected
MOVWF ADCON0 ;
BCF PIR1, ADIF ; Clear A/D interrupt flag bit
BSF INTCON, PEIE ; Enable peripheral interrupts
BSF INTCON, GIE ; Enable all interrupts
;
; Ensure that the required sampling time for the selected input
; channel has elapsed. Then the conversion may be started.
;
BSF ADCON0, GO ; Start A/D Conversion
: ; The ADIF bit will be set and the GO/DONE
: ; bit is cleared upon completion of the
: ; A/D Conversion.
TAD1TAD2TAD3TAD4TAD5TAD6TAD7TAD8TAD9TAD10
Set GO bit
Holding capacitor is disconnected
from analog input
Holding capacitor is connected to analog input
GO bit is cleared
Next Q4: ADRES is loaded
b7 b6 b5 b4 b3 b2 b1 b0 b0
TAD11
ADIF bit is set
1997 Microchip Technology Inc. DS31021A-page 21-11
Section 21. 8-bit A/D Converter
8-bit A/D
Converter
21
Figure 21-5: Flowchart of A/D Operation
Acquire
ADON = 0
ADON = 0?
GO = 0?
A/D Clock
GO = 0
ADIF = 0
Abort Conversion
SLEEP
Power-down A/D Wait 2TAD
Wake-up
Yes
No
Yes
No
No
Yes
Finish Conversion
GO = 0
ADIF = 1
Device in
No
Yes
Finish Conversion
GO = 0
ADIF = 1
Wait 2TAD
Stay in Sleep
Selected Channel
= RC? SLEEP
No
Yes
Instruction?
Start of A/D
Conversion Delayed
1 Instruction Cycle
From Sleep?
Power-down A/D
Yes
No
Wait 2TAD
Finish Conversion
GO = 0
ADIF = 1
SLEEP?
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DS31021A-page 21-12 1997 Microchip Technology Inc.
21.7.1 Faster Conversion - Lower Resolution Trade-off
Not all applications require a result with 8-bits of resolution, but ma y instead require a f aster con-
version time. The A/D module allows users to make the trade-off of conversion speed to resolu-
tion. Regardless of the resolution required, the acquisition time is the same. To speed up the
conversion, the clock source of the A/D module may be switched so that the TAD time violates
the minimum specified time (see the applicable electr ical specification). Once the TAD time vio-
lates the minimum specified time, all the following A/D result bits are not valid (see A/D Conver-
sion Timing in the Electrical Specifications section). The clock sources may only be switched
between the three oscillator versions (cannot be switched from/to RC). The equation to deter-
mine the time before the oscillator can be switched is as follows:
Conversion time = TAD + N • TAD + (10 - N)(2TOSC)
Where: N = number of bits of resolution required.
Since the TAD is based from the de vice oscillator, the user must use some method (a timer , soft-
ware loop, etc.) to deter mine when the A/D oscillator may be changed. Example 21-3 shows a
comparison of time required for a con version with 4-bits of resolution, versus the 8-bit resolution
conversion. The example is for devices operating at 20 MHz (The A/D clock is programmed for
32TOSC), and assumes that immediately after 5TAD, the A/D clock is programmed for 2TOSC.
The 2TOSC violates the minimum TAD time since the last 4-bits will not be conver ted to correct
values.
Example 21-3: 4-bit vs. 8-bit Conversion Times
21.8 A/D Operation During Sleep
The A/D module can operate during SLEEP mode. This requires that the A/D clock source be set
to RC (ADCS1:ADCS0 = 11). When the RC clock source is selected, the A/D module waits one
instruction cycle before starting the conversion. This allows the SLEEP instruction to be ex ecuted,
which eliminates all internal digital switching noise from the conversion. When the conversion is
completed the GO/DONE bit will be cleared, and the result loaded into the ADRES register . If the
A/D interrupt is enabled, the de vice will w ake-up from SLEEP. If the A/D interrupt is not enabled,
the A/D module will then be turned off (to conser ve power), although the ADON bit will remain
set.
When the A/D clock source is another clock option (not RC), a SLEEP instruction will cause the
present conversion to be aborted and the A/D module to be turned off, though the ADON bit will
remain set.
Turning off the A/D places the A/D module in its lowest current consumption state.
Freq.
(MHz)(1) Resolution
4-bit 8-bit
TAD 20 1.6 µs 1.6 µs
TOSC 20 50 ns 50 ns
TAD + N • TAD + (10 - N)(2TOSC) 20 8.6 µs 17.6 µs
Note 1: A minimum TAD time of 1.6 µs is required.
2: If the full 8-bit conversion is required, the A/D clock source should not be changed.
Note: For the A/D module to operate in SLEEP, the A/D clock source must be set to RC
(ADCS1:ADCS0 = 11). To perform an A/D conversion in SLEEP, the GO/DONE bit
must be set, followed by the SLEEP instruction.
1997 Microchip Technology Inc. DS31021A-page 21-13
Section 21. 8-bit A/D Converter
8-bit A/D
Converter
21
21.9 A/D Accuracy/Error
In systems where the de vice frequency is low, use of the A/D RC clock is preferred. At moderate
to high frequencies, TAD should be derived from the device oscillator.
The absolute accuracy specified for the A/D conver ter includes the sum of all contributions for
quantization error, integral error, differential error, full scale error, offset error, and monotonicity.
It is defined as the maximum de viation from an actual transition v ersus an ideal transition f or an y
code. The absolute error of the A/D conver ter is specified at < ±1 LSb for VDD = VREF (over the
device’s specified operating range). However, the accuracy of the A/D converter will degrade as
VDD diverges from VREF.
For a given range of analog inputs, the output digital code will be the same. This is due to the
quantization of the analog input to a digital code. Quantization error is typically ± 1/2 LSb and is
inherent in the analog to digital conv ersion process . The only way to reduce quantization error is
to increase the resolution of the A/D converter.
Offset error measures the first actual transition of a code v ersus the first ideal transition of a code.
Offset error shifts the entire transfer function. Offset error can be calibrated out of a system or
introduced into a system through the interaction of the total leakage current and source imped-
ance at the analog input.
Gain error measures the maximum deviation of the last actual transition and the last ideal tran-
sition adjusted for offset error. This error appears as a change in slope of the transfer function.
The difference in gain error to full scale error is that full scale does not take offset error into
account. Gain error can be calibrated out in software.
Linearity error refers to the uniformity of the code changes. Linearity errors cannot be calibrated
out of the system. Integral non-linearity error measures the actual code transition v ersus the ideal
code transition adjusted by the gain error for each code.
Diff erential non-linearity measures the maximum actual code width versus the ideal code width.
This measure is unadjusted.
The maximum pin leakage current is specified in the Device Data Sheet electrical specification
parameter D060.
In systems where the de vice frequency is low, use of the A/D RC clock is preferred. At moderate
to high frequencies, TAD should be derived from the device oscillator. TAD must not violate the
minimum and should be minimized to reduce inaccuracies due to noise and sampling capacitor
bleed off.
In systems where the de vice will enter SLEEP mode after the start of the A/D conv ersion, the RC
clock source selection is required. In this mode, the digital noise from the modules in SLEEP are
stopped. This method gives high accuracy.
21.10 Effects of a RESET
A de vice reset forces all registers to their reset state . This forces the A/D module to be turned off,
and any conversion is aborted. The value that is in the ADRES register is not modified for a
Power-on Reset. The ADRES register will contain unknown data after a Power-on Reset.
PICmicro MID-RANGE MCU FAMILY
DS31021A-page 21-14 1997 Microchip Technology Inc.
21.11 Use of the CCP Trigger
An A/D conversion may be started by the “special event trigger” of a CCP module. This requires
that the CCPxM3:CCPxM0 bits (CCPxCON<3:0>) be programmed as 1011 and that the A/D
module is enabled (ADON bit is set). When the trigger occurs, the GO/DONE bit will be set, start-
ing the A/D conversion, and the Timer1 counter will be reset to zero. Timer1 is reset to automat-
ically repeat the A/D acquisition period with minimal software overhead (moving the ADRES to
the desired location). The appropr iate analog input channel must be selected and the minimum
acquisition done before the “special event trigger” sets the GO/DONE bit (starts a conversion).
If the A/D module is not enabled (ADON is cleared), then the “special event trigger” will be
ignored by the A/D module, but will still reset the Timer1 counter.
21.12 Connection Considerations
If the input voltage exceeds the rail values (VSS or VDD) by greater than 0.3V, then the accuracy
of the conversion is out of specification.
An e xternal RC filter can sometimes be added for anti-aliasing of the input signal. The R compo-
nent should be selected to ensure that the total source impedance is kept under the 10 k rec-
ommended specification. Any external components connected (via hi-impedance) to an analog
input pin (capacitor, zener diode, etc.) should have very little leakage current at the pin.
21.13 Transfer Function
The ideal transfer function of the A/D converter is as follows: the first transition occurs when the
analog input voltage (VAIN) is 1 LSb (or Analog VREF / 256) (Figure 21-6).
Figure 21-6: A/D Transfer Function
Digital code output
FFh
FEh
04h
03h
02h
01h
00h
0.5 LSb
1 LSb
2 LSb
3 LSb
4 LSb
255 LSb
256 LSb
(full scale)
Analog input voltage
1997 Microchip Technology Inc. DS31021A-page 21-15
Section 21. 8-bit A/D Converter
8-bit A/D
Converter
21
21.14 Initialization
Example 21-4 shows the initialization of the A/D module for the PIC16C74A
Example 21-4: A/D Initialization (for PIC16C74A)
BSF STATUS, RP0 ; Select Bank1
CLRF ADCON1 ; Configure A/D inputs
BSF PIE1, ADIE ; Enable A/D interrupts
BCF STATUS, RP0 ; Select Bank0
MOVLW 0xC1 ; RC Clock, A/D is on, Channel 0 is selected
MOVWF ADCON0 ;
BCF PIR1, ADIF ; Clear A/D interrupt flag bit
BSF INTCON, PEIE ; Enable peripheral interrupts
BSF INTCON, GIE ; Enable all interrupts
;
; Ensure that the required sampling time for the selected input
; channel has elapsed. Then the conversion may be started.
;
BSF ADCON0, GO ; Start A/D Conversion
: ; The ADIF bit will be set and the GO/DONE
: ; bit is cleared upon completion of the
: ; A/D Conversion.
PICmicro MID-RANGE MCU FAMILY
DS31021A-page 21-16 1997 Microchip Technology Inc.
21.15 Design Tips
Question 1:
I am using one of your PIC16C7X de vices, and I find that the Analog to Dig-
ital Con verter result is not alwa ys accurate. What can I do to impr o ve accu-
racy?
Answer 1:
1. Make sure y ou are meeting all of the timing specifications. If you are turning the A/D mod-
ule off and on, there is a minimum delay you must wait before taking a sample, if you are
changing input channels, there is a minimum delay you must wait for this as well, and
finally there is Tad, which is the time selected for each bit conversion. This is selected in
ADCON0 and should be between 2 and 6µs. If TAD is too short, the result ma y not be fully
conv erted before the con v ersion is terminated, and if TAD is made too long the voltage on
the sampling capacitor can droop before the conversion is complete. These timing speci-
fications are provided in the data book in a table or by way of a formula, and should be
looked up for your specific part and circumstances.
2. Often the source impedance of the analog signal is high (greater than 1k ohms) so the
current drawn from the source to charge the sample capacitor can affect accuracy. If the
input signal does not change too quickly, try putting a 0.1 µF capacitor on the analog input.
This capacitor will charge to the analog voltage being sampled, and supply the instanta-
neous current needed to charge the 51.2 pf internal holding capacitor.
3. Finally, str aight from the data book: “In systems where the de vice frequency is lo w, use of
the A/D clock derived from the device oscillator is preferred...this reduces, to a large
extent, the effects of digital switching noise.” and “In systems where the device will enter
SLEEP mode after start of A/D conv ersion, the RC clock source selection is required. This
method gives the highest accuracy.
Question 2:
After starting an A/D conversion may I change the input channel (for my
next conversion)?
Answer 2:
After the holding capacitor is disconnected from the input channel, one TAD after the GO bit is
set, the input channel may be changed.
Question 3:
Do you know of a good reference on A/D’s?
Answer 3:
A very good reference for understanding A/D conversions is the “Analog-Digital Conversion
Handbook” third edition, published by Prentice Hall (ISBN 0-13-03-2848-0).
1997 Microchip Technology Inc. DS31021A-page 21-17
Section 21. 8-bit A/D Converter
8-bit A/D
Converter
21
21.16 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the 8-bit A/D
are:
Title Application Note #
Using the Analog to Digital Converter AN546
Four Channel Digital Voltmeter with Display and Keyboard AN557
PICmicro MID-RANGE MCU FAMILY
DS31021A-page 21-18 1997 Microchip Technology Inc.
21.17 Revision History
Revision A
This is the initial released revision of the 8-bit A/D module description.
1997 Microchip Technology Inc. DS31022A page 22-1
M
Basic 8-bit
A/D Converter
22
Section 22. Basic 8-bit A/D Converter
HIGHLIGHTS
This section of the manual contains the following major topics:
22.1 Introduction..................................................................................................................22-2
22.2 Control Registers .........................................................................................................22-3
22.3 A/D Acquisition Requirements .....................................................................................22-6
22.4 Selecting the A/D Conversion Clock ............................................................................22-8
22.5 Configuring Analog Port Pins.....................................................................................22-10
22.6 A/D Conversions........................................................................................................22-11
22.7 A/D Operation During Sleep ......................................................................................22-14
22.8 A/D Accuracy/Error ....................................................................................................22-15
22.9 Effects of a RESET....................................................................................................22-16
22.10 Connection Considerations........................................................................................22-16
22.11 Transfer Function .......................................................................................................22-16
22.12 Initialization................................................................................................................22-17
22.13 Design Tips................................................................................................................22-18
22.14 Related Application Notes..........................................................................................22-19
22.15 Revision History.........................................................................................................22-20
Note: Please refer to Appendix C.2 or the device Data Sheet to determine which devices
use this module.
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-2 1997 Microchip Technology Inc.
22.1 Introduction
This Analog-to-Digital (A/D) converter module has four analog inputs.
The A/D allows con v ersion of an analog input signal to a corresponding 8-bit digital number. The
output of the sample and hold is the input into the converter, which generates the result via suc-
cessive appro ximation. The analog ref erence v oltage is software selectab le to either the de vice’ s
positive supply voltage (VDD) or the voltage level on the AN3/VREF pin. The A/D converter has a
unique feature of being able to operate while the device is in SLEEP mode.
The A/D module has three registers. These registers are:
A/D Result Register (ADRES)
A/D Control Register0 (ADCON0)
A/D Control Register1 (ADCON1)
The ADCON0 register, shown in Figure 22-1 controls the operation of the A/D module. The
ADCON1 register, shown in Figure 22-2, configures the functions of the port pins. The port pins
can be configured as analog inputs (or a voltage reference) or as digital I/O.
Figure 22-1: Basic 8-bit A/D Block Diagram
(Input voltage)
VAIN
VREF
(Reference
voltage)
VDD
PCFG1:PCFG0
CHS1:CHS0
00 or
10 or
11
01
AN3/VREF
AN0
AN2
AN1
11
10
01
00
Basic 8-bit
Converter
A/D
1997 Microchip Technology Inc. DS31022A-page 22-3
Section 22. Basic 8-bit A/D Converter
Basic 8-bit
A/D Converter
22
22.2 Control Registers
Register 22-1: ADCON0 Register
R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
ADCS1 ADCS0 (1) CHS1 CHS0 GO/DONE ADIF / — (2) ADON
bit 7 bit 0
bit 7:6 ADCS1:ADCS0: A/D Conversion Clock Select bits
00 = FOSC/2
01 = FOSC/8
10 = FOSC/32
11 = FRC (clock derived from the internal A/D RC oscillator)
bit 5 Unimplemented: Read as '0'.
bit 4:3 CHS1:CHS0: Analog Channel Select bits
00 = channel 0, (AN0)
01 = channel 1, (AN1)
10 = channel 2, (AN2)
11 = channel 3, (AN3)
bit 2 GO/DONE: A/D Conversion Status bit
If ADON = 1
1 = A/D conversion in progress (setting this bit starts the A/D conversion)
0 = A/D conversion not in progress (This bit is automatically cleared by hardware when the
A/D conversion is complete)
bit 1 ADIF (2): A/D Conversion Complete Interrupt Flag bit
1 = conversion is complete (must be cleared in software)
0 = conversion is not complete
bit 0 ADON: A/D On bit
1 = A/D converter module is operating
0 = A/D converter module is shutoff and consumes no operating current
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note 1: For the PIC16C71, Bit5 of ADCON0 is a General Purpose R/W bit. For the
PIC16C710/711/715, this bit is unimplemented, read as '0'.
Note 2: For the PIC12CXXX de vices , this bit is reserved. The ADIF bit is implemented in the
PIR register. Use of this bit a a general purpose R/W bit is not recommended.
Always maintain this bit cleared.
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-4 1997 Microchip Technology Inc.
Register 22-2: ADCON1 Register
U-0 U-0 U-0 U-0 U-0 U-0 / R/W-0 R/W-0 R/W-0
— / PCFG2 (1) PCFG1 PCFG0
bit 7 bit 0
bit 7:2 Unimplemented: Read as '0'
Note: Some devices implement bit2 as the PCFG2 bit.
bit 1:0 PCFG1:PCFG0: A/D Port Configuration Control bits
bit 2:0 PCFG2:PCFG0: A/D Port Configuration Control bits (1)
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note 1: Some devices add an additional P ort configuration bit (PCFG2). This allows the min-
imum number of analog channels to be one. This is of most benefit to the 8-pin
devices with the A/D converter, since in an 8-pin device I/O is a premium resource.
In the other devices this bit is unimplemented, and read as ‘0’.
Note 2: On any device reset, the Port pins multiplexed with analog functions (ANx) are
forced to be an analog input.
A = Analog input
D = Digital I/O
Note: When AN3 is selected as VREF+, the A/D reference is the voltage on the AN3
pin. When AN3 is selected as an analog input (A), then the v oltage ref erence f or
the A/D is the device VDD.
PCFG1:PCFG0 AN3 AN2 AN1 AN0
00 AAAA
01 VREF+A A A
10 DDAA
11 DDDD
A = Analog input
D = Digital I/O
Note: When AN1 is selected as VREF+, the A/D reference is the voltage on the AN1
pin. When AN1 is selected as an analog input (A), then the v oltage ref erence f or
the A/D is the device VDD.
PCFG2:PCFG0 AN3 AN2 AN1 AN0
000 AAAA
001 AAV
REF+A
010 DAAA
011 DAV
REF+A
100 DDAA
101 DDV
REF+A
110 DDDA
111 DDDD
1997 Microchip Technology Inc. DS31022A-page 22-5
Section 22. Basic 8-bit A/D Converter
Basic 8-bit
A/D Converter
22
The ADRES register contains the result of the A/D conv ersion. When the A/D conv ersion is com-
plete, the result is loaded into the ADRES register, the GO/DONE bit (ADCON0<2>) is cleared,
and A/D interrupt flag bit ADIF is set. The block diagram of the A/D module is shown in
Figure 22-1.
After the A/D module has been configured as desired, the selected channel must be acquired
bef ore the con v ersion is started. The analog input channels must hav e their corresponding TRIS
bits selected as an input. To determine sample time, see Subsection 22.3 “A/D Acquisition
Requirements” After this acquisition time has elapsed the A/D conversion can be star ted. The
following steps should be followed for doing an A/D conversion:
1. Configure the A/D module:
Configure analog pins / voltage reference / and digital I/O (ADCON1)
Select A/D input channel (ADCON0)
Select A/D conversion clock (ADCON0)
Turn on A/D module (ADCON0)
2. Configure A/D interrupt (if desired):
Clear the ADIF bit
Set the ADIE bit
Set the GIE bit
3. Wait the required acquisition time.
4. Start conversion:
Set the GO/DONE bit (ADCON0)
5. Wait for A/D conversion to complete, by either:
Polling for the GO/DONE bit to be cleared
OR
Waiting for the A/D interrupt
6. Read A/D Result register (ADRES), clear the ADIF bit, if required.
7. F or ne xt con version, go to step 1 or step 2 as required. The A/D conv ersion time per bit is
defined as TAD. A minimum wait of 2TAD is required before next acquisition starts.
Figure 22-2 shows the con version sequence , and the terms that are used. Acquisition time is the
time that the A/D module’s holding capacitor is connected to the external voltage level. Then
there is the conv ersion time of 10 TAD, which is started when the GO bit is set. The sum of these
two times is the sampling time. There is a minimum acquisition time to ensure that the holding
capacitor is charged to a level that will give the desired accuracy for the A/D conversion.
Figure 22-2: A/D Conversion Sequence
Acquisition Time A/D Conversion Time
A/D Sample Time
When A/D holding capacitor start to charge.
After A/D conversion, or new A/D channel is selected
When A/D conversion is started (setting the GO bit)
A/D conversion complete,
result is loaded in ADRES register.
Holding capacitor begins acquiring
voltage level on selected channel
ADIF bit is set
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-6 1997 Microchip Technology Inc.
22.3 A/D Acquisition Requirements
F or the A/D con v erter to meet its specified accuracy, the charge holding capacitor (CHOLD) m ust
be allowed to fully charge to the input channel voltage level. The analog input model is shown in
Figure 22-3. The source impedance (RS) and the internal sampling switch (RSS) impedance
directly affect the time required to charge the capacitor CHOLD. The sampling switch (RSS) imped-
ance varies over the device voltage (VDD), see Figure 22-3. The maximum recommended
impedance for analog sources is 10 k. After the analog input channel is selected (changed)
this acquisition must be done before the conversion can be started.
To calculate the minimum acquisition time, Equation 22-1 may be used. This equation assumes
that 1/2 LSb error is used (512 steps f or the A/D). The 1/2 LSb error is the maxim um error allowed
for the A/D to meet its specified resolution.
Equation 22-1:Acquisition Time
Equation 22-2:A/D Minimum Charging Time
Example 22-1 shows the calculation of the minimum required acquisition time T ACQ. This calcu-
lation is based on the following system assumptions.
Rs = 10 k
Conversion Error 1/2 LSb
VDD = 5V Rss = 7 k (see graph in Figure 22-3)
Temperature = 50°C (system max.)
VHOLD = 0V @ time = 0
Example 22-1: Calculating the Minimum Required Acquisition Time
TACQ =Amplifier Settling Time +
Holding Capacitor Charging Time +
Temperature Coefficient
=TAMP + TC + TCOFF
VHOLD = (VREF - (VREF/512)) • (1 - e(-Tc/CHOLD(RIC + RSS + RS)))
or
Tc = -(51.2 pF)(1 k + RSS + RS) ln(1/511)
TACQ =TAMP + TC + TCOFF
TACQ =5 µs + Tc + [(Temp - 25°C)(0.05 µs/°C)]
TC =-CHOLD (RIC + RSS + RS) ln(1/512)
-51.2 pF (1 k + 7 k + 10 k) ln(0.0020)
-51.2 pF (18 k) ln(0.0020)
-0.921 µs (-6.2146)
5.724 µs
TACQ =5 µs + 5.724 µs + [(50°C - 25°C)(0.05 µs/°C)]
10.724 µs + 1.25 µs
11.974 µs
1997 Microchip Technology Inc. DS31022A-page 22-7
Section 22. Basic 8-bit A/D Converter
Basic 8-bit
A/D Converter
22
Figure 22-3: Analog Input Model
Note 1: The reference voltage (VREF) has no effect on the equation, since it cancels itself
out.
Note 2: The charge holding capacitor (CHOLD) is not discharged after each conversion.
Note 3: The maximum recommended impedance for analog sources is 10 k. This is
required to meet the pin leakage specification.
Note 4: After a conv ersion has completed, a 2.0 TAD dela y must complete before acquisition
can begin again. During this time the holding capacitor is not connected to the
selected A/D input channel.
CPIN
VA
Rs RAx
5 pF
VDD
VT = 0.6V
VT = 0.6V I leakage
RIC 1k
Sampling
Switch
SS RSS
CHOLD = 51.2 pF
VSS
6V
Sampling Switch
5V
4V
3V
2V
5 6 7 8 9 10 11
( k )
VDD
± 500 nA
Legend CPIN
VT
I LEAKAGE
RIC
SS
CHOLD
= input capacitance
= threshold voltage
= leakage current at the pin due to
= interconnect resistance
= sampling switch
= sample/hold capacitance (from DAC)
VARIOUS JUNCTIONS
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-8 1997 Microchip Technology Inc.
22.4 Selecting the A/D Conversion Clock
The A/D conv ersion time per bit is defined as TAD. The A/D con v ersion requires 9.5 TAD per 8-bit
conversion. The source of the A/D conversion clock is software selected. The four possible
options for TAD are:
•2T
OSC
•8TOSC
32TOSC
Internal RC oscillator
For correct A/D conversions, the A/D conversion clock (TAD) must be selected to ensure a mini-
mum TAD time of:
2.0 µs for the PIC16C71, as shown in parameter 130 of devices electrical specifications.
1.6 µs for all other devices, as shown in parameter 130 of devices electrical specifications.
Table 22-1 through Table 22-4 show the resultant TAD times derived from the device operating
frequencies and the A/D clock source selected.
Table 22-1: TAD vs. Device Operating Frequencies, All Devices (except PIC16C71)
(C Devices)
Table 22-2: TAD vs. Device Operating Frequencies, All Devices (except PIC16LC71)
(LC Devices)
AD Clock Source (TAD) Device Frequency
Operation ADCS1:ADCS0 20 MHz 5 MHz 1.25 MHz 333.33 kHz
2TOSC 00 100 ns(2) 400 ns(2) 1.6 µs6 µs
8TOSC 01 400 ns(2) 1.6 µs 6.4 µs 24 µs(3)
32TOSC 10 1.6 µs 6.4 µs 25.6 µs(3) 96 µs(3)
RC(5) 11 2 - 6 µs(1,4) 2 - 6 µs(1,4) 2 - 6 µs(1,4) 2 - 6 µs(1)
Note 1: The RC source has a typical TAD time of 4 µs.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion, or the A/D
accuracy may be out of specification.
AD Clock Source (TAD) Device Frequency
Operation ADCS1:ADCS0 4 MHz 2 MHz 1.25 MHz 333.33 kHz
2TOSC 00 500 ns(2) 1.0 µs(2) 1.6 µs(2) 6 µs
8TOSC 01 2.0 µs(2) 4.0 µs 6.4 µs 24 µs(3)
32TOSC 10 8.0 µs 16.0 µs 25.6 µs(3) 96 µs(3)
RC(5) 11 3 - 9 µs(1,4) 3 - 9 µs(1,4) 3 - 9 µs(1,4) 3 - 9 µs(1)
Note 1: The RC source has a typical TAD time of 6 µs.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion, or the A/D
accuracy may be out of specification.
1997 Microchip Technology Inc. DS31022A-page 22-9
Section 22. Basic 8-bit A/D Converter
Basic 8-bit
A/D Converter
22
Table 22-3: TAD vs. Device Operating Frequencies, PIC16C71 ( C Devices)
Table 22-4: TAD vs. Device Operating Frequencies, PIC16LC71 ( LC Devices)
AD Clock Source (TAD) Device Frequency
Operation ADCS1:ADCS0 20 MHz 16 MHz 4 MHz 1 MHz 333.33 kHz
2TOSC 00 100 ns(2) 125 ns(2) 500 ns(2) 2.0 µs6 µs
8TOSC 01 400 ns(2) 500 ns(2) 2.0 µs 8.0 µs 24 µs(3)
32TOSC 10 1.6 µs(2) 2.0 µs 8.0 µs 32.0 µs(3) 96 µs(3)
RC 11 2 - 6 µs(1,4) 2 - 6 µs(1,4) 2 - 6 µs(1,4) 2 - 6 µs(1) 2 - 6 µs(1)
Legend: Shaded cells are outside of recommended range.
Note 1: The RC source has a typical TAD time of 4 µs.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion, or the A/D
accuracy may be out of specification.
AD Clock Source (TAD) Device Frequency
Operation ADCS1:ADCS0 4 MHz 2 MHz 1.25 MHz 333.33 kHz
2TOSC 00 500 ns(2) 1.0 µs(2) 1.6 µs(2) 6 µs
8TOSC 01 2.0 µs(2) 4.0 µs 6.4 µs 24 µs(3)
32TOSC 10 8.0 µs 16.0 µs 25.6 µs(3) 96 µs(3)
RC 11 3 - 9 µs(1,4) 3 - 9 µs(1,4) 3 - 9 µs(1,4) 3 - 9 µs(1)
Legend: Shaded cells are outside of recommended range.
Note 1: The RC source has a typical TAD time of 6 µs.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion, or the A/D
accuracy may be out of specification.
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-10 1997 Microchip Technology Inc.
22.5 Configuring Analog Port Pins
The ADCON1 and TRISA registers control the operation of the A/D port pins. The port pins that
are desired as analog inputs must have their corresponding TRIS bits set (input). If the TRIS bit
is cleared (output), the digital output level (VOH or VOL) will be converted.
The A/D operation is independent of the state of the CHS1:CHS0 bits and the TRIS bits.
Note 1: When reading the port register , all pins configured as analog input channel will read
as cleared (a low level). Pins configured as digital inputs, will convert an analog
input. Analog levels on a digitally configured input will not affect the conversion
accuracy.
Note 2: Analog levels on any pin that is defined as a digital input (including the AN3:AN0
pins), ma y cause the input buff er to consume current that is out of the devices spec-
ification.
1997 Microchip Technology Inc. DS31022A-page 22-11
Section 22. Basic 8-bit A/D Converter
Basic 8-bit
A/D Converter
22
22.6 A/D Conversions
Example 22-2 show how to perform an A/D conversion. The RA pins are configured as analog
inputs. The analog ref erence (VREF) is the device VDD. The A/D interrupt is enab led, and the A/D
conversion clock is FRC. The conversion is performed on the RA0 channel.
Clearing the GO/DONE bit during a conversion will abort the current conversion. The ADRES
register will NOT be updated with the partially completed A/D conversion sample. That is, the
ADRES register will continue to contain the value of the last completed conversion (or the last
value written to the ADRES register). After the A/D con version is aborted, a 2TAD wait is required
bef ore the next acquisition is started. After this 2TAD wait, an acquisition is automatically started
on the selected channel.
Example 22-2: Doing an A/D Conversion
Figure 22-4: A/D Conversion TAD Cycles
Note: The GO/DONE bit should NOT be set in the same instruction that turns on the A/D,
due to the required acquisition time.
BSF STATUS, RP0 ; Select Bank1
CLRF ADCON1 ; Configure A/D inputs
BCF STATUS, RP0 ; Select Bank0
MOVLW 0xC1 ; RC Clock, A/D is on, Channel 0 selected
MOVWF ADCON0 ;
BSF INTCON, ADIE ; Enable A/D Interrupt
BSF INTCON, GIE ; Enable all interrupts
;
; Ensure that the required sampling time for the selected input
; channel has elapsed. Then the conversion may be started.
;
BSF ADCON0, GO ; Start A/D Conversion
: ; The ADIF bit will be set and the GO/DONE bit
: ; is cleared upon completion of the
; A/D Conversion.
TAD1TAD2TAD3TAD4TAD5TAD6TAD7TAD8TAD9TAD10
Set GO bit
Holding capacitor is disconnected
from analog input
Holding capacitor is connected to analog input
GO bit is cleared
Next Q4: ADRES is loaded
b7 b6 b5 b4 b3 b2 b1 b0 b0
TAD11
ADIF bit is set
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-12 1997 Microchip Technology Inc.
Figure 22-5: Flowchart of A/D Operation
Acquire
ADON = 0
ADON = 0?
GO = 0?
A/D Clock
GO = 0
ADIF = 0
Abort Conversion
SLEEP
Power-down A/D Wait 2TAD
Wake-up
Yes
No
Yes
No
No
Yes
Finish Conversion
GO = 0
ADIF = 1
Device in
No
Yes
Finish Conversion
GO = 0
ADIF = 1
Wait 2TAD
Stay in Sleep
Selected Channel
= RC? SLEEP
No
Yes
Instruction?
Start of A/D
Conversion Delayed
1 Instruction Cycle
From Sleep?
Power-down A/D
Yes
No
Wait 2TAD
Finish Conversion
GO = 0
ADIF = 1
SLEEP?
1997 Microchip Technology Inc. DS31022A-page 22-13
Section 22. Basic 8-bit A/D Converter
Basic 8-bit
A/D Converter
22
22.6.1 Faster Conversion - Lower Resolution Trade-off
Not all applications require a result with 8-bits of resolution, but ma y instead require a f aster con-
version time. The A/D module allows users to make the trade-off of conversion speed to resolu-
tion. Regardless of the resolution required, the acquisition time is the same. To speed up the
conversion, the clock source of the A/D module may be switched so that the TAD time violates
the minimum specified time (see the applicable electr ical specification). Once the TAD time vio-
lates the minimum specified time, all the following A/D result bits are not valid (see A/D Conver-
sion Timing in the Electrical Specifications section.) The clock sources may only be switched
between the three oscillator versions (cannot be switched from/to RC). The equation to deter-
mine the time before the oscillator can be switched is as follows:
Conversion time = TAD + N • TAD + (10 - N)(2TOSC)
Where: N = number of bits of resolution required.
Since the TAD is based from the de vice oscillator, the user must use some method (a timer , soft-
ware loop, etc.) to deter mine when the A/D oscillator may be changed. Example 22-3 shows a
comparison of time required for a con version with 4-bits of resolution, versus the 8-bit resolution
conversion. The example is for devices operating at 20 MHz and 16 MHz (The A/D clock is pro-
grammed for 32TOSC), and assumes that immediately after 5TAD, the A/D clock is programmed
for 2TOSC.
The 2TOSC violates the minimum TAD time since the last 4-bits will not be conver ted to correct
values.
Example 22-3: 4-bit vs. 8-bit Conversion Times
Freq.
(MHz)(1) Resolution
4-bit 8-bit
TAD 20 1.6 µs 1.6 µs
16 2.0 µs 2.0 µs
TOSC 20 50 ns 50 ns
16 62.5 ns 62.5 ns
TAD + N • TAD + (10 - N)(2TOSC) 20 8.6 µs 17.6 µs
16 10.75 µs 22 µs
Note 1: The PIC16C71 has a minimum TAD time of 2.0 µs.
All other devices have a minimum TAD time of 1.6 µs.
2: If the full 8-bit conversion is required, the A/D clock source should not be changed.
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-14 1997 Microchip Technology Inc.
22.7 A/D Operation During Sleep
The A/D module can operate during SLEEP mode. This requires that the A/D clock source be set
to RC (ADCS1:ADCS0 = 11). When the RC clock source is selected, the A/D module waits one
instruction cycle before starting the conversion. This allows the SLEEP instruction to be ex ecuted,
which eliminates all internal digital switching noise from the conversion. When the conversion is
completed the GO/DONE bit will be cleared, and the result loaded into the ADRES register . If the
A/D interrupt is enabled, the de vice will w ake-up from SLEEP. If the A/D interrupt is not enabled,
the A/D module will then be turned off, although the ADON bit will remain set.
When the A/D clock source is another clock option (not RC), a SLEEP instruction will cause the
present conversion to be aborted and the A/D module to be turned off, though the ADON bit will
remain set.
Turning off the A/D places the A/D module in its lowest current consumption state.
Note: For the A/D module to operate in SLEEP, the A/D clock source must be set to RC
(ADCS1:ADCS0 = 11). To perform an A/D conversion in SLEEP, the GO/DONE bit
must be set, followed by the SLEEP instruction.
1997 Microchip Technology Inc. DS31022A-page 22-15
Section 22. Basic 8-bit A/D Converter
Basic 8-bit
A/D Converter
22
22.8 A/D Accuracy/Error
In systems where the de vice frequency is low, use of the A/D RC clock is preferred. At moderate
to high frequencies, TAD should be derived from the device oscillator.
The absolute accuracy specified for the A/D conver ter includes the sum of all contributions for
quantization error, integral error, differential error, full scale error, offset error, and monotonicity.
It is defined as the maximum de viation from an actual transition v ersus an ideal transition f or an y
code. The absolute error of the A/D conver ter is specified at < ±1 LSb for VDD = VREF (over the
device’s specified operating range). However, the accuracy of the A/D converter will degrade as
VDD diverges from VREF.
For a given range of analog inputs, the output digital code will be the same. This is due to the
quantization of the analog input to a digital code. Quantization error is typically ± 1/2 LSb and is
inherent in the analog to digital conv ersion process . The only way to reduce quantization error is
to increase the resolution of the A/D converter.
Offset error measures the first actual transition of a code v ersus the first ideal transition of a code.
Offset error shifts the entire transfer function. Offset error can be calibrated out of a system or
introduced into a system through the interaction of the total leakage current and source imped-
ance at the analog input.
Gain error measures the maximum deviation of the last actual transition and the last ideal tran-
sition adjusted for offset error. This error appears as a change in slope of the transfer function.
The difference in gain error to full scale error is that full scale does not take offset error into
account. Gain error can be calibrated out in software.
Linearity error refers to the uniformity of the code changes. Linearity errors cannot be calibrated
out of the system. Integral non-linearity error measures the actual code transition v ersus the ideal
code transition adjusted by the gain error for each code.
Diff erential non-linearity measures the maximum actual code width versus the ideal code width.
This measure is unadjusted.
The maximum pin leakage current is specified in the Device Data Sheet electrical specification
parameter D060.
In systems where the de vice frequency is low, use of the A/D RC clock is preferred. At moderate
to high frequencies, TAD should be derived from the device oscillator. TAD must not violate the
minimum and should be minimized to reduce inaccuracies due to noise and sampling capacitor
bleed off.
In systems where the de vice will enter SLEEP mode after the start of the A/D conv ersion, the RC
clock source selection is required. In this mode, the digital noise from the modules in SLEEP are
stopped. This method gives high accuracy.
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-16 1997 Microchip Technology Inc.
22.9 Effects of a RESET
A de vice reset forces all registers to their reset state . This forces the A/D module to be turned off,
and any conversion is aborted. The value that is in the ADRES register is not modified for a
Power-on Reset. The ADRES register will contain unknown data after a Power-on Reset.
22.10 Connection Considerations
If the input voltage exceeds the rail values (VSS or VDD) by greater than 0.2V, then the accuracy
of the conversion is out of specification.
An exter nal RC filter is sometimes added for anti-aliasing of the input signal. The R component
should be selected to ensure that the total source impedance is kept under the 10 k recom-
mended specification. Any external components connected (via hi-impedance) to an analog
input pin (capacitor, zener diode, etc.) should have very little leakage current at the pin.
22.11 Transfer Function
The ideal transfer function of the A/D converter is as follows: the first transition occurs when the
analog input voltage (VAIN) is 1 LSb (or Analog VREF / 256) (Figure 22-6).
Figure 22-6: A/D Transfer Function
Note: Care must be tak en when using the RA0 pin in A/D conv ersions due to its proximity
to the OSC1 pin.
Digital code output
FFh
FEh
04h
03h
02h
01h
00h
0.5 LSb
1 LSb
2 LSb
3 LSb
4 LSb
255 LSb
256 LSb
(full scale)
Analog input voltage
1997 Microchip Technology Inc. DS31022A-page 22-17
Section 22. Basic 8-bit A/D Converter
Basic 8-bit
A/D Converter
22
22.12 Initialization
Example 22-4 shows the initialization of the A/D module in the PIC16C711.
Example 22-4: A/D Initialization (for PIC16C711)
BSF STATUS, RP0 ; Select Bank1
CLRF ADCON1 ; Configure A/D inputs
BCF STATUS, RP0 ; Select Bank0
MOVLW 0xC1 ; RC Clock, A/D is on, Channel 0 selected
MOVWF ADCON0 ;
BSF INTCON, ADIE ; Enable A/D Interrupt
BSF INTCON, GIE ; Enable all interrupts
;
; Ensure that the required sampling time for the selected input
; channel has elapsed. Then the conversion may be started.
;
BSF ADCON0, GO ; Start A/D Conversion
: ; The ADIF bit will be set and the GO/DONE bit
: ; is cleared upon completion of the
; A/D Conversion.
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-18 1997 Microchip Technology Inc.
22.13 Design Tips
Question 1:
I am using one of your PIC16C7X de vices, and I find that the Analog to Dig-
ital Con verter result is not alwa ys accurate. What can I do to impr o ve accu-
racy?
Answer 1:
1. Make sure you are meeting all of the timing specifications. If you are turning the ADC off
and on, there is a minimum dela y y ou must w ait before taking a sample, if you are chang-
ing input channels, there is a minimum delay you must wait for this as well, and finally
there is TAD, which is the time selected for each bit conversion. This is selected in
ADCON0 and should be between 2 and 6 µs . If TAD is too short, the result ma y not be fully
converted bef ore the con version is terminated, and if Tad is made too long the v oltage on
the sampling capacitor can droop before the conversion is complete. These timing speci-
fications are provided in the data book in a table or by way of a formula, and should be
looked up for your specific part and circumstances.
2. Often the source impedance of the analog signal is high (greater than 1k ohms) so the
current drawn from the source to charge the sample capacitor can affect accuracy. If the
input signal does not change too quickly, try putting a 0.1 µF capacitor on the analog input.
This capacitor will charge to the analog voltage being sampled, and supply the instanta-
neous current needed to charge the 51.2 pf internal holding capacitor.
3. On the PIC16C71, one of the analog input pins is next to an oscillator pin. Naturally if
these traces are next to each other some noise can couple from the oscillator to the ana-
log circuit. This is especially tr ue when the clock source is an external canned oscillator,
since its output is a square wave with a high frequency component to its sharp edge, as
opposed to a crystal circuit which pro vides a slower rise sine wa v e . Again, decoupling the
analog pin can help , or if y ou can spare it, turn the pin into an output and drive it low. This
will really help eliminate cross coupling into the analog circuit.
4. Finally, str aight from the data book: “In systems where the de vice frequency is lo w, use of
the A/D clock derived from the device oscillator is preferred...this reduces, to a large
extent, the effects of digital switching noise.” and “In systems where the device will enter
SLEEP mode after start of A/D conv ersion, the RC clock source selection is required. This
method gives the highest accuracy.
Question 2:
After starting an A/D conversion may I change the input channel (for my
next conversion)?
Answer 2:
After the holding capacitor is disconnected from the input channel, one TAD after the GO bit is
set, the input channel may be changed.
Question 3:
Do you know of a good reference on A/D’s?
Answer 3:
A very good reference for understanding A/D conversions is the “Analog-Digital Conversion
Handbook” third edition, published by Prentice Hall (ISBN 0-13-03-2848-0).
1997 Microchip Technology Inc. DS31022A-page 22-19
Section 22. Basic 8-bit A/D Converter
Basic 8-bit
A/D Converter
22
22.14 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the Basic
8-bit A/D module are:
Title Application Note #
Using the Analog to Digital Converter AN546
Four Channel Digital Voltmeter with Display and Keyboard AN557
PICmicro MID-RANGE MCU FAMILY
DS31022A-page 22-20 1997 Microchip Technology Inc.
22.15 Revision History
Revision A
This is the initial released revision of the Basic 8-bit A/D Converter module description.
1997 Microchip Technology Inc. Preliminary DS31023A page 23-1
M
10-bit
A/D Converter
23
Section 23. 10-bit A/D Converter
HIGHLIGHTS
This section of the manual contains the following major topics:
23.1 Introduction..................................................................................................................23-2
23.2 Control Register...........................................................................................................23-3
23.3 Operation .....................................................................................................................23-5
23.4 A/D Acquisition Requirements .....................................................................................23-6
23.5 Selecting the A/D Conversion Clock ............................................................................23-8
23.6 Configuring Analog Port Pins.......................................................................................23-9
23.7 A/D Conversions........................................................................................................23-10
23.8 Operation During Sleep .............................................................................................23-14
23.9 Effects of a Reset.......................................................................................................23-14
23.10 A/D Accuracy/Error....................................................................................................23-15
23.11 Connection Considerations........................................................................................23-16
23.12 Transfer Function .......................................................................................................23-16
23.13 Initialization................................................................................................................23-17
23.14 Design Tips................................................................................................................23-18
23.15 Related Application Notes..........................................................................................23-19
23.16 Revision History.........................................................................................................23-20
Note 1: At present NO released mid-range MCU devices are available with this module.
Devices are planned, but there is no schedule for availability. Please refer to Micro-
chip’s Web site or BBS for release of Product Briefs which detail the features of
devices.
If your current design requires a 10-bit A/D , please look at the PIC17C756 which has
a 12-channel 10-bit A/D . This A/D has characteristics which are identical to this mod-
ule’s description.
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-2 Preliminary 1997 Microchip Technology Inc.
23.1 Introduction
The analog-to-digital (A/D) converter module can have up to eight analog inputs for a device.
The analog input charges a sample and hold capacitor . The output of the sample and hold capac-
itor is the input into the conv erter . The conv erter then generates a digital result of this analog lev el
via successive approximation. This A/D conv ersion, of the analog input signal, results in a corre-
sponding 10-bit digital number.
The analog reference voltages (positive and negative supply) are software selectable to either
the de vice’ s supply voltages (AVDD, AVss) or the v oltage lev el on the AN3/VREF+ and AN2/VREF-
pins.
The A/D conver ter has a unique feature of being able to operate while the device is in SLEEP
mode.
The A/D module has four registers. These registers are:
A/D Result High Register (ADRESH)
A/D Result Low Register (ADRESL)
A/D Control Register0 (ADCON0)
A/D Control Register1 (ADCON1)
The ADCON0 register, shown in Figure 23-1, controls the operation of the A/D module. The
ADCON1 register, shown in Figure 23-2, configures the functions of the port pins. The port pins
can be configured as analog inputs (AN3 and AN2 can also be the voltage ref erences) or as dig-
ital I/O.
Figure 23-1: 10-bit A/D Block Diagram
(Input voltage)
VAIN
VREF+
Reference
voltage
AVDD
PCFG0
CHS2:CHS0
AN7
AN6
AN5
AN4
AN3
AN2
AN1
AN0
111
110
101
100
011
010
001
000
10-bit
Converter
VREF-
AVSS
A/D
1997 Microchip Technology Inc. Preliminary DS31023A-page 23-3
Section 23. 10-bit A/D Converter
10-bit
A/D Converter
23
23.2 Control Register
Register 23-1: ADCON0 Register
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 U-0 R/W-0
ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE ADON
bit 7 bit 0
bit 7:6 ADCS1:ADCS0: A/D Conversion Clock Select bits
00 = FOSC/2
01 = FOSC/8
10 = FOSC/32
11 = FRC (clock derived from the internal A/D RC oscillator)
bit 5:3 CHS2:CHS0: Analog Channel Select bits
000 = channel 0, (AN0)
001 = channel 1, (AN1)
010 = channel 2, (AN2)
011 = channel 3, (AN3)
100 = channel 4, (AN4)
101 = channel 5, (AN5)
110 = channel 6, (AN6)
111 = channel 7, (AN7)
Note: For devices that do not implement the full 8 A/D channels, the unimplemented selec-
tions are reserved. Do not select any unimplemented channel.
bit 2 GO/DONE: A/D Conversion Status bit
When ADON = 1
1 = A/D conversion in progress (setting this bit starts the A/D conversion which is
automatically cleared by hardware when the A/D conversion is complete)
0 = A/D conversion not in progress
bit 1 Unimplemented: Read as '0'
bit 0 ADON: A/D On bit
1 = A/D converter module is powered up
0 = A/D converter module is shut off and consumes no operating current
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-4 Preliminary 1997 Microchip Technology Inc.
Register 23-2: ADCON1 Register
U-0 U-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0
ADFM PCFG3 PCFG2 PCFG1 PCFG0
bit 7 bit 0
bit 7:6 Unimplemented: Read as '0'
bit 5 ADFM: A/D Result format select (also see Figure 23-6).
1 = Right justified. 6 Most Significant bits of ADRESH are read as ’0’.
0 = Left justified. 6 Least Significant bits of ADRESL are read as ’0’.
bit 4 Unimplemented: Read as '0'
bit 3:0 PCFG3:PCFG0: A/D Port Configuration Control bits
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
A = Analog input D = Digital I/O
C/R = # of analog input channels / # of A/D voltage references
PCFG AN7 AN6 AN5 AN4 AN3 AN2 AN1 AN0 VREF+VREF- C / R
0000 AAAA A A AAAV
DD AVSS 8 / 0
0001 AAAAV
REF+ A A A AN3 AVSS 7 / 1
0010 DDDA A A AAAV
DD AVSS 5 / 0
0011 DDDAV
REF+ A A A AN3 AVSS 4 / 1
0100 DDDD A D AAAV
DD AVSS 3 / 0
0101 DDDDV
REF+ D A A AN3 AVSS 2 / 1
011x D D D D D D D D 0 / 0
1000 AAAAV
REF+VREF- A A AN3 AN2 6 / 2
1001 DDAA A A AAAV
DD AVSS 6 / 0
1010 DDAAV
REF+ A A A AN3 AVSS 5 / 1
1011 DDAAV
REF+VREF- A A AN3 AN2 4 / 2
1100 DDDAV
REF+VREF- A A AN3 AN2 3 / 2
1101 DDDDV
REF+VREF- A A AN3 AN2 2 / 2
1110 DDDD D D DAAV
DD AVSS 1 / 0
1111 DDDDV
REF+VREF- D A AN3 AN2 1 / 2
Note 1: On any device reset, the port pins that are multiplexed with analog functions (ANx)
are forced to be an analog input.
1997 Microchip Technology Inc. Preliminary DS31023A-page 23-5
Section 23. 10-bit A/D Converter
10-bit
A/D Converter
23
23.3 Operation
The ADRESH:ADRESL registers contains the 10-bit result of the A/D conversion. When the A/D
conversion is complete, the result is loaded into this A/D result register pair, the GO/DONE bit
(ADCON0<2>) is cleared, and A/D interrupt flag bit, ADIF, is set. The block diagrams of the A/D
module are shown in Figure 23-1.
After the A/D module has been configured as desired, the selected channel must be acquired
bef ore the con v ersion is started. The analog input channels must hav e their corresponding TRIS
bits selected as inputs. To determine sample time, see Subsection 23.4 “A/D Acquisition
Requirements. After this acquisition time has elapsed the A/D con version can be started. The
following steps should be followed for doing an A/D conversion:
1. Configure the A/D module:
Configure analog pins / voltage reference/ and digital I/O (ADCON1)
Select A/D input channel (ADCON0)
Select A/D conversion clock (ADCON0)
Turn on A/D module (ADCON0)
2. Configure A/D interrupt (if desired):
Clear the ADIF bit
Set the ADIE bit
Set the GIE bit
3. Wait the required acquisition time.
4. Start conversion:
Set the GO/DONE bit (ADCON0)
5. Wait for A/D conversion to complete, by either:
Polling for the GO/DONE bit to be cleared or ADIF bit to be set
OR
Waiting for the A/D interrupt
6. Read A/D Result register pair (ADRESH:ADRESL), clear the ADIF bit, if required.
7. For next conversion, go to step 1 or step 2 as required.
Figure 23-2 shows the con version sequence , and the terms that are used. Acquisition time is the
time that the A/D module’s holding capacitor is connected to the external voltage level. Then
there is the conv ersion time of 12 TAD, which is started when the GO bit is set. The sum of these
two times is the sampling time. There is a minimum acquisition time to ensure that the holding
capacitor is charged to a level that will give the desired accuracy for the A/D conversion.
Figure 23-2: A/D Conversion Sequence
Acquisition Time A/D Conversion Time
A/D Sample Time
When A/D holding capacitor starts to charge.
After A/D conversion, or when new A/D channel is selected
When A/D conversion is started (setting the GO bit)
A/D conversion complete,
result is loaded in ADRES register.
Holding capacitor begins acquiring
voltage level on selected channel
ADIF bit is set
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-6 Preliminary 1997 Microchip Technology Inc.
23.4 A/D Acquisition Requirements
F or the A/D con v erter to meet its specified accuracy, the charge holding capacitor (CHOLD) m ust
be allowed to fully charge to the input channel voltage level. The analog input model is shown in
Figure 23-3. The source impedance (RS) and the internal sampling switch (RSS) impedance
directly affect the time required to charge the capacitor CHOLD. The sampling switch (RSS) imped-
ance varies over the device voltage (VDD), Figure 23-3. The maximum recommended imped-
ance for analog sour ces is 10 k. As the impedance is decreased, the acquisition time may be
decreased. After the analog input channel is selected (changed) this acquisition must be done
before the conversion can be started.
To calculate the minimum acquisition time, Equation 23-1 may be used. This equation assumes
that 1/2 LSb error is used (1024 steps for the A/D). The 1/2 LSb error is the maximum error
allowed for the A/D to meet its specified resolution.
Equation 23-1: Acquisition Time
Equation 23-2: A/D Minimum Charging Time
Example 23-1 shows the calculation of the minimum required acquisition time TACQ.
This calculation is based on the following application system assumptions.
CHOLD = 120 pF
Rs = 10 k
Conversion Error 1/2 LSb
VDD = 5V Rss = 7 k (see graph in Figure 23-3)
Temperature = 50°C (system max.)
VHOLD = 0V @ time = 0
Example 23-1: Calculating the Minimum Required Acquisition Time (Case 1)
TACQ =Amplifier Settling Time +
Holding Capacitor Charging Time +
Temperature Coefficient
=TAMP + TC + TCOFF
VHOLD = (VREF - (VREF/2048))(1 - e(-Tc/CHOLD(RIC + RSS + RS)))
or
Tc = -(120 pF)(1 k + RSS + RS) ln(1/2047)
TACQ = TAMP + TC + TCOFF
Temperature coefficient is only required for temperatures > 25°C.
TACQ =2 µs + Tc + [(Temp - 25°C)(0.05 µs/°C)]
TC =-CHOLD (RIC + RSS + RS) ln(1/2047)
-120 pF (1 k + 7 k + 10 k) ln(0.0004885)
-120 pF (18 k) ln(0.0004885)
-2.16 µs (-7.6241)
16.47 µs
TACQ =2 µs + 16.47 µs + [(50°C - 25°C)(0.05 µs/°C)]
18.47 µs + 1.25 µs
19.72 µs
1997 Microchip Technology Inc. Preliminary DS31023A-page 23-7
Section 23. 10-bit A/D Converter
10-bit
A/D Converter
23
Now to get an idea what happens to the acquisition time when the source impedance is a mini-
mal value (
R
S
= 50 ). Example 23-2 shows the same conditions as in Example 23-1 with only
the source impedance made a minimal value (
R
S
= 50 ).
Example 23-2: Calculating the Minimum Required Acquisition Time (Case 2)
Figure 23-3: Analog Input Model
TACQ = TAMP + TC + TCOFF
Temperature coefficient is only required for temperatures > 25°C.
TACQ =2 µs + Tc + [(Temp - 25°C)(0.05 µs/°C)]
TC =-CHOLD (RIC + RSS + RS) ln(1/2047)
-120 pF (1 k + 7 k + 50 ) ln(0.0004885)
-120 pF (8050 ) ln(0.0004885)
-0.966 µs (-7.6241)
7.36 µs
TACQ =2 µs + 16.47 µs + [(50°C - 25°C)(0.05 µs/°C)]
9.36 µs + 1.25 µs
10.61 µs
Note 1: The reference voltage (VREF) has no effect on the equation, since it cancels itself
out.
Note 2: The charge holding capacitor (CHOLD) is not discharged after each conversion.
Note 3: The maximum recommended impedance for analog sources is 10 k. This is
required to meet the pin leakage specification.
Note 4: After a conv ersion has completed, a 2.0TAD dela y must complete bef ore acquisition
can begin again. During this time the holding capacitor is not connected to the
selected A/D input channel.
VAIN CPIN
Rs ANx
5 pF
VDD
VT = 0.6V
VT = 0.6V I leakage
RIC 1k
Sampling
Switch
SS RSS
CHOLD = 120 pF
VSS
6V
Sampling Switch
5V
4V
3V
2V
5 6 7 8 9 10 11
( k )
VDD
± 100 nA
Legend CPIN
VT
I LEAKAGE
RIC
SS
CHOLD
= input capacitance
= threshold voltage
= leakage current at the pin due to
= interconnect resistance
= sampling switch
= sample/hold capacitance (from DAC)
various junctions
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-8 Preliminary 1997 Microchip Technology Inc.
23.5 Selecting the A/D Conversion Clock
The A/D conversion time per bit is defined as TAD. The A/D conversion requires 11.5TAD per
10-bit conv ersion. The source of the A/D conv ersion cloc k is software selected. The four possib le
options for TAD are:
•2T
OSC
•8TOSC
32TOSC
Internal RC oscillator
For correct A/D conversions, the A/D conversion clock (TAD) must be selected to ensure a mini-
mum TAD time of 1.6 µs as shown in parameter 130 of the “Electrical Specifications” section.
Table 23-1 show the resultant TAD times derived from the device operating frequencies and the
A/D clock source selected. These times are for standard voltage range devices.
Table 23-1: TAD vs. Device Operating Frequencies (for Standard, C, Devices)
Table 23-2: TAD vs. Device Operating Frequencies (for Extended, LC, Devices)
AD Clock Source (TAD) Device Frequency
Operation ADCS1:ADCS0 20 MHz 5 MHz 1.25 MHz 333.33 kHz
2TOSC 00 100 ns(2) 400 ns(2) 1.6 µs6 µs
8TOSC 01 400 ns(2) 1.6 µs 6.4 µs 24 µs(3)
32TOSC 10 1.6 µs 6.4 µs 25.6 µs(3) 96 µs(3)
RC 11 2 - 6 µs(1,4) 2 - 6 µs(1,4) 2 - 6 µs(1,4) 2 - 6 µs(1)
Legend: Shaded cells are outside of recommended range.
Note 1: The RC source has a typical TAD time of 4 µs.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion, or the A/D
accuracy may be out of specification.
AD Clock Source (TAD) Device Frequency
Operation ADCS1:ADCS0 4 MHz 2 MHz 1.25 MHz 333.33 kHz
2TOSC 00 500 ns(2) 1.0 µs(2) 1.6 µs(2) 6 µs
8TOSC 01 2.0 µs(2) 4.0 µs 6.4 µs 24 µs(3)
32TOSC 10 8.0 µs 16.0 µs 25.6 µs(3) 96 µs(3)
RC 11 3 - 9 µs(1,4) 3 - 9 µs(1,4) 3 - 9 µs(1,4) 3 - 9 µs(1,4)
Legend: Shaded cells are outside of recommended range.
Note 1: The RC source has a typical TAD time of 6 µs.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion, or the A/D
accuracy may be out of specification.
1997 Microchip Technology Inc. Preliminary DS31023A-page 23-9
Section 23. 10-bit A/D Converter
10-bit
A/D Converter
23
23.6 Configuring Analog Port Pins
The ADCON1 and TRIS registers control the operation of the A/D por t pins. The por t pins that
are desired as analog inputs must have their corresponding TRIS bits set (input). If the TRIS bit
is cleared (output), the digital output level (VOH or VOL) will be converted.
The A/D operation is independent of the state of the CHS2:CHS0 bits and the TRIS bits.
Note 1: When reading the por t register, any pin configured as an analog input channel will
read as cleared (a low le vel). Pins configured as digital inputs , will convert an analog
input. Analog levels on a digitally configured input will not affect the conversion
accuracy.
Note 2: Analog levels on any pin that is defined as a digital input (including the AN7:AN0
pins), ma y cause the input buff er to consume current that is out of the devices spec-
ification.
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-10 Preliminary 1997 Microchip Technology Inc.
23.7 A/D Conversions
Example 23-3 shows how to perform an A/D conversion for the PIC17C756. The PORTF and
lower four PORTG pins are configured as analog inputs. The analog references (VREF+ and
VREF-) are the device AVDD and AVSS. The A/D interrupt is enabled, and the A/D conversion
clock is FRC. The conversion is performed on the AN0 pin (channel 0).
Clearing the GO/DONE bit during a conversion will abort the current conversion. The A/D result
register pair will NOT be updated with the par tially completed A/D conversion sample. That is,
the ADRESH:ADRESL registers will continue to contain the value of the last completed conver-
sion (or the last value written to the ADRESH:ADRESL registers). After the A/D conversion is
aborted, a 2TAD wait is required bef ore the ne xt acquisition is started. After this 2T AD wait, acqui-
sition on the selected channel is automatically started.
Example 23-3: A/D Conversion
Figure 23-4: A/D Conversion TAD Cycles
Note: The GO/DONE bit should NOT be set in the same instruction that turns on the A/D,
due to the required acquisition time requirement.
BSF STATUS, RP0 ; Select Bank1
CLRF ADCON1 ; Configure A/D inputs,
; result is left justified
BSF PIE1, ADIE ; Enable A/D interrupts
BCF STATUS, RP0 ; Select Bank0
MOVLW 0xC1 ; RC Clock, A/D is on, Channel 0 is selected
MOVWF ADCON0 ;
BCF PIR1, ADIF ; Clear A/D interrupt flag bit
BSF INTCON, PEIE ; Enable peripheral interrupts
BSF INTCON, GIE ; Enable all interrupts
;
; Ensure that the required sampling time for the selected input
; channel has elapsed. Then the conversion may be started.
;
BSF ADCON0, GO ; Start A/D Conversion
: ; The ADIF bit will be set and the GO/DONE
: ; bit is cleared upon completion of the
: ; A/D Conversion.
TAD1TAD2TAD3TAD4TAD5TAD6TAD7TAD8TAD11
Set GO bit
Holding capacitor is disconnected from analog input (typically 100 ns)
holding capacitor is connected to analog input.
b9 b8 b7 b6 b5 b4 b3 b2 TAD9TAD10
b1 b0
Tcy - TAD
GO bit is cleared,
Next Q4: ADRES is loaded,
ADIF bit is set,
Conversion Starts
b0
1997 Microchip Technology Inc. Preliminary DS31023A-page 23-11
Section 23. 10-bit A/D Converter
10-bit
A/D Converter
23
Figure 23-5: Flowchart of A/D Operation
Acquire
ADON = 0
ADON = 0?
GO = 0?
A/D Clock
GO = 0,
ADIF = 0
Abort Conversion
SLEEP
Power-down A/D Wait 2TAD
Wake-up
Yes
No
Yes
No
No
Yes
Finish Conversion
GO = 0,
ADIF = 1
Device in
No
Yes
Finish Conversion
GO = 0,
ADIF = 1
Wait 2TAD
Stay in Sleep
Selected Channel
= RC? SLEEP
No
Yes
Instruction?
Start of A/D
Conversion Delayed
1 Instruction Cycle
From Sleep?
Power-down A/D
Yes
No
Wait 2TAD
Finish Conversion
GO = 0,
ADIF = 1
SLEEP?
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-12 Preliminary 1997 Microchip Technology Inc.
23.7.1 Faster Conversion - Lower Resolution Trade-off
Not all applications require a result with 10-bits of resolution, but may instead require a faster
conversion time. The A/D module allows users to mak e the tr ade-off of conversion speed to res-
olution. Regardless of the resolution required, the acquisition time is the same. To speed up the
conversion, the clock source of the A/D module may be switched so that the TAD time violates
the minimum specified time (see the applicable electr ical specification). Once the TAD time vio-
lates the minimum specified time, all the following A/D result bits are not valid (see A/D Conver-
sion Timing in the Electrical Specifications section). The clock sources may only be switched
between the three oscillator versions (cannot be switched from/to RC). The equation to deter-
mine the time before the oscillator can be switched is as follows:
Conversion time = TAD + N • TAD + (11 - N)(2TOSC)
Where: N = number of bits of resolution required.
Since the TAD is based from the de vice oscillator, the user must use some method (a timer , soft-
ware loop, etc.) to deter mine when the A/D oscillator may be changed. Example 23-4 shows a
comparison of time required for a con version with 4-bits of resolution, v ersus the 10-bit resolution
conversion. The example is for devices operating at 20 MHz (The A/D clock is programmed for
32TOSC), and assumes that immediately after 6TAD, the A/D clock is programmed for 2TOSC.
The 2TOSC violates the minimum TAD time since the last 4 bits will not be conver ted to correct
values.
Example 23-4: 4-bit vs. 8-bit Conversion Times
Freq.
(MHz)(1) Resolution
4-bit 10-bit
TAD 20 1.6 µs 1.6 µs
TOSC 20 50 ns 50 ns
2TAD + N • TAD + (11 - N)(2TOSC) 20 8.7 µs 17.6 µs
Note 1: A minimum TAD time of 1.6 µs is required.
2: If the full 8-bit conversion is required, the A/D clock source should not be changed.
1997 Microchip Technology Inc. Preliminary DS31023A-page 23-13
Section 23. 10-bit A/D Converter
10-bit
A/D Converter
23
23.7.2 A/D Result Registers
The ADRESH:ADRESL register pair is the location where the 10-bit A/D result is loaded at the
completion of the A/D conversion. This register pair is 16-bits wide. The A/D module gives the
fle xibility to left or right justify the 10-bit result in the 16-bit result register. The A/D Format Select
bit (ADFM) controls this justification. Figure 23-6 shows the operation of the A/D result justifica-
tion. The extr a bits are loaded with ‘0’s’. When an A/D result will not ov erwrite these locations (A/D
disable), these registers may be used as two general purpose 8-bit registers.
Figure 23-6: A/D Result Justification
10-Bit Result
ADRESH ADRESL
0000 00
ADFM = 0
0
2 1 0 7
7
10-bits
RESULT
ADRESH ADRESL
10-bits
0000 00
70 7 6 5 0
RESULT
ADFM = 1
Right Justified Left Justified
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-14 Preliminary 1997 Microchip Technology Inc.
23.8 Operation During Sleep
The A/D module can operate during SLEEP mode. This requires that the A/D clock source be set
to RC (ADCS1:ADCS0 = 11). When the RC clock source is selected, the A/D module waits one
instruction cycle before starting the conversion. This allows the SLEEP instruction to be ex ecuted,
which eliminates all internal digital switching noise from the conversion. When the conversion is
completed the GO/DONE bit will be cleared, and the result is loaded into the ADRES register. If
the A/D interrupt is enabled, the device will wake-up from SLEEP. If the A/D interrupt is not
enabled, the A/D module will then be turned off, although the ADON bit will remain set.
When the A/D clock source is another clock option (not RC), a SLEEP instruction will cause the
present conversion to be aborted and the A/D module to be turned off (to conserve power),
though the ADON bit will remain set.
Turning off the A/D places the A/D module in its lowest current consumption state.
23.9 Effects of a Reset
A de vice reset forces all registers to their reset state . This forces the A/D module to be turned off,
and any conversion is aborted.
The value that is in the ADRESH:ADRESL registers is not modified for a Power-on Reset. The
ADRESH:ADRESL registers will contain unknown data after a Power-on Reset.
Note: For the A/D module to operate in SLEEP, the A/D clock source must be set to RC
(ADCS1:ADCS0 = 11). To allow the conversion to occur dur ing SLEEP, ensure the
SLEEP instruction immediately follows the instruction that sets the GO/DONE bit.
1997 Microchip Technology Inc. Preliminary DS31023A-page 23-15
Section 23. 10-bit A/D Converter
10-bit
A/D Converter
23
23.10 A/D Accuracy/Error
In systems where the de vice frequency is low, use of the A/D RC clock is preferred. At moderate
to high frequencies, TAD should be derived from the device oscillator.
The absolute accuracy specified for the A/D conver ter includes the sum of all contributions for
quantization error, integral error, differential error, full scale error, offset error, and monotonicity.
It is defined as the maximum de viation from an actual transition v ersus an ideal transition f or an y
code. The absolute error of the A/D conver ter is specified at < ±1 LSb for VDD = VREF (over the
device’s specified operating range). However, the accuracy of the A/D converter will degrade as
VDD diverges from VREF.
For a given range of analog inputs, the output digital code will be the same. This is due to the
quantization of the analog input to a digital code. Quantization error is typically ± 1/2 LSb and is
inherent in the analog to digital conv ersion process . The only way to reduce quantization error is
to increase the resolution of the A/D converter.
Offset error measures the first actual transition of a code v ersus the first ideal transition of a code.
Offset error shifts the entire transfer function. Offset error can be calibrated out of a system or
introduced into a system through the interaction of the total leakage current and source imped-
ance at the analog input.
Gain error measures the maximum deviation of the last actual transition and the last ideal tran-
sition adjusted for offset error. This error appears as a change in slope of the transfer function.
The difference in gain error to full scale error is that full scale does not take offset error into
account. Gain error can be calibrated out in software.
Linearity error refers to the uniformity of the code changes. Linearity errors cannot be calibrated
out of the system. Integral non-linearity error measures the actual code transition v ersus the ideal
code transition adjusted by the gain error for each code.
Diff erential non-linearity measures the maximum actual code width versus the ideal code width.
This measure is unadjusted.
The maximum pin leakage current is specified in the Device Data Sheet electrical specification
parameter D060.
In systems where the de vice frequency is low, use of the A/D RC clock is preferred. At moderate
to high frequencies, TAD should be derived from the device oscillator. TAD must not violate the
minimum and should be minimized to reduce inaccuracies due to noise and sampling capacitor
bleed off.
In systems where the de vice will enter SLEEP mode after the start of the A/D conv ersion, the RC
clock source selection is required. In this mode, the digital noise from the modules in SLEEP are
stopped. This method gives high accuracy.
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-16 Preliminary 1997 Microchip Technology Inc.
23.11 Connection Considerations
If the input voltage exceeds the rail values (VSS or VDD) by greater than 0.3V, then the accuracy
of the conversion is out of specification.
An exter nal RC filter is sometimes added for anti-aliasing of the input signal. The R component
should be selected to ensure that the total source impedance is kept under the 10 k recom-
mended specification. Any external components connected (via hi-impedance) to an analog
input pin (capacitor, zener diode, etc.) should have very little leakage current at the pin.
23.12 Transfer Function
The ideal transfer function of the A/D converter is as follows: the first transition occurs when the
analog input voltage (VAIN) is 1 LSb (or Analog VREF / 1024) (Figure 23-7).
Figure 23-7: A/D Transfer Function
Digital code output
3FEh
003h
002h
001h
000h
0.5 LSb
1 LSb
1.5 LSb
2 LSb
2.5 LSb
1022 LSb
1022.5 LSb
3 LSb
Analog input voltage
3FFh
1023 LSb
1023.5 LSb
1997 Microchip Technology Inc. Preliminary DS31023A-page 23-17
Section 23. 10-bit A/D Converter
10-bit
A/D Converter
23
23.13 Initialization
Example 23-5 shows an initialization of the A/D module.
Example 23-5: A/D Initialization
BSF STATUS, RP0 ; Select Bank1
CLRF ADCON1 ; Configure A/D inputs
BSF PIE1, ADIE ; Enable A/D interrupts
BCF STATUS, RP0 ; Select Bank0
MOVLW 0xC1 ; RC Clock, A/D is on, Channel 0 is selected
MOVWF ADCON0 ;
BCF PIR1, ADIF ; Clear A/D interrupt flag bit
BSF INTCON, PEIE ; Enable peripheral interrupts
BSF INTCON, GIE ; Enable all interrupts
;
; Ensure that the required sampling time for the selected input
; channel has elapsed. Then the conversion may be started.
;
BSF ADCON0, GO ; Start A/D Conversion
: ; The ADIF bit will be set and the GO/DONE
: ; bit is cleared upon completion of the
: ; A/D Conversion.
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-18 Preliminary 1997 Microchip Technology Inc.
23.14 Design Tips
Question 1:
I find that the Analog to Digital Converter result is not always accurate.
What can I do to improve accuracy?
Answer 1:
1. Make sure you are meeting all of the timing specifications. If you are turning the module
off and on, there is a minimum delay you must wait before taking a sample. If you are
changing input channels, there is a minimum delay you must wait for this as well, and
finally there is TAD, which is the time selected for each bit conversion. This is selected in
ADCON0 and should be between 1.6 and 6 µs. If TAD is too shor t, the result may not be
fully conv erted before the conversion is terminated, and if TAD is made too long the voltage
on the sampling capacitor can droop before the conversion is complete. These timing
specifications are provided in the “Electrical Specifications” section. See the device
data sheet for device specific information.
2. Often the source impedance of the analog signal is high (greater than 1k ohms) so the
current drawn from the source to charge the sample capacitor can affect accuracy. If the
input signal does not change too quickly, try putting a 0.1 µF capacitor on the analog input.
This capacitor will charge to the analog voltage being sampled and supply the instanta-
neous current needed to charge the 120 pF internal holding capacitor.
3. Finally, str aight from the data book: “In systems where the de vice frequency is lo w, use of
the A/D clock derived from the device oscillator is preferred...this reduces, to a large
extent, the effects of digital switching noise.” and “In systems where the device will enter
SLEEP mode after start of A/D conv ersion, the RC cloc k source selection is required.This
method gives the highest accuracy.
Question 2:
After starting an A/D conversion may I change the input channel (for my
next conversion)?
Answer 2:
After the holding capacitor is disconnected from the input channel, typically 100 ns after the GO
bit is set, the input channel may be changed.
Question 3:
Do you know of a good reference on A/D’s?
Answer 3:
A very good reference for understanding A/D conversions is the “Analog-Digital Conversion
Handbook” third edition, published by Prentice Hall (ISBN 0-13-03-2848-0).
1997 Microchip Technology Inc. Preliminary DS31023A-page 23-19
Section 23. 10-bit A/D Converter
10-bit
A/D Converter
23
23.15 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the 10-bit A/D
module are:
Title Application Note #
Using the Analog to Digital Converter AN546
Four Channel Digital Voltmeter with Display and Keyboard AN557
PICmicro MID-RANGE MCU FAMILY
DS31023A-page 23-20 1997 Microchip Technology Inc.
23.16 Revision History
Revision A
This is the initial released revision of the 10-bit A/D module description.
1997 Microchip Technology Inc. DS31024A page 24-1
M
Slope A/D
24
Section 24. Slope A/D
HIGHLIGHTS
This section of the manual contains the following major topics:
24.1 Introduction..................................................................................................................24-2
24.2 Control Registers .........................................................................................................24-3
24.3 Conversion Process.....................................................................................................24-6
24.4 Other Analog Modules ...............................................................................................24-12
24.5 Calibration Parameters ..............................................................................................24-13
24.6 Design Tips ................................................................................................................24-14
24.7 Related Application Notes..........................................................................................24-15
24.8 Revision History.........................................................................................................24-16
PICmicro MID-RANGE MCU FAMILY
DS31024A-page 24-2 1997 Microchip Technology Inc.
24.1 Introduction
The components required to create a Slope A/D converter include:
Precision comparator
4-bit programmable current source
16-channel analog MUX
16-bit timer with capture register
This section will discuss using these components for a Slope A/D.
Each analog input channel is multiplexed to a single analog input source to be converted by
means of a slope conversion method (using a single precision comparator). The programmable
current source f eeds an e xternal capacitor to generate the ramp v oltage used in the conv ersion.
Figure 24-1: Slope A/D Block Diagram
ADOFF
OSC1
1
0
FOSC
(Configuration Bit)
Internal
ADTMRH ADTMRL
Clock
Stop
Logic
Timer
ADCAPH ADCAPL
Oscillator
Analog
MUX
AN12 7
6
5
4
3
2
1
0
AN11 SREFLO
SREFHI
AN2
AN1
AN0
Slope A/D Capture
Slope A/D
Capture Interrupt (ADCIF)
ADOFF
CDAC
~2.5uA~5uA~10uA~20uA
ADCON1<7:4>
ADRST (ADCON0<1>)
AN3
8
~100
ADOFF
Bandgap Ref.
AN13 9
~ 1 k
AN4
AN5
AN6
AN7
10
11
12
13
AN14
AN15 14
15
AMUXOE
Overflow
Internal
Data
Bus
ADRST
4
Note 2
Note 1: All current sources are disabled if ADRST = ‘1’
2: Approximately 3.5 microsecond time constant
3: Dependent on A/D resolution and input voltage
range (see Table 24-2)
4-Bit Current DAC (Note 1)
ADCON0<7:4>
(SLPCON<0>)
(ADCON0<2>)
AN0
Note 3 C
1997 Microchip Technology Inc. DS31024A-page 24-3
Section 24. Slope A/D
Slope A/D
24
24.2 Control Registers
Two A/D control registers are provided to control the con version process . The y are ADCON0 and
ADCON1. Both registers are readable and writable.
Register 24-1: ADCON0 Register
R/W-0 R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-1 R/W-0
ADCS3 ADCS2 ADCS1 ADCS0 AMUXOE ADRST ADZERO
bit 7 bit 0
bit 7-4: ADCS3:ADCS0: Analog Channel Select bits
0000 = AN0 input
0001 = AN1 input
0010 = AN2 input
0011 = AN3 input
0100 = Bandgap reference voltage input
0101 = Slope reference SREFHI input
0110 = Slope reference SREFLO input
0111 = AN11 input
1000 = AN12 input
1001 = AN13 input
1010 = AN4 input
1011 = AN5 input
1100 = AN6 input
1101 = AN7 input
1110 = AN14 input
1111 = AN15 input
Note: For devices that do not use the full 16 A/D input channels, the unimplemented selec-
tions are reserved. Do not select any unimplemented channels.
bit 3: Unimplemented: Read as '0'
bit 2: AMUXOE: Analog MUX Output Enable
1 = Connect AMUX Output to AN0 pin (overrides TRIS setting)
0 = AN0 pin normal
bit 1: ADRST: A/D Reset Control Bit
1 = Stop the A/D Timer, discharge CDAC capacitor
0 = Normal operation (A/D running)
bit 0: ADZERO: A/D Zero Select Control
1 = Enable zeroing operation on AN1 and AN5
0 = Normal operation, sample AN1 and AN5 pins
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31024A-page 24-4 1997 Microchip Technology Inc.
Register 24-2: ADCON1 Register
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
ADDAC3 ADDAC2 ADDAC1 ADDAC0 PCFG3 PCFG2 PCFG1 PCFG0
bit 7 bit 0
bit 7-4: ADDAC3:ADDAC0: Programmable Current Source Select bits
0000 = OFF - all current sources disabled
0001 = 2.25 µA
0010 = 4.5 µA
0011 = 6.75 µA
0100 = 9 µA
0101 = 11.25 µA
0110 = 13.5 µA
0111 = 15.75 µA
1000 = 18 µA
1001 = 20.25 µA
1010 = 22.5 µA
1011 = 24.75 µA
1100 = 27 µA
1101 = 29.25 µA
1110 = 31.5 µA
1111 = 33.75 µA
bit 3-0: PCFG3:PCFG0: Port Configuration Selects
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
A = Analog input D = Digital I/O
PCFG3:PCFG2 AN4 AN5 AN6 AN7
00 AAAA
01 AAAD
10 AADD
11 DDDD
PCFG1:PCFG0 AN0 AN1 AN2 AN3
00 AAAA
01 AAAD
10 AADD
11 DDDD
Note: On any device reset, all port pins multiplexed with analog functions (ANx pins), are
forced to be an analog input.
1997 Microchip Technology Inc. DS31024A-page 24-5
Section 24. Slope A/D
Slope A/D
24
Register 24-3: SLPCON Register
R/W-0 U-0 R/W-1 R/W-1 U-1 R/W-1 R/W-1 R/W-1
Resv REFOFF Resv OSCOFF Resv Resv ADOFF
bit 7 bit 0
bit 7: Reserved: Always maintain this bit cleared.
bit 6: Unimplemented: Read as '0'
bit 5: REFOFF: Slope A/D Voltage Reference Power Control bit
1 = Voltage references are disabled (not consuming current)
0 = Voltage references are powered (consuming current)
bit 4: Reserved: Always maintain this bit cleared.
bit 3: OSCOFF: Slope A/D Oscillator Sleep Control bit
1 = Slope A/D Oscillator is disabled during SLEEP mode (not consuming current)
0 = Slope A/D Oscillator is enabled during SLEEP mode (consuming current)
bit 2: Reserved: Always maintain this bit cleared.
bit 1: Reserved: Always maintain this bit cleared.
bit 0: ADOFF: Slope A/D Power Control bit
1 = Slope A/D is disabled (not consuming current)
0 = Slope A/D is powered (consuming current)
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
PICmicro MID-RANGE MCU FAMILY
DS31024A-page 24-6 1997 Microchip Technology Inc.
24.3 Conversion Process
There are two methods f or perf orming a conversion. To determine the end of conversion, the first
method uses the ADTMR overflow interrupt (OVFIF bit). The second method uses the A/D Cap-
ture Interrupt (ADCIF bit). At the end of conversion both bits are used to deter mine if an over-
range condition has occurred.
Method 1 uses a fixed conversion time, this means that the capacitor voltage always ramps to
the full scale voltage. Immediately after the overflow of the ADTMR, we recommend that the
ADRST bit is set to discharge the e xternal capacitor. This will ensure that the residual voltage on
the exter nal capacitor, due to dielectr ic absorption, is independent of input voltage or previous
conversions.
Method 2 uses a variab le conversion time , which results in faster con versions f or low er input volt-
ages.
Steps for Method 1 (“fixed conversion time”):
1. Initialize the Slope A/D module:
a)Clear the REFOFF bit (SLPCON<5>)
b)Clear the ADOFF bit (SLPCON<0>)
c)Initialize ADCON1<7:4> to select the programmable current source.
2. Set the ADRST bit (ADCON0<1>), until the ramp capacitor reaches ground. This is capac-
itor dependent. A minimum of 200 µs is recommended.
3. Select Input Channel
4. Clear the OVFIF and ADCIF bits.
5. Initialize Slope A/D Timer (ADTMR). ADTMR v alue depends on bits of resolution required
(see Table 24-1).
6. To start a conv ersion, clear the ADRST bit, this allo ws the ramp capacitor to begin charg-
ing and the ADTMR to increment.
7. Conversion is complete when the Slope A/D timer (ADTMR) overflows from FFFFh to
0000h. This causes the OVFIF bit to be set.
8. Check if the ADCIF bit is set. If this bit is set, the value in the capture register ADCAP is
valid. This method depends on minimum latency to v erify the capture interrupt flag bit after
the ADTMR overflows. If the ADCIF bit is cleared, then the input voltage was out of the
A/D input range.
9. Set the ADRST bit (ADCON0<1>) to stop ADTMR and discharge external capacitor
10. Do Conversion Calculations
11. Goto Step 2
1997 Microchip Technology Inc. DS31024A-page 24-7
Section 24. Slope A/D
Slope A/D
24
Steps for Method 2 (“variable conversion time”):
1. Initialize the Slope A/D module:
a)Clear the REFOFF bit (SLPCON<5>).
b)Clear the ADOFF bit (SLPCON<0>).
c)Initialize ADCON1<7:4> to select the programmable current source.
2. Set the ADRST bit (ADCON0<1>), until the ramp capacitor reaches ground. This is capac-
itor dependent. A minimum of 200 µs is recommended.
3. Select Input Channel.
4. Clear the OVFIF and ADCIF bits.
5. Initialize Slope A/D Timer (ADTMR). ADTMR v alue depends on bits of resolution required
(see Table 24-1).
6. To start a conv ersion, clear the ADRST bit, this allo ws the ramp capacitor to begin charg-
ing and the ADTMR to increment.
7. Conversion is complete when the ramp voltage exceeds the analog input so the compar-
ator output changes from high to low. This causes the ADCIF bit to be set.
8. Check if the ADTMR did not increment more counts than the maximum resolution allowed.
If there were more counts, then the input voltage was out of the A/D input range.
9. Set the ADRST bit (ADCON0<1>) to stop ADTMR and discharge external capacitor
10. Do Conversion Calculations.
11. Go to Step 2.
The maximum Slope A/D timer count is 65,536. It can be cloc ked b y the on-chip or external oscil-
lator . At a 4 MHz oscillation frequency, the maximum con v ersion time is 16.38 ms for a full count.
A typical conversion should complete before full-count is reached. The timer overflow flag is set
once the timer rolls over (FFFFh to 0000h), and an interrupt occurs, if enabled.
End-user calibration is simplified or eliminated by making use of the on-chip EPROM. Inter nal
component values are measured at factor y final test and stored in the memory for use by the
application firmware.
Periodic conversion cycles should be performed on the bandgap and slope references
(described in Subsection 24.4 “Other Analog Modules” ) to compensate for Slope A/D compo-
nent drift. Measurements for the ref erence voltage counts are equated to the v oltage value stored
into EPROM during calibration. Since all measurements are relative to the reference, offset
voltages inherent in the compar ator are minimized. The Slope A/D cloc k source does not require
a precise frequency, only a stable frequency.
See AN624, “PIC14000 Slope A/D Theor y and Implementation” for further details of Slope A/D
operation.
Note: The Slope A/D timer continues to run following a capture event.
PICmicro MID-RANGE MCU FAMILY
DS31024A-page 24-8 1997 Microchip Technology Inc.
24.3.1 Slope A/D Timer (ADTMR)
The Slope A/D timer (ADTMR) is comprised of a 16-bit timer (ADTMRH:ADTMRL), which is
incremented every oscillator cycle. The ADTMR registers are cleared by a power-on reset; oth-
erwise the software must initialize it after each conversion. A separate 16-bit capture register
(ADCAPH:ADCAPL) is used to capture the ADTMR count if a Slope A/D capture e v ent occurs
(see below). Both the Slope A/D timer and capture registers are readab le and writable. The 16-bit
timer is a read/write register and is cleared on any device reset.
During a conversion one or both of the following events will occur:
capture event
timer overflow
In a capture e vent, the comparator trips when the slope v oltage on the CD AC output e xceeds the
input voltage from the selected Slope A/D channel, causing the comparator output to transition
from high to low. This causes a transf er of the current timer count to the capture register and sets
the ADCIF flag bit.
An interrupt will be generated if the ADCIE bit is set (interrupt enabled). In addition, GIE and PIE
bits must be set. Software is responsible for clearing the ADCIF flag bit prior to the next conver-
sion cycle. This interrupt can only occur once per conversion cycle.
In a timer overflow condition, the timer rolls over from FFFFh to 0000h, and a capture overflow
flag (O VFIF) is asserted. The timer continues to increment f ollowing a timer ov erflow. An interrupt
can be generated if bit OVFIE is set (interr upt enabled). In addition, the GIE and PIE bits must
be set. Software is responsible for clearing the OVFIF flag bit prior to the next conversion cycle.
Figure 24-2: Example Slope A/D Conversion Cycle
Note 1: Reading or writing the ADTMR register dur ing an Slope A/D conversion cycle can
produce unpredictable results and is not recommended.
Note 2: The correct sequence for writing the ADTMR register is HI b yte follow ed by LO byte .
Reversing this order will prevent the Slope A/D timer from running.
XX
CAPTURE
CLK
ADRST
ADCON0<1>
Capture
Register
CDAC
XX+8
COMPARE
ADCIF (must be cleared by software)
ADTMR INCREMENTS
XX+1 XX+2 XX+3
ADTMR
COUNT XX+8 XX+9XX
1997 Microchip Technology Inc. DS31024A-page 24-9
Section 24. Slope A/D
Slope A/D
24
24.3.2 Sleep Operation
The Slope A/D may operate when the device is in Sleep mode. For the Slope A/D to do a con-
version during Sleep mode, the Slope A/D module must have a device clock. For a clock to be
present the OSCOFF bit must be cleared bef ore going to SLEEP. Also the REFOFF and ADOFF
bits must be cleared to ensure that the results reflect the voltage on the input channel. By doing
an A/D conversion during Sleep mode, the result has improved accuracy due to a reduction of
system noise.
When the device clock is disabled, the Slope A/D Timer (ADTMRH:ADTMRL) stops increment-
ing. Even if the Slope A/D module is not disabled, the slope A/D cannot w ak e-up the de vice. This
is because the ADCIF bit cannot be set, which is one of the control bits used to wak e the device
from SLEEP mode. When the device awakes, if the comparator value has tripped, the capture
and interrupt will occur. The value in the ADCAP registers is meaningless.
For maximum power savings, all analog components of the Slope A/D module should be disabled
(no conversion in progress).
24.3.3 Effects of a Reset
After any device reset, the Slope A/D module is disabled (lowest current state) and the device
I/O are configured as analog channels.
24.3.4 Slope A/D Comparator
This module includes a high gain comparator for Slope A/D conversions. The non-inver ting
input terminal of the Slope A/D comparator is connected to the output of an analog MUX through
an RC low-pass filter. The inverting input terminal is connected to the external ramp capacitor.
The output of the comparator is used to cause the capture e vent to occur. This causes the value
in the ADTMR registers to be loaded into the ADCAP registers. This output will also cause the
ADCIF bit to be set.
24.3.5 Analog MUX
A total of 16 channels are internally multiplex ed to the single Slope A/D comparator positive input.
Four configuration bits (ADCON0<7:4>) select the channel to be converted.
24.3.6 Programmable Current Source
Four configuration bits (ADCON1<7:4>) are used to control a programmable current source for
generating the ramp v oltage to the Slope A/D comparator . This allows compensation f or full-scale
input voltage, clock frequency and the external capacitor tolerance variations.
Setting the ADRST bit disconnects the current source from the CDAC pin. Current flow begins
when the ADRST bit is cleared.
The programmable current source output is tied to the CDAC pin. This current source is used to
charge an exter nal capacitor, which generates the ramp voltage for the Slope A/D comparator
(Figure 24-1).
PICmicro MID-RANGE MCU FAMILY
DS31024A-page 24-10 1997 Microchip Technology Inc.
24.3.7 Slope A/D Resolution, Speed, Voltage Range, and Capacitor Selection
The Slope A/D module allows man y tr ade-offs . F or a conversion the user needs to make the fol-
lowing Trade-offs:
The Resolution of the Result
The Speed of the Conversion
The Analog Input Voltage Range
The External Capacitor
The resolution is the number of bits that is used b y the ADTMR to represent the measured input
voltage. This resolution affects the time that the conversion can be completed in. Table 24-1
shows the trade-off betw een the resolution of the conv ersion and the maxim um conv ersion time .
The conversion time for the Slope A/D converter can be calculated using the equation:
Conversion Time = (1/Fosc) x 2N
Where Fosc is the oscillator frequency and N is the number of bits of resolution desired.
Theref ore at 4 MHz, the conv ersion time f or 16 bits is 16.384 msec. Conv ersely, it is 256 µsec f or
10-bits.
Table 24-1: ADTMR Initialization Values and Conversion Times
Resolution
Bits Value Loaded
into ADTMR Maximum Conversion Time
Cycles 20 MHz 4 MHz
16 0000h 65536 TOSC 3.28 ms 16.38 ms
15 8000h 32768 TOSC 1.64 ms 8.2 ms
14 C000h 16384 TOSC 820 µs 4.1 ms
13 E000h 8192 TOSC 410 µs 2.05 ms
12 F000h 4096 TOSC 204.8 µs 1.03 ms
11 F800h 2048 TOSC 102.4 µs 500 µs
10 FC00h 1024 TOSC 51.2 µs 250 µs
.
1997 Microchip Technology Inc. DS31024A-page 24-11
Section 24. Slope A/D
Slope A/D
24
The selection of the external capacitor is determined by the desired characteristics of the appli-
cation. These include
Input Voltage Range (widest range of all input channels)
Conv ersion Time
Programmable Current Source Output Values
The selection of these values should be done to minimize the time between a comparator trip
(ADCIF bit is set) to the ADTMR overflow (OVFIF is set). This ensures that the entire range of
the ADTMR is used for the A/D conversion process.
The equation for selecting the ramp capacitor value is:
Capacitor = (conversion time in seconds) X
(current source output in amps) / (full scale in volts)
Table 24-2 provides example capacitor values for the desired Slope A/D resolution, conversion
time, and full scale voltage measurement.
This capacitor on the CD A C pin should hav e a lo w voltage-coefficient as f ound in teflon, polypro-
pylene, or polystyrene capacitors, for optimum results. This external capacitor must be dis-
charged at the beginning of each conv ersion cycle b y setting the ADRST bit (ADCON0<1>). The
time for the ADRST bit to be set depends on the characteristics of the external capacitor for a
complete discharge.
Table 24-2: External Capacitor Selection (@ 4 MHz)
Slope A/D
Resolution
(Bits)
Conversion
Time (ms)
Full
Scale
(Volts)
Slope A/D Current Source Select Calculated
CDAC
Capacitor
CDAC Capacitor
Nearest Standard
Value
ADDAC3:ADDC0 Typical Output
(µamps)
16 16.384 3.5 1100 27 0.126 µF 0.12 µF
2.0 1010 22.5 0.184 µF 0.18 µF
1.5 1011 24.75 0.270 µF 0.27 µF
14 4.096 3.5 1101 29.25 34 nF 33 nF
2.0 1011 24.75 50.7 nF 47 nF
1.5 1100 27 73.7 nF 68 nF
12 1.024 3.5 1101 29.25 8.56 nF 8.2 nF
2.0 1001 20.25 10.4 nF 10 nF
1.5 1010 22.5 15.4 nF 15 nF
10 0.256 3.5 1011 24.75 1.81 nF 1.8 nF
2.0 1010 22.5 2.88 nF 2.7 nF
1.5 1011 24.75 4.22 nF 3.9 nF
.
PICmicro MID-RANGE MCU FAMILY
DS31024A-page 24-12 1997 Microchip Technology Inc.
24.4 Other Analog Modules
Additional analog modules for mixed signal applications are required. These include:
bandgap voltage reference
slope reference voltage divider
24.4.1 Bandgap V oltage Reference
The bandgap reference circuit is used to generate a 1.2V nominal stable voltage reference for
the Slope A/D, the low-v oltage detector, and the slope reference divider. The bandgap reference
voltage is available on the analog MUX. To enable the bandgap reference REFOFF (SLP-
CON<5>) must be cleared. The bandgap reference must be enabled for any slope A/D conver-
sion.
The bandgap reference calibration factor is stored in the calibration space EPROM.
24.4.2 Slope Reference Voltage Divider
The slope ref erence v oltage divider circuit, consisting of a buff er amplifier and resistor divider, is
connected to the internal bandgap reference producing two other voltage references called
SREFHI and SREFLO (see Figure 24-3). SREFHI is nominally the same as the bandgap voltage ,
1.2V, and SREFLO is nominally 0.13V. These ref erence v oltages are av ailab le on two of the ana-
log multiplexer channels. The Slope A/D module and firmware can measure the SREFHI and
SREFLO voltages, and in conjunction with the KREF and KBG calibration data correct for the
ADC's offset and slope errors.
See AN624 for further details.
Figure 24-3: Slope Reference Divider
+
Bandgap
Reference _
REFOFF (SLPCON<5>)
ADOFF (SLPCON<0>)
SREFHI
SREFLO
VREF
To Slope A/D
MUX
SREFLO SREFHI
~9SREFLO
SREFHI - SREFLO
KREF =
1997 Microchip Technology Inc. DS31024A-page 24-13
Section 24. Slope A/D
Slope A/D
24
24.5 Calibration Parameters
The Slope A/D module has several analog components. Like all CMOS circuitry the parametric
values vary with process, temperature, voltage, and time. Devices have been designed to mini-
mize the effect of these variations. In addition, each device, with the slope A/D module, is cali-
brated at f actory test by measuring several k ey parameters and storing these values into EPR OM
at specified locations. The customer’s application program may access this data and use it to
mathematically compensate for device variations.
Collectively, these data values are referred to as calibration constants. The calibration constants
are listed in Table 24-3. The 32-bit floating point representation has an exponent byte, and three
bytes of mantissa. For information on floating point algorithms, refer to AN575.
Table 24-3: Calibration Constants
For additional information on using the calibration parameters see Application Note 624.
24.5.1 Using Calibration Data
The calibration constants should be used b y the application firmware to obtain the best accuracy.
KREF and KBG are used in A/D conversions.
24.5.2 Parameter V ariation
Table 24-4 lists the “Maximum Parameter Variation” attainable when the calibration data is not
used as well as the “Expected Parameter Variation with Calibration.
If the accuracies without calibration are adequate for the task at hand, no further calibrations of
the module are necessary. If greater accuracy is needed, the calibration constants m ust be used.
Table 24-4: Parameter Variation
24.5.3 Device Programming
24.5.3.1 Non-Windowed Parts
Non-windowed parts are programmed just like any PIC16CXXX processor. The calibration area
is write-protected during factory calibration.
24.5.3.2 Windowed Parts
Calibration data must be read out and sa v ed bef ore er asing a windo wed part. There is no wa y to
recreate these values, so if they are lost the part can no longer be calibrated.
Parameter Symbol Number of
Bytes Representation of
Value
A/D Slope reference ratio KREF 4 32-bit Floating Point
Bandgap reference voltage KBG 4 32-bit Floating Point
Symbol Parameter Maximum V ariation
Without Calibration Achievable V ariation
with Calibration
KREF A/D slope reference ratio +/- 2.2% +/- 0.13%
KBG Bandgap reference voltage +/- 4.2% +/- 0.058%
Caution:
Windowed parts must not be write-protected. If the par ts are erased by ultraviolet light, the
calibration parameters are lost and cannot be reprogrammed once the part has been
write-protected.
PICmicro MID-RANGE MCU FAMILY
DS31024A-page 24-14 1997 Microchip Technology Inc.
24.6 Design Tips
Question 1:
What are some recommended Capacitor types?
Answer 1:
Polypropylene film capacitor is a good trade-off between cost, availability and performance
Question 2:
Can you suggest some sources for Capacitors
Answer 2:
A source is:
Southern Electronics Company
Telephone: (203) 876-7488
Question 3:
I used the recommended capacitor and Programmable Current Source from
Table 24-2, and my A/D input range does not match.
Answer 3:
That table is meant to be a good starting point, but does not include variation that is the result of
the device not operating at exactly 4 MHz; tolerance of the exter nal capacitor and variations of
the Programmable Current Source, due to process and application temperature.
A conversion on the Bandgap Reference can be used to judge how to adjust the Programmab le
Current Source Output to ensure proper A/D full scale conversions. Example code (routine
ad_optimize, in P14_RV10.ASM) for this adjustment is available with the PICDEM-14A Demo
Board, and may be also available on the Microchip web site.
Question 4:
I am using the PIC14C000 which also has the on-chip Temperature sensor.
The sensor results seem to be a little high.
Answer 4:
This may be caused by self heating of the DIE. Self heating of the DIE may be caused by a few
things, including:
I/O sinking and/or sourcing significant amount of current
Power dissipation of the device running
(remember the PIC14C000 can operate in sleep mode)
Package type due to junction to ambient temperature coefficient of package
For best results the power dissipation should be kept lo w . Calibration is performed with the device
in a low power state.
Question 5:
My A/D conversion results seem affected by the operation of high current
components on my board. What can I do to minimize this?
Answer 5:
The high current components on your board may cause the ground potential difference across
the ground trace or g round plane. To minimize this eff ect, you should emplo y two system grounds
on the application board. The first ground, analog ground, used for the reference analog signals
(Slope A/D e xternal capacitor ground, Resistor Divider ground, and etc.). No high current nor an y
digital power returns should go through this analog ground system.
The second ground, digital ground, is used for all other digital logic in the system. The applica-
tion’s digital logic will inject noise onto this ground. Proper g rounding techniques should be used
to minimize this noise.
These two grounds are connected at the PICmicro’s ground pin. Ideally the two grounds are
implemented using separate ground planes. In most cases, this can still be implemented on a
two la y er board. One lay er is used f or both g round systems , where the two planes are separated
by a gap. The second layer is used as the trace layer.
1997 Microchip Technology Inc. DS31024A-page 24-15
Section 24. Slope A/D
Slope A/D
24
24.7 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the Slope
A/D are:
Title Application Note #
PIC14C000 Calibration Parameters AN621
PIC14C000 A/D Theory and Implementation AN624
Lead Acid Battery Charger Implementation using the PIC14C000 AN626
PICmicro MID-RANGE MCU FAMILY
DS31024A-page 24-16 1997 Microchip Technology Inc.
24.8 Revision History
Revision A
This is the initial released revision of the Slope A/D module description.
1997 Microchip Technology Inc. DS31025A page 25-1
M
LCD
25
Section 25. LCD
HIGHLIGHTS
This section of the manual contains the following major topics:
25.1 Introduction..................................................................................................................25-2
25.2 Control Register...........................................................................................................25-3
25.3 LCD Timing ..................................................................................................................25-6
25.4 LCD Interrupts............................................................................................................25-12
25.5 Pixel Control...............................................................................................................25-13
25.6 Voltage Generation ....................................................................................................25-15
25.7 Operation During Sleep .............................................................................................25-16
25.8 Effects of a Reset.......................................................................................................25-17
25.9 Configuring the LCD Module......................................................................................25-17
25.10 Discrimination Ratio...................................................................................................25-18
25.11 LCD V oltage Generation ............................................................................................25-20
25.12 Contrast .....................................................................................................................25-22
25.13 LCD Glass..................................................................................................................25-22
25.14 Initialization................................................................................................................25-23
25.15 Design Tips................................................................................................................25-24
25.16 Related Application Notes..........................................................................................25-25
25.17 Revision History.........................................................................................................25-26
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-2 1997 Microchip Technology Inc.
25.1 Introduction
The LCD module generates the timing control to drive a static or multiplexed LCD panel, with
suppor t for up to 32 segments multiplexed with up to four commons. It also provides control of
the LCD pixel data.
The interface to the module consists of three control registers (LCDCON, LCDSE, and LCDPS)
used to define the timing requirements of the LCD panel and up to 16 LCD data registers
(LCD00-LCD15) that represent the arra y of the pixel data. In normal operation, the control regis-
ters are configured to match the LCD panel being used. Pr imarily, the initialization information
consists of selecting the number of commons and segments required by the LCD panel, and then
specifying the LCD Frame clock rate to be used by the panel.
Once the module is initialized f or the LCD panel, the individual bits of the LCD data registers are
cleared/set to represent a turned-on pixel respectively.
Once the module is configured, the LCDEN bit (LCDCON<7>) is used to enable or disable the
LCD module. The LCD panel can also operate during sleep by clearing the SLPEN bit
(LCDCON<6>).
Figure 25-1: LCD Module Block Diagram
COM3:COM0
32 x 4
Clock
Source
Timing Control
Data Bus
Select
and
Divide
Internal RC osc
Fosc/4
T1CKI
RAM 128
to
32
MUX
SEG<31:0>
TO I/O PADS
TO I/O PADS
LCDCON
LCDPS
LCDSE
LCD
1997 Microchip Technology Inc. DS31025A-page 25-3
Section 25. LCD
LCD
25
25.2 Control Register
Register 25-1: LCDCON Register
R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
LCDEN SLPEN VGEN CS1 CS0 LMUX1 LMUX0
bit 7 bit 0
bit 7 LCDEN: Module Drive Enable bit
1 = LCD drive enabled
0 = LCD drive disabled
bit 6 SLPEN: LCD Display Sleep Enable bit
1 = LCD module will stop operating during SLEEP
0 = LCD module will continue to display during SLEEP
bit 5 Unimplemented: Read as '0'
bit 4 VGEN: Voltage Generator Enable bit
1 = Internal LCD Voltage Generator Enabled, (powered-up)
0 = Internal LCD Voltage Generator powered-down, voltage is expected to be
provided externally
bit 3:2 CS1:CS0: Clock Source Select bits
00 = Fosc/256
01 = T1CKI (Timer1)
1x = Internal RC oscillator
bit 1:0 LMUX1:LMUX0: Common Selection bits
Specifies the number of commons and the bias method
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
LMUX1:LMUX0 MULTIPLEX BIAS Max # of Segments
00
01
10
11
Static (COM0)
1/2 (COM0, 1)
1/3 (COM0, 1, 2)
1/4 (COM0, 1, 2, 3)
Static
1/3
1/3
1/3
32
31
30
29
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-4 1997 Microchip Technology Inc.
Register 25-2: LCDPS Register
Register 25-3: Generic LCDD (Pixel Data) Register Layout
U-0 U-0 U-0 U-0 R/W-x R/W-x R/W-x R/W-x
LP3 LP2 LP1 LP0
bit 7 bit 0
bit 7:4 Unimplemented, read as '0'
bit 3:0 LP3:LP0: Frame Clock Prescale Selection bits
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
LMUX1:LMUX0 Multiplex Frame Frequency =
00 Static Clock source / (128 * (LP3:LP0 + 1))
01 1/2 Clock source / (128 * (LP3:LP0 + 1))
10 1/3 Clock source / ( 96 * (LP3:LP0 + 1))
11 1/4 Clock source / (128 * (LP3:LP0 + 1))
R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x
SEGs
COMc SEGs
COMc SEGs
COMc SEGs
COMc SEGs
COMc SEGs
COMc SEGs
COMc SEGs
COMc
bit 7 bit 0
bit 7:0 SEGsCOMc: Pixel Data bit for segment s and common c
1 = Pixel on (dark)
0 = Pixel off (clear)
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
1997 Microchip Technology Inc. DS31025A-page 25-5
Section 25. LCD
LCD
25
Register 25-4: LCDSE Register
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
SE29 SE27 SE20 SE16 SE12 SE9 SE5 SE0
bit 7 bit 0
bit 7 SE29: Pin Function Select bits for COM1/SEG31 - COM3/SEG29
1 = pins have LCD segment driver function
0 = pins have digital Input function
Note: The LMUX1:LMUX0 setting takes precedence over the SE29 bit, causing pins to
become common drivers.
bit 6 SE27: Pin Function Select for SEG28 and SEG27
1 = pins have LCD segment driver function
0 = pins have digital Input function
bit 5 SE20: Pin Function Select bits for SEG26 - SEG20
1 = pins have LCD segment driver function
0 = pins have digital Input function
bit 4 SE16: Pin Function Select bits for SEG19 - SEG16
1 = pins have LCD segment driver function
0 = pins have digital Input function
bit 3 SE12: Pin Function Select bits for SEG15 - SEG12
1 = pins have LCD segment driver function
0 = pins have digital Input function
bit 2 SE9: Pin Function Select bits for SEG11 - SEG09
1 = pins have LCD segment driver function
0 = pins have digital Input function
bit 1 SE5: Pin Function Select bits for SEG08 - SEG05
1 = pins have LCD segment driver function
0 = pins have digital Input function
bit 0 SE0: Pin Function Select bits for SEG04 - SEG00
1 = pins have LCD segment driver function
0 = pins have digital I/O function
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
Note: On a Power-on Reset, the LCD pins are configured for LCD drive function.
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-6 1997 Microchip Technology Inc.
25.3 LCD Timing
The LCD module has 3 possible clock source inputs and supports static, 1/2, 1/3, and 1/4 multi-
plexing.
25.3.1 Timing Clock Source Selection
The clock sources for the LCD timing generation are:
Internal RC oscillator used for device low frequency or sleep operation
Timer1 oscillator used for device low frequency or sleep operation
System clock divided by 256
The first timing source is an internal RC oscillator which runs at a nominal frequency of 14 kHz.
This oscillator provides a lower speed clock which may be used to continue running the LCD
while the processor is in sleep . The RC oscillator will po wer-down when it is not selected or when
the LCD module is disabled.
The second source is the Timer1 external oscillator. This oscillator provides a lower speed clock
which may be used to continue running the LCD while the processor is in sleep. It is assumed
that the frequency provided on this oscillator will be 32 kHz. To use the Timer1 oscillator as a LCD
module clock source, it is only necessary to set the T1OSCEN (T1CON<3>) bit.
The third source is the system clock divided b y 256. This divider ratio is chosen to provide about
32 kHz output when the external oscillator is 8 MHz. The divider is not programmable. Instead
the LCDPS register is used to set the LCD frame clock rate.
The clock sources are selected with bits CS1:CS0 (LCDCON<3:2>). Refer to Figure 25-1 for
details of the register programming.
Figure 25-2: LCD Clock Generation
CS1:CS0
TMR1 32 kHz
crystal oscillator
Internal RC oscillator
Nominal FRC = 14 kHz
Static
1/2
1/3
1/4
÷4÷32
LMUX1:LMUX0
4-bit Programmable
LCDPS<3:0>
÷1,2,3,4
Ring Counter
LMUX1:LMUX0
internal
data bus
COM2
÷256
÷2
FOSC
Prescaler
COM0
COM1
COM3
1997 Microchip Technology Inc. DS31025A-page 25-7
Section 25. LCD
LCD
25
25.3.2 Multiplex Timing Generation
The timing generation circuitry will generate 1 to 4 common’s based on the display mode
selected. The mode is specified by bits LMUX1:LMUX0 (LCDCON<1:0>). Table 25-1 shows the
formulas for calculating the frame frequency.
Table 25-1: Frame Frequency Formulas
Table 25-2: Approximate Frame Frequency in Hz using Timer1 @ 32.768 kHz or
Fosc @ 8 MHz
Table 25-3: Approximate Frame Frequency in Hz using internal RC osc @ 14 kHz
Multiplex Frame Frequency =
Static Clock source / (128 * (LP3:LP0 + 1))
1/2 Clock source / (128 * (LP3:LP0 + 1))
1/3 Clock source / (96 * (LP3:LP0 + 1))
1/4 Clock source / (128 * (LP3:LP0 + 1))
LP3:LP0 Static 1/2 1/3 1/4
2 85 85 114 85
3 64 648564
4 51 516851
5 43 435743
6 37 374937
7 32 324332
LP3:LP0 Static 1/2 1/3 1/4
0 109 109 146 109
1 55 557355
2 36 364936
3 27 273627
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-8 1997 Microchip Technology Inc.
Figure 25-3: STATIC Waveforms
V1
V0
COM0
SEG0
COM0-SEG0
COM0-SEG1
SEG1
V1
V0
V1
V0
V0
V1
-V1
V0
1 Frame
(selected pixel waveform)
(non-selected pixel waveform)
COM0
SEG7
SEG6
SEG5
SEG1
SEG2
SEG3
SEG4
SEG0
Liquid Crystal Display
and Terminal Connection
1997 Microchip Technology Inc. DS31025A-page 25-9
Section 25. LCD
LCD
25
Figure 25-4: 1/2 MUX, 1/3 BIAS Waveform
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
-V3
-V2
-V1
V3
V2
V1
V0
-V3
-V2
-V1
COM0-SEG3
COM0-SEG1
1 Frame
(non-selected pixel waveform)
COM1
SEG1
SEG2
SEG3
SEG0
COM0
Liquid Crystal Display
and Terminal Connection
(selected pixel waveform)
COM0
COM1
SEG3
SEG1
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-10 1997 Microchip Technology Inc.
Figure 25-5: 1/3 MUX, 1/3 BIAS Waveform
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
-V3
-V2
-V1
V3
V2
V1
V0
-V3
-V2
-V1
COM0
COM1
COM2
SEG0
SEG2
COM0-SEG0
COM0-SEG2
1 Frame
COM2
SEG2SEG0
COM0
Liquid Crystal Display
and Terminal Connection
COM1
SEG1
(non-selected pixel waveform)
(selected pixel waveform)
1997 Microchip Technology Inc. DS31025A-page 25-11
Section 25. LCD
LCD
25
Figure 25-6: 1/4 MUX, 1/3 BIAS Waveform
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
-V3
-V2
-V1
V3
V2
V1
V0
-V3
-V2
-V1
COM0
COM1
COM2
COM3
SEG0
SEG1
COM0-SEG1
COM0-SEG0
1 Frame
COM2
SEG1
SEG0
COM0
Liquid Crystal Display
and Terminal Connection
COM3
COM1
(selected pixel waveform)
(non-selected pixel waveform)
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-12 1997 Microchip Technology Inc.
25.4 LCD Interrupts
The LCD timing generation provides an interrupt that defines the LCD frame timing. This interrupt
can be used to coordinate the writing of the pixel data with the start of a new frame. Writing pix el
data at the frame boundary allows a visually crisp transition of the image. This interrupt can also
be used to synchronize e xternal e vents to the LCD. F or e xample, the interface to an e xternal seg-
ment driver, such as a Microchip AY0438, can be synchronized for segment data update to the
LCD frame.
A new frame is defined to begin at the leading edge of the COM0 common signal. The interrupt
will be set immediately after the LCD controller completes accessing all pix el data required for a
frame. This will occur at a certain fixed time bef ore the fr ame boundary as shown in Figure 25-7.
The LCD controller will begin to access data for the next frame within TFWR after the interrupt.
Figure 25-7: Example Waveforms in 1/4 MUX Drive
COM0
COM1
COM2
COM3
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
V3
V2
V1
V0
Frame
Boundary Frame
Boundary
1 Frame
LCD
Interrupt
occurs
Controller accesses
next frame data
TFINT
TFWR
TFWR = TFRAME/(LMUX1:LMUX0 + 1)
TFINT = (TFWR /2 - (2TCY + 40 ns)) min.
(TFWR /2 - (1TCY + 40 ns)) max.
1997 Microchip Technology Inc. DS31025A-page 25-13
Section 25. LCD
LCD
25
25.5 Pixel Control
25.5.1 LCDD (Pixel Data) Registers
The pix el registers contain bits which define the state of each pixel. Each bit defines one unique
pixel.
Table 25-4 shows the correlation of each bit in the LCDD registers to the respectiv e common and
segment signals.
Any LCD pixel location not being used for display can be used as general purpose RAM.
Table 25-4: LCDD Registers
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on
POR,
BOR
Value on
all other
Resets
LCDD00 SEG07
COM0 SEG06
COM0 SEG05
COM0 SEG04
COM0 SEG03
COM0 SEG02
COM0 SEG01
COM0 SEG00
COM0 xxxx xxxx xxxx xxxx
LCDD01 SEG15
COM0 SEG14
COM0 SEG13
COM0 SEG12
COM0 SEG11
COM0 SEG10
COM0 SEG09
COM0 SEG08
COM0 xxxx xxxx xxxx xxxx
LCDD02 SEG23
COM0 SEG22
COM0 SEG21
COM0 SEG20
COM0 SEG19
COM0 SEG18
COM0 SEG17
COM0 SEG16
COM0 xxxx xxxx xxxx xxxx
LCDD03 SEG31
COM0 SEG30
COM0 SEG29
COM0 SEG28
COM0 SEG27
COM0 SEG26
COM0 SEG25
COM0 SEG24
COM0 xxxx xxxx xxxx xxxx
LCDD04 SEG07
COM1 SEG06
COM1 SEG05
COM1 SEG04
COM1 SEG03
COM1 SEG02
COM1 SEG01
COM1 SEG00
COM1 xxxx xxxx xxxx xxxx
LCDD05 SEG15
COM1 SEG14
COM1 SEG13
COM1 SEG12
COM1 SEG11
COM1 SEG10
COM1 SEG09
COM1 SEG08
COM1 xxxx xxxx xxxx xxxx
LCDD06 SEG23
COM1 SEG22
COM1 SEG21
COM1 SEG20
COM1 SEG19
COM1 SEG18
COM1 SEG17
COM1 SEG16
COM1 xxxx xxxx xxxx xxxx
LCDD07 SEG31
COM1 (1) SEG30
COM1 SEG29
COM1 SEG28
COM1 SEG27
COM1 SEG26
COM1 SEG25
COM1 SEG24
COM1 xxxx xxxx xxxx xxxx
LCDD08 SEG07
COM2 SEG06
COM2 SEG05
COM2 SEG04
COM2 SEG03
COM2 SEG02
COM2 SEG01
COM2 SEG00
COM2 xxxx xxxx xxxx xxxx
LCDD09 SEG15
COM2 SEG14
COM2 SEG13
COM2 SEG12
COM2 SEG11
COM2 SEG10
COM2 SEG09
COM2 SEG08
COM2 xxxx xxxx xxxx xxxx
LCDD10 SEG23
COM2 SEG22
COM2 SEG21
COM2 SEG20
COM2 SEG19
COM2 SEG18
COM2 SEG17
COM2 SEG16
COM2 xxxx xxxx xxxx xxxx
LCDD11 SEG31
COM2 (1) SEG30
COM2 (1) SEG29
COM2 SEG28
COM2 SEG27
COM2 SEG26
COM2 SEG25
COM2 SEG24
COM2 xxxx xxxx xxxx xxxx
LCDD12 SEG07
COM3 SEG06
COM3 SEG05
COM3 SEG04
COM3 SEG03
COM3 SEG02
COM3 SEG01
COM3 SEG00
COM3 xxxx xxxx xxxx xxxx
LCDD13 SEG15
COM3 SEG14
COM3 SEG13
COM3 SEG12
COM3 SEG11
COM3 SEG10
COM3 SEG09
COM3 SEG08
COM3 xxxx xxxx xxxx xxxx
LCDD14 SEG23
COM3 SEG22
COM3 SEG21
COM3 SEG20
COM3 SEG19
COM3 SEG18
COM3 SEG17
COM3 SEG16
COM3 xxxx xxxx xxxx xxxx
LCDD15 SEG31
COM3 (1) SEG30
COM3 (1) SEG29
COM3 (1) SEG28
COM30 SEG27
COM3 SEG26
COM30 SEG25
COM3 SEG24
COM3 xxxx xxxx xxxx xxxx
Note 1: These pixels do not display, but can be used as general purpose RAM.
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-14 1997 Microchip Technology Inc.
25.5.2 Segment Enables
The LCDSE register is used to select the pin function for groups of pins. The selection allows
each group of pins to operate as either LCD drivers or digital only pins. To configure the pins as
a digital port, the corresponding bits in the LCDSE register must be cleared.
If the pin is a digital input the corresponding TRIS bit controls the data direction. Any bit set in the
LCDSE register overrides any bit settings in the corresponding TRIS register.
Example 25-1: Static MUX with 32 Segments
Example 25-2: 1/3 MUX with 13 Segments
Note 1: On a Power-on Reset, the LCD pins are configured as LCD drivers.
Note 2: The LMUX1:LMUX0 bits take precedence o ver the LCDSE bit settings f or pins RD7,
RD6 and RD5.
BCF STATUS,RP0 ; Select Bank2
BSF STATUS,RP1 ;
BCF LCDCON,LMUX1 ; Select Static MUX
BCF LCDCON,LMUX0 ;
MOVLW 0xFF ; Make PortD,E,F,G LCD pins
MOVWF LCDSE ; configure rest of LCD
BCF STATUS,RP0 ; Select Bank2
BSF STATUS,RP1 ;
BSF LCDCON,LMUX1 ; Select 1/3 MUX
BCF LCDCON,LMUX0 ;
MOVLW 0x87 ; Make PORTD<7:0> & PORTE<6:0> LCD pins
MOVWF LCDSE ; configure rest of LCD
1997 Microchip Technology Inc. DS31025A-page 25-15
Section 25. LCD
LCD
25
25.6 V oltage Generation
There are two methods for LCD voltage generation, internal charge pump, or external resistor
ladder.
25.6.1 Charge Pump
The LCD charge pump is shown in Figure 25-8. The 1.0V - 2.3V regulator will establish a stable
base voltage from the varying batter y voltage. This regulator is adjustable through the range by
connecting a variable external resistor from VLCDADJ to ground. The potentiometer provides
contrast adjustment for the LCD. This base voltage is connected to VLCD1 on the charge pump.
The charge pump boosts VLCD1 into VLCD2 = 2 * VLCD1 and VLCD3 = 3 * VLCD1. When the charge
pump is not operating, VLCD3 will be internally tied to VDD. See the Electrical Specifications sec-
tion for charge pump capacitor and potentiometer values.
25.6.2 External R-Ladder
The LCD module can also use an external resistor ladder (R-Ladder) to generate the LCD volt-
ages. Figure 25-8 sho ws external connections for static and 1/3 bias. The V GEN (LCDCON<4>)
bit must be cleared to use an external R-Ladder.
Figure 25-8: Charge Pump and Resistor Ladder Block Diagram
C2VLCD2 VLCD1 VLCD3 C1
VDD
VLCDADJ
10 µA
connections for
internal charge
pump, VGEN = 1.
VDD
VDD
connections for
external R-ladder,
1/3 Bias,
VGEN = 0.
connections for
external R-ladder,
Static Bias,
VGEN = 0.
nominal
Charge Pump LCDEN
SLPEN
0.47 µF(2) 0.47 µF(2) 0.47 µF(2)
0.47 µF(2)
10k* 10k(2) 10k* 5k(2)
5k(2)
10k(2)
130k(2)
100k(2) External
External
External
(1) (1) (1)
(1)
Note 1: Location of optional filter capacitor.
2: These values are provided for design guidance only and should be optimized to the application by
the designer.
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-16 1997 Microchip Technology Inc.
25.7 Operation During Sleep
The LCD module can operate during sleep. The selection is controlled by bit SLPEN
(LCDCON<6>). Setting the SLPEN bit allows the LCD module to go to sleep. Clearing the
SLPEN bit allows the module to continue to operate during sleep.
If a SLEEP instruction is executed and SLPEN = '1', the LCD module will cease all functions and
go into a very low current consumption mode. The module will stop operation immediately and
drive the minimum LCD voltage on both segment and common lines. Figure 25-9 shows this
operation. To ensure that the LCD completes the frame, the SLEEP instruction should be exe-
cuted immediately after a LCD frame boundary. The LCD interrupt can be used to determine the
frame boundary. See 25.4 “LCD Interrupts” for the formulas to calculate the delay.
If a SLEEP instruction is ex ecuted and SLPEN = '0', the module will continue to displa y the current
contents of the LCDD registers. To allow the module to continue operation while in sleep, the
clock source m ust be either the internal RC oscillator or Timer1 e xternal oscillator . While in sleep ,
the LCD data cannot be changed. The LCD module current consumption will not decrease in this
mode, however the overall consumption of the device will be lower due to shutdown of the core
and other peripheral functions.
Figure 25-9:Sleep Entry/exit When SLPEN = 1 or CS1:CS0 = 00
Note: The internal RC oscillator or external Timer1 oscillator must be used to oper ate the
LCD module during sleep.
COM0
COM1
COM3
3/3V
1/3V
0/3V
3/3V
3/3V
1/3V
2/3V
2/3V
1/3V
0/3V
2/3V
0/3V
3/3V
2/3V
1/3V
0/3V
SEG0
SLEEP instruction execution Wake-up
interrupted
frame
Pin
Pin
Pin
Pin
1997 Microchip Technology Inc. DS31025A-page 25-17
Section 25. LCD
LCD
25
25.8 Effects of a Reset
The LCD module is disabled, but the LCD pins are configured as LCD drivers. This ensures that
the microcontroller does not damage the LCD glass by accidently having a DC voltage across a
segment.
25.9 Configuring the LCD Module
The following is the sequence of steps to follow to configure the LCD module.
1. Select the frame clock prescale using the LP3:LP0 bits (LCDPS<3:0>).
2. Configure the appropriate pins to function as segment drivers using the LCDSE register.
3. Configure the LCD module for the following using the LCDCON register.
- Multiplex mode and Bias, selected by the LMUX1:LMUX0 bits
- Timing source, selected by the CS1:CS0 bits
- Voltage generation, enabled by the VGEN bit
- Sleep mode operation, enabled by the SLPEN bit
4. Write initial values to pixel data registers, LCDD00 through LCDD15.
5. Clear LCD interrupt flag bit, LCDIF, and if desired, enable the interrupt by setting the
LCDIE bit.
6. Enable the LCD module, by setting the LCDEN bit (LCDCON<7>).
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-18 1997 Microchip Technology Inc.
25.10 Discrimination Ratio
Discrimination ratio is a way to calculate the contrast levels that a panel can achieve. The first
example is a static waveform from Figure 25-3. The voltages V1 and V0 will be assigned values
of 1 and 0. The next step is to construct an equation for one frame to help visualize the DC and
RMS voltages present on an individual pixel that is ON and OFF. The rest of the following shows
the calculation of the DC, RMS, and Discrimination Ratio.
Example 25-3: Discrimination Ratio Calculation for Static MUX
COMx - SEGx [ON]
COMx - SEGx [OFF]
= 1 - 1,
= 0 + 0,
VDC = 0
VDC = 0
VRMS [ON] =V(1)2 + (-1)2
21V
=
VRMS [OFF] =V(0)2 + (0)2
20V
=
D = VRMS [ON]
VRMS [OFF] = 1V
0V =
See Figure 25-3 for Static waveform.
1997 Microchip Technology Inc. DS31025A-page 25-19
Section 25. LCD
LCD
25
The next example is for Figure 25-6 which is a 1/4 MUX, 1/3 BIAS waveform. For this example,
the values 3, 2, 1 and 0 will be assigned to V3, V2, V1, and V0 respectively. The frame equation,
DC voltage, RMS voltage and discrimination ratio calculations are shown in Example 25-4.
Example 25-4: Discrimination Ratio Calculation 1/4 MUX
As shown in these examples, static displays have excellent contrast. The higher the multiplex
ratio of the LCD, the lower the discrimination ratio, and therefore, the lower the contrast of the
display.
Table 25-5 shows the VOFF, VON and discr imination ratios of the various combinations of MUX
and BIAS.
As the multiplex of the LCD panel increases, the discrimination ratio decreases. The contrast of
the panel will also decrease, so to provide better contrast the LCD voltages must be increased
to provide greater separation between each level.
Table 25-5: Discrimination Ratio vs. MUX and Bias
COM0 - SEGx [ON] = 3 - 3 + 1 - 1 + 1 - 1 + 1 - 1 VDC = 0
COM0 - SEGx [OFF] = 1 - 1 - 1 + 1 - 1 + 1 - 1 + 1 VDC = 0
Note: Refer to Figure 25-6
VRMS [ON] =V(3)2 + (-3)2 + (1)2 + (-1)2 + (1)2 + (-1)2 + (1)2 + (-1)2
8
3 V
=
VRMS [OFF] =VV
=
(1)2 + (-1)2 + (-1)2 + (1)2 + (-1)2 + (1)2 + (-1)2 + (1)2
8
D = VRMS [ON]
VRMS [OFF] = 3 V
1 V = 1.732
1/3 BIAS
VOFF VON D
STATIC 01
1/2 MUX 0.333 0.745 2.236
1/3 MUX 0.333 0.638 1.915
1/4 MUX 0.333 0.577 1.732
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-20 1997 Microchip Technology Inc.
25.11 LCD Voltage Generation
Among the many ways to generate LCD voltage, two methods stand out above the crowd:
resistor ladder
charge pump.
The resistor ladder method, shown in Figure 25-10, is most commonly used for higher VCC volt-
ages. This method uses ine xpensiv e resistors to create the multi-le v el LCD v oltages. Regardless
of the number of pixels that are energized the current remains constant. The voltage at point V3
is typically tied to VCC, either internally or externally.
The resistance values are determined by two factors: display quality and power consumption.
Display quality is a function of the LCD drive waveforms. Since the LCD panel is a capacitive
load, the wa veform is distorted due to the charging and discharging currents. This distortion can
be reduced by decreasing the value of resistance. However, this change increases the power
consumption due to the increased current now flowing through the resistors. As the LCD panel
increases in size, the resistance value must be decreased to maintain the image quality of the
display.
Sometimes the addition of parallel capacitors to the resistance can reduce the distortion caused
by charging/discharging currents . The capacitors act as charge storage to pro vide current as the
display waveform transitions. In general, R is 1 k to 50 k and the potentiometer is 5 k to
200 k.
Figure 25-10: Resistor Ladder
Figure 25-11: Resistor Ladder with Capacitors
R
V2
V1
V0
V3
R
R
V3
V2
V1
V0
R
R
R
C
C
C
+5V
1997 Microchip Technology Inc. DS31025A-page 25-21
Section 25. LCD
LCD
25
A charge pump is ideal f or low voltage battery operation because the VDD voltage can be boosted
up to drive the LCD panel. The charge pump requires a charging capacitor and filter capacitor f or
each of the LCD voltages as seen in Figure 25-12. These capacitors are typically low leakage
types such as polyester, polypropylene, or polystyrene material. Another feature that makes the
charge pump ideal for battery applications is that the current consumption is proportional to the
number of pixels that are energized.
Figure 25-12: Charge Pump
C1
C2
V3
V2
V1
V0
VADJ
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-22 1997 Microchip Technology Inc.
25.12 Contrast
Although contrast is heavily dependent on the light source available and the multiplex mode, it
also varies with the LCD voltage levels. As previously seen, a potentiometer is used to control
the contrast of the LCD panel. The potentiometer sets the separation between each of the LCD
voltages. The larger the separation, the better the contrast achievable.
25.13 LCD Glass
The characteristics of the LCD glass vary depending on the materials used. Appendix B gives a
list of some LCD manufacturers. Please contact them for the characteristics of your desired
glass.
1997 Microchip Technology Inc. DS31025A-page 25-23
Section 25. LCD
LCD
25
25.14 Initialization
Example 25-5 shows the code for initializing the LCD module with all segments cleared.
Example 25-5: LCD Initialization Code
BCF PIR1,LCDIF ; Clear LCD interrupt flag
BCF STATUS,RP0 ; Go to Bank2
BSF STATUS,RP1
MOVLW 0x06 ; Set frame freq to ~37Hz
MOVWF LCDPS
MOVLW 0xff ; Make all pin functions LCD drivers
MOVWF LCDSE
MOVLW 0x17 ; Drive during SLEEP, Charge pump enabled
MOVWF LCDCON ; Timer1 clock source, 1/4 MUX
CLRF LCDD00 ; Clear all data registers to turn
CLRF LCDD01 ; all pixels off
CLRF LCDD02
CLRF LCDD03
CLRF LCDD04
CLRF LCDD05
CLRF LCDD06
CLRF LCDD07
CLRF LCDD08
CLRF LCDD09
CLRF LCDD10
CLRF LCDD11
CLRF LCDD12
CLRF LCDD13
CLRF LCDD14
CLRF LCDD15
BSF PIE1,LCDIE ; Enable LCD interrupts
BSF LCDCON,LCDEN ; Enable LCD Module
BCF STATUS,RP1 ; Go to Bank0
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-24 1997 Microchip Technology Inc.
25.15 Design Tips
Question 1:
I’m trying to use some of the LCD pins as inputs.
Answer 1:
Ensure that you ha ve the control bits in the LCDSE properly configured, since these bits ov erride
the TRIS bits.
Question 2:
My LCD panel is flickering.
Answer 2:
Your frame frequency may be too low. The frame frequency can be changed in the LCDPS
register.
Question 3:
The LCD segments are not very visible.
Answer 3:
This may be due to misadjusted LCD voltage, some possibilities include:
1. If you are using the R-ladder, tr y different values of R, var y the R-ladder potentiometer.
The VLCDADJ pin should be connected to ground.
2. If you are using the charge pump, adjust the resistance value on the VLCDADJ pin.
1997 Microchip Technology Inc. DS31025A-page 25-25
Section 25. LCD
LCD
25
25.16 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the LCD driv-
ers are:
Title Application Note #
Yet Another Clock Using the PIC16C92X AN649
LCD Fundamentals Using PIC16C92x Microcontrollers AN658
PICDEM3 Demo Board User’s Guide DS51079
PICmicro MID-RANGE MCU FAMILY
DS31025A-page 25-26 1997 Microchip Technology Inc.
25.17 Revision History
Revision A
This is the initial released revision of the LCD module description.
1997 Microchip Technology Inc. DS31026A page 26-1
Watchdog Timer
and Sleep Mode
26
M
Section 26. Watchdog Timer and Sleep Mode
HIGHLIGHTS
This section of the manual contains the following major topics:
26.1 Introduction..................................................................................................................26-2
26.2 Control Register...........................................................................................................26-3
26.3 Watchdog Timer (WDT) Operation...............................................................................26-4
26.4 SLEEP (Power-Down) Mode........................................................................................26-7
26.5 Initialization..................................................................................................................26-9
26.6 Design Tips ................................................................................................................26-10
26.7 Related Application Notes..........................................................................................26-11
26.8 Revision History.........................................................................................................26-12
PICmicro MID-RANGE MCU FAMILY
DS31026A-page 26-2 1997 Microchip Technology Inc.
26.1 Introduction
The Watchdog Timer (WDT) is a free running on-chip RC oscillator which does not require any
external components. The block diagram is shown in Figure 26-1. This RC oscillator is separate
from the device RC oscillator of the OSC1/CLKIN pin. This means that the WDT will run, even if
the clock on the OSC1 and OSC2 pins has been stopped, f or e xample, b y e x ecution of a SLEEP
instruction.
The Watchdog Timer (WDT) is enabled/disabled by a device configuration bit. If the WDT is
enabled, software execution may not disable this function.
Figure 26-1: Watchdog Timer Block Diagram
From TMR0 Clock Source
To TMR0
Postscaler
WDT Timer
WDT
Enable Bit
0
1M
U
X
PSA
8 - to - 1 MUX PS2:PS0
01
MUX PSA
WDT
Time-out
Note: PSA and PS2:PS0 are bits in the OPTION register.
8
1997 Microchip Technology Inc. DS31026A-page 26-3
Section 26. Watchdog Timer and Sleep Mode
Watchdog Timer
and Sleep Mode
26
26.2 Control Register
The OPTION_REG register is a readable and writable register which contains v arious control bits
to configure the TMR0 prescaler/WDT postscaler, the External INT Interrupt, TMR0, and the
weak pull-ups on PORTB.
Register 26-1: OPTION_REG Register
Note: To achieve a 1:1 prescaler assignment for the TMR0 register, assign the prescaler
to the Watchdog Timer.
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
RBPU (1) INTEDG T0CS T0SE PSA PS2 PS1 PS0
bit 7 bit 0
bit 7 RBPU (1): Weak Pull-up Enable bit
1 = Weak pull-ups are disabled
0 = Weak pull-ups are enabled by individual port latch values
bit 6 INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of INT pin
0 = Interrupt on falling edge of INT pin
bit 5 T0CS: TMR0 Clock Source Select bit
1 = Transition on T0CKI pin
0 = Internal instruction cycle clock (CLKOUT)
bit 4 T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on T0CKI pin
0 = Increment on low-to-high transition on T0CKI pin
bit 3 PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
bit 2:0 PS2:PS0: TMR0 Prescaler/WDT Postscaler Rate Select bits
Legend
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ - n = Value at POR reset
000
001
010
011
100
101
110
111
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
Bit Value TMR0 Rate WDT Rate
Note 1: Some devices call this bit GPPU. Devices that have the RBPU bit, have the weak
pull-ups on PORTB, while devices that have the GPPU have the weak pull-ups on
the GP Port.
PICmicro MID-RANGE MCU FAMILY
DS31026A-page 26-4 1997 Microchip Technology Inc.
26.3 Watchdog Timer (WDT) Operation
During normal operation, a WDT time-out generates a device RESET. If the device is in SLEEP
mode, a WDT time-out causes the device to wak e-up and continue with normal operation, this is
known as a WDT wake-up. The WDT can be per manently disabled by clearing the WDTE con-
figuration bit.
The postscaler assignment is fully under software control, i.e ., it can be changed “on the fly” dur-
ing program execution.
In Example 26-1, the first modification of the OPTION_REG does not need to be included if the
final desired prescaler is other then 1:1. If the final prescaler value is 1:1, then a temporary pres-
cale value is set (other than 1:1), and the final prescale v alue is set in the last modification of the
OPTION_REG. This sequence must be followed since the value in the TMR0 prescaler is
unknown, and is being used as the WDT postscaler . If the OPTION_REG is changed without this
code sequence, the time before a WDT reset is unknown.
Note: To avoid an unintended device RESET, the following instruction sequence (shown
in Example 26-1) must be executed when changing the prescaler assignment from
Timer0 to the postscaler of the WDT. This sequence must be followed even if the
WDT is disabled.
1997 Microchip Technology Inc. DS31026A-page 26-5
Section 26. Watchdog Timer and Sleep Mode
Watchdog Timer
and Sleep Mode
26
Example 26-1: Changing Prescaler (Timer0WDT)
To change prescaler from the WDT to the Timer0 module use the sequence shown in
Example 26-2.
Example 26-2: Changing Prescaler (WDTTimer0)
BSF STATUS, RP0 ; Bank1
MOVLW B’xx0x0xxx’ ; Select clock source and postscale value
MOVWF OPTION_REG ; other than 1:1
BCF STATUS, RP0 ; Bank0
CLRF TMR0 ; Clear TMR0 & Prescaler
BSF STATUS, RP0 ; Bank1
MOVLW B’xxxx1xxx’ ; Select WDT, do not change prescale value
MOVWF OPTION_REG ;
CLRWDT ; Clears WDT
MOVLW b'xxxx1xxx' ; Select new prescale value and WDT
MOVWF OPTION_REG ;
BCF STATUS, RP0 ; Bank0
CLRWDT ; Clear WDT and postscaler
BSF STATUS, RP0 ; Bank1
MOVLW b'xxxx0xxx' ; Select TMR0, new prescale
MOVWF OPTION_REG ; value and clock source
BCF STATUS, RP0 ; Bank0
PICmicro MID-RANGE MCU FAMILY
DS31026A-page 26-6 1997 Microchip Technology Inc.
26.3.1 WDT Period
The WDT has a nominal time-out period of 18 ms, (with no postscaler). The time-out period v ar-
ies with temperature, VDD and process variations from part to part (see DC specs). If longer
time-outs are desired, a postscaler with a division ratio of up to 1:128 can be assigned to the
WDT, under software control, by writing to the OPTION_REG register. Thus, time-out periods of
up to 2.3 seconds can be realized.
The CLRWDT and SLEEP instructions clear the WDT and the postscaler (if assigned to the WDT)
and prevent it from timing out and generating a device RESET.
The T O bit in the STATUS register will be cleared upon a Watchdog Timer time-out (WDT Reset
and WDT wak e-up).
26.3.2 WDT Programming Considerations
It should also be taken in account that under worst case conditions (VDD = Minimum, Tempera-
ture = Maximum, maximum WDT postscaler) it ma y tak e sev eral seconds bef ore a WDT time-out
occurs.
Table 26-1: Summary of Watchdog Timer Registers
Note: When the postscaler is assigned to the WDT, always execute a CLRWDT instruction
before changing the postscale value, otherwise a WDT reset may occur.
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Config. bits MPEEN BODEN CP1 CP0 PWRTE WDTE FOSC1 FOSC0
OPTION_REG RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0
Legend: Shaded cells are not used by the Watchdog Timer.
1997 Microchip Technology Inc. DS31026A-page 26-7
Section 26. Watchdog Timer and Sleep Mode
Watchdog Timer
and Sleep Mode
26
26.4 SLEEP (Power-Down) Mode
Sleep (Power-down) mode is a mode where the device is placed in it’s lowest current consump-
tion state. The device oscillator is turned off, so no system clocks are occurring in the device.
Sleep mode is entered by executing a SLEEP instruction.
If enabled, the Watchdog Timer will be cleared but k eeps running, the PD bit in the STATUS reg-
ister is cleared, the TO bit is set, and the oscillator driver is turned off . The I/O ports maintain the
status they had, bef ore the SLEEP instruction was e xecuted (driving high, low, or hi-impedance).
F or lowest current consumption in this mode , all I/O pins should be either at VDD, or VSS, with no
exter nal circuitr y drawing current from the I/O pin and the modules that are specified to have a
delta sleep current should be disabled. I/O pins that are hi-impedance inputs should be pulled
high or low externally to avoid switching currents caused by floating inputs. The T0CKI input
should also be at VDD or VSS for lowest current consumption. The contribution from on-chip
pull-ups on PORTB should be considered.
The MCLR pin must be at a logic high level (VIHMC).
Some f eatures of the device that consume a delta sleep current are enab led / disab led by de vice
configuration bits. These include the Watchdog Timer (WDT) and Brown-out Reset (BOR) cir-
cuitry modules.
26.4.1 Wake-up from SLEEP
The device can wake-up from SLEEP through one of the following events:
1. Any device reset.
2. Watchdog Timer Wake-up (if WDT was enabled).
3. Any peripheral module which can set its interrupt flag while in sleep, such as:
- External INT pin
- Change on port pin
- Comparators
- A/D
- Timer1
- LCD
- SSP
- Capture
The first event will reset the device upon wake-up. However the latter two events will wake the
device and then resume program execution. The TO and PD bits in the STATUS register can be
used to determine the cause of device reset. The PD bit, which is set on power-up is cleared
when SLEEP is invoked. The TO bit is cleared if WDT wake-up occurred.
When the SLEEP instruction is being executed, the next instruction (PC + 1) is pre-fetched. For
the de vice to wak e-up through an interrupt e v ent, the corresponding interrupt enab le bit must be
set (enabled). Wake-up is regardless of the state of the GIE bit. If the GIE bit is clear (disabled),
the de vice continues execution at the instruction after the SLEEP instruction. If the GIE bit is set
(enabled), the device ex ecutes the instruction after the SLEEP instruction and then branches to
the interrupt address (0004h). In cases where the execution of the instr uction following SLEEP
is not desirable, the user should have an NOP after the SLEEP instruction.
PICmicro MID-RANGE MCU FAMILY
DS31026A-page 26-8 1997 Microchip Technology Inc.
26.4.2 Wake-up Using Interrupts
When interrupts are globally disabled (GIE cleared) and any interrupt source has both its inter-
rupt enable bit and interrupt flag set, one of the following events will occur:
If the interrupt occurs before the e xecution of a SLEEP instruction, the SLEEP instruction will
complete as an NOP. Therefore, the WDT and WDT postscaler will not be cleared, the TO
bit will not be set and PD bit will not be cleared.
If the interrupt occurs during or after the execution of a SLEEP instruction, the device will
immediately wak e-up from sleep. The SLEEP instruction will be completely executed bef ore
the wak e-up. Therefore , the WDT and WDT postscaler will be cleared, the T O bit will be set
and the PD bit will be cleared.
Even if the flag bits were checked before executing a SLEEP instruction, it may be possible for
flag bits to become set before the SLEEP instruction completes. To deter mine whether a SLEEP
instruction executed, test the PD bit. If the PD bit is set, the SLEEP instruction was executed as
an NOP.
To ensure that the WDT is clear , a CLRWDT instruction should be e xecuted bef ore a SLEEP instruc-
tion.
Figure 26-2: Wake-up from Sleep Through Interrupt
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
CLKOUT(4)
INT pin
INTF flag
(INTCON<1>)
GIE bit
(INTCON<7>)
INSTRUCTION FLOW
PC
Instruction
fetched
Instruction
executed
PC PC+1 PC+2
Inst(PC) = SLEEP
Inst(PC - 1)
Inst(PC + 1)
SLEEP
Processor in
SLEEP
Interrupt Latency(2)
Inst(PC + 2)
Inst(PC + 1)
Inst(0004h) Inst(0005h)
Inst(0004h)
Dummy cycle
PC + 2 0004h 0005h
Dummy cycle
TOST(2)
PC+2
Note 1: XT, HS or LP oscillator mode assumed.
2: TOST = 1024TOSC (drawing not to scale) This delay will not be there for RC osc mode.
3: GIE = '1' assumed. In this case after wake- up, the processor jumps to the interrupt routine. If GIE = '0', execution will
continue in-line.
4: CLKOUT is not available in these osc modes, but shown here for timing reference.
1997 Microchip Technology Inc. DS31026A-page 26-9
Section 26. Watchdog Timer and Sleep Mode
Watchdog Timer
and Sleep Mode
26
26.5 Initialization
No initialization code at this time.
PICmicro MID-RANGE MCU FAMILY
DS31026A-page 26-10 1997 Microchip Technology Inc.
26.6 Design Tips
Question 1:
My system voltage drops and then returns to the specified device voltage
range. The device is not operating correctly and the WDT does not reset and
return the device to proper operation.
Answer 1:
The WDT was not designed to be a recovery from a brown-out condition. It was designed to
recover from errant software operation (the device remaining in the specified operating ranges).
If your system can be subjected to brown-outs, either the on-chip brown-out circuitry should be
enabled or an external brown-out circuit should be implemented.
Question 2:
Device resets even though I do the CLRWDT instruction in my loop.
Answer 2:
Make sure that the loop with the CLRWDT instruction meets the minimum specification of the WDT
(not the typical).
Question 3:
Device never gets out of resets.
Answer 3:
On power-up, you must take into account the Oscillator Start-up time (Tost). Sometimes it helps
to put the CLRWDT instruction at the beginning of the loop, since this start-up time may be v ariable .
1997 Microchip Technology Inc. DS31026A-page 26-11
Section 26. Watchdog Timer and Sleep Mode
Watchdog Timer
and Sleep Mode
26
26.7 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the WDT and
Sleep Mode are:
Title Application Note #
P ower-up Troub le Shooting AN607
PICmicro MID-RANGE MCU FAMILY
DS31026A-page 26-12 1997 Microchip Technology Inc.
26.8 Revision History
Revision A
This is the initial released revision of the Watchdog Timer and Sleep mode description.
1997 Microchip Technology Inc. DS31027A page 27-1
M
Device
Configuration Bits
27
Section 27. Device Configuration Bits
HIGHLIGHTS
This section of the manual contains the following major topics:
27.1 Introduction..................................................................................................................27-2
27.2 Configuration Word Bits ...............................................................................................27-4
27.3 Program V erification/Code Protection..........................................................................27-8
27.4 ID Locations.................................................................................................................27-9
27.5 Design Tips ................................................................................................................27-10
27.6 Related Application Notes..........................................................................................27-11
27.7 Revision History.........................................................................................................27-12
PICmicro MID-RANGE MCU FAMILY
DS31027A-page 27-2 1997 Microchip Technology Inc.
27.1 Introduction
The device configuration bits allow each user to customize certain aspects of the device to the
needs of the application. When the device powers up, the state of these bits determines the
modes that the de vice uses. Subsection 27.2 “Configuration Word Bits” discusses the config-
uration bits, and the modes that they can be configured to. These bits are mapped in program
memor y location 2007h. This location is not accessible during nor mal device operation (can be
accessed only during programming mode).
The configuration bits can be programmed (read as '0') or left unprogrammed (read as '1') to
select various device configurations. The ability to change these settings once they have been
programmed depends on the memory technology and the package type.
For Read Only Memory (ROM) devices, these bits are specified at time of ROM code submittal
and once the de vice is masked may not be changed f or those devices (w ould require a new mask
code).
F or One Time Programmab le (O TP) de vices, once these bits are programmed (’0’), the y ma y not
be changed.
For windowed EPROM devices, once these bits are programmed (’0’), the device must be UV
erased to return the configuration word to the erased state. UV erasing the device also erases
the program memory.
For Flash devices, these bits may be erased and reprogrammed.
Note: Microchip does not recommend code protecting windowed devices.
1997 Microchip Technology Inc. DS31027A-page 27-3
Section 27. Device Configuration Bits
Device
Configuration Bits
27
Section 27.2 is forced to the next page for formatting purposes.
PICmicro MID-RANGE MCU FAMILY
DS31027A-page 27-4 1997 Microchip Technology Inc.
27.2 Configuration Word Bits
These configuration bits specify some of the modes of the device, and are programmed by a
device programmer , or by using the In-Circuit Serial Programming (ICSP) f eature of the midrange
de vices . The device is not able to read the values of these bits, and there placement is automat-
ically taken care of when you select the device in you device programmer. For additional infor-
mation, please refer to the Programming Specification of the Device.
Note 1: Always ensure that your device programmer has the same device selected as you
are programming.
Note 2: Microchip recommends that the desired configuration bit states be embedded in to
the application source code. This is easily done in the MPASM assemb ler by the use
of the CONFIG directive. See Subsection 27.2.1 “MPASM’s CONFIG Directive.
CP1:CP0: Code Protection bits
11 = Code protection off
10 = See device data sheet
01 = See device data sheet
00 = All memory is code protected
Note: Some devices may use more or less bits to determine the code protect. Presently
there are also some devices that use only one bit (CP0). For these devices the bit
description is:
1 = Code protection off
0 = Code protection on
DP: Data EEPROM Memory Code Protection bit
1 = Code protection off
0 = Data EEPROM Memory is code protected
Note: This bit is used when a de vice with ROM prog ram memory also has Data EEPROM
memory.
BODEN: Brown-out Reset Enable bit
1 = BOR enabled
0 = BOR disabled
Note: Enabling Brown-out Reset automatically enables the Power-up Timer (PWRT)
regardless of the value of bit PWRTE. Ensure the Power-up Timer is enabled any-
time Brown-out Reset is enabled.
PWRTE: Power-up Timer Enable bit
1 = PWRT disabled
0 = PWRT enabled
Note 1: Enabling Brown-out Reset automatically enables Power-up Timer (PWRT) regard-
less of the value of bit PWRTE. Ensure the Power-up Timer is enabled anytime
Brown-out Reset is enabled.
Note 2: Some original PICmicros have the polarity of this bit reversed.
Note 3:
MCLRE: MCLR Pin Function Select bit
1 = Pin’s function is MCLR
0 = Pin’s function is as a digital I/O. MCLR is internally tied to VDD.
WDTE: Watchdog Timer Enable bit
1 = WDT enabled
0 = WDT disabled
1997 Microchip Technology Inc. DS31027A-page 27-5
Section 27. Device Configuration Bits
Device
Configuration Bits
27
FOSC1:FOSC0: Oscillator Selection bits
11 = RC oscillator
10 = HS oscillator
01 = XT oscillator
00 = LP oscillator
FOSC2:FOSC0: Oscillator Selection bits
111 = EXTRC oscillator, with CLKOUT
110 = EXTRC oscillator
101 = INTRC oscillator, with CLKOUT
100 = INTRC oscillator
011 = Reserved
010 = HS oscillator
001 = XT oscillator
000 = LP oscillator
Unimplemented: Read as '1'
Legend
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’
- n = Value at POR reset u = Unchanged from programmed state
Note: The bit position of the configuration bits is device dependent. Please refer to the
device programming specification for bit placement. The use of a Microchip device
programmer does not require you to know the bit locations.
PICmicro MID-RANGE MCU FAMILY
DS31027A-page 27-6 1997 Microchip Technology Inc.
27.2.1 MPASM’s CONFIG Directive
Microchip’ s assemb ler, MPASM, has a nice feature that allows y ou to specify, in the source code
file, the selected states of the configuration bits for this program. This ensures that when pro-
gramming a device for an application the required configuration is also programmed. This mini-
mizes the risk of programming the wrong device configuration, and wondering why it no longer
works in the application.
Example 27-1 show a template for using the CONFIG directive.
Example 27-1:Using the CONFIG Directive, a Source File Template
The Symbols that are currently in the Microchip Device Header files that make using the CONFIG
directive straight forward are shown in Table 27-1. For the symbols available for your device,
please refer to that device’s Microchip Include file.
LIST p = p16C77 ; List Directive,
; Revision History
;
#INCLUDE <P16C77.INC> ; Microchip Device Header File
;
#INCLUDE <MY_STD.MAC> ; File which includes my standard macros
#INCLUDE <APP.MAC> ; File which includes macros specific
; to this application
;
; Specify Device Configuration Bits
;
__CONFIG _XT_OSC & _PWRTE_ON & _BODEN_OFF & _CP_OFF & _WDT_ON
;
org 0x00 ; Start of Program Memory
RESET_ADDR : ; First instruction to execute after a reset
end
Note: As long as the correct de vice is specified (in the LIST and INCLUDE file directiv es),
the correct polarity of all bits is ensured.
1997 Microchip Technology Inc. DS31027A-page 27-7
Section 27. Device Configuration Bits
Device
Configuration Bits
27
Table 27-1: __CONFIG Directive Symbols (From Microchip Header Files)
Feature SYMBOLS
Oscillators
_RC_OSC
_EXTRC_OSC
_EXTRC_OSC_CLKOUT
_EXTRC_OSC_NOCLKOUT
_INTRC_OSC
_INTRC_OSC_CLKOUT
_INTRC_OSC_NOCLKOUT
_LP_OSC
_XT_OSC
_HS_OSC
Watch Dog Timer _WDT_ON
_WDT_OFF
P ower-up Timer _PWRTE_ON
_PWRTE_OFF
Brown-out Reset _BODEN_ON
_BODEN_OFF
Master Clear Enable _MCLRE_ON
_MCLRE_OFF
Code Protect
_CP_ALL
_CP_ON
_CP_75
_CP_50
_CP_OFF
Code Protect Data EEPROM _DP_ON
_DP_OFF
Code Protect Calibration Space _CPC_ON
_CPC_OFF
Note 1: Not all configuration bit symbols may be available on any one device. Please refer to
the MIcrochip include file of that device for available symbols.
PICmicro MID-RANGE MCU FAMILY
DS31027A-page 27-8 1997 Microchip Technology Inc.
27.3 Program Verification/Code Protection
If the code protection bit(s) have not been programmed, the on-chip program memory can be
read out for verification purposes.
27.3.1 ROM Devices
When a ROM device also has Data EEPROM memory, an additional code protect configuration
bit ma y be implemented. The progr am memory configuration bit is submitted as part of the ROM
code submittal. The Data EEPROM memory code protect configuration bit will be an EEPROM
bit. When ROM de vices complete testing, the EEPROM data memory code protect bit will be pro-
grammed to the same state as the prog ram memory code protect bit. That is data EEPROM code
protect is off, when program memory code protect is off, and data EEPROM code protect is on
for all other selections.
In applications where the device is code protected and the data EEPROM needs to be pro-
grammed before the application can be released, the data EEPROM memory must have the
entire data EEPROM memory erased. The device prog ramming specification details the steps to
do this. Microchip device programmers implement the specified sequence. Once this sequence
is complete, the Data EEPROM memor y code protect is disabled. This allows the desired data
to be programmed into the de vice. After programming the data EEPR OM memory array, the data
EEPROM memory code protect configuration bit should be programmed as desired.
Note: Microchip does not recommend code protecting windowed devices.
1997 Microchip Technology Inc. DS31027A-page 27-9
Section 27. Device Configuration Bits
Device
Configuration Bits
27
27.4 ID Locations
F our memory locations (2000h - 2003h) are designated as ID locations where the user can store
checksum or other code-identification numbers. These locations are not accessible during nor-
mal execution but are readable and writable during program/verify. It is recommended that only
the 4 least significant bits of the ID location are used.
PICmicro MID-RANGE MCU FAMILY
DS31027A-page 27-10 1997 Microchip Technology Inc.
27.5 Design Tips
Question 1:
I have a JW de vice and I can no longer program it (reads scrambled data or
all '0's). What’s wrong with the device?
Answer 1:
Nothing. You probably code protected the device. If this is the case, the device is no longer
usable. See Subsection 27.3 “Program V erification/Code Protection” for more details.
Question 2:
In converting from a PIC16C74 to a PIC16C74A, my application no longer
works.
Answer 2:
1. Did you re-assemble the source file specifying the PIC16C74A in the INCLUDE file and
LIST directives. The use of the CONFIG directive is highly recommended.
2. On the de vice programmer , did you specify the PIC16C74A, and were all the configuration
bits as desired?
Question 3:
When I erase the device, the program memory is blank but the configura-
tion word is not yet erased.
Answer 3:
That is by design. Also remember that Microchip does not recommend code protecting windo wed
devices.
1997 Microchip Technology Inc. DS31027A-page 27-11
Section 27. Device Configuration Bits
Device
Configuration Bits
27
27.6 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to Configuration
Word are:
Title Application Note #
No related Application Notes at this time.
PICmicro MID-RANGE MCU FAMILY
DS31027A-page 27-12 1997 Microchip Technology Inc.
27.7 Revision History
Revision A
This is the initial released revision of the Configuration Word description.
1997 Microchip Technology Inc. DS31028A page 28-1
M
ICSP
28
Section 28. In-Circuit Serial Programming™ (ICSP™)
HIGHLIGHTS
This section of the manual contains the following major topics:
28.1 Introduction..................................................................................................................28-2
28.2 Entering In-Circuit Serial Programming Mode .............................................................28-3
28.3 Application Circuit ........................................................................................................28-4
28.4 Programmer.................................................................................................................28-6
28.5 Programming Environment ..........................................................................................28-6
28.6 Other Benefits..............................................................................................................28-7
28.7 Field Programming of PICmicro OTP MCUs................................................................28-8
28.8 Field Programming of FLASH PICmicros...................................................................28-10
28.9 Design Tips ................................................................................................................28-12
28.10 Related Application Notes..........................................................................................28-13
28.11 Revision History.........................................................................................................28-14
PICmicro MID-RANGE MCU FAMILY
DS31028A-page 28-2 1997 Microchip Technology Inc.
28.1 Introduction
All midrange de vices can be In-Circuit Serial Progr ammed (ICSP™) while in the end application
circuit. This is simply done with two lines for clock and data, and three other lines for power,
ground, and the programming voltage.
In-Circuit Serial Programming (ICSP™) is a great way to reduce your inventory overhead and
time-to-market f or your product. By assemb ling your product with a blank Microchip microcontrol-
ler (MCU), you can stock one design. When an order has been placed, these units can be pro-
grammed with the latest revision of firmware, tested, and shipped in a very short time. This
method also reduces scrapped in ventory due to old firmware re visions . This type of manufactur-
ing system can also facilitate quick turnarounds on custom orders for your product.
Most people would think to use ICSP with PICmicro™ OTP MCUs only on an assembly line
where the de vice is programmed once . However, there is a method by which an O TP de vice can
be programmed several times depending on the size of the firmware. This method, explained
later , provides a w a y to field upgrade y our firmware in a wa y similar to EEPROM- or Flash-based
devices.
1997 Microchip Technology Inc. DS31028A-page 28-3
Section 28. ICSP
ICSP
28
28.2 Entering In-Circuit Serial Programming Mode
The de vice is placed into a program/v erify mode by holding the RB6 and RB7 pins low while rais-
ing the MCLR (VPP) pin from VIL to VIHH (see programming specification) and ha ving VDD at the
programming voltage. RB6 becomes the programming clock and RB7 becomes the program-
ming data. Both RB6 and RB7 are Schmitt Trigger inputs in this mode, and when RB7 is driving
data it is a CMOS output driver.
After reset, to place the device into programming/verify mode, the program counter (PC) is at
location 00h. A 6-bit command is then supplied to the device. Some commands then specify that
14-bits of program data are then supplied to or read from the device, depending on if the com-
mand was a load or a read. F or complete details of serial programming, please refer to the de vice
specific Programming Specifications.
During the In-Circuit Serial Programming Mode, the WDT circuitry is disabled from generating a
device reset.
PICmicro MID-RANGE MCU FAMILY
DS31028A-page 28-4 1997 Microchip Technology Inc.
28.3 Application Circuit
The application circuit must be designed to allow all the prog r amming signals to be directly con-
nected to the PICmicro MCU. Figure 28-1 shows a typical circuit that is a starting point for when
designing with ICSP. The application must compensate for the following issues:
Isolation of the MCLR/VPP pin from the rest of the circuit
Loading of pins RB6 and RB7
Capacitance on each of the VDD, MCLR/VPP, RB6, and RB7 pins
Minimum and maximum operating voltage for VDD
PICmicro Oscillator
Interface to the programmer
The MCLR/VPP pin is normally connected to an RC circuit. The pull-up resistor is tied to V DD and
a capacitor is tied to ground. This circuit can affect the operation of ICSP depending on the size
of the capacitor since the VPP voltage m ust be isolated from the rest of the circuit (in most cases
a resistor is not capable of isolating the circuit). It is, therefore, recommended that the circuit in
Figure 28-1 be used when an RC is connected to MCLR/VPP. The diode should be a Schot-
tky-type de vice. Another issue with MCLR/VPP is that when the PICmicro device is prog rammed,
this pin is driven to appro ximately 13V and also to ground. Therefore, the application circuit must
be isolated from this voltage provided by the programmer.
Pins RB6 and RB7 are used by the PICmicro for ser ial programming. RB6 is the clock line and
RB7 is the data line. RB6 is driven by the programmer. RB7 is a bi-directional pin that is dr iven
by the programmer when programming, and driven by the PICmicro when verifying. These pins
must be isolated from the rest of the application circuit so as not to aff ect the signals during pro-
gramming. You must take into consideration the output impedance of the progr ammer when iso-
lating RB6 and RB7 from the rest of the circuit. This isolation circuit must account for RB6 being
an input on the PICmicro, and for RB7 being bi-directional (can be driven by both the PICmicro
and the programmer). For instance, PRO MATE® II has an output impedance of 1k. If the
design permits, these pins should not be used by the application. This is not the case with most
applications so it is recommended that the designer evaluate whether these signals need to be
buffered. As a designer, you must consider what type of circuitry is connected to RB6 and RB7
and then make a decision on how to isolate these pins. Figure 28-1 does not show any circuitry
to isolate RB6 and RB7 on the application circuit because this is very application dependent.
To simplify this interface the optimal usage of these I/O in the application are (in order):
1. Do not use RB6/RB7 so they are dedicated to ICSP.
2. Use these pins as outputs with minimal loading on signal line.
3. Isolation circuitry so that these signals can be driven to the ICSP specifications.
Figure 28-1: Typical In-Circuit Serial Programming (ICSP) Application Circuit
Application PCB
PIC16CXXX
MCLR/VPP
VDD
VSS
RB7
RB6
VDD VDD
To application circuit
Isolation circuits
ICSP Connector
1997 Microchip Technology Inc. DS31028A-page 28-5
Section 28. ICSP
ICSP
28
The total capacitance on the programming pins aff ects the rise rates of these signals as the y are
driven out of the progr ammer . Typical circuits use se ver al hundred microfar ads of capacitance on
VDD which helps to dampen noise and ripple. However, this capacitance requires a fairly strong
driver in the programmer to meet the rise rate timings for VDD. Most programmers are designed
to simply program the PICmicro itself and don’t have strong enough drivers to power the appli-
cation circuit. One solution is to use a driv er board betw een the prog r ammer and the application
circuit. The driver board requires a separate power supply that is capable of driving the VPP and
VDD pins with the correct rise rates and should also provide enough current to power the appli-
cation circuit. RB6 and RB7 are not b uffered on this schematic b ut may require b uffering depend-
ing upon the application. A sample driver board schematic is shown in Figure 28-2.
The Microchip programming specification states that the device should be programmed at 5V.
Special considerations must be made if your application circuit operates at 3V only. These con-
siderations ma y include totally isolating the PICmicro during programming. The other issue is that
the device must be verified at the minimum and maximum v oltages at which the application circuit
will be operating. For instance , a battery operated system may operate from three 1.5V cells giv-
ing an operating voltage range of 2.7V to 4.5V. The programmer must program the device at 5V
and must verify the program memory contents at both 2.7V and 4.5V to ensure that proper pro-
gramming margins have been achieved. This ensures the PICmicro operation over the voltage
range of the system.
The final issue deals with the oscillator circuit on the application board. The voltage on
MCLR/VPP must rise to the specified program mode entry voltage bef ore the device executes any
code. The crystal modes available on the PICmicro are not affected by this issue because the
Oscillator Star t-up Timer waits for 1024 oscillations before any code is executed. However, RC
oscillators do not require any start-up time and, therefore, the Oscillator Start-up Timer is not
used. The programmer must drive MCLR/VPP to the program mode entry voltage before the RC
oscillator toggles f our times. If the RC oscillator toggles four or more times, the progr am counter
will be incremented to some value X. Now when the device enters programming mode, the pro-
gram counter will not be zero and the programmer will start progr amming your code at an offset
of X. There are several alternatives that can compensate for a slow rise rate on MCLR/VPP. The
first method would be to not populate the R, progr am the device , and then insert the R. The other
method would be to have the programming interface drive the OSC1 pin of the PICmicro to
ground while progr amming. This will prev ent any oscillations from occurring during progr amming.
Now all that is left is ho w to connect the application circuit to the programmer. This depends a lot
on the programming environment and will be discussed in that section.
Note: The driver board design MUST be tested in the user's application to determine the
effects of the application circuit on the programming signals timing. Changes may
be required if the application places a significant load on VDD, VPP, RB6 OR RB7.
PICmicro MID-RANGE MCU FAMILY
DS31028A-page 28-6 1997 Microchip Technology Inc.
28.4 Programmer
The second consideration is the programmer. PIC16CXXX MCUs only use serial programming
and therefore all programmers suppor ting these devices will suppor t ICSP. One issue with the
programmer is the drive capability. As discussed before, it must be able to provide the specified
rise rates on the ICSP signals and also provide enough current to power the application circuit.
Figure 28-2 shows an example driver board. This driv er schematic does not show any b uffer cir-
cuitry for RB6 and RB7. It is recommended that an ev aluation be performed to determine if b uff-
ering is required. Another issue with the programmer is what VDD levels are used to verify the
memor y contents of the PICmicro. For instance, the PRO MATE II verifies program memory at
the minimum and maximum VDD le vels f or the specified de vice and is therefore considered a pro-
duction quality programmer. On the other hand, the PICSTART® Plus only verifies at 5V and is
f or prototyping use only. The Microchip programming specifications state that the program mem-
ory contents should be v erified at both the minimum and maximum V DD levels that the application
circuit will be operating. This implies that the application circuit must be ab le to handle the varying
VDD voltages.
There are also several third party programmers that are available. You should select a program-
mer based on the features it has and how it fits into your programming environment. The
Micro-
chip Development Systems Ordering Guide
(DS30177) provides detailed information on all our
de velopment tools. The
Microchip Third P arty Guide
(DS00104) provides inf ormation on all of our
third par ty tool developers. Please consult these two references when selecting a programmer.
Many options exist including serial or parallel PC host connection, stand-alone operation, and
single or gang programmers. Some of the third party developers include Advanced Transdata
Corporation, BP Microsystems, Data I/O, Emulation Technology and Logical Devices.
28.5 Programming Environment
The programming environment will affect the type of programmer used, the programmer cable
length, and the application circuit interface. Some programmers are well suited for a manual
assembly line while others are desirable for an automated assembly line. You may want to choose
a gang programmer to program multiple systems at a time.
The physical distance between the programmer and the application circuit aff ects the load capac-
itance on each of the programming signals. This will directly affect the dr ive strength needed to
provide the correct signal rise rates and current. This programming cable must also be as short
as possible and properly terminated and shielded, or the programming signals ma y be corrupted
by ringing or noise.
Finally, the application circuit interf ace to the prog rammer depends on the siz e constraints of the
application circuit itself and the assembly line . A simple header can be used to interface the appli-
cation circuit to the programmer. This might be more desirable f or a man ual assemb ly line where
a technician plugs the programmer cable into the board. A different method is the use of spring
loaded test pins (commonly referred to as pogo pins). The application circuit has pads on the
board f or each of the programming signals. Then there is a fixture that has pogo pins in the same
configuration as the pads on the board. The application circuit or fixture is moved into position
such that the pogo pins come into contact with the board. This method might be more suitable
for an automated assembly line.
After taking into consideration the issues with the application circuit, the programmer, and the
programming en vironment, any one can b uild a high quality, reliable manuf acturing line based on
ICSP.
1997 Microchip Technology Inc. DS31028A-page 28-7
Section 28. ICSP
ICSP
28
28.6 Other Benefits
ICSP provides other benefits, such as calibration and serialization. If program memory permits,
it would be cheaper and more reliab le to store calibr ation constants in program memory instead
of using an external serial EEPROM. For example, if y our system has a thermistor which can vary
from one system to another, storing some calibration information in a table format allows the
microcontroller to compensate (in software) f or e xternal component tolerances. System cost can
be reduced without affecting the required performance of the system by using software calibra-
tion techniques. But how does this relate to ICSP? The PICmicro has already been programmed
with firmware that performs a calibration cycle. The calibr ation data is transferred to a calibration
fixture. When all calibration data has been transferred, the fixture places the PICmicro in pro-
gramming mode and programs the PICmicro with the calibration data. Application note
AN656,
In-Circuit Serial Programming of Calibration Parameters Using a PICmicro Microcontroller
,
shows exactly how to implement this type of calibration data programming.
The other benefit of ICSP is serialization. Each individual system can be programmed with a
unique or random serial number. One such application of a unique serial number would be for
security systems. A typical system might use DIP switches to set the serial number. Instead, this
number can be b urned into program memory, thus reducing the o verall system cost and lo wering
the risk of tampering.
PICmicro MID-RANGE MCU FAMILY
DS31028A-page 28-8 1997 Microchip Technology Inc.
28.7 Field Programming of PICmicro OTP MCUs
An OTP device is not normally capable of being reprogrammed, but the PICmicro architecture
gives y ou this flexibility provided the size of your firmware is at least half that of the desired de vice
and the de vice is not code protected. If your target device does not have enough program mem-
or y, Microchip provides a wide spectrum of devices from 0.5K to 8K program memory with the
same set of peripheral features that will help meet the criteria.
The PIC16CXXX microcontrollers hav e two v ectors , reset and interrupt, at locations 0x0000 and
0x0004. When the PICmicro encounters a reset or interrupt condition, the code located at one of
these two locations in program memory is executed. The first listing of Example 28-2 shows the
code that is first programmed into the PICmicro. The second listing of Example 28-2 shows the
code that is programmed into the PICmicro for the second time.
Example 28-2 shows that to program the PICmicro a second time the memory location 0x0000,
originally goto Main (0x2808), is reprogrammed to all 0’ s which happens to be a NOP instruction.
This location cannot be reprogrammed to the ne w opcode (0x2860) because the bits that are 0’ s
cannot be reprogrammed to 1’ s, only bits that are 1’ s can be reprogr ammed to 0’s . The ne xt mem-
ory location 0x0001 w as originally blank (all 1’ s) and no w becomes a goto Main (0x2860). When
a reset condition occurs, the PICmicro executes the instruction at location 0x0000 which is the
NOP, a completely benign instruction, and then executes the goto Main to start the execution of
code. The example also shows that all program memory locations after 0x005A are blank in the
original program so that the second time the PICmicro is programmed, the revised code can be
programmed at these locations. The same descriptions can be given for the interrupt vector at
location 0x0004.
This method changes slightly for PICmicros with >2K words of program memory. Each of the
goto Main and goto ISR instructions are replaced by the following code segment is
Example 28-1 due to paging on devices with >2K words of program memory.
Example 28-1: Crossing Program Memory Pages
Now your one-time programmable PICmicro is exhibiting EEPROM- or Flash-like qualities.
movlw <page> movlw <page>
movwf PCLATH movwf PCLATH
goto Main goto ISR
1997 Microchip Technology Inc. DS31028A-page 28-9
Section 28. ICSP
ICSP
28
Example 28-2: Programming Cycle Listing Files
First Program Cycle Second Program Cycle
_________________________________________________________________________________________
Prog Opcode Assembly | Prog Opcode Assembly
Mem Instruction | Mem Instruction
-----------------------------------------------------------------------------------------
0000 2808 goto Main ;Main loop | 0000 0000 nop
0001 3FFF <blank> ; at 0x0008 | 0001 2860 goto Main; Main now
0002 3FFF <blank> | 0002 3FFF <blank> ; at 0x0060
0003 3FFF <blank> | 0003 3FFF <blank>
0004 2848 goto ISR ; ISR at | 0004 0000 nop
0005 3FFF <blank> ; 0x0048 | 0005 28A8 goto ISR ; ISR now at
0006 3FFF <blank> | 0006 3FFF <blank> ; 0x00A8
0007 3FFF <blank> | 0007 3FFF <blank>
0008 1683 bsf STATUS,RP0 | 0008 1683 bsf STATUS,RP0
0009 3007 movlw 0x07 | 0009 3007 movlw 0x07
000A 009F movwf ADCON1 | 000A 009F movwf ADCON1
. | .
. | .
. | .
0048 1C0C btfss PIR1,RBIF | 0048 1C0C btfss PIR1,RBIF
0049 284E goto EndISR | 0049 284E goto EndISR
004A 1806 btfsc PORTB,0 | 004A 1806 btfsc PORTB,0
. | .
. | .
. | .
0060 3FFF <blank> | 0060 1683 bsf STATUS,RP0
0061 3FFF <blank> | 0061 3005 movlw 0x05
0062 3FFF <blank> | 0062 009F movwf ADCON1
. | .
. | .
. | .
00A8 3FFF <blank> | 00A8 1C0C btfss PIR1,RBIF
00A9 3FFF <blank> | 00A9 28AE goto EndISR
00AA 3FFF <blank> | 00AA 1806 btfsc PORTB,0
. | .
. | .
. | .
-----------------------------------------------------------------------------------------
PICmicro MID-RANGE MCU FAMILY
DS31028A-page 28-10 1997 Microchip Technology Inc.
28.8 Field Programming of FLASH PICmicros
With the ICSP interf ace circuitry already in place, FLASH-based PICmicros can be easily repro-
grammed in the field. These FLASH devices allow you to reprogram them even if they are code
protected. A portable ICSP programming station might consist of a laptop computer and pro-
grammer. The technician plugs the ICSP interface cable into the application circuit and down-
loads the new firmware into the PICmicro . The next thing you know the system is up and running
without those anno ying “b ugs.” Another instance w ould be that you want to add an additional f ea-
ture to your system. All of your current inventory can be conv erted to the new firmware and field
upgrades can be perfor med to bring your installed base of systems up to the latest revision of
firmware.
1997 Microchip Technology Inc. DS31028A-page 28-11
Section 28. ICSP
ICSP
28
Figure 28-2: Example Driver Board Schematic
C6
0.1
PRB6
PVDD
2 3
1
14
7
U2A
74HC126
5 6
4U2B
74HC126
R3
1
RB6
+8V
PVDD
R6
100
R7
100
3
2 1Q1
2N2907
1
2
3
Q3
2N2222
12
13 14
U1D
TLE2144A
R5
100
C7
0.001
VDD
3
2 1
4
11U1A
TLE2144A
C3
0.1
+15V R1
5.1k
R8
100
3
2 1Q2
2N2907
R4
1PVPP
9 8
10U2C
74HC126
12 11
13U2D
74HC126
RB7
PRB6
PVPP
PVDD 1
2
3
4
5
JP3
HEADER
+15V
R2
5.1k
R9
100 1
2
3
Q4
2N2222
10
9 8
U1C
TLE2144A
R10
100
C8
0.001
RB7
VPP
VPP
VDD
1
2
3
4
5
JP1
HEADER
5
6 7
U1B
TLE2144A
RB6
+15V1
2
JP2
HEADER
C5
0.1
VIN
1
GND
3
VOUT 2
VR1
LM7808
C9
100
+15V
C4
0.1
+8V Note: All resistors are in Ohms,
all capacitors are in µF.
PICmicro MID-RANGE MCU FAMILY
DS31028A-page 28-12 1997 Microchip Technology Inc.
28.9 Design Tips
Question 1:
When I try to do ICSP, the entire program is shifted (offset) in the device
program memory.
Answer 1:
If the MCLR pin does not rise fast enough, while the device’s voltage is in the valid operating
range, the internal Program Counter (PC) can increment. This means that the PC is no longer
pointing to the address that you expected to be at. The exact location depends on the number of
device clocks that occurred in the valid operating region of the device.
Question 2:
I am using a PRO MATE II with a socket that I designed to bring the pro-
gramming signal to m y application board. Sometimes when I try to do ICSP,
the program memory is programmed wrong.
Answer 2:
The voltages / timings may be violated at the device. This could be due to the:
Application board circuitry
Cable length from programmer to target
Large capacitance on VDD which affects levels / timings
1997 Microchip Technology Inc. DS31028A-page 28-13
Section 28. ICSP
ICSP
28
28.10 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to In-Circuit
Serial Programming are:
Title Application Note #
In-Circuit Serial Programming of Calibration Parameters using a
PICmicro AN656
In-Circuit Serial Programming Guide DS30277
PICmicro MID-RANGE MCU FAMILY
DS31028A-page 28-14 1997 Microchip Technology Inc.
28.11 Revision History
Revision A
This is the initial released revision of the In-Circuit Serial Programming description.
1997 Microchip Technology Inc. DS31029A page 29-1
M
Instruction
Set
29
Section 29. Instruction Set
HIGHLIGHTS
This section of the manual contains the following major topics:
29.1 Introduction..................................................................................................................29-2
29.2 Instruction Formats......................................................................................................29-4
29.3 Special Function Registers as Source/Destination......................................................29-6
29.4 Q Cycle Activity............................................................................................................29-7
29.5 Instruction Descriptions................................................................................................29-8
29.6 Design Tips ................................................................................................................29-45
29.7 Related Application Notes..........................................................................................29-47
29.8 Revision History.........................................................................................................29-48
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-2 1997 Microchip Technology Inc.
29.1 Introduction
Each midrange instruction is a 14-bit word divided into an OPCODE which specifies the instruc-
tion type and one or more operands which fur ther specify the operation of the instruction. The
midrange Instruction Set Summary in Table 29-1 lists the instructions recognized b y the MPASM
assembler. The instruction set is highly orthogonal and is grouped into three basic categories:
Byte-oriented operations
Bit-oriented operations
Literal and control operations
Table 29-2 gives the opcode field descriptions.
For byte-oriented instr uctions, 'f' represents a file register designator and 'd' represents a des-
tination designator. The file register designator specifies which file register is to be used by the
instruction.
The destination designator specifies where the result of the operation is to be placed. If 'd' is zero ,
the result is placed in the W register. If 'd' is one, the result is placed in the file register specified
in the instruction.
For bit-oriented instructions, 'b' represents a bit field designator which selects the n umber of the
bit aff ected by the oper ation, while 'f' represents the number of the file in which the bit is located.
F or literal and control operations, 'k' represents an eight or eleven bit constant or literal value.
All instructions are ex ecuted in one single instruction cycle, unless a conditional test is true or the
program counter is changed as a result of an instruction. In these cases, the e xecution tak es two
instruction cycles with the second cycle executed as an NOP. One instr uction cycle consists of
four oscillator per iods. Thus, for an oscillator frequency of 4 MHz, the normal instruction execu-
tion time is 1 µs. If a conditional test is true or the program counter is changed as a result of an
instruction, the instruction execution time is 2 µs.
1997 Microchip Technology Inc. DS31029A-page 29-3
Section 29. Instruction Set
Instruction
Set
29
Table 29-1: Midrange Instruction Set
Mnemonic,
Operands Description Cycles 14-Bit Instruction Word Status
Affected Notes
MSb LSb
BYTE-ORIENTED FILE REGISTER OPERATIONS
ADDWF
ANDWF
CLRF
CLRW
COMF
DECF
DECFSZ
INCF
INCFSZ
IORWF
MOVF
MOVWF
NOP
RLF
RRF
SUBWF
SWAPF
XORWF
f, d
f, d
f
-
f, d
f, d
f, d
f, d
f, d
f, d
f, d
f
-
f, d
f, d
f, d
f, d
f, d
Add W and f
AND W with f
Clear f
Clear W
Complement f
Decrement f
Decrement f, Skip if 0
Increment f
Increment f, Skip if 0
Inclusive OR W with f
Move f
Move W to f
No Operation
Rotate Left f through Carry
Rotate Right f through Carry
Subtract W from f
Swap nibbles in f
Exclusive OR W with f
1
1
1
1
1
1
1(2)
1
1(2)
1
1
1
1
1
1
1
1
1
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
0111
0101
0001
0001
1001
0011
1011
1010
1111
0100
1000
0000
0000
1101
1100
0010
1110
0110
dfff
dfff
lfff
0xxx
dfff
dfff
dfff
dfff
dfff
dfff
dfff
lfff
0xx0
dfff
dfff
dfff
dfff
dfff
ffff
ffff
ffff
xxxx
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
0000
ffff
ffff
ffff
ffff
ffff
C,DC,Z
Z
Z
Z
Z
Z
Z
Z
Z
C
C
C,DC,Z
Z
1,2
1,2
2
1,2
1,2
1,2,3
1,2
1,2,3
1,2
1,2
1,2
1,2
1,2
1,2
1,2
BIT-ORIENTED FILE REGISTER OPERATIONS
BCF
BSF
BTFSC
BTFSS
f, b
f, b
f, b
f, b
Bit Clear f
Bit Set f
Bit Test f, Skip if Clear
Bit Test f, Skip if Set
1
1
1 (2)
1 (2)
01
01
01
01
00bb
01bb
10bb
11bb
bfff
bfff
bfff
bfff
ffff
ffff
ffff
ffff
1,2
1,2
3
3
LITERAL AND CONTROL OPERATIONS
ADDLW
ANDLW
CALL
CLRWDT
GOTO
IORLW
MOVLW
RETFIE
RETLW
RETURN
SLEEP
SUBLW
XORLW
k
k
k
-
k
k
k
-
k
-
-
k
k
Add literal and W
AND literal with W
Call subroutine
Clear W atchdog Timer
Go to address
Inclusive OR literal with W
Move literal to W
Return from interrupt
Return with literal in W
Return from Subroutine
Go into standby mode
Subtract W from literal
Exclusive OR literal with W
1
1
2
1
2
1
1
2
2
2
1
1
1
11
11
10
00
10
11
11
00
11
00
00
11
11
111x
1001
0kkk
0000
1kkk
1000
00xx
0000
01xx
0000
0000
110x
1010
kkkk
kkkk
kkkk
0110
kkkk
kkkk
kkkk
0000
kkkk
0000
0110
kkkk
kkkk
kkkk
kkkk
kkkk
0100
kkkk
kkkk
kkkk
1001
kkkk
1000
0011
kkkk
kkkk
C,DC,Z
Z
TO,PD
Z
TO,PD
C,DC,Z
Z
Note 1: When an I/O register is modified as a function of itself (e.g., MOVF PORTB, 1), the value used will be that
value present on the pins themselves. For example, if the data latch is '1' for a pin configured as input and is
driven low by an external device, the data will be written back with a '0'.
2: If this instruction is executed on the TMR0 register (and, where applicable, d = 1), the prescaler will be
cleared if assigned to the Timer0 Module.
3: If Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The sec-
ond cycle is executed as a NOP.
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-4 1997 Microchip Technology Inc.
29.2 Instruction Formats
Figure 29-1 shows the three general f ormats that the instructions can have . As can be seen from
the general format of the instructions, the opcode portion of the instruction word varies from
3-bits to 6-bits of inf ormation. This is what allows the midrange instruction set to hav e 35 instruc-
tions.
All instruction examples use the following format to represent a hexadecimal number:
0xhh
where h signifies a hexadecimal digit.
To represent a binary number:
00000100b
where b is a binary string identifier.
Figure 29-1: General Format for Instructions
Note 1: Any unused opcode is Reserved. Use of any reserved opcode may cause unex-
pected operation.
Note 2: To maintain upward compatibility with future midrange products, do not use the
OPTION and TRIS instructions.
Byte-oriented file register operations
13 8 7 6 0
d = 0 for destination W
OPCODE d f (FILE #)
d = 1 for destination f
f = 7-bit file register address
Bit-oriented file register operations
13 10 9 7 6 0
OPCODE b (BIT #) f (FILE #)
b = 3-bit bit address
f = 7-bit file register address
Literal and control operations
13 8 7 0
OPCODE k (literal)
k = 8-bit literal (immediate) value
13 11 10 0
OPCODE k (literal)
k = 11-bit literal (immediate) value
General
CALL and GOTO instructions only
1997 Microchip Technology Inc. DS31029A-page 29-5
Section 29. Instruction Set
Instruction
Set
29
Table 29-2: Instruction Description Conventions
Field Description
fRegister file address (0x00 to 0x7F)
WWorking register (accumulator)
bBit address within an 8-bit file register (0 to 7)
kLiteral field, constant data or label (may be either an 8-bit or an 11-bit value)
xDon't care (0 or 1)
The assembler will gener ate code with x = 0. It is the recommended form of use for
compatibility with all Microchip software tools.
dDestination select;
d = 0: store result in W,
d = 1: store result in file register f.
dest Destination either the W register or the specified register file location
label Label name
TOS Top of Stack
PC Program Counter
PCLATH Program Counter High Latch
GIE Global Interrupt Enable bit
WDT W atchdog Timer
TO Time-out bit
PD Power-down bit
[ ] Optional
( ) Contents
Assigned to
< > Register bit field
In the set of
italics
User defined term (font is courier)
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-6 1997 Microchip Technology Inc.
29.3 Special Function Registers as Source/Destination
The Section 29. Instruction Set’s orthogonal instruction set allows read and write of all file regis-
ters, including special function registers . Some special situations the user should be aware of are
explained in the following subsections:
29.3.1 STATUS Register as Destination
If an instruction wr ites to the STATUS register, the Z, C, DC and OV bits may be set or cleared
as a result of the instruction and overwrite the original data bits written. For example, executing
CLRF STATUS will clear register STATUS, and then set the Z bit leaving 0000 0100b in the reg-
ister.
29.3.2 PCL as Source or Destination
Read, write or read-modify-write on PCL may have the following results:
Read PC: PCL dest; PCLATH does not change;
Write PCL: PCLATH PCH;
8-bit destination value PCL
Read-Modify-Write: PCL ALU operand
PCLATH PCH;
8-bit result PCL
Where PCH = program counter high byte (not an addressable register), PCLATH = Program
counter high holding latch, dest = destination, W register or register file f.
29.3.3 Bit Manipulation
All bit manipulation instructions will first read the entire register, operate on the selected bit and
then write the result back (read-modify-write (R-M-W)) the specified register. The user should
keep this in mind when operating on some special function registers, such as ports.
Note: Status bits that are manipulated by the device (including the interr upt flag bits) are
set or cleared in the Q1 cycle. So there is no issue with e x ecuting R-M-W instructions
on registers which contain these bits.
1997 Microchip Technology Inc. DS31029A-page 29-7
Section 29. Instruction Set
Instruction
Set
29
29.4 Q Cycle Activity
Each instruction cycle (Tcy) is compr ised of four Q cycles (Q1-Q4). The Q cycle is the same as
the device oscillator cycle (TOSC). The Q cycles provide the timing/designation for the Decode,
Read, Process Data, Write etc., of each instruction cycle. The following diagram shows the rela-
tionship of the Q cycles to the instruction cycle.
The four Q cycles that make up an instruction cycle (Tcy) can be generalized as:
Q1: Instruction Decode Cycle or forced No Operation
Q2: Instruction Read Cycle or No Operation
Q3: Process the Data
Q4: Instruction Write Cycle or No Operation
Each instruction will show the detailed Q cycle operation for the instruction.
Figure 29-2: Q Cycle Activity
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Tcy1 Tcy2 Tcy3
Tosc
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-8 1997 Microchip Technology Inc.
29.5 Instruction Descriptions
ADDLW Add Literal and W
Syntax: [
label
] ADDLW k
Operands: 0 k 255
Operation: (W) + k W
Status Affected: C, DC, Z
Encoding: 11 111x kkkk kkkk
Description: The contents of the W register are added to the eight bit literal 'k' and the result is
placed in the W register.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal 'k' Process
data Write to W
register
Example1 ADDLW 0x15
Before Instruction
W = 0x10
After Instruction
W = 0x25
Example 2 ADDLW MYREG
Before Instruction
W = 0x10
Address of MYREG = 0x37
MYREG is a symbol for a data memory location
After Instruction
W = 0x47
Example 3 ADDLW HIGH (LU_TABLE)
Before Instruction
W = 0x10
Address of LU_TABLE = 0x9375
LU_TABLE is a label for an address in program memory
After Instruction
W = 0xA3
Example 4 ADDLW MYREG
Before Instruction
W = 0x10
Address of PCL = 0x02
PCL is the symbol for the Program Counter low byte location
After Instruction
W = 0x12
1997 Microchip Technology Inc. DS31029A-page 29-9
Section 29. Instruction Set
Instruction
Set
29
ADDWF Add W and f
Syntax: [
label
] ADDWF f,d
Operands: 0 f 127
d ∈ [0,1]
Operation: (W) + (f) destination
Status Affected: C, DC, Z
Encoding: 00 0111 dfff ffff
Description: Add the contents of the W register with register 'f'. If 'd' is 0 the result is stored in the
W register. If 'd' is 1 the result is stored back in register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 ADDWF FSR, 0
Before Instruction
W = 0x17
FSR = 0xC2
After Instruction
W = 0xD9
FSR = 0xC2
Example 2 ADDWF INDF, 1
Before Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x20
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x37
Example 3 ADDWF PCL
Case 1: Before Instruction
W = 0x10
PCL = 0x37
C = x
After Instruction
PCL = 0x47
C= 0
Case 2: Before Instruction
W = 0x10
PCL = 0xF7
PCH = 0x08
C = x
After Instruction
PCL = 0x07
PCH = 0x08
C = 1
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-10 1997 Microchip Technology Inc.
ANDLW And Literal with W
Syntax: [
label
] ANDLW k
Operands: 0 k 255
Operation: (W).AND. (k) W
Status Affected: Z
Encoding: 11 1001 kkkk kkkk
Description: The contents of W register are AND’ed with the eight bit literal 'k'. The result is
placed in the W register.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read literal
'k' Process
data Write to W
register
Example 1 ANDLW 0x5F
Before Instruction
W = 0xA3
After Instruction
W = 0x03
; 0101 1111 (0x5F)
; 1010 0011 (0xA3)
;---------- ------
; 0000 0011 (0x03)
Example 2 ANDLW MYREG
Before Instruction
W = 0xA3
Address of MYREG = 0x37
MYREG is a symbol for a data memory location
After Instruction
W = 0x23
Example 3 ANDLW HIGH (LU_TABLE)
Before Instruction
W = 0xA3
Address of LU_TABLE = 0x9375
LU_TABLE is a label for an address in program memory
After Instruction
W = 0x83
1997 Microchip Technology Inc. DS31029A-page 29-11
Section 29. Instruction Set
Instruction
Set
29
ANDWF AND W with f
Syntax: [
label
] ANDWF f,d
Operands: 0 f 127
d ∈ [0,1]
Operation: (W).AND. (f) destination
Status Affected: Z
Encoding: 00 0101 dfff ffff
Description: AND the W register with register 'f'. If 'd' is 0 the result is stored in the W register. If
'd' is 1 the result is stored back in register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 ANDWF FSR, 1
Before Instruction
W = 0x17
FSR = 0xC2
After Instruction
W = 0x17
FSR = 0x02
; 0001 0111 (0x17)
; 1100 0010 (0xC2)
;---------- ------
; 0000 0010 (0x02)
Example 2 ANDWF FSR, 0
Before Instruction
W = 0x17
FSR = 0xC2
After Instruction
W = 0x02
FSR = 0xC2
; 0001 0111 (0x17)
; 1100 0010 (0xC2)
;---------- ------
; 0000 0010 (0x02)
Example 3 ANDWF INDF, 1
Before Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x5A
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x15
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-12 1997 Microchip Technology Inc.
BCF Bit Clear f
Syntax: [
label
] BCF f,b
Operands: 0 f 127
0 b 7
Operation: 0 f<b>
Status Affected: None
Encoding: 01 00bb bfff ffff
Description: Bit 'b' in register 'f' is cleared.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write
register 'f'
Example 1 BCF FLAG_REG, 7
Before Instruction
FLAG_REG = 0xC7
After Instruction
FLAG_REG = 0x47
; 1100 0111
; 0100 0111
Example 2 BCF INDF, 3
Before Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x2F
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x27
1997 Microchip Technology Inc. DS31029A-page 29-13
Section 29. Instruction Set
Instruction
Set
29
BSF Bit Set f
Syntax: [
label
] BSF f,b
Operands: 0 f 127
0 b 7
Operation: 1 f<b>
Status Affected: None
Encoding: 01 01bb bfff ffff
Description: Bit 'b' in register 'f' is set.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write
register 'f'
Example 1 BSF FLAG_REG, 7
Before Instruction
FLAG_REG =0x0A
After Instruction
FLAG_REG =0x8A
; 0000 1010
; 1000 1010
Example 2 BSF INDF, 3
Before Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x20
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x28
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-14 1997 Microchip Technology Inc.
BTFSC Bit Test, Skip if Clear
Syntax: [
label
] BTFSC f,b
Operands: 0 f 127
0 b 7
Operation: skip if (f<b>) = 0
Status Affected: None
Encoding: 01 10bb bfff ffff
Description: If bit 'b' in register 'f' is '0' then the next instruction is skipped.
If bit 'b' is '0' then the next instruction (fetched during the current instruction execu-
tion) is discarded, and a NOP is executed instead, making this a 2 cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data No
operation
If skip (2nd cycle):
Q1 Q2 Q3 Q4
No
operation No
operation No
operation No
operation
Example 1 HERE
FALSE
TRUE
BTFSC
GOTO
FLAG, 4
PROCESS_CODE
Case 1: Before Instruction
PC = addressHERE
FLAG= xxx0 xxxx
After Instruction
Since FLAG<4>= 0,
PC = addressTRUE
Case 2: Before Instruction
PC = addressHERE
FLAG= xxx1 xxxx
After Instruction
Since FLAG<4>=1,
PC = addressFALSE
1997 Microchip Technology Inc. DS31029A-page 29-15
Section 29. Instruction Set
Instruction
Set
29
BTFSS Bit Test f, Skip if Set
Syntax: [
label
] BTFSS f,b
Operands: 0 f 127
0 b < 7
Operation: skip if (f<b>) = 1
Status Affected: None
Encoding: 01 11bb bfff ffff
Description: If bit 'b' in register 'f' is '1' then the next instruction is skipped.
If bit 'b' is '1', then the next instruction (fetched during the current instruc-
tion e xecution) is discarded and a NOP is executed instead, making this a
2 cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data No
operation
If skip (2nd cycle):
Q1 Q2 Q3 Q4
No
operation No
operation No
operation No
operation
Example 1 HERE
FALSE
TRUE
BTFSS
GOTO
FLAG, 4
PROCESS_CODE
Case 1: Before Instruction
PC = addressHERE
FLAG= xxx0 xxxx
After Instruction
Since FLAG<4>= 0,
PC = addressFALSE
Case 2: Before Instruction
PC = addressHERE
FLAG= xxx1 xxxx
After Instruction
Since FLAG<4>=1,
PC = addressTRUE
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-16 1997 Microchip Technology Inc.
CALL Call Subroutine
Syntax: [
label
] CALL k
Operands: 0 k 2047
Operation: (PC)+ 1 TOS,
k PC<10:0>,
(PCLATH<4:3>) PC<12:11>
Status Affected: None
Encoding: 10 0kkk kkkk kkkk
Description: Call Subroutine. First, the 13-bit return address (PC+1) is pushed onto the
stack. The ele v en bit immediate address is loaded into PC bits <10:0>. The
upper bits of the PC are loaded from PCLATH<4:3>. CALL is a two cycle
instruction.
Words: 1
Cycles: 2
Q Cycle Activity:
1st cycle:
Q1 Q2 Q3 Q4
Decode Read literal
'k' Process
data No
operation
2nd cycle:
Q1 Q2 Q3 Q4
No
operation No
operation No
operation No
operation
Example 1 HERE CALL THERE
Before Instruction
PC = AddressHERE
After Instruction
TOS = Address HERE+1
PC = Address THERE
1997 Microchip Technology Inc. DS31029A-page 29-17
Section 29. Instruction Set
Instruction
Set
29
CLRF Clear f
Syntax: [
label
] CLRF f
Operands: 0 f 127
Operation: 00h f
1 Z
Status Affected: Z
Encoding: 00 0001 1fff ffff
Description: The contents of register 'f' are cleared and the Z bit is set.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write
register 'f'
Example 1 CLRF FLAG_REG
Before Instruction
FLAG_REG=0x5A
After Instruction
FLAG_REG=0x00
Z=1
Example 2 CLRF INDF
Before Instruction
FSR = 0xC2
Contents of Address (FSR)=0xAA
After Instruction
FSR = 0xC2
Contents of Address (FSR)=0x00
Z=1
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-18 1997 Microchip Technology Inc.
CLRW Clear W
Syntax: [
label
] CLRW
Operands: None
Operation: 00h W
1 Z
Status Affected: Z
Encoding: 00 0001 0xxx xxxx
Description: W register is cleared. Zero bit (Z) is set.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write
register 'W'
Example 1 CLRW
Before Instruction
W = 0x5A
After Instruction
W = 0x00
Z=1
1997 Microchip Technology Inc. DS31029A-page 29-19
Section 29. Instruction Set
Instruction
Set
29
CLRWDT Clear Watchdog Timer
Syntax: [
label
] CLRWDT
Operands: None
Operation: 00h WDT
0 WDT prescaler count,
1 TO
1 PD
Status Affected: TO, PD
Encoding: 00 0000 0110 0100
Description: CLRWDT instruction clears the Watchdog Timer. It also clears the pres-
caler count of the WDT. Status bits TO and PD are set.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation Process
data Clear
WDT
Counter
Example 1 CLRWDT
Before Instruction
WDT counter= x
WDT prescaler =1:128
After Instruction
WDT counter=0x00
WDT prescaler count=0
TO =1
PD =1
WDT prescaler =1:128
Note: The CLRWDT instruction does not affect the assignment of the WDT prescaler.
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-20 1997 Microchip Technology Inc.
COMF Complement f
Syntax: [
label
] COMF f,d
Operands: 0 f 127
d [0,1]
Operation: (f) destination
Status Affected: Z
Encoding: 00 1001 dfff ffff
Description: The contents of register 'f' are 1’s complemented. If 'd' is 0 the result is
stored in W. If 'd' is 1 the result is stored back in register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 COMF REG1, 0
Before Instruction
REG1= 0x13
After Instruction
REG1= 0x13
W = 0xEC
Example 2 COMF INDF, 1
Before Instruction
FSR = 0xC2
Contents of Address (FSR)=0xAA
After Instruction
FSR = 0xC2
Contents of Address (FSR)=0x55
Example 3 COMF REG1, 1
Before Instruction
REG1= 0xFF
After Instruction
REG1= 0x00
Z=1
1997 Microchip Technology Inc. DS31029A-page 29-21
Section 29. Instruction Set
Instruction
Set
29
DECF Decrement f
Syntax: [
label
] DECF f,d
Operands: 0 f 127
d [0,1]
Operation: (f) - 1 destination
Status Affected: Z
Encoding: 00 0011 dfff ffff
Description: Decrement register 'f'. If 'd' is 0 the result is stored in the W register. If 'd' is 1 the
result is stored back in register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 DECF CNT, 1
Before Instruction
CNT= 0x01
Z=0
After Instruction
CNT= 0x00
Z=1
Example 2 DECF INDF, 1
Before Instruction
FSR = 0xC2
Contents of Address (FSR) = 0x01
Z=0
After Instruction
FSR = 0xC2
Contents of Address (FSR) = 0x00
Z=1
Example 3 DECF CNT, 0
Before Instruction
CNT= 0x10
W=x
Z=0
After Instruction
CNT= 0x10
W = 0x0F
Z=0
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-22 1997 Microchip Technology Inc.
DECFSZ Decrement f, Skip if 0
Syntax: [
label
] DECFSZ f,d
Operands: 0 f 127
d [0,1]
Operation: (f) - 1 destination; skip if result = 0
Status Affected: None
Encoding: 00 1011 dfff ffff
Description: The contents of register 'f' are decremented. If 'd' is 0 the result is placed
in the W register. If 'd' is 1 the result is placed back in register 'f'.
If the result is 0, then the next instruction (fetched during the current
instruction execution) is discarded and a NOP is executed instead, mak-
ing this a 2 cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
If skip (2nd cycle):
Q1 Q2 Q3 Q4
No
operation No
operation No
operation No
operation
Example HERE DECFSZ CNT, 1
GOTO LOOP
CONTINUE •
Case 1: Before Instruction
PC = address HERE
CNT = 0x01
After Instruction
CNT = 0x00
PC = address CONTINUE
Case 2: Before Instruction
PC = address HERE
CNT = 0x02
After Instruction
CNT = 0x01
PC = address HERE + 1
1997 Microchip Technology Inc. DS31029A-page 29-23
Section 29. Instruction Set
Instruction
Set
29
GOTO Unconditional Branch
Syntax: [
label
] GOTO k
Operands: 0 k 2047
Operation: k PC<10:0>
PCLATH<4:3> PC<12:11>
Status Affected: None
Encoding: 10 1kkk kkkk kkkk
Description: GOTO is an unconditional branch. The eleven bit immediate value is loaded
into PC bits <10:0>. The upper bits of PC are loaded from PCLATH<4:3>.
GOTO is a two cycle instruction.
Words: 1
Cycles: 2
Q Cycle Activity:
1st cycle:
Q1 Q2 Q3 Q4
Decode Read literal
'k'<7:0> Process
data No
operation
2nd cycle:
Q1 Q2 Q3 Q4
No
operation No
operation No
operation No
operation
Example GOTO THERE
After Instruction
PC =AddressTHERE
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-24 1997 Microchip Technology Inc.
INCF Increment f
Syntax: [
label
] INCF f,d
Operands: 0 f 127
d [0,1]
Operation: (f) + 1 destination
Status Affected: Z
Encoding: 00 1010 dfff ffff
Description: The contents of register 'f' are incremented. If 'd' is 0 the result is placed in
the W register. If 'd' is 1 the result is placed back in register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 INCF CNT, 1
Before Instruction
CNT= 0xFF
Z=0
After Instruction
CNT= 0x00
Z=1
Example 2 INCF INDF, 1
Before Instruction
FSR = 0xC2
Contents of Address (FSR) = 0xFF
Z=0
After Instruction
FSR = 0xC2
Contents of Address (FSR) = 0x00
Z=1
Example 3 INCF CNT, 0
Before Instruction
CNT= 0x10
W=x
Z=0
After Instruction
CNT= 0x10
W = 0x11
Z=0
1997 Microchip Technology Inc. DS31029A-page 29-25
Section 29. Instruction Set
Instruction
Set
29
INCFSZ Increment f, Skip if 0
Syntax: [
label
] INCFSZ f,d
Operands: 0 f 127
d [0,1]
Operation: (f) + 1 destination, skip if result = 0
Status Affected: None
Encoding: 00 1111 dfff ffff
Description: The contents of register 'f' are incremented. If 'd' is 0 the result is placed in
the W register. If 'd' is 1 the result is placed back in register 'f'.
If the result is 0, then the next instruction (fetched during the current
instruction ex ecution) is discarded and a NOP is e x ecuted instead, making
this a 2 cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
If skip (2nd cycle):
Q1 Q2 Q3 Q4
No
operation No
operation No
operation No
operation
Example HERE INCFSZ CNT, 1
GOTO LOOP
CONTINUE •
Case 1: Before Instruction
PC = address HERE
CNT = 0xFF
After Instruction
CNT = 0x00
PC = address CONTINUE
Case 2: Before Instruction
PC = address HERE
CNT = 0x00
After Instruction
CNT = 0x01
PC = address HERE + 1
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-26 1997 Microchip Technology Inc.
IORLW Inclusive OR Literal with W
Syntax: [
label
] IORLW k
Operands: 0 k 255
Operation: (W).OR. k W
Status Affected: Z
Encoding: 11 1000 kkkk kkkk
Description: The contents of the W register is OR’ed with the eight bit literal 'k'. The result is
placed in the W register.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal 'k' Process
data Write to W
register
Example 1 IORLW 0x35
Before Instruction
W = 0x9A
After Instruction
W = 0xBF
Z=0
Example 2 IORLW MYREG
Before Instruction
W = 0x9A
Address of MYREG = 0x37
MYREG is a symbol for a data memory location
After Instruction
W = 0x9F
Z=0
Example 3 IORLW HIGH (LU_TABLE)
Before Instruction
W = 0x9A
Address of LU_TABLE = 0x9375
LU_TABLE is a label for an address in program memory
After Instruction
W = 0x9B
Z=0
Example 4 IORLW 0x00
Before Instruction
W = 0x00
After Instruction
W = 0x00
Z=1
1997 Microchip Technology Inc. DS31029A-page 29-27
Section 29. Instruction Set
Instruction
Set
29
IORWF Inclusive OR W with f
Syntax: [
label
] IORWF f,d
Operands: 0 f 127
d [0,1]
Operation: (W).OR. (f) destination
Status Affected: Z
Encoding: 00 0100 dfff ffff
Description: Inclusive OR the W register with register 'f'. If 'd' is 0 the result is placed in
the W register. If 'd' is 1 the result is placed back in register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 IORWF RESULT, 0
Before Instruction
RESULT=0x13
W = 0x91
After Instruction
RESULT=0x13
W = 0x93
Z=0
Example 2 IORWF INDF, 1
Before Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x30
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x37
Z=0
Example 3 IORWF RESULT, 1
Case 1: Before Instruction
RESULT=0x13
W = 0x91
After Instruction
RESULT=0x93
W = 0x91
Z=0
Case 2: Before Instruction
RESULT=0x00
W = 0x00
After Instruction
RESULT=0x00
W = 0x00
Z=1
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-28 1997 Microchip Technology Inc.
MOVLW Move Literal to W
Syntax: [
label
] MOVLW k
Operands: 0 k 255
Operation: k W
Status Affected: None
Encoding: 11 00xx kkkk kkkk
Description: The eight bit literal 'k' is loaded into W register. The don’t cares will assemble as 0’s.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal 'k' Process
data Write to W
register
Example 1 MOVLW 0x5A
After Instruction
W = 0x5A
Example 2 MOVLW MYREG
Before Instruction
W = 0x10
Address of MYREG = 0x37
MYREG is a symbol for a data memory location
After Instruction
W = 0x37
Example 3 MOVLW HIGH (LU_TABLE)
Before Instruction
W = 0x10
Address of LU_TABLE = 0x9375
LU_TABLE is a label for an address in program memory
After Instruction
W = 0x93
1997 Microchip Technology Inc. DS31029A-page 29-29
Section 29. Instruction Set
Instruction
Set
29
MOVF Move f
Syntax: [
label
] MOVF f,d
Operands: 0 f 127
d [0,1]
Operation: (f) destination
Status Affected: Z
Encoding: 00 1000 dfff ffff
Description: The contents of register ’f is moved to a destination dependent upon the
status of ’d’. If ’d’ = 0, destination is W register. If ’d’ = 1, the destination is
file register ’f itself.d’ = 1 is useful to test a file register since status flag Z
is affected.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 MOVF FSR, 0
Before Instruction
W = 0x00
FSR = 0xC2
After Instruction
W = 0xC2
Z= 0
Example 2 MOVF INDF, 0
Before Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x00
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x00
Z= 1
Example 3 MOVF FSR, 1
Case 1: Before Instruction
FSR = 0x43
After Instruction
FSR = 0x43
Z= 0
Case 2: Before Instruction
FSR = 0x00
After Instruction
FSR = 0x00
Z= 1
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-30 1997 Microchip Technology Inc.
MOVWF Move W to f
Syntax: [
label
] MOVWF f
Operands: 0 f 127
Operation: (W) f
Status Affected: None
Encoding: 00 0000 1fff ffff
Description: Move data from W register to register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write
register 'f'
Example 1 MOVWF OPTION_REG
Before Instruction
OPTION_REG=0xFF
W = 0x4F
After Instruction
OPTION_REG=0x4F
W = 0x4F
Example 2 MOVWF INDF
Before Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x00
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x17
1997 Microchip Technology Inc. DS31029A-page 29-31
Section 29. Instruction Set
Instruction
Set
29
NOP No Operation
Syntax: [
label
] NOP
Operands: None
Operation: No operation
Status Affected: None
Encoding: 00 0000 0xx0 0000
Description: No operation.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation No
operation No
operation
Example HERE NOP
: Before Instruction
PC = address HERE
After Instruction
PC = address HERE + 1
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-32 1997 Microchip Technology Inc.
OPTION Load Option Register
Syntax: [
label
] OPTION
Operands: None
Operation: (W) OPTION
Status Affected: None
Encoding: 00 0000 0110 0010
Description: The contents of the W register are loaded in the OPTION register. This
instruction is supported for code compatibility with PIC16C5X products.
Since OPTION is a readable/writable register, the user can directly
address it.
Words: 1
Cycles: 1
To maintain upward compatibility with future PIC16CXX products, do
not use this instruction.
1997 Microchip Technology Inc. DS31029A-page 29-33
Section 29. Instruction Set
Instruction
Set
29
RETFIE Return from Interrupt
Syntax: [
label
] RETFIE
Operands: None
Operation: TOS PC,
1 GIE
Status Affected: None
Encoding: 00 0000 0000 1001
Description: Return from Interrupt. The 13-bit address at the Top of Stack (TOS) is
loaded in the PC. The Global Interrupt Enable bit, GIE (INTCON<7>), is
automatically set, enabling Interrupts. This is a two cycle instruction.
Words: 1
Cycles: 2
Q Cycle Activity:
1st cycle:
Q1 Q2 Q3 Q4
Decode No
operation Process
data No
operation
2nd cycle:
Q1 Q2 Q3 Q4
No
operation No
operation No
operation No
operation
Example RETFIE
After Instruction
PC = TOS
GIE = 1
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-34 1997 Microchip Technology Inc.
RETLW Return with Literal in W
Syntax: [
label
] RETLW k
Operands: 0 k 255
Operation: k W;
T OS PC
Status Affected: None
Encoding: 11 01xx kkkk kkkk
Description: The W register is loaded with the eight bit literal 'k'. The prog ram counter is
loaded 13-bit address at the Top of Stack (the return address). This is a
two cycle instruction.
Words: 1
Cycles: 2
Q Cycle Activity:
1st cycle:
Q1 Q2 Q3 Q4
Decode Read
literal 'k' Process
data Write to W
register
2nd cycle:
Q1 Q2 Q3 Q4
No
operation No
operation No
operation No
operation
Example
HERE
TABLE
CALL TABLE ; W contains table
; offset value
• ; W now has table value
ADDWF PC ;W = offset
RETLW k1 ;Begin table
RETLW k2 ;
RETLW kn ; End of table
Before Instruction
W = 0x07
After Instruction
W = value of k8
PC = TOS = Address Here + 1
1997 Microchip Technology Inc. DS31029A-page 29-35
Section 29. Instruction Set
Instruction
Set
29
RETURN Return from Subroutine
Syntax: [
label
] RETURN
Operands: None
Operation: TOS PC
Status Affected: None
Encoding: 00 0000 0000 1000
Description: Return from subroutine. The stack is POPed and the top of the stack
(TOS) is loaded into the program counter. This is a two cycle instruc-
tion.
Words: 1
Cycles: 2
Q Cycle Activity:
1st cycle:
Q1 Q2 Q3 Q4
Decode No
operation Process
data No
operation
2nd cycle:
Q1 Q2 Q3 Q4
No
operation No
operation No
operation No
operation
Example HERE RETURN
After Instruction
PC = TOS
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-36 1997 Microchip Technology Inc.
RLF Rotate Left f through Carry
Syntax: [
label
] RLF f,d
Operands: 0 f 127
d [0,1]
Operation: See description below
Status Affected: C
Encoding: 00 1101 dfff ffff
Description: The contents of register 'f' are rotated one bit to the left through the Carry
Flag. If 'd' is 0 the result is placed in the W register. If 'd' is 1 the result is
stored back in register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 RLF REG1,0
Before Instruction
REG1= 1110 0110
C=0
After Instruction
REG1=1110 0110
W=1100 1100
C=1
Example 2 RLF INDF, 1
Case 1: Before Instruction
W=xxxx xxxx
FSR = 0xC2
Contents of Address (FSR) = 0011 1010
C=1
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0111 0101
C=0
Case 2: Before Instruction
W=xxxx xxxx
FSR = 0xC2
Contents of Address (FSR) = 1011 1001
C=0
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0111 0010
C=1
Register fC
1997 Microchip Technology Inc. DS31029A-page 29-37
Section 29. Instruction Set
Instruction
Set
29
RRF Rotate Right f through Carry
Syntax: [
label
] RRF f,d
Operands: 0 f 127
d [0,1]
Operation: See description below
Status Affected: C
Encoding: 00 1100 dfff ffff
Description: The contents of register 'f' are rotated one bit to the right through the Carry
Flag. If 'd' is 0 the result is placed in the W register. If 'd' is 1 the result is
placed back in register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 RRF REG1,0
Before Instruction
REG1= 1110 0110
W= xxxx xxxx
C=0
After Instruction
REG1= 1110 0110
W= 0111 0011
C=0
Example 2 RRF INDF, 1
Case 1: Before Instruction
W=xxxx xxxx
FSR = 0xC2
Contents of Address (FSR) = 0011 1010
C=1
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 1001 1101
C=0
Case 2: Before Instruction
W=xxxx xxxx
FSR = 0xC2
Contents of Address (FSR) = 0011 1001
C=0
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0001 1100
C=1
Register fC
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-38 1997 Microchip Technology Inc.
SLEEP
Syntax: [
label
] SLEEP
Operands: None
Operation: 00h WDT,
0 WDT prescaler count,
1 TO,
0 PD
Status Affected: TO, PD
Encoding: 00 0000 0110 0011
Description: The power-down status bit, PD is cleared. Time-out status bit, TO is set.
Watchdog Timer and its prescaler count are cleared.
The processor is put into SLEEP mode with the oscillator stopped.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation No
operation Go to sleep
Example: SLEEP
Note: The SLEEP instruction does not affect the assignment of the WDT prescaler
1997 Microchip Technology Inc. DS31029A-page 29-39
Section 29. Instruction Set
Instruction
Set
29
SUBLW Subtract W from Literal
Syntax: [
label
] SUBLW k
Operands: 0 k 255
Operation: k - (W) W
Status Affected: C, DC, Z
Encoding: 11 110x kkkk kkkk
Description: The W register is subtracted (2’s complement method) from the eight bit
literal 'k'. The result is placed in the W register.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal 'k' Process
data Write to W
register
Example 1: SUBLW 0x02
Case 1: Before Instruction
W = 0x01
C=x
Z=x
After Instruction
W = 0x01
C = 1 ; result is positive
Z=0
Case 2: Before Instruction
W = 0x02
C=x
Z=x
After Instruction
W = 0x00
C = 1 ; result is zero
Z=1
Case 3: Before Instruction
W = 0x03
C=x
Z=x
After Instruction
W = 0xFF
C = 0 ; result is negative
Z=0
Example 2 SUBLW MYREG
Before Instruction
W = 0x10
Address of MYREG = 0x37
MYREG is a symbol for a data memory location
After Instruction
W = 0x27
C = 1 ; result is positive
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-40 1997 Microchip Technology Inc.
SUBWF Subtract W from f
Syntax: [
label
] SUBWF f,d
Operands: 0 f 127
d [0,1]
Operation: (f) - (W) destination
Status Affected: C, DC, Z
Encoding: 00 0010 dfff ffff
Description: Subtract (2’ s complement method) W register from register 'f'. If 'd' is 0 the
result is stored in the W register. If 'd' is 1 the result is stored back in reg-
ister 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1: SUBWF REG1,1
Case 1: Before Instruction
REG1= 3
W=2
C=x
Z=x
After Instruction
REG1= 1
W=2
C = 1 ; result is positive
Z=0
Case 2: Before Instruction
REG1= 2
W=2
C=x
Z=x
After Instruction
REG1= 0
W=2
C = 1 ; result is zero
Z=1
Case 3: Before Instruction
REG1= 1
W=2
C=x
Z=x
After Instruction
REG1= 0xFF
W=2
C = 0 ; result is negative
Z=0
1997 Microchip Technology Inc. DS31029A-page 29-41
Section 29. Instruction Set
Instruction
Set
29
SWAPF Swap Nibbles in f
Syntax: [
label
] SWAPF f,d
Operands: 0 f 127
d [0,1]
Operation: (f<3:0>) destination<7:4>,
(f<7:4>) destination<3:0>
Status Affected: None
Encoding: 00 1110 dfff ffff
Description: The upper and lower nibbles of register 'f' are exchanged. If 'd' is 0 the
result is placed in W register. If 'd' is 1 the result is placed in register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 SWAPF REG, 0
Before Instruction
REG1= 0xA5
After Instruction
REG1= 0xA5
W = 0x5A
Example 2 SWAPF INDF, 1
Before Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x20
After Instruction
W = 0x17
FSR = 0xC2
Contents of Address (FSR) = 0x02
Example 3 SWAPF REG, 1
Before Instruction
REG1= 0xA5
After Instruction
REG1= 0x5A
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-42 1997 Microchip Technology Inc.
TRIS Load TRIS Register
Syntax: [
label
] TRIS f
Operands: 5 f 7
Operation: (W) TRIS register f;
Status Affected: None
Encoding: 00 0000 0110 0fff
Description: The instruction is supported for code compatibility with the PIC16C5X prod-
ucts. Since TRIS registers are readable and writable, the user can directly
address them.
Words: 1
Cycles: 1
Example To maintain upward compatibility with future PIC16CXX products, do
not use this instruction.
1997 Microchip Technology Inc. DS31029A-page 29-43
Section 29. Instruction Set
Instruction
Set
29
XORLW Exclusive OR Literal with W
Syntax: [
label
] XORLW k
Operands: 0 k 255
Operation: (W).XOR. k W
Status Affected: Z
Encoding: 11 1010 kkkk kkkk
Description: The contents of the W register are XOR’ed with the eight bit liter al 'k'. The
result is placed in the W register.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal 'k' Process
data Write to W
register
Example 1 XORLW 0xAF ; 1010 1111 (0xAF)
Before Instruction ; 1011 0101 (0xB5)
W = 0xB5 ; --------- ------
After Instruction ; 0001 1010 (0x1A)
W = 0x1A
Z=0
Example 2 XORLW MYREG
Before Instruction
W = 0xAF
Address of MYREG = 0x37
MYREG is a symbol for a data memory location
After Instruction
W = 0x18
Z=0
Example 3 XORLW HIGH (LU_TABLE)
Before Instruction
W = 0xAF
Address of LU_TABLE = 0x9375
LU_TABLE is a label for an address in program memory
After Instruction
W = 0x3C
Z=0
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-44 1997 Microchip Technology Inc.
XORWF Exclusive OR W with f
Syntax: [
label
] XORWF f,d
Operands: 0 f 127
d [0,1]
Operation: (W).XOR. (f) destination
Status Affected: Z
Encoding: 00 0110 dfff ffff
Description: Exclusive OR the contents of the W register with register 'f'. If 'd' is 0 the
result is stored in the W register. If 'd' is 1 the result is stored back in regis-
ter 'f'.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register 'f' Process
data Write to
destination
Example 1 XORWF REG, 1 ; 1010 1111 (0xAF)
Before Instruction ; 1011 0101 (0xB5)
REG= 0xAF
W = 0xB5 ; --------- ------
; 0001 1010 (0x1A)
After Instruction
REG= 0x1A
W = 0xB5
Example 2 XORWF REG, 0 ; 1010 1111 (0xAF)
Before Instruction ; 1011 0101 (0xB5)
REG= 0xAF
W = 0xB5 ; --------- ------
; 0001 1010 (0x1A)
After Instruction
REG= 0xAF
W = 0x1A
Example 3 XORWF INDF, 1
Before Instruction
W = 0xB5
FSR = 0xC2
Contents of Address (FSR) = 0xAF
After Instruction
W = 0xB5
FSR = 0xC2
Contents of Address (FSR) = 0x1A
1997 Microchip Technology Inc. DS31029A-page 29-45
Section 29. Instruction Set
Instruction
Set
29
29.6 Design Tips
Question 1:
How can I modify the value of W directly? I want to decrement W.
Answer 1:
There are a few possibilities, two are:
1. F or the midrange de vices, there are se v er al instructions that work with a literal and W. For
instance, if it were desired to decrement W, this can be done with an ADDLW 0xFF. (the 0x
prefix denotes hex to the assembler)
2. Notice that all of the instructions can modify a value right where it sits in the file register.
This means you can decrement it right where it is. You do not even need to move it to W.
If you want to decrement it AND move it somewhere else, then you make W the DESTI-
NATION of the decrement (DECF register,W) then put it where you want it. It is the same
number of instructions as a straight move, but it gets decremented along the way.
Question 2:
Is there any danger in using the TRIS instruction for the PIC16CXXX since
there is a warning in the Data book suggesting it not be used?
Answer 2:
For code compatibility and upgrades to later parts, the use of the TRIS instruction is not recom-
mended. You should note the TRIS instruction is limited to ports A, B and C. Future de vices may
not support these instructions.
Question 3:
Do I have to s witch to Bank1 of data memory before using the TRIS instruc-
tion (for parts with TRIS registers in the memory map)?
Answer 3:
No . The TRIS instruction is Bank independent. Again the use of the TRIS instruction is not rec-
ommended.
Question 4:
I have seen references to “Read-Modify-Write” instructions in your data
sheet, but I do not know what that is. Can you explain what it is and why I
need to know this?
Answer 4:
An easy e xample of a Read-Modify-Write (R-M-W) instruction is the bit clear instruction BCF. You
might think that the processor just clears the bit, which on a port output pin would clear the pin.
What actually happens is the whole por t (or register) is first read, THEN the bit is cleared, then
the new modified value is written back to the port (or register). Actually, any instruction that
depends on a value currently in the register is going to be a Read-Modify-Write instruction. This
includes ADDWF, SUBWF, BCF, BSF, INCF, XORWF, etc... Instructions that do not depend on
the current register value, like MOVWF, CLRF, and so on are not R-M-W instructions.
One situation where you w ould want to consider the affects of a R-M-W instruction is a port that
is continuously changed from input to output and bac k. F or example, say you have TRISB set to
all outputs, and write all ones to the POR TB register , all of the PORTB pins will go high. Now, sa y
you turn pin RB3 into an input, which happens to go low. A BCF PORTB,6 is then executed to
drive pin RB6 low. If you then turn RB3 back into an output, it will now drive lo w, e v en though the
last value you put there was a one. What happened was that the BCF of the other pin (RB6)
caused the whole por t to be read, including the zero on RB3 when it was an input. Then, bit 6
was changed as requested, b ut since RB3 was read as a z ero , z ero will also be placed bac k into
that port latch, overwriting the one that was there before. When the pin is turned back into an
output, the new value was reflected.
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-46 1997 Microchip Technology Inc.
Question 5:
When I perform a BCF other pins get cleared in the port. Why?
Answer 5:
There are a few possibilities, two are:
1. Another case where a R-M-W instruction may seem to change other pin v alues une xpect-
edly can be illustrated as follows: Suppose you make PORTC all outputs and drive the
pins low. On each of the port pins is an LED connected to ground, such that a high output
lights it. Across each LED is a 100 µF capacitor. Let's also suppose that the processor is
running very fast, sa y 20 MHz. Now if you go down the port setting each pin in order; BSF
PORTC,0 then BSF POR TC,1 then BSF PORTC,2 and so on, y ou may see that only the last
pin was set, and only the last LED actually turns on. This is because the capacitors take
a while to charge. As each pin was set, the pin before it was not charged yet and so was
read as a zero. This zero is written back out to the por t latch (R-M-W, remember) which
clears the bit you just tried to set the instruction before. This is usually only a concern at
high speeds and for successive por t operations, but it can happen so take it into consid-
eration.
2. If this is on a PIC16C7X de vice, you may not have configured the I/O pins properly in the
ADCON1 register. If a pin is configured for analog input, any read of that pin will read a
zero, regardless of the voltage on the pin. This is an exception to the normal rule that the
pin state is alwa ys read. You can still configure an analog pin as an output in the TRIS reg-
ister , and drive the pin high or low b y writing to it, but you will alwa ys read a zero . Theref ore
if you e x ecute a Read-Modify-Write instruction (see previous question) all analog pins are
read as zero, and those not directly modified by the instruction will be wr itten back to the
port latch as zero. A pin configured as analog is e xpected to ha ve values that may be nei-
ther high nor low to a digital pin, or floating. Floating inputs on digital pins are a no-no , and
can lead to high current draw in the input buffer, so the input buffer is disabled.
1997 Microchip Technology Inc. DS31029A-page 29-47
Section 29. Instruction Set
Instruction
Set
29
29.7 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the instr uc-
tion set are:
Currently No related Application Notes
PICmicro MID-RANGE MCU FAMILY
DS31029A-page 29-48 1997 Microchip Technology Inc.
29.8 Revision History
Revision A
This is the initial released revision of the Instruction Set description.
1997 Microchip Technology Inc. DS31030A page 30-1
M
Electrical
Specifications
30
Section 30. Electrical Specifications
HIGHLIGHTS
30.1 Introduction..................................................................................................................30-2
30.2 Absolute Maximums.....................................................................................................30-3
30.3 Device Selection Table.................................................................................................30-4
30.4 Device Voltage Specifications......................................................................................30-5
30.5 Device Current Specifications......................................................................................30-6
30.6 Input Threshold Levels.................................................................................................30-9
30.7 I/O Current Specifications..........................................................................................30-10
30.8 Output Drive Levels....................................................................................................30-11
30.9 I/O Capacitive Loading...............................................................................................30-12
30.10 Data EEPROM / Flash...............................................................................................30-13
30.11 LCD............................................................................................................................30-14
30.12 Comparators and Voltage Reference.........................................................................30-15
30.13 Timing Parameter Symbology....................................................................................30-16
30.14 Example External Clock Timing Waveforms and Requirements................................30-17
30.15 Example Power-up and Reset Timing Waveforms and Requirements.......................30-19
30.16 Example Timer0 and Timer1 Timing Wa vef orms and Requirements.........................30-20
30.17 Example CCP Timing Waveforms and Requirements................................................30-21
30.18 Example Parallel Slave Port (PSP) Timing Waveforms and Requirements ...............30-22
30.19 Example SSP and Master SSP SPI Mode Timing Waveforms and Requirements....30-23
30.20 Example SSP I2C Mode Timing Waveforms and Requirements................................30-27
30.21 Example Master SSP I2C Mode Timing Waveforms and Requirements....................30-30
30.22 Example USART/SCI Timing Waveforms and Requirements....................................30-32
30.23 Example 8-bit A/D Timing Waveforms and Requirements .........................................30-34
30.24 Example 10-bit A/D Timing Waveforms and Requirements .......................................30-36
30.25 Example Slope A/D Timing Waveforms and Requirements.......................................30-38
30.26 Example LCD Timing Waveforms and Requirements................................................30-40
30.27 Related Application Notes..........................................................................................30-41
30.28 Revision History.........................................................................................................30-42
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-2 1997 Microchip Technology Inc.
30.1 Introduction
This section is intended to show you the electrical specifications that may be specified in a par-
ticular de vice data sheet and what is meant b y the specification. This section is NOT intended to
give the values of these specifications. For the device specific values you must refer to the
device’s data sheet. All values show in this section should be considered as Example Values.
In the description of the device and the functional modules (previous sections), there have been
ref erences to electrical specification parameters. These ref erences ha v e been h yperlinked in the
electronic version to aid in the use of this manual.
Throughout this section, cer tain terms will be used. Table 30-1 shows the conventions that will
be used.
Table 30-1: Term Conventions
Note: Before starting any design, Microchip HIGHLY recommends
that you acquire the most recent copy of the device data sheet
and review the electrical specifications to ensure that they will
meet your requirements.
Term Description
PIC16CXXX For devices tested to standard voltage range
PIC16LCXXX For devices tested to extended voltage range
PIC16FXXX For devices tested to standard voltage range
PIC16LFXXX For devices tested to extended voltage range
PIC16CRXXX For devices tested to standard voltage range
PIC16LCRXXX For devices tested to extended voltage range
PIC16XXXX-04 For devices that have been tested up to 4 MHz operation
PIC16XXXX-08 For devices that have been tested up to 8 MHz operation
PIC16XXXX-10 For devices that have been tested up to 10 MHz operation
PIC16XXXX-20 For devices that have been tested up to 20 MHz operation
LP osc For devices configured with the LP device oscillator selected
XT osc For devices configured with the XT device oscillator selected
HS osc For devices configured with the HS device oscillator selected
RC osc For devices configured with the RC device oscillator selected
Commercial For devices with the commercial temperature range grading
(0˚C TA +70˚C)
Industrial For devices with the industrial temperature range grading
(-40˚C TA +85˚C)
Extended For devices with the extended temperature range grading
(-40˚C TA +125˚C)
1997 Microchip Technology Inc. DS31030A-page 30-3
Section 30. Electrical Specifications
Electrical
Specifications
30
30.2 Absolute Maximums
The Absolute Maximum Ratings specify the worst case conditions that can be applied to the
de vice. These ratings are not meant as operational specifications, and stresses above the listed
values may cause damage to the device. Specifications are not always stand-alone, that is, the
specification may have other requirements as well.
An e xample of this is the “maximum current sourced/sunk b y any I/O pin”. The number of I/O pins
that can be sinking/sourcing current, at any one time, is dependent upon the maximum current
sunk/source by the port(s) (combined) and the maximum current into the VDD pin or out of the
VSS pin. In this example, the physical reason is the Po w er and Ground b us width to the I/O ports
and internal logic. If these specifications are exceeded, then electromigration ma y occur on these
Power and Ground buses . Ov er time electromig r ation would cause these buses to open (be dis-
connected from the pin), and theref ore cause the logic attached to these buses to stop operating.
So exceeding the absolute specifications may cause device reliability issues.
Input Clamp Current is defined as the current through the diode to VSS/VDD if pin voltage exceeds
specification.
Example Absolute Maximum Ratings
Ambient temperature under bias............................................................................ -55 to +125˚C
Storage temperature.......................................................................................... -65˚C to +150˚C
Voltage on any pin with respect to VSS (except VDD, MCLR, and RA4)..... -0.3V to (VDD + 0.3V)
Voltage on VDD with respect to VSS ....................................................................... -0.3 to +7.5V
Voltage on MCLR with respect to VSS (2)...................................................................... 0 to +14V
Voltage on RA4 with respect to Vss .............................................................................. 0 to +14V
Total power dissipation (1) .................................................................................................... 1.0W
Maximum current out of VSS pin ...................................................................................... 300 mA
Maximum current into VDD pin......................................................................................... 250 mA
Input clamp current, IIK (VI < 0 or VI > VDD).................................................................... ± 20 mA
Output clamp current, IOK (VO < 0 or VO > VDD)............................................................. ± 20 mA
Maximum output current sunk by any I/O pin..................................................................... 25 mA
Maximum output current sourced by any I/O pin ............................................................... 25 mA
Maximum current sunk by PORTA, PORTB, and PORTE (combined)............................. 200 mA
Maximum current sourced by PORTA, PORTB, and PORTE (combined) ....................... 200 mA
Maximum current sunk by PORTC and PORTD (combined)........................................... 200 mA
Maximum current sourced by PORTC and PORTD (combined)...................................... 200 mA
Maximum current sourced by PORTC and PORTD (combined)...................................... 200 mA
Maximum current sourced by PORTF and PORTG (combined)...................................... 100 mA
Maximum current sourced by PORTF and PORTG (combined)...................................... 100 mA
Note 1: Power dissipation is calculated as follows:
Pdis = VDD x {IDD - IOH} + {(VDD - VOH) x IOH} + (VOl x IOL)
Note 2: Voltage spikes below VSS at the MCLR pin, inducing currents greater than 80 mA,
may cause latch-up. Thus, a series resistor of 50-100 should be used when apply-
ing a “low” level to the MCLR pin rather than pulling this pin directly to VSS.
NOTICE: Stresses abov e those listed under “Absolute Maximum Ratings” may cause perma-
nent damage to the de vice. This is a stress r ating only and functional operation of the de vice at
those or any other conditions above those indicated in the operation listings of this specifica-
tion is not implied. Exposure to maximum rating conditions for extended periods may affect
device reliability.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-4 1997 Microchip Technology Inc.
30.3 Device Selection Table
This table in the De vice Data Sheet is intended to assist y ou in determining which oscillators are
tested for which devices, and some of the specifications that are tested. Any oscillator may be
selected at time of programming, but only the specified oscillator is tested by Microchip.
Since the RC and XT oscillators are only rated to 4 MHz, the y are only tested on the -04 (4 MHz)
de vices.
PICmicros rated for 10 MHz or 20 MHz are only tested in HS mode. In Table 30-2 the IPD is
gra y ed out f or the HS mode since there is not an IPD test point within the voltage r ange of the HS
oscillator. The value shown is a typical value from characterization.
Battery applications usually require an extended voltage range. Devices marked LC have an
extended voltage range and have the RC, XT, and LP oscillators tested.
Windowed devices are superset devices and have had the oscillators tested to all the specifica-
tion ranges of the -04, -20, and LC devices. The temperature range that the device is tested to
should be considered commercial, though at a later time they may be tested to industrial or
extended temperature levels.
Table 30-2: Example Cross Reference of Device Specifications for Oscillator
Configurations and Frequencies of Operation (Commercial Devices)
OSC PIC16CXXX-04 PIC16CXXX-10 PIC16CXXX-20 PIC16LCXXX-04 Windowed Devices
RC
VDD: 4.0V to 6.0V
IDD: 5 mA max. at 5.5V
IPD: 16 µA max. at 4V
Freq: 4 MHz max.
VDD: 4.5V to 5.5V
IDD: 2.7 mA typ. at 5.5V
IPD: 1.5 µA typ. at 4V
Freq: 4 MHz max.
VDD: 4.5V to 5.5V
IDD: 2.7 mA typ. at 5.5V
IPD: 1.5 µA typ. at 4V
Freq: 4 MHz max.
VDD: 2.5V to 6.0V
IDD: 3.8 mA max. at 3.0V
IPD: 5 µA max. at 3V
Freq: 4 MHz max.
VDD: 2.5V to 6.0V
IDD: 3.8 mA max. at 5.5V
IPD: 16 µA max. at 4V
Freq: 4 MHz max.
XT
VDD: 4.0V to 6.0V
IDD: 5 mA max. at 5.5V
IPD: 16 µA max. at 4V
Freq: 4 MHz max.
VDD: 4.5V to 5.5V
IDD: 2.7 mA typ. at 5.5V
IPD: 1.5 µA typ. at 4V
Freq: 4 MHz max.
VDD: 4.5V to 5.5V
IDD: 2.7 mA typ. at 5.5V
IPD: 1.5 µA typ. at 4V
Freq: 4 MHz max.
VDD: 2.5V to 6.0V
IDD: 3.8 mA max. at 3.0V
IPD: 5 µA max. at 3V
Freq: 4 MHz max.
VDD: 2.5V to 6.0V
IDD: 3.8 mA max. at 5.5V
IPD: 16 µA max. at 4V
Freq: 4 MHz max.
HS
VDD: 4.5V to 5.5V VDD: 4.5V to 5.5V VDD: 4.5V to 5.5V
Not recommended for
use in HS mode
VDD: 4.5V to 5.5V
IDD: 13.5 mA typ. at 5.5V IDD: 10 mA max. at 5.5V IDD: 20 mA max. at 5.5V IDD: 20 mA max. at 5.5V
IPD: 1.5 µA typ. at 4.5V IPD: 1.5 µA typ. at 4.5V IPD: 1.5 µA typ. at 4.5V IPD: 1.5 µA typ. at 4.5V
Freq: 4 MHz max. Freq: 10 MHz max. Freq: 20 MHz max. Freq: 20 MHz max.
LP
VDD: 4.0V to 6.0V
IDD: 52.5 µA typ. at
32 kHz, 4.0V
IPD: 0.9 µA typ. at 4.0V
Freq: 200 kHz max.
Not recommended for
use in LP mode Not recommended for
use in LP mode
VDD: 2.5V to 6.0V
IDD: 48 µA max. at
32 kHz, 3.0V
IPD: 5.0 µA max. at 3.0V
Freq: 200 kHz max.
VDD: 2.5V to 6.0V
IDD: 48 µA max. at
32 kHz, 3.0V
IPD: 5.0 µA max. at 3.0V
Freq: 200 kHz max.
The shaded sections indicate oscillator selections which are tested for functionality, but not for MIN/MAX specifications.
It is recommended that the user select the device type that ensures the specifications required.
Note: De vices that are marked with Engineering Sample (ENG SMP) are tested to the cur-
rent engineering test program at time of the de vice testing. There is no implied war-
ranty that these devices have been tested to any or all specifications in the Device
Data Sheet.
1997 Microchip Technology Inc. DS31030A-page 30-5
Section 30. Electrical Specifications
Electrical
Specifications
30
30.4 Device Voltage Specifications
These specifications relate to the device VDD and the device power-up and function.
Supply Voltage is the voltage level that must be applied to the device for the proper functional
operation.
Ram Data Retention Voltage is the level that the device voltage may be at and still retain the
data value.
VDD Start Voltage to ensure the internal Power-on Reset signal, is the le v el that VDD m ust start
from to ensure that the POR circuitry will operate properly.
VDD Rise Rate to ensure internal Power-on Reset signal, is the minimum slope that VDD must
rise at to cause the POR circuitry to trip.
Bro wn-out Reset Voltage is the voltage range where the brown-out circuitry may trip . When the
BOR circuitry trips, the device will either be in brown-out reset, or just came out of brown-out
reset.
Table 30-3: Example DC Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial and
-40˚C TA +85˚C for industrial
-40˚C TA +125˚C for extended
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
VDD Supply V oltage
D001 PIC16CXXX 4.0 6.0 V XT, RC and LP osc mode
PIC16LCXXX 2.5 6.0 V
D001A PIC16CXXX 4.5 5.5 V HS osc mode
D002 VDR RAM Data Retention
Voltage(1) 1.5 V
D003 VPOR VDD Start Voltage to
ensure internal
Power-on Reset signal
—VSS V See section on Power-on Reset for details
D004 SVDD VDD Rise Rate to
ensure internal
Power-on Reset signal
0.05 V/ms See section on Power-on Reset for details
VBOR Brown-out Reset
Voltage
D005 3.7 4.0 4.3 V BODEN bit in Configuration Word enabled
D005A 3.7 4.0 4.4 V Extended Temperature Range Devices Only
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note 1: This is the limit to which VDD can be lowered in SLEEP mode without losing RAM data.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-6 1997 Microchip Technology Inc.
30.5 Device Current Specifications
IDD is the current (I) that the de vice consumes when the de vice is in oper ating mode . This test is
taken with all I/O as inputs , either pulled high or lo w. That is, there are no floating inputs, nor are
any pins driving an output (with a load).
IPD is the current (I) that the device consumes when the device is in sleep mode (power-down),
ref erred to as pow er-down current. These tests are tak en with all I/O as inputs , either pulled high
or low. That is , there are no floating inputs , nor are an y pins driving an output (with a load), weak
pull-ups are disabled.
A device may have cer tain features and modules that can operate while the device is in sleep
mode. Some on these modules are:
W atchdog Timer (WDT)
Brown-out Reset (BOR) circuitry
Timer1
Analog to Digital converter
LCD module
Comparators
Voltage Reference
When all f eatures are disabled, the de vice will consume the lo west possib le current (the leakage
current). If any of these features are operating while the device is in sleep, a higher current will
occur. The difference between the lowest power mode (everything off) at only that one feature
enabled (such as the WDT) is what we call the Module Differential Current. If more then one
f eature is enabled then the expected current can easily be calculated as: the base current (e very-
thing disabled and in sleep mode) plus all Module Differential Currents (delta currents).
Example 30-1 shows an example of calculating the typical currents for a device at 5V, with the
WDT and Timer1 oscillator enabled.
Example 30-1: IPD Calculations with WDT and Timer1 Oscillator Enabled (@ 5V)
Base Current 14 nA ; Device leakage current
WDT Delta Current 14 µA ; 14 µA - 14 nA = 14 µA
Timer1 Delta Current 22 µA ; 22 µA - 14 nA = 22 µA
Total Sleep Current 36 µA ;
1997 Microchip Technology Inc. DS31030A-page 30-7
Section 30. Electrical Specifications
Electrical
Specifications
30
Table 30-4: Example DC Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial and
-40˚C TA +85˚C for industrial
-40˚C TA +125˚C for extended
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
D010
D010A
D010C
D013
IDD Supply Current(2,4,5)
2.7
2.0
22.5
7.7
13.5
5
3.8
48
5
30
mA
mA
µA
mA
mA
XT, RC osc configuration (PIC16CXXX-04)
FOSC = 4 MHz, VDD = 5.5V
FOSC = 4 MHz, VDD = 3.0V
LP osc configuration
FOSC = 32 kHz,
VDD = 3.0V, WDT disabled
INTRC osc configuration,
Fosc = 4 MHz, VDD = 5.5V
HS osc configuration (PIC16CXXX-20)
Fosc = 20 MHz, VDD = 5.5V
D020
D021
D021A
D021B
IPD Power-down Current(3,5)
10.5
7.5
1.5
0.9
1.5
0.9
1.5
42
30
21
13.5
24
18
µA
µA
µA
µA
µA
µA
µA
VDD = 4.0V, WDT enabled, -40°C to +85°C
VDD = 3.0V, WDT enabled, -40°C to +85°C
VDD = 4.0V, WDT disabled, -0°C to +70°C
VDD = 3.0V, WDT disabled, 0°C to +70°C
VDD = 4.0V, WDT disabled, -40°C to +85°C
VDD = 3.0V, WDT disabled, -40°C to +85°C
VDD = 4.0V, WDT disabled, -40°C to +125°C
* These parameters are characterized but not tested.
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only
and are not tested.
Note 1: Not Applicable.
2: The supply current is mainly a function of the operating voltage and frequency. Other factors such as I/O pin
loading and switching rate, oscillator type, internal code execution pattern, and temperature also have an
impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail to rail; all I/O pins tristated, pulled to VDD
MCLR = VDD; WDT enabled/disabled as specified.
3: The power-down current in SLEEP mode does not depend on the oscillator type . Power-down current is mea-
sured with the part in SLEEP mode, with all I/O pins in hi-impedance state and tied to VDD and VSS.
4: For RC osc configuration, current through Rext is not included. The current through the resistor can be esti-
mated by the formula Ir = VDD/2Rext (mA) with Rext in kOhm.
5: Timer1 oscillator (when enabled) adds approximately 20 µA to the specification. This value is from character-
ization and is for design guidance only. This is not tested.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-8 1997 Microchip Technology Inc.
Table 30-5: Example DC Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
Module Differential Current (5)
D022 IWDT W atchdog Timer
6.0
20
25 µA
µAVDD = 4.0V
-40°C to +125°C
D022A IBOR Brown-out Reset 350 425 µA BODEN bit is clear, VDD =
5.0V
D023 ICOMP Comparator (per Comparator) 85 100 µAVDD = 4.0V
D023A IVREF Voltage Reference 94 300 µAVDD = 4.0V
D024 ILCDRC LCD internal RC osc enabled 6.0 20 µAVDD = 3.0V
D024A ILCDVG LCD voltage generation TBD TBD µAVDD = 3.0V
D025 IT1OSC Timer1 oscillator 3.1 6.5 µAVDD = 3.0V
D026 IAD A/D Converter 1.0 µA A/D on, not converting
D027 ISAD Slope A/D (Total) 165 * 250 * µA REFOFF = 0
D027A ISADVR Slope A/D
Bandgap Voltage Reference 20 * 30 * µA REFOFF = 0
D027B ISADCDAC Slope A/D
Programmable Current Source 50 * 70 * µA ADCON1<7:4> = 1111b
D027C ISADSREF Slope A/D
Ref erence V oltage Divider 55 * 85 * µA ADOFF = 0
D027D ISADCMP Slope A/D
Comparator 40 * 65 * µA ADOFF = 0
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only
and are not tested.
1997 Microchip Technology Inc. DS31030A-page 30-9
Section 30. Electrical Specifications
Electrical
Specifications
30
30.6 Input Threshold Levels
The Input Low Voltage (VIL) is the voltage level that will be read as a logic ’0’. An input may not
read a ’0’ at a voltage level above this. All designs should be to the specification since device to
device (and to a much lesser extent pin to pin) variations will cause this level to vary.
The Input High Voltage (VIH) is the voltage level that will be read as a logic ’1’. An input may
read a ’1’ at a voltage level below this. All designs should be to the specification since device to
device (and to a much lesser extent pin to pin) variations will cause this level to vary.
The I/O pins with TTL levels are shown with tw o specifications. One is the industry standard TTL
specification, which is specified f or the v oltage range of 4.5V to 5.5V. The other is a specification
that operates over the entire voltage range of the device. The better of these two specifications
may be used in the design.
Table 30-6: Example DC Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec Table 30-3.
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
VIL Input Low Voltage
I/O ports:
D030 with TTL buff er VSS 0.15VDD V For entire VDD range (4)
D030A 0.8 V 4.5V VDD 5.5V (4)
D031 with Schmitt Trigger buffer VSS 0.2VDD V For entire VDD range
D032 MCLR, OSC1 (RC mode) VSS 0.2VDD V
D033 OSC1
(XT, HS and LP modes)(1) VSS 0.3VDD V
VIH Input High Voltage
I/O ports:
D040 with TTL buff er 0.25VDD
+ 0.8V —VDD V For entire VDD range (4)
D040A 2.0 VDD V 4.5V VDD 5.5V (4)
D041 with Schmitt Trigger buffer 0.8VDD —VDD V For entire VDD range
D042 MCLR 0.8VDD —VDD V
D042A OSC1
(XT, HS and LP modes)(1) 0.7VDD —VDD V
D043 OSC1 (RC mode) 0.9VDD —VDD V
D050 VHYS Hysteresis of Schmitt Trigger
Inputs TBD V
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only
and are not tested.
Note 1: In RC oscillator configuration, the OSC1/CLKIN pin is a Schmitt Trigger input. It is not recommended that the
PICmicro be driven with an external clock while in RC mode.
2: Not Applicable.
3: Not Applicable.
4: The better of the two specifications may be used. For VIL this would be the higher voltage and for VIH this
would be the lower voltage.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-10 1997 Microchip Technology Inc.
30.7 I/O Current Specifications
The PORT/GIO Weak Pull-up Current is the additional current that the device will draw when
the weak pull-ups are enabled.
Leakage Currents are the currents that the device consumes, since the devices are manufac-
tured in the real world and do not adhere to their ideal characteristics. Ideally there should be no
current on an input, but due to the real w orld there is always some parasitic path that consumes
negligible current.
Table 30-7: Example DC Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec Table 30-3.
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
IIL Input Leakage Current(2,3)
D060 I/O ports ±1µA Vss VPIN VDD,
Pin at hi-impedance
D060A CDAC ±1µA Vss VPIN VDD,
Pin at hi-impedance
D061 MCLR ——±5µA Vss VPIN VDD
D063 ——±5µA Vss VPIN VDD,
XT, HS and LP osc modes
IPU Weak Pull-up Current
D070 IPURB PORTB weak pull-up current 50 250 400 µAVDD = 5V, VPIN = VSS
D070A IPUGIO GIO weak pull-up current 50 250 400 µAVDD = 5V, VPIN = VSS
Programmable Current
Source (Slope A/D devices) CDAC pin = 0V
D160 Output Current 18.75 33.75 48.75 µA ADCON1<7:4> = 1111b
(full-scale)
D160A 1.25 2.25 3.25 µA ADCON1<7:4> = 0001b (1 LSB)
D160B -0.5 0 0.5 µA ADCON1<7:4> = 0000b
(zero-scale)
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only
and are not tested.
Note 1: In RC oscillator configuration, the OSC1/CLKIN pin is a Schmitt Trigger input. It is not recommended that the
PICmicro be driven with an external clock while in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified lev-
els represent normal operating conditions. Higher leakage current may be measured at different input volt-
ages.
3: Negative current is defined as current sourced by the pin.
1997 Microchip Technology Inc. DS31030A-page 30-11
Section 30. Electrical Specifications
Electrical
Specifications
30
30.8 Output Drive Levels
The Output Low Voltage (VOL) of an I/O pin depends on the external connections to that I/O. If
an I/O pin is shorted to V DD, no matter the drive capability of the I/O pin, a low level would not be
reached (and the de vice would consume excessive drive current). The VOL is the output voltage
that the I/O pin will drive, given the I/O does not need to sink more then the IOL current (at the
specified device voltage) as specified in the conditions portion of the specification.
The Output High Voltage (VOH) of an I/O pin depends on the external connections to that I/O. If
an I/O pin is shor ted to VSS, no matter the drive capability of the I/O pin, a high level would not
be reached (and the de vice would consume excessive drive current). The VOH is the output v olt-
age that the I/O pin will drive, given the I/O does not need to source more then the IOH current
(at the specified device voltage) as specified in the conditions portion of the specification.
Table 30-8: Example DC Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec Table 30-3.
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
VOL Output Low Voltage
D080 I/O ports 0.6 V IOL = 8.5 mA, VDD = 4.5V,
-40°C to +85°C
D080A 0.6 V IOL = 7.0 mA, VDD = 4.5V,
-40°C to +125°C
D083 OSC2/CLKOUT (RC mode) 0.6 V IOL = 1.6 mA, VDD = 4.5V,
-40°C to +85°C
D083A 0.6 V IOL = 1.2 mA, VDD = 4.5V,
-40°C to +125°C
VOH Output High Voltage(3)
D090 I/O ports VDD - 0.7 V IOH = -3.0 mA, VDD = 4.5V,
-40°C to +85°C
D090A VDD - 0.7 V IOH = -2.5 mA, VDD = 4.5V,
-40°C to +125°C
D092 OSC2/CLKOUT (RC mode) VDD - 0.7 V IOH = -1.3 mA, VDD = 4.5V,
-40°C to +85°C
D092A VDD - 0.7 V IOH = -1.0 mA, VDD = 4.5V,
-40°C to +125°C
D150 VOD Open-drain High Voltage 12 V RA4 pin
Programmable Current
Source
D170 VPCS Output Voltage Range Vss VDD 1.4 V CDAC pin
D171 SNPCS Output Voltage Sensitivity 0.1 0.01 %/V Vss VCDAC VDD 1.4
Bandgap Reference
D180 VBGR Output Voltage Range 1.14 1.19 1.24 V on AN0 pin when
AMUXOE =1 and
ADCS3:ADSC0 = 0100b
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only
and are not tested.
Note 1: In RC oscillator configuration, the OSC1/CLKIN pin is a Schmitt Trigger input. It is not recommended that the
PICmicro be driven with an external clock while in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified lev-
els represent normal operating conditions. Higher leakage current may be measured at different input volt-
ages.
3: Negative current is defined as current sourced by the pin.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-12 1997 Microchip Technology Inc.
30.9 I/O Capacitive Loading
These specifications indicate the conditions that the I/O pins hav e on them from the device tester .
These loadings effect the specifications for the timing specifications. If the loading in you appli-
cation are different, then you will need to determine how this will effect the character istic of the
de vice in your system. Capacitances less then these specifications should not have effects on a
system.
Table 30-9: Example DC Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec Table 30-3.
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
Capacitive Loading Specs
on Output Pins
D100 COSC2 OSC2 pin 15 pF In XT, HS and LP modes when
external clock is used to drive
OSC1.
D101 CIO All I/O pins and OSC2
(in RC mode) 50 pF To meet the Timing Specifications
of the Device
D102 CBSCL, SDA 400 pF In I2C mode
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only
and are not tested.
Note 1: In RC oscillator configuration, the OSC1/CLKIN pin is a Schmitt Trigger input. It is not recommended that
the PICmicro be driven with external clock in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified lev-
els represent normal operating conditions. Higher leakage current may be measured at different input volt-
ages.
3: Negative current is defined as current sourced by the pin.
1997 Microchip Technology Inc. DS31030A-page 30-13
Section 30. Electrical Specifications
Electrical
Specifications
30
30.10 Data EEPROM / Flash
Table 30-10: Example Data EEPROM / Flash Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec Table 30-3.
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
Data EEPROM Memory
D120 EDEndurance 1M 10M E/W 25°C at 5V
D121 VDRW VDD for read/write VMIN 6.0 V VMIN = Minimum operating
voltage
D122 TDEW Erase/Write cycle time ——10 ms
Program Flash Memory
D130 EPEndurance 100 1000 E/W
D131 VPR VDD for read VMIN 6.0 V VMIN = Minimum operating
voltage
D132 VPEW VDD for erase/write 4.5 5.5 V
D133 TPEW Erase/Write cycle time ——10
ms
Data in “Typ” column is at 5.0V, 25°C unless otherwise stated. These parameters are for design guidance only
and are not tested.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-14 1997 Microchip Technology Inc.
30.11 LCD
Table 30-11: Example LCD Module Electrical Characteristics
Table 30-12: Example VLCD Charge Pump Electrical Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec Table 30-3.
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
D200 VLCD3 LCD Voltage on pin
VLCD3VDD - 0.3 Vss + 7.0 V
D201 VLCD2 LCD Voltage on pin
VLCD2——V
LCD3V
D202 VLCD1 LCD Voltage on pin
VLCD1——V
DD V
D210 RCOM Com Output Source
Impedance ——1kCOM outputs
D211 RSEG Seg Output Source
Impedance 10k SEG outputs
D220 VOH Output High Voltage Max (VLCDN)
- 0.1 Max (VLCDN) V COM outputs IOH = 25 µA
SEG outputs IOH = 3 µA
D221 VOL Output Low Voltage Min (VLCDN) — Min (VLCDN)
+ 0.1 V COM outputs IOL = 25 µA
SEG outputs IOL = 3 µA
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only
and are not tested.
Note 1: 0 ohm source impedance at VLCD.
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec
Table 30-3.
Param
No. Symbol Characteristic Min Typ Max Units Conditions
D250 IVADJ VLCDADJ Regulated Current Output 10 µA
D251 Ivr VLCDADJ Current Consumption 20 µA
D252 IVADJ
VDD VLCDADJ Current VDD Rejection 0.1/1 µA/V
D253 IVADJ
T VLCDADJ Current V ariation With Tem-
perature 0.1/70 µA/˚C
D260(1) RVADJ VLCDADJ External Resistor 100 230 k
D265 VVADJ VLCD ADJ V oltage Limits 1.0 2.3 V
D271(1) CECPC External Charge Pump Capacitance 0.5 µF
Note 1: For design guidance only.
1997 Microchip Technology Inc. DS31030A-page 30-15
Section 30. Electrical Specifications
Electrical
Specifications
30
30.12 Comparators and Voltage Reference
Table 30-13: Example Comparator Characteristics
Table 30-14: Example Voltage Reference Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec Table 30-3.
Param
No. Symbol Characteristics Min Typ Max Units Comments
D300 VIOFF Input offset voltage ± 5.0 ± 10 mV
D301 VICM Input common mode voltage 0 VDD - 1.5 V
D302 CMRR Common Mode Rejection Ratio 35 70 db
300 TRESP Response Time(1) PIC16CXXX 150 400 ns
300A PIC16LCXXX 210 600 ns
301 TMC2OV Comparator Mode Change to Output
Valid —— 10 µs
Note 1: Response time measured with one comparator input at (VDD - 1.5)/2 while the other input transitions from
VSS to VDD.
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec Table 30-3.
Param
No. Symbol Characteristics Min Typ Max Units Comments
D310 VRES Resolution VDD/32 VDD/24 V
D311 VRAA Absolute Accuracy
1/4
1/2 LSb
LSb Low Range (VRR = 1)
High Range (VRR = 0)
D312 VRUR Unit Resistor Value (R) 2k
310 TSET Settling Time(1) —— 10 µs
Note 1: Settling time measured while VRR = 1 and VR3:VR0 transitions from 0000 to 1111.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-16 1997 Microchip Technology Inc.
30.13 Timing Parameter Symbology
The timing parameter symbols have been created with one of the following formats:
Figure 30-1: Example Load Conditions
1. TppS2ppS 3. TCC:ST (I2C specifications only)
2. TppS 4. Ts (I2C specifications only)
T
F Frequency T Time
Lowercase letters (pp) and their meanings:
pp
cc CCP1 osc OSC1
ck CLKOUT rd RD
cs CS rw RD or WR
di SDI sc SCK
do SDO ss SS
dt Data in t0 T0CKI
io I/O port t1 T1CKI
mc MCLR wr WR
Uppercase letters and their meanings:
S
F Fall P Period
H High R Rise
I Invalid (Hi-impedance) V Valid
L Low Z Hi-impedance
I2C only
AA output access High High
BUF Bus free Low Low
TCC:ST (I2C specifications only)
CC
HD Hold SU Setup
ST
DAT DATA input hold STO STOP condition
STA START condition
VDD/2
CL
RL
Pin Pin
VSS VSS
CL
RL= 464
CL= 50 pF for all pins except OSC2
15 pF for OSC2 output
Load condition 1 Load condition 2
1997 Microchip Technology Inc. DS31030A-page 30-17
Section 30. Electrical Specifications
Electrical
Specifications
30
30.14 Example External Clock Timing Waveforms and Requirements
Figure 30-2: Example External Clock Timing Waveforms
Table 30-15: Example External Clock Timing Requirements
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
1A Fosc External CLKIN
Frequency(1) DC 4 MHz XT and RC osc PIC16CXXX-04
PIC16LCXXX-04
DC 10 MHz HS osc PIC16CXXX-10
DC 20 MHz PIC16CXXX-20
DC 200 kHz LP osc PIC16LCXXX-04
Oscillator Frequency(1) DC 4 MHz RC osc PIC16CXXX-04
PIC16LCXXX-04
0.1 4 MHz XT osc PIC16CXXX-04
PIC16LCXXX-04
4 10 MHz HS osc PIC16CXXX-10
4 20 MHz PIC16CXXX-20
5 200 kHz LP osc mode PIC16LCXXX-04
1Tosc External CLKIN Period(1) 250 ns XT and RC osc PIC16CXXX-04
PIC16LCXXX-04
100 ns HS osc PIC16CXXX-10
50 ns PIC16CXXX-20
5— µs LP osc PIC16LCXXX-04
Oscillator Period(1) 250 ns RC osc PIC16CXXX-04
PIC16LCXXX-04
250 10,000 ns XT osc PIC16CXXX-04
PIC16LCXXX-04
100
50
250
250 ns
ns HS osc PIC16CXXX-10
PIC16CXXX-20
5— µs LP osc PIC16LCXXX-04
2TCY Instruction Cycle Time(1) 200 DC ns TCY = 4/FOSC
3TosL,
TosH External Clock in (OSC1)
High or Low Time 50 — ns XT osc PIC16CXXX-04
60 ns XT osc PIC16LCXXX-04
2.5 µs LP osc PIC16LCXXX-04
15 ns HS osc PIC16CXXX-20
4TosR,
TosF External Clock in (OSC1)
Rise or Fall Time — — 25 ns XT osc PIC16CXXX-04
— — 50 ns LP osc PIC16LCXXX-04
15 ns HS osc PIC16CXXX-20
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only
and are not tested.
Note 1: Instruction cycle period (TCY) equals f our times the input oscillator time-base period. All specified values are
based on characterization data for that particular oscillator type under standard operating conditions with
the device executing code. Exceeding these specified limits may result in an unstable oscillator operation
and/or higher than expected current consumption. All devices are tested to operate at "min." values with an
external clock applied to the OSC1/CLKIN pin.
When an external clock input is used, the "Max." cycle time limit is "DC" (no clock) for all devices.
OSC1
CLKOUT
Q4 Q1 Q2 Q3 Q4 Q1
1
23344
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-18 1997 Microchip Technology Inc.
Figure 30-3: Example CLKOUT and I/O Timing Waveforms
Table 30-16: Example CLKOUT and I/O Timing Requirements
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
10 TosH2ckL OSC1 to CLKOUT 75 200 ns (1)
11 TosH2ckH OSC1 to CLKOUT 75 200 ns (1)
12 TckR CLKOUT rise time 35 100 ns (1)
13 TckF CLKOUT fall time 35 100 ns (1)
14 TckL2ioV CLKOUT to Port out valid 0.5TCY +
20 ns (1)
15 TioV2ckH Port in valid before CLKOUT 0.25TCY + 25 ns (1)
16 TckH2ioI Port in hold after CLKOUT 0—ns
(1)
17 TosH2ioV OSC1 (Q1 cycle) to Port out valid 50 150 ns
18 TosH2ioI OSC1 (Q2 cycle) to
Port input invalid
(I/O in hold time)
PIC16CXXX 100 ns
18A PIC16LCXXX 200 ns
19 TioV2osH Port input valid to OSC1
(I/O in setup time) 0—ns
20 TioR Port output rise time PIC16CXXX 10 25 ns
20A PIC16LCXXX 60 ns
21 TioF Port output fall time PIC16CXXX 10 25 ns
21A PIC16LCXXX 60 ns
22†† Tinp INT pin high or low time TCY ——ns
23†† Trbp RB7:RB4 change INT high or low time TCY ——ns
24†† Trcp RC7:RC4 change INT high or low time 20 ns
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance
only and are not tested.
††These parameters are asynchronous events not related to any internal clock edges.
Note 1: Measurements are taken in RC Mode where CLKOUT output is 4 x TOSC.
Note: Refer to Figure 30-1 for load conditions.
OSC1
CLKOUT
I/O Pin
(input)
I/O Pin
(output)
Q4 Q1 Q2 Q3
10
13 14
17
20, 21
19 18
15
11
12 16
old value new value
1997 Microchip Technology Inc. DS31030A-page 30-19
Section 30. Electrical Specifications
Electrical
Specifications
30
30.15 Example Power-up and Reset Timing Waveforms and Requirements
Figure 30-4: Example Reset, W atchdog Timer , Oscillator Start-up Timer and Po wer-up
Timer Timing Waveforms
Figure 30-5: Brown-out Reset Timing
Table 30-17: Example Reset, Watchdog Timer, Oscillator Start-up Timer, Brown-out
Reset, and Power-up Timer Requirements
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
30 TmcL MCLR Pulse Width (low) 2 µsVDD = 5V, -40˚C to +125˚C
31 Twdt Watchdog Timer Time-out
Period (No Prescaler) 71833msVDD = 5V, -40˚C to +125˚C
32 Tost Oscillation Start-up Timer
Period 1024TOSC ——TOSC = OSC1 period
33 Tpwrt Power up Timer Period 28 72 132 ms VDD = 5V, -40˚C to +125˚C
34 TIOZ I/O Hi-impedance from MCLR
Low or Watchdog Timer Reset 2.1 µs
35 TBOR Brown-out Reset Pulse Width 100 µsVDD BVDD (See D005)
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only and are not
tested.
VDD
MCLR
Internal
POR
PWRT
Time-out
OSC
Time-out
Internal
RESET
Watchdog
Timer
RESET
33
32
30
31
34
I/O Pins
34
Note: Refer to Figure 30-1 for load conditions.
VDD BVDD
35
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-20 1997 Microchip Technology Inc.
30.16 Example Timer0 and Timer1 Timing Waveforms and Requirements
Figure 30-6: Example Timer0 and Timer1 External Clock Timings Waveforms
Table 30-18: Example Timer0 and Timer1 External Clock Requirements
Param
No. Symbol Characteristic Min Typ
Max Units Conditions
40 Tt0H T0CKI High Pulse Width No Prescaler 0.5TCY + 20 ns
With Prescaler 10 ns
41 Tt0L T0CKI Low Pulse Width No Prescaler 0.5TCY + 20 ns
With Prescaler 10 ns
42 Tt0P T0CKI Period GREATER OF:
20 µS OR TCY +
40
N
—— ns
N = prescale
value
(1, 2, 4,..., 256)
45 Tt1H T1CKI
High
Time
Synchronous, no prescaler 0.5TCY + 20 ns
Synchronous,
with prescaler PIC16CXXX 15 ns
PIC16LCXXX 25 ns
Asynchronous PIC16CXXX 30 ns
PIC16LCXXX 50 ns
46 Tt1L T1CKI
Low Time Synchronous, no prescaler 0.5TCY + 20 ns
Synchronous,
with prescaler PIC16CXXX 15 ns
PIC16LCXXX 25 ns
Asynchronous PIC16CXXX 2TCY —— ns
PIC16LCXXX
47 Tt1P T1CKI
input
period
Synchronous GREATER OF:
20 µS OR TCY +
40
N
—— ns
N = prescale
value
(1, 2, 4, 8)
Asynchronous Greater of:
20µS or 4TCY —— ns
Ft1 Timer1 oscillator input frequency range
(oscillator enabled by setting the T1OSCEN bit) DC 200 kHz
48 Tcke2tmr
IDelay from external clock edge to timer
increment 2Tosc 7Tosc
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note: Refer to Figure 30-1 for load conditions.
46
47
45
48
41
42
40
T0CKI
T1OSO/T1CKI
TMR0 or
TMR1
1997 Microchip Technology Inc. DS31030A-page 30-21
Section 30. Electrical Specifications
Electrical
Specifications
30
30.17 Example CCP Timing Waveforms and Requirements
Figure 30-7: Example Capture/Compare/PWM Timings Waveforms
Table 30-19: Example Capture/Compare/PWM Requirements
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
50 TccL CCPx input
low time No Prescaler 0.5TCY + 20 ns
With
Prescaler PIC16CXXX 10 ns
PIC16LCXXX 20 ns
51 TccH CCPx input
high time No Prescaler 0.5TCY + 20 ns
With
Prescaler PIC16CXXX 10 ns
PIC16LCXXX 20 ns
52 TccP CCPx input period 3TCY + 40
N ns N = prescale
value (1,4 or 16)
53 TccR CCPx output fall time PIC16CXXX 10 25 ns
PIC16LCXXX 25 45 ns
54 TccF CCPx output fall time PIC16CXXX 10 25 ns
PIC16LCXXX 25 45 ns
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note: Refer to Figure 30-1 for load conditions.
(Capture Mode)
50 51
52
53 54
CCPx
CCPx
(Compare or PWM Mode)
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-22 1997 Microchip Technology Inc.
30.18 Example Parallel Slave Port (PSP) Timing Waveforms and Requirements
Figure 30-8: Example Parallel Slave Port Timing Waveforms
Table 30-20: Example Parallel Slave Port Requirements
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
62 TdtV2wrH Data in valid before WR or CS
(setup time) 20 ns
63 TwrH2dtI WR or CS to data–in invalid
(hold time) PIC16CXXX 20 ns
PIC16LCXXX 35 ns
64 TrdL2dtV RD and CS to data–out valid 80 ns
65 TrdH2dtI RD or CS to data–out invalid 10 30 ns
66 TibfINH Inhibit of the IBF flag bit being cleared from
WR or CS 3Tcy§
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only and are not
tested.
§This specification ensured by design.
Note: Refer to Figure 30-1 for load conditions.
RE2/CS
RE0/RD
RE1/WR
RD7:RD0
62
63
64
65
1997 Microchip Technology Inc. DS31030A-page 30-23
Section 30. Electrical Specifications
Electrical
Specifications
30
30.19 Example SSP and Master SSP SPI Mode Timing Waveforms and Requirements
Figure 30-9: Example SPI Master Mode Timing (CKE = 0)
Table 30-21: Example SPI Mode Requirements (Master Mode, CKE = 0)
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
70 TssL2scH,
TssL2scL SS to SCK or SCK input TCY ——ns
71 TscH SCK input high time
(slave mode) Continuous 1.25TCY + 30 ns
71A Single Byte 40 ns Note 1
72 TscL SCK input low time
(slave mode) Continuous 1.25TCY + 30 ns
72A Single Byte 40 ns Note 1
73 TdiV2scH,
TdiV2scL Setup time of SDI data input to SCK edge 100 ns
73A TB2BLast clock edge of Byte1 to the 1st clock
edge of Byte2 1.5TCY + 40 ns Note 1
74 TscH2diL,
TscL2diL Hold time of SDI data input to SCK edge 100 ns
75 TdoR SDO data output rise time PIC16CXXX 10 25 ns
PIC16LCXXX 20 45 ns
76 TdoF SDO data output fall time 10 25 ns
78 TscR SCK output rise time
(master mode) PIC16CXXX 10 25 ns
PIC16LCXXX 20 45 ns
79 TscF SCK output fall time (master mode) 10 25 ns
80 TscH2doV,
TscL2doV SDO data output valid
after SCK edge PIC16CXXX 50 ns
PIC16LCXXX 100 ns
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note 1: Specification 73A is only required if specifications 71A and 72A are used.
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
70
71 72
73 74
75, 76
78
79
80
79
78
MSb LSb
BIT6 - - - - - -1
MSb IN LSb IN
BIT6 - - - -1
Refer to Figure 30-1 for load conditions.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-24 1997 Microchip Technology Inc.
Figure 30-10: Example SPI Master Mode Timing (CKE = 1)
Table 30-22: Example SPI Mode Requirements (Master Mode, CKE = 1)
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
71 TscH SCK input high time
(slave mode) Continuous 1.25TCY + 30 ns
71A Single Byte 40 ns Note 1
72 TscL SCK input low time
(slave mode) Continuous 1.25TCY + 30 ns
72A Single Byte 40 ns Note 1
73 TdiV2scH,
TdiV2scL Setup time of SDI data input to SCK
edge 100 ns
73A TB2BLast clock edge of Byte1 to the 1st clock
edge of Byte2 1.5TCY + 40 ns Note 1
74 TscH2diL,
TscL2diL Hold time of SDI data input to SCK edge 100 ns
75 TdoR SDO data output rise
time PIC16CXXX 10 25 ns
PIC16LCXXX 20 45 ns
76 TdoF SDO data output fall time 10 25 ns
78 TscR SCK output rise time
(master mode) PIC16CXXX 10 25 ns
PIC16LCXXX 20 45 ns
79 TscF SCK output fall time (master mode) 10 25 ns
80 TscH2doV,
TscL2doV SDO data output valid
after SCK edge PIC16CXXX 50 ns
PIC16LCXXX 100 ns
81 TdoV2scH,
TdoV2scL SDO data output setup to SCK edge TCY ——ns
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note 1: Specification 73A is only required if specifications 71A and 72A are used.
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
81
71 72
74
75, 76
78
80
MSb
79
73
MSb IN
BIT6 - - - - - -1
LSb IN
BIT6 - - - -1
LSb
Refer to Figure 30-1 for load conditions.
1997 Microchip Technology Inc. DS31030A-page 30-25
Section 30. Electrical Specifications
Electrical
Specifications
30
Figure 30-11: Example SPI Slave Mode Timing (CKE = 0)
Table 30-23: Example SPI Mode Requirements (Slave Mode Timing (CKE = 0)
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
70 TssL2scH,
TssL2scL SS to SCK or SCK input TCY ——ns
71 TscH SCK input high time
(slave mode) Continuous 1.25TCY + 30 ns
71A Single Byte 40 ns Note 1
72 TscL SCK input low time
(slave mode) Continuous 1.25TCY + 30 ns
72A Single Byte 40 ns Note 1
73 TdiV2scH,
TdiV2scL Setup time of SDI data input to SCK edge 100 ns
73A TB2BLast clock edge of Byte1 to the 1st clock
edge of Byte2 1.5TCY + 40 ns Note 1
74 TscH2diL,
TscL2diL Hold time of SDI data input to SCK edge 100 ns
75 TdoR SDO data output rise time PIC16CXXX 10 25 ns
PIC16LCXXX 20 45 ns
76 TdoF SDO data output fall time 10 25 ns
77 TssH2doZ SS to SDO output hi-impedance 10 50 ns
78 TscR SCK output rise time
(master mode) PIC16CXXX 10 25 ns
PIC16LCXXX 20 45 ns
79 TscF SCK output fall time (master mode) 10 25 ns
80 TscH2doV,
TscL2doV SDO data output valid
after SCK edge PIC16CXXX 50 ns
PIC16LCXXX 100 ns
83 TscH2ssH,
TscL2ssH SS after SCK edge 1.5TCY + 40 ns
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note 1: Specification 73A is only required if specifications 71A and 72A are used.
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
70
71 72
73 74
75, 76 77
78
79
80
79
78
SDI
MSb LSb
BIT6 - - - - - -1
MSb IN BIT6 - - - -1 LSb IN
83
Refer to Figure 30-1 for load conditions.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-26 1997 Microchip Technology Inc.
Figure 30-12: Example SPI Slave Mode Timing (CKE = 1)
Table 30-24: Example SPI Slave Mode Mode Requirements (CKE = 1)
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
70 TssL2scH,
TssL2scL SS to SCK or SCK input TCY ——ns
71 TscH SCK input high time
(slave mode) Continuous 1.25TCY + 30 ns
71A Single Byte 40 ns Note 1
72 TscL SCK input low time
(slave mode) Continuous 1.25TCY + 30 ns
72A Single Byte 40 ns Note 1
73A TB2BLast clock edge of Byte1 to the 1st cloc k
edge of Byte2 1.5TCY + 40 ns Note 1
74 TscH2diL,
TscL2diL Hold time of SDI data input to SCK edge 100 ns
75 TdoR SDO data output rise
time PIC16CXXX 10 25 ns
PIC16LCXXX 20 45 ns
76 TdoF SDO data output fall time 10 25 ns
77 TssH2doZ SS to SDO output hi-impedance 10 50 ns
78 TscR SCK output rise time
(master mode) PIC16CXXX 10 25 ns
PIC16LCXXX 20 45 ns
79 TscF SCK output fall time (master mode) 10 25 ns
80 TscH2doV,
TscL2doV SDO data output valid
after SCK edge PIC16CXXX 50 ns
PIC16LCXXX 100 ns
82 TssL2doV SDO data output valid
after SS edge PIC16CXXX 50 ns
PIC16LCXXX 100 ns
83 TscH2ssH,
TscL2ssH SS after SCK edge 1.5TCY + 40 ns
Data in “Typ” column is at 5V, 25˚C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note 1: Specification 73A is only required if specifications 71A and 72A are used.
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
70
71 72
82
SDI
74
75, 76
MSb BIT6 - - - - - -1 LSb
77
MSb IN BIT6 - - - -1 LSb IN
80
83
Refer to Figure 30-1 for load conditions.
1997 Microchip Technology Inc. DS31030A-page 30-27
Section 30. Electrical Specifications
Electrical
Specifications
30
30.20 Example SSP I2C Mode Timing Waveforms and Requirements
Figure 30-13: Example SSP I2C Bus Start/Stop Bits Timing Waveforms
Table 30-25: Example SSP I2C Bus Start/Stop Bits Requirements
Param.
No. Symbol Characteristic Min Typ Max Units Conditions
90 TSU:STA START condition 100 kHz mode 4700 ns Only relevant for repeated
START condition
Setup time 400 kHz mode 600
91 THD:STA START condition 100 kHz mode 4000 ns After this period the first
clock pulse is generated
Hold time 400 kHz mode 600
92 TSU:STO STOP condition 100 kHz mode 4700 ns
Setup time 400 kHz mode 600
93 THD:STO STOP condition 100 kHz mode 4000 ns
Hold time 400 kHz mode 600
Note: Refer to Figure 30-1 for load conditions.
91 93
SCL
SDA
START
Condition STOP
Condition
90 92
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-28 1997 Microchip Technology Inc.
Figure 30-14: Example SSP I2C Bus Data Timing Waveforms
Note: Refer to Figure 30-1 for load conditions.
90
91 92
100
101
103
106 107
109 109 110
102
SCL
SDA
In
SDA
Out
1997 Microchip Technology Inc. DS31030A-page 30-29
Section 30. Electrical Specifications
Electrical
Specifications
30
Table 30-26: Example SSP I2C Bus Data Requirements
Param.
No. Symbol Characteristic Min Max Units Conditions
100 THIGH Clock high time 100 kHz mode 4.0 µs PIC16CXXX must operate
at a minimum of 1.5 MHz
400 kHz mode 0.6 µs PIC16CXXX must operate
at a minimum of 10 MHz
SSP Module 1.5TCY
101 TLOW Clock low time 100 kHz mode 4.7 µs PIC16CXXX must operate
at a minimum of 1.5 MHz
400 kHz mode 1.3 µs PIC16CXXX must operate
at a minimum of 10 MHz
SSP Module 1.5TCY
102 TRSDA and SCL rise
time 100 kHz mode 1000 ns
400 kHz mode 20 + 0.1Cb 300 ns Cb is specified to be from
10 to 400 pF
103 TFSDA and SCL fall
time 100 kHz mode 300 ns
400 kHz mode 20 + 0.1Cb 300 ns Cb is specified to be from
10 to 400 pF
90 TSU:STA START condition
setup time 100 kHz mode 4.7 µs Only relevant for repeated
START condition
400 kHz mode 0.6 µs
91 THD:STA START condition
hold time 100 kHz mode 4.0 µs After this period the first
clock pulse is generated
400 kHz mode 0.6 µs
106 THD:DAT Data input hold
time 100 kHz mode 0 ns
400 kHz mode 0 0.9 µs
107 TSU:DAT Data input setup
time 100 kHz mode 250 ns Note 2
400 kHz mode 100 ns
92 TSU:STO STOP condition
setup time 100 kHz mode 4.7 µs
400 kHz mode 0.6 µs
109 TAA Output valid from
clock 100 kHz mode 3500 ns Note 1
400 kHz mode ns
110 TBUF Bus free time 100 kHz mode 4.7 µs Time the bus must be free
before a new transmission
can start
400 kHz mode 1.3 µs
D102 Cb Bus capacitive loading 400 pF
Note 1: As a transmitter, the device must provide this internal minimum delay time to bridge the undefined region
(min. 300 ns) of the falling edge of SCL to avoid unintended generation of START or STOP conditions.
2: A fast-mode I2C-bus device can be used in a standard-mode I2C-bus system, but the requirement
tsu;DAT 250 ns must then be met. This will automatically be the case if the device does not stretch the
LO W period of the SCL signal. If such a de vice does stretch the LO W period of the SCL signal, it must output
the next data bit to the SDA line.
TR max. + tsu;DAT = 1000 + 250 = 1250 ns (according to the standard-mode I2C bus specification) before
the SCL line is released.
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-30 1997 Microchip Technology Inc.
30.21 Example Master SSP I2C Mode Timing Waveforms and Requirements
Figure 30-15: Example Master SSP I2C Bus Start/Stop Bits Timing Waveforms
Table 30-27: Example Master SSP I2C Bus Start/Stop Bits Requirements
Param.
No. Symbol Characteristic Min Typ Max Units Conditions
90 TSU:STA START
condition 100 kHz mode 2(TOSC)(BRG + 1) § ——
ns
Only relevant for repeated
START condition
Setup time 400 kHz mode 2(TOSC)(BRG + 1) § ——
1 MHz mode (1) 2(TOSC)(BRG + 1) § ——
91 THD:STA START
condition 100 kHz mode 2(TOSC)(BRG + 1) § ——
ns
After this period the first
clock pulse is generated
Hold time 400 kHz mode 2(TOSC)(BRG + 1) § ——
1 MHz mode (1) 2(TOSC)(BRG + 1) § ——
92 TSU:STO STOP condition 100 kHz mode 2(TOSC)(BRG + 1) § —— ns
Setup time 400 kHz mode 2(TOSC)(BRG + 1) § ——
1 MHz mode (1) 2(TOSC)(BRG + 1) § ——
93 THD:STO STOP condition 100 kHz mode 2(TOSC)(BRG + 1) § —— ns
Hold time 400 kHz mode 2(TOSC)(BRG + 1) § ——
1 MHz mode (1) 2(TOSC)(BRG + 1) § ——
§ This specification ensured by design. For the value required by the I2C specification, please refer to Figure A-11 of the
“Appendix.
Maximum pin capacitance = 10 pF for all I2C pins.
Note: Refer to Figure 30-1 for load conditions.
91 93
SCL
SDA
START
Condition STOP
Condition
90 92
1997 Microchip Technology Inc. DS31030A-page 30-31
Section 30. Electrical Specifications
Electrical
Specifications
30
Figure 30-16: Example Master SSP I2C Bus Data Timing
Table 30-28: Example Master SSP I2C Bus Data Requirements
Param.
No. Symbol Characteristic Min Max Units Conditions
100 THIGH Clock high time 100 kHz mode 2(TOSC)(BRG + 1) § —ms
400 kHz mode 2(TOSC)(BRG + 1) § —ms
1 MHz mode (1) 2(TOSC)(BRG + 1) § —ms
101 TLOW Clock low time 100 kHz mode 2(TOSC)(BRG + 1) § —ms
400 kHz mode 2(TOSC)(BRG + 1) § —ms
1 MHz mode (1) 2(TOSC)(BRG + 1) § —ms
102 TRSDA and SCL
rise time 100 kHz mode 1000 ns Cb is specified to be from
10 to 400 pF
400 kHz mode 20 + 0.1Cb 300 ns
1 MHz mode (1) 300 ns
103 TFSDA and SCL
fall time 100 kHz mode 300 ns Cb is specified to be from
10 to 400 pF
400 kHz mode 20 + 0.1Cb 300 ns
1 MHz mode (1) 100 ns
90 TSU:STA START condition
setup time 100 kHz mode 2(TOSC)(BRG + 1) § ms Only relevant f or repeated
START condition
400 kHz mode 2(TOSC)(BRG + 1) § —ms
1 MHz mode (1) 2(TOSC)(BRG + 1) § —ms
91 THD:STA START condition
hold time 100 kHz mode 2(TOSC)(BRG + 1) § ms After this period the first
clock pulse is generated
400 kHz mode 2(TOSC)(BRG + 1) § —ms
1 MHz mode (1) 2(TOSC)(BRG + 1) § —ms
106 THD:DAT Data input
hold time 100 kHz mode 0 —ns
400 kHz mode 0 0.9 ms
1 MHz mode (1) TBD —ns
107 TSU:DAT Data input
setup time 100 kHz mode 250 ns Note 2
400 kHz mode 100 —ns
1 MHz mode (1) TBD —ns
92 TSU:STO STOP condition
setup time 100 kHz mode 2(TOSC)(BRG + 1) § —ms
400 kHz mode 2(TOSC)(BRG + 1) § —ms
1 MHz mode (1) 2(TOSC)(BRG + 1) § —ms
109 TAA Output valid from
clock 100 kHz mode 3500 ns
400 kHz mode 1000 ns
1 MHz mode (1) —ns
110 TBUF Bus free time 100 kHz mode 4.7 ‡ ms Time the bus must be free
before a new transmis-
sion can start
400 kHz mode 1.3 ‡ —ms
1 MHz mode (1) TBD —ms
D102 ‡ Cb Bus capacitive loading 400 pF
§ This specification ensured by design. For the value required by the I2C specification, please refer to Figure A-11 of the
“Appendix.
These parameters are for design guidance only and are not tested, nor characterized.
Note 1: Maximum pin capacitance = 10 pF for all I2C pins.
2: A fast-mode I2C-bus device can be used in a standard-mode I2C-bus system, but parameter 107 250 ns
must then be met. This will automatically be the case if the device does not stretch the LOW period of the
SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit
to the SDA line. Parameter 102.+ parameter 107 = 1000 + 250 = 1250 ns (for 100 kHz-mode) before the
SCL line is released.
Note: Refer to Figure 30-1 for load conditions.
90 91 92
100 101
103
106 107
109 109 110
102
SCL
SDA
In
SDA
Out
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-32 1997 Microchip Technology Inc.
30.22 Example USART/SCI Timing Waveforms and Requirements
Figure 30-17: Example USART Synchronous Transmission (Master/Slave) Timing
Waveforms
Table 30-29: Example USART Synchronous Transmission Requirements
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
120 TckH2dtV SYNC XMIT (MASTER &
SLAVE)
Clock high to data out valid PIC16CXXX 80 ns
PIC16LCXXX 100 ns
121 Tckrf Clock out rise time and fall time
(Master Mode) PIC16CXXX 45 ns
PIC16LCXXX 50 ns
122 Tdtrf Data out rise time and fall time PIC16CXXX 45 ns
PIC16LCXXX 50 ns
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note: Refer to Figure 30-1 for load conditions.
121 121
122
TX/CK pin
RX/DT pin
120
1997 Microchip Technology Inc. DS31030A-page 30-33
Section 30. Electrical Specifications
Electrical
Specifications
30
Figure 30-18: Example USART Synchronous Receive (Master/Slave) Timing Waveforms
Table 30-2: Example USART Synchronous Receive Requirements
Param.
No. Symbol Characteristic Min Typ† Max Units Conditions
125 TdtV2ckl SYNC RCV (MASTER & SLAVE)
Data hold before CK (DT hold time) 15 ns
126 TckL2dtl Data hold after CK (DT hold time) 15 ns
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note: Refer to Figure 30-1 for load conditions.
125
126
TX/CK pin
RX/DT pin
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-34 1997 Microchip Technology Inc.
30.23 Example 8-bit A/D Timing Waveforms and Requirements
Table 30-30: Example 8-bit A/D Converter Characteristics
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
A01 NRResolution 8-bits bit VREF = VDD = 5.12V,
VSS VAIN VREF
A02 EABS Total Absolute error ——
< ± 1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A03 EIL Integral linearity error < ± 1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A04 EDL Differential linearity error < ± 1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A05 EFS Full scale error < ± 1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A06 EOFF Offset error < ± 1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A10 Monotonicity guaran-
teed ——VSS VAIN VREF
A20 VREF Reference voltage 3.0V VDD + 0.3 V
A25 VAIN Analog input voltage VSS - 0.3 VREF + 0.3 V
A30 ZAIN Recommended impedance
of
analog voltage source
10.0 k
A40 IAD A/D
conversion
current (VDD)
PIC16CXXX 180 µA Average current con-
sumption when A/D is
on(Note 1)
PIC16LCXXX 90 µA
A50 IREF VREF input current (Note 2) 10
1000
10
µA
µA
During VAIN acquisition.
Based on differential of
VHOLD to VAIN to charge
CHOLD
See the “8-bit A/D Con-
verter” section
During A/D Conversion
cycle
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note 1: When A/D is off, it will not consume any current other than minor leakage current.
The power-down current spec includes any such leakage from the A/D module.
VREF current is from RA3 pin or VDD pin, whichever is selected as reference input.
1997 Microchip Technology Inc. DS31030A-page 30-35
Section 30. Electrical Specifications
Electrical
Specifications
30
Figure 30-19: Example 8-bit A/D Conversion Timing Waveforms
Table 30-31: Example 8-bit A/D Conversion Requirements
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
130 TAD A/D clock period PIC16CXXX 1.6 µsTOSC based, VREF 3.0V
PIC16LCXXX 2.0 µsT
OSC based, VREF full range
PIC16CXXX 2.0 4.0 6.0 µs A/D RC Mode
PIC16LCXXX 3.0 6.0 9.0 µs A/D RC Mode
131 TCNV Conversion time
(not including S/H time) (Note 1) 11 11 TAD
132 TACQ Acquisition time Note 2
5
20
µs
µsThe minimum time is the amplifier
settling time. This may be used if
the “new” input voltage has not
changed by more than 1 LSb (i.e .,
20.0 mV @ 5.12V) from the last
sampled voltage (as stated on
CHOLD).
134 TGO Q4 to A/D clock start 2TOSC
§——
If the A/D clock source is selected
as RC, a time of TCY is added
before the A/D clock starts. This
allows the SLEEP instruction to be
executed.
136 TAMP Amplifier settling time (Note 2) 1 µsThis may be used if the “new”
input voltage has not changed by
more than 1LSb (i.e. 5 mV @
5.12V) from the last sampled volt-
age (as stated on CHOLD).
135 TSWC Switching Time from
conv ert sample 1 § 1 § TAD
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are not
tested.
§ This specification ensured by design.
Note 1: ADRES register may be read on the following TCY cycle.
See the “8-bit A/D Converter” section for minimum requirements.
131
130
132
BSF ADCON0, GO
Q4
A/D CLK
A/D DATA
ADRES
ADIF
GO
SAMPLE
OLD_DATA
SAMPLING STOPPED
DONE
NEW_DATA
(TOSC/2) (1)
7 6543210
Note 1: If the A/D clock source is selected as RC, a time of TCY is added before the A/D clock starts. This
allows the SLEEP instruction to be executed.
1 TCY
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-36 1997 Microchip Technology Inc.
30.24 Example 10-bit A/D Timing Waveforms and Requirements
Table 30-32: Example 10-bit A/D Converter Characteristics
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
A01 NRResolution 10 bit VREF = VDD = 5.12V,
VSS VAIN VREF
A02 EABS Absolute error <±1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A03 EIL Integral linearity error <±1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A04 EDL Differential linearity error <±1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A05 EFS Full scale error <±1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A06 EOFF Offset error <±1 LSb VREF = VDD = 5.12V,
VSS VAIN VREF
A10 Monotonicity guaran-
teed ——VSS VAIN VREF
A20 VREF Reference voltage
(VREFH - VREFL)0V V For no latch-up
A20A 3V V For 10-bit resolution
A21 VREFH Reference voltage High AVSS —AVDD +
0.3V V
A22 VREFL Reference voltage Low AVSS - 0.3V AVDD V
A25 VAIN Analog input voltage AVSS - 0.3V VREF + 0.3V V
A30 ZAIN Recommended impedance of
analog voltage source 10.0 k
A40 IAD A/D conversion
current (VDD)PIC16CXXX 180 µA Average current con-
sumption when
A/D is on. (Note 1)
PIC16LCXXX —90—µA
A50 IREF VREF input current (Note 2) 10
1000
10
µA
µA
During VAIN acquisition.
Based on differential of
VHOLD to VAIN. To charge
CHOLD see the “10-bit
A/D Converter” section.
During A/D conversion
cycle
Data in “Typ” column is at 5V, 25C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note 1: When A/D is off, it will not consume any current other than minor leakage current. The power-down current
spec includes any such leakage from the A/D module.
VREF current is from RG0 and RG1 pins or AVDD and AVSS pins, whichever is selected as reference input.
1997 Microchip Technology Inc. DS31030A-page 30-37
Section 30. Electrical Specifications
Electrical
Specifications
30
Figure 30-20: Example 10-bit A/D Conversion Timing Waveforms
Table 30-33: Example 10-bit A/D Conversion Requirements
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
130 TAD A/D clock period PIC16CXXX 1.6 µsTOSC based, VREF 3.0V
PIC16LCXXX 3.0 µsTOSC based, VREF full range
PIC16CXXX 2.0 4.0 6.0 µs A/D RC Mode
PIC16LCXXX 3.0 6.0 9.0 µs A/D RC Mode
131 TCNV Conversion time
(not including acquisition time)
(Note 1)
11 § 12 § TAD
132 TACQ Acquisition time (Note 3) 15
10
µs
µs-40°C Temp 125°C
0°C Temp 125°C
136 TAMP Amplifier settling time (Note 2) 1 µsThis may be used if the “new”
input voltage has not changed
by more than 1LSb (i.e . 5 mV @
5.12V) from the last sampled
voltage (as stated on CHOLD).
135 TSWC Switching Time from
conv ert sample Note 4
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are not
tested.
§ This specification ensured by design.
Note 1: ADRES register may be read on the following TCY cycle.
2: See the “10-bit A/D Converter” section f or minimum conditions when input v oltage has changed more than
1 LSb.
3: The time for the holding capacitor to acquire the “New” input voltage when the voltage changes full scale
after the conv ersion (AVDD to AVSS, or AVSS to AVDD). The source impedance (
R
S
) on the input channels is
50 .
4: On the next Q4 cycle of the device clock
131
130
132
BSF ADCON0, GO
Q4
A/D CLK
A/D DATA
ADRES
ADIF
GO
SAMPLE
OLD_DATA
SAMPLING STOPPED
DONE
NEW_DATA
Note 2
987 21 0
Note 1: If the A/D clock source is selected as RC, a time of TCY is added before the A/D clock starts.
This allows the SLEEP instruction to be executed.
2: This is a minimal RC delay (typically 100 nS), which also disconnects the holding capacitor from the
analog input.
. . . . . .
TCY
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-38 1997 Microchip Technology Inc.
30.25 Example Slope A/D Timing Waveforms and Requirements
Figure 30-21: Example Slope A/D Conversion Cycle
XX
CAPTURE
CLK
ADRST
ADCON0<1>
Capture
Register
CDAC
XX+8
COMPARE
ADCIF (must be cleared by software)
ADTMR INCREMENTS
XX+1 XX+2 XX+3
ADTMR
COUNT XX+8 XX+9XX
1997 Microchip Technology Inc. DS31030A-page 30-39
Section 30. Electrical Specifications
Electrical
Specifications
30
Table 30-34: Example Slope A/D Component Characteristics
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature 0˚C TA +70˚C for commercial,
-40˚C TA +85˚C for industrial and
-40˚C TA +125˚C for extended
Operating voltage VDD range as described in DC spec Table 30-3.
Param
No. Symbol Characteristic Min Typ Max Units Conditions
Slope A/D Comparator
A100 VAIN Analog Input Voltage
Range VSS —VDD 1.4 V
A101 Input Offset Voltage 10 2 10 mV Measured over common-mode
range
A102 GDV Diff erential V oltage Gain
(Note 1) 100 dB
A103 CMRR Common Mode Rejection
Ratio (Note 1) 80 dB VDD = 5V, TA = 25°C, over
common-mode range
A104 RRadc Power Supply Rejection
Ratio (Note 1) 70 dB TA = 25°C,
VDDmin VDD VDDmax
TSET Turn-on Settling Time
140 Band Gap Reference
(to < 0.1% (Note 1) 1 10 ms REFOFF bit in SLPCON
register 1 0
141 Programmable Current
Source (to < 0.1%) 1 10 ms Bias generator (reference) turn-on
time (REFOFF 1 0)
(reference start-up) (Note 1)
141A 1 10 µs REFOFF = 0 (constant),
ADCON1<7:4> 0000b 1111b
(reference already on and stable)
(Note 3)
TC Temperature
Coefficient (Note 1)
A110 TCBGR Band Gap Reference
+50
50
ppm/°C40°C TA +25°C
25°C TA +85°C
A110A
+20
20
ppm/°C0°C TA +25°C
25°C TA +70°C
A111 TCPCS Programmable Current
Source
+0.1
0.1
%/°C40°C TA +25°C
25°C TA +85°C
A112 TCkref Slope Reference Divider 20 ppm/°C40°C TA +85°C
CA Calibration Accuracy
(Note3, 5) All parameters calibrated at
VDD = 5V and TA = +25°C
A120 CABGR Band Gap Reference 0.01 %
A121 CASRV Slope Reference Divider 0.02 %
SN Supply Sensitivity
(Note 1)
A130 SNBGR Band Gap Reference 0.04 %/V From VDDmin to VDDmax
A131 SNPCS Programmable Current
Source 0.2 %/V From VDDmin to VDDmax
A132 SNkref Slope Reference Divider %/V From VDDmin to VDDmax
Programmable Current
Source
A140 IRES Resolution 1.25 2.25 3.25 µA 1 LSb
A141 EIL Relative accuracy
(linearity error) 1/2 +1/2 LSb CDAC = 0V
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-40 1997 Microchip Technology Inc.
30.26 Example LCD Timing Waveforms and Requirements
Figure 30-22: Example LCD Voltage Waveform
Table 30-35: Example LCD Module Timing Requirements
Param
No. Symbol Characteristic Min Typ† Max Units Conditions
200 FLCDRC LCDRC Oscillator
Frequency 14 22 kHz VDD = 5V, -40˚C to +85˚C
201 TrLCD Output Rise Time 200 µs COM outputs Cload = 5,000 pF
SEG outputs Cload = 500 pF
VDD = 5.0V, T = 25°C
202 TfLCD Output Fall Time
(Note 1) TrLCD -
0.05TrLCD —TrLCD +
0.05TrLCD µs COM outputs Cload = 5,000 pF
SEG outputs Cload = 500 pF
VDD = 5.0V, T = 25°C
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are not
tested.
Note 1: 0 source impedance at VLCD.
VLCD3
VLCD2
VLCD1
VSS
201 202
1997 Microchip Technology Inc. DS31030A-page 30-41
Section 30. Electrical Specifications
Electrical
Specifications
30
30.27 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten for the Base-Line, or High-End families), but the concepts are per tinent, and could be used
(with modification and possible limitations). The current application notes related to the Electrical
Specifications are:
Title Application Note #
No related Application Notes
PICmicro MID-RANGE MCU FAMILY
DS31030A-page 30-42 1997 Microchip Technology Inc.
30.28 Revision History
Revision A
This is the initial released revision of the Electrical Specifications description.
1997 Microchip Technology Inc. DS31031A page 31-1
Device
Characteristics
31
M
Section 31. Device Characteristics
HIGHLIGHTS
31.1 Introduction..................................................................................................................31-2
31.2 Characterization vs. Electrical Specification ................................................................31-2
31.3 DC and AC Characteristics Graphs and Tables ...........................................................31-2
31.4 Revision History.........................................................................................................31-22
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-2 1997 Microchip Technology Inc.
31.1 Introduction
Microchip Technology Inc. provides characterization infor mation on the devices that it manufac-
tures. This information becomes available after the devices have undergone a complete charac-
terization and the data has been analyzed. This data is taken on both device testers and on
bench setups. The char acterization data giv es the designer a better understanding of the de vice
characteristics, to better judge the acceptability of the device to the application.
31.2 Characterization vs. Electrical Specification
The difference between this information and the Electrical specifications can be classified as
what the user should e xpect the devices to do vs. what Microchip tests the de vices to. The char-
acterization graphs and tables provided are for design guidance and are not tested or guaran-
teed.
There may be differences between what the character ization shows as the limits vs. that which
is tested, as shown in the Electrical Specification section. This results from capabilities of the pro-
duction tester equipment, plus whatever guard band that may be necessary.
31.3 DC and AC Characteristics Graphs and Tables
Each table gives specific information that may be useful design information. These values are
taken under fixed circumstances. Measurements taken in your application may not lead to the
same values if your circumstances are not the same.
In some graphs or tables the data presented are outside specified operating range (i.e., outside
specified VDD range). This is f or information only and devices will oper ate properly only within the
specified range.
Note: The data presented in the de vice Data Sheet Characterization section is a statistical
summary of data collected on units from different lots over a period of time and
matrix samples. 'Typical' represents the mean of the distribution at, 25°C, while
'max' or 'min' represents (mean +3σ) and (mean -3σ) respectively where σ is stan-
dard deviation.
1997 Microchip Technology Inc. DS31031A-page 31-3
Section 31. Device Characteristics
Device
Characteristics
31
31.3.1 IPD vs. VDD
IPD is the current (I) that the device consumes when the device is in sleep mode (power-down),
ref erred to as pow er-down current. These tests are tak en with all I/O as inputs , either pulled high
or low. That is, there are no floating inputs, nor are any pins driving an output (with a load).
The characterization shows graphs for both the Watchdog Timer (WDT) disabled and enabled.
This is required since the WDT requires an on-chip RC oscillator which consumes additional cur-
rent.
Since the device may have cer tain features and modules that can operate while the device is in
sleep mode. Some of these modules are:
W atchdog Timer (WDT)
Brown-out Reset (BOR) circuitry
Timer1
Analog to Digital converter
LCD module
Comparators
Voltage Reference
If these features are operating while the device is in sleep mode, a higher current will be con-
sumed. When all features are disabled, the device will consume the lowest possible current (the
leakage current). If more then one f eature is enabled then the e xpected current can easily be cal-
culated as the base current (everything disabled and in sleep mode) plus all delta currents.
Example 31-1 shows an example of calculating the typical currents for a device at 5V, with the
WDT and Timer1 oscillator enabled.
Example 31-1:IPD Calculations with WDT and TIMER1 Oscillator Enabled (@ 5V)
Base Current 14 nA ; Device leakage current
WDT Delta Current 14 µA ; 14 µA - 14 nA = 14 µA
Timer1 Delta Current 22 µA ; 22 µA - 14 nA = 22 µA
Total Sleep Current 36 µA ;
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-4 1997 Microchip Technology Inc.
Figure 31-1: Example Typical IPD vs. VDD (WDT Disabled, RC Mode)
Figure 31-2: Example Maximum IPD vs. VDD (WDT Disabled, RC Mode)
35
30
25
20
15
10
5
02.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
IPD (nA)
VDD (Volts)
IPD (µA)
VDD (Volts)
10.000
1.000
0.100
0.010
0.001
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
85°C
70°C
25°C
0°C
-40°C
1997 Microchip Technology Inc. DS31031A-page 31-5
Section 31. Device Characteristics
Device
Characteristics
31
Figure 31-3: Example Typical IPD vs. VDD @ 25°C (WDT Enabled, RC Mode)
Figure 31-4: Example Maximum IPD vs. VDD (WDT Enabled, RC Mode)
25
20
15
10
5
02.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
IPD (µA)
VDD (Volts)
35
30
25
20
15
10
5
02.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
IPD (µA)
VDD (Volts)
-40°C
0°C
70°C
85°C
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-6 1997 Microchip Technology Inc.
Figure 31-5: Example Typical IPD vs. VDD Brown-out Detect Enabled (RC Mode)
Figure 31-6: Example Maximum IPD vs. VDD Brown-out Detect Enabled (85°C to -40°C, RC Mode)
The shaded region represents the built-in hysteresis of the brown-out reset circuitry.
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
1400
1200
1000
800
600
400
200
0
VDD (Volts)
IPD (µA)
Device in
Brown-out
Device NOT in
Brown-out Reset
Reset
The shaded region represents the built-in hysteresis of the Brown-out Reset circuitry.
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
1400
1200
1000
800
600
400
200
0
VDD (Volts)
IPD (µA)
4.3
1600
Device NOT in
Brown-out Reset
Device in
Brown-out
Reset
1997 Microchip Technology Inc. DS31031A-page 31-7
Section 31. Device Characteristics
Device
Characteristics
31
Figure 31-7: Example Typical IPD vs. Timer1 Enabled (32 kHz, RC0/RC1 = 33 pF/33 pF, RC Mode)
Figure 31-8: Example Maximum IPD vs. Timer1 Enabled
(32 kHz, RC0/RC1 = 33 pF/33 pF, 85°C to -40°C, RC Mode)
30
25
20
15
10
5
0
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
VDD (Volts)
IPD (µA)
30
25
20
15
10
5
0
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
VDD (Volts)
IPD (µA)
35
40
45
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-8 1997 Microchip Technology Inc.
31.3.2 IDD vs. Frequency
IDD is the current (I) that the de vice consumes when the de vice is in oper ating mode . This test is
taken with all I/O as inputs , either pulled high or lo w. That is, there are no floating inputs, nor are
any pins driving an output (with a load).
The IDD vs. F requency charts measure the results on a Microchip automated bench setup , called
the DCS (Data Collection System). The DCS accurately reflects the device and specified com-
ponent values, that is, it does not add stray capacitance or current.
31.3.2.1 RC Measurements
For the RC measurement, the DCS selects a resistor and capacitor value, and then varies the
voltage o v er the specified range. As the voltage is changed, the frequency of oper ation changes.
For a fixed RC, as VDD increases, the frequency increases. After the measurement, at this RC,
has been taken, the RC v alue is changed and the measurements are tak en again. Each point on
the graph corresponds to a device voltage, resistor value (R), and capacitor value (C).
Figure 31-9: Example Typical IDD vs. Frequency (RC Mode @ 22 pF, 25°C)
2000
1800
1600
1400
1200
800
1000
600
400
200
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
Frequency (MHz)
IDD (µA)
Shaded area is
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
beyond recommended range
‡ R = 5 k
† R = 10 k
1997 Microchip Technology Inc. DS31031A-page 31-9
Section 31. Device Characteristics
Device
Characteristics
31
Figure 31-10: Example Maximum IDD vs. Frequency (RC Mode @ 22 pF, -40°C to 85°C)
Figure 31-11: Example Typical IDD vs. Frequency (RC Mode @ 100 pF, 25°C)
2000
1800
1600
1400
1200
800
1000
600
400
200
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
Frequency (MHz)
IDD (µA)
Shaded area is
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
beyond recommended range
1600
1400
1200
1000
800
600
400
200
00 200 400 600 800 1000 1200 1400 1600 1800
Frequency (kHz)
IDD (µA)
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
Shaded area is
beyond recommended range
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-10 1997 Microchip Technology Inc.
Figure 31-12: Example Maximum IDD vs. Frequency (RC Mode @ 100 pF, -40°C to 85°C)
Figure 31-13: Example Typical IDD vs. Frequency (RC Mode @ 300 pF, 25°C)
1600
1400
1200
1000
800
600
400
200
00 200 400 600 800 1000 1200 1400 1600 1800
Frequency (kHz)
IDD (µA)
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
Shaded area is
beyond recommended range
1200
1000
800
600
400
200
00 100 200 300 400 500 600 700
Frequency (kHz)
IDD (µA)
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
1997 Microchip Technology Inc. DS31031A-page 31-11
Section 31. Device Characteristics
Device
Characteristics
31
Figure 31-14: Example Maximum IDD vs. Frequency (RC Mode @ 300 pF, -40°C to 85°C)
Figure 31-15: Example Typical IDD vs. Capacitance @ 500 kHz (RC Mode)
1200
1000
800
600
400
200
00 100 200 300 400 500 600 700
Frequency (kHz)
IDD (µA)
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
Capacitance (pF)
600
IDD (µA)
500
400
300
200
100
0
20 pF 100 pF 300 pF
5.0V
4.0V
3.0V
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-12 1997 Microchip Technology Inc.
31.3.2.2 Crystal Oscillator Measurements
On the Data Collection System, there are several crystals. For this test a crystal is multiplexed
into the device circuit, and the crystal’s capacitance values can be varied. The capacitance and
voltage v alues are v aried to determine the best characteristics (current, oscillator wa v eform, and
oscillator star t-up), and then the currents are measured over voltage. The next crystal oscillator
is then switched in and the procedure is repeated.
Figure 31-16: Example Typical IDD vs. Frequency (LP Mode, 25°C)
Figure 31-17: Example Maximum IDD vs. Frequency (LP Mode, 85°C to -40°C)
120
100
80
60
40
20
00 50 100 150 200
Frequency (kHz)
IDD (µA)
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
120
100
80
60
40
20
00 50 100 150 200
Frequency (kHz)
IDD (µA)
140
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
1997 Microchip Technology Inc. DS31031A-page 31-13
Section 31. Device Characteristics
Device
Characteristics
31
Figure 31-18: Example Typical IDD vs. Frequency (XT Mode, 25°C)
Figure 31-19: Example Maximum IDD vs. Frequency (XT Mode, -40°C to 85°C)
1200
1000
800
600
400
200
00.0 0.4
Frequency (MHz)
IDD (µA)
1400
1600
1800
0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
1200
1000
800
600
400
200
00.0 0.4
Frequency (MHz)
IDD (µA)
1400
1600
1800
0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-14 1997 Microchip Technology Inc.
Figure 31-20: Example Typical IDD vs. Frequency (HS Mode, 25°C)
Figure 31-21: Example Maximum IDD vs. Frequency (HS Mode, -40°C to 85°C)
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0 12 4 6 8 10 12 14 16 18 20
Frequency (MHz)
IDD (mA)
6.0V
5.5V
5.0V
4.5V
4.0V
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0 12 4 6 8 10 12 14 16 18 20
Frequency (MHz)
IDD (mA)
6.0V
5.5V
5.0V
4.5V
4.0V
1997 Microchip Technology Inc. DS31031A-page 31-15
Section 31. Device Characteristics
Device
Characteristics
31
31.3.3 RC Oscillator Frequency
These tables show the effects of the RC oscillator frequency as the device voltage varies. In
these measurements a capacitor and resistor value are selected and then the frequency of the
RC is measured as the de vice voltage varies. The table shows the typical frequency for a R and
C value at 5V, as well as the var iation from this frequency that can be expected due to device
processing.
Figure 31-22: Example Typical RC Oscillator Frequency vs. VDD
Figure 31-23: Example Typical RC Oscillator Frequency vs. VDD
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
VDD (Volts)
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Fosc (MHz)
CEXT = 22 pF, T = 25°C
R = 100k
R = 10k
R = 5k
Shaded area is beyond recommended range.
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
VDD (Volts)
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Fosc (MHz)
CEXT = 100 pF, T = 25°C
R = 100k
R = 10k
R = 5k
R = 3.3k
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-16 1997 Microchip Technology Inc.
Figure 31-24: Example Typical RC Oscillator Frequency vs. VDD
Table 31-1: Example RC Oscillator Frequencies
CEXT REXT Average
Fosc @ 5V, 25°C
22 pF 5k 4.12 MHz ± 1.4%
10k 2.35 MHz ± 1.4%
100k 268 kHz ± 1.1%
100 pF 3.3k 1.80 MHz ± 1.0%
5k 1.27 MHz ± 1.0%
10k 688 kHz ± 1.2%
100k 77.2 kHz ± 1.0%
300 pF 3.3k 707 kHz ± 1.4%
5k 501 kHz ± 1.2%
10k 269 kHz ± 1.6%
100k 28.3 kHz ± 1.1%
The percentage variation indicated here is part to part variation due to normal process distri-
bution. The variation indicated is ±3 standard deviation from average value for VDD = 5V.
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
VDD (Volts)
1000
900
800
700
600
500
400
300
200
100
0
Fosc (kHz)
CEXT = 300 pF, T = 25°C
R = 3.3k
R = 5k
R = 10k
R = 100k
1997 Microchip Technology Inc. DS31031A-page 31-17
Section 31. Device Characteristics
Device
Characteristics
31
31.3.4 Oscillator Transconductance
Transconductance of the oscillator indicates the gain of the oscillator. As the transconductance
increases, the gain of the oscillator circuit increases which causes the current consumption of
the oscillator circuit to increase. Also as the transconductance increases the maxim um frequency
that the oscillator circuit can support also increases, or the start-up time of the oscillator
decreases.
Figure 31-25: Example Transconductance (gm) of HS Oscillator vs. VDD
Figure 31-26: Example Transconductance (gm) of LP Oscillator vs. VDD
4.0
3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
gm (mA/V)
VDD (Volts)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Max -40°C
Typ 25°C
Min 85°C
Shaded area is
beyond recommended range
110
100
90
80
70
60
50
40
30
20
10
02.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
gm (mA/V)
VDD (Volts)
Max -40°C
Typ 25°C
Min 85°C
Shaded areas are
beyond recommended range
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-18 1997 Microchip Technology Inc.
Figure 31-27: Example Transconductance (gm) of XT Oscillator vs. VDD
1000
900
800
700
600
500
400
300
200
100
02.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
gm (mA/V)
VDD (Volts)
Max -40°C
Typ 25°C
Min 85°C
Shaded areas are
beyond recommended range
1997 Microchip Technology Inc. DS31031A-page 31-19
Section 31. Device Characteristics
Device
Characteristics
31
31.3.5 Crystal Start-up Time
These graphs sho w the start-up time that one should e xpect to see at the specified voltage le v el,
for a given crystal/capacitor combination.
Figure 31-28: Example Typical XTAL Start-up Time vs. VDD (LP Mode, 25°C)
Figure 31-29: Example Typical XTAL Start-up Time vs. VDD (HS Mode, 25°C)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.02.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
VDD (Volts)
Start-up Time (Seconds)
32 kHz, 33 pF/33 pF
200 kHz, 15 pF/15 pF
7
6
5
4
3
2
14.0 4.5 5.0 5.5 6.0
VDD (Volts)
Start-up Time (ms)
20 MHz, 33 pF/33 pF
8 MHz, 33 pF/33 pF
8 MHz, 15 pF/15 pF
20 MHz, 15 pF/15 pF
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-20 1997 Microchip Technology Inc.
Figure 31-30: Example Typical XTAL Start-up Time vs. VDD (XT Mode, 25°C)
70
60
50
40
30
20
10
03.0 3.52.5 4.0 5.0 5.5 6.04.5
VDD (Volts)
Start-up Time (ms)
200 kHz, 68 pF/68 pF
200 kHz, 47 pF/47 pF
1 MHz, 15 pF/15 pF
4 MHz, 15 pF/15 pF
1997 Microchip Technology Inc. DS31031A-page 31-21
Section 31. Device Characteristics
Device
Characteristics
31
31.3.6 Tested Crystals and Their Capacitor Values
This table sho ws the crystal frequency and manufacturer that w as used for e very tests in this sec-
tion, as well as the capacitor values/ranges that exhibited the best characteristics.
Table 31-2: Example Capacitor Selection for Crystal Oscillators
31.3.7 Example EPROM Memory Erase Times
The UV erase time of an EPR OM cell depends on the geometry size of the EPROM cell and the
manuf acturing technology. Table 31-3 sho ws some of the e xpected erase times for each diff erent
device.
Table 31-3: Example of Typical EPROM Erase Time Recommendations
Table 31-4: Refer to the device data sheet for the typical erase times for a device.
Osc Type Crystal Frequency Capacitor Range
C1 Capacitor Range
C2
LP 32 kHz 33 pF 33 pF
200 kHz 15 pF 15 pF
XT 200 kHz 47-68 pF 47-68 pF
1 MHz 15 pF 15 pF
4 MHz 15 pF 15 pF
HS 4 MHz 15 pF 15 pF
8 MHz 15-33 pF 15-33 pF
20 MHz 15-33 pF 15-33 pF
Note: Higher capacitance increases the stability of the oscillator but also increases the start-up time.
These values are for design guidance only. Rs may be required in HS mode as well as XT
mode to av oid o v erdriving crystals with low drive lev el specification. Since each crystal has its
own characteristics, the user should consult the crystal manuf acturer for appropriate v alues of
external components or verify oscillator performance.
Crystals Used:
32 kHz Epson C-001R32.768K-A ± 20 PPM
200 kHz STD XTL 200.000KHz ± 20 PPM
1 MHz ECS ECS-10-13-1 ± 50 PPM
4 MHz ECS ECS-40-20-1 ± 50 PPM
8 MHz EPSON CA-301 8.000M-C ± 30 PPM
20 MHz EPSON CA-301 20.000M-C ± 30 PPM
Example
Device Wavelength
(Angstroms) Intensity
(µW/cm2)Distance from UV
lamp (inches) Typical Time (1)
(minutes)
1 2537 12,000 1 15 - 20
2 2537 12,000 1 20
3 2537 12,000 1 40
4 2537 12,000 1 60
Note 1: If these criteria are not met, the erase times will be different.
PICmicro MID-RANGE MCU FAMILY
DS31031A-page 31-22 1997 Microchip Technology Inc.
31.4 Revision History
Revision A
This is the initial released revision of the Device Characteristics description.
1997 Microchip Technology Inc. DS31032A page 32-1
M
Development
Tools
32
Section 32. Development Tools
HIGHLIGHTS
This section of the manual contains the following major topics:
32.1 Introduction..................................................................................................................32-2
32.2 The Integrated Development Environment (IDE).........................................................32-3
32.3 MPLAB Software Language Support...........................................................................32-6
32.4 MPLAB-SIM Simulator Software..................................................................................32-8
32.5 MPLAB Emulator Hardware Support...........................................................................32-9
32.6 MPLAB Programmer Support....................................................................................32-10
32.7 Supplemental Tools....................................................................................................32-11
32.8 Development Boards..................................................................................................32-12
32.9 Development Tools for Other Microchip Products......................................................32-14
32.10 Related Application Notes..........................................................................................32-15
32.11 Revision History.........................................................................................................32-16
PICmicro MID-RANGE MCU FAMILY
DS31032A-page 32-2 1997 Microchip Technology Inc.
32.1 Introduction
Microchip offers a wide range of tightly integrated development tools to ease the application
development process. These can be broken down into the core development tools and the sup-
plemental tools.
The core tools are as follows:
MPLAB Integrated Development Environment, including full featured editor
Language Products
- MPASM Assembler
- MPLAB-C C Compiler
MPLAB-SIM Software Simulator
Real-Time In-Circuit Emulators
- PICMASTER/PICMASTER CE Emulator with Full Featured Trace and Breakpoint
debug capabilities
- ICEPIC Low-Cost Emulator with Breakpoint debug capabilities
Device Programmers
- PRO MATE II Universal Programmer
- PICSTART Plus Entry-Level Prototype Programmer
Supplemental Tools:
Other Software Programming Tools
- fuzzyTECHMP Fuzzy logic development system
- MP-Driveway Application Code Generator
Development Boards
- PICDEM-1 Low-Cost Demonstration Board
- PICDEM-2 Low-Cost Demonstration Board
- PICDEM-3 Low-Cost Demonstration Board
- PICDEM-14A Low-Cost Demonstration Board
The minimum configuration of MPLAB, is the Integrated Development Environment (IDE), the
assembler (MPASM), and the software sim ulator (MPLAB-SIM). Other tools are added to MPLAB
as they are installed. This gives a common platform for the design activity, from the writing and
assembling of the source code, through the simulation/emulation, to the programming of proto-
type devices.
In addition to Microchip, there are many third par ty vendors. Microchip’s Third Par ty Handbook
gives an overview of the manufactures and their tools.
Note: The most current version may be downloaded from Microchip’s web site or BBS f or
free.
1997 Microchip Technology Inc. DS31032A-page 32-3
Section 32. Development Tools
Development
Tools
32
32.2 The Integrated Development Environment (IDE)
The core set of development tools operate under the IDE umbrella, called MPLAB. This gives a
consistent look and f eel to all the development tools so that minimal learning of the new tool inter-
face is required. The MPLAB IDE integrates all the following aspects of development:
Source code editing
Project management
Machine code generation (from assembly or “C”)
Device simulation
Device emulation
Device programming
MPLAB is a PC based Windo ws® 3.x application. It has been e xtensiv ely tested using Windows
95 and recommended in either of these operating environments.
This comprehensive tool suite allows the complete development of a project without leaving the
MPLAB environment.
Windows is a registered trademark of Microsoft Corporation.
PICmicro MID-RANGE MCU FAMILY
DS31032A-page 32-4 1997 Microchip Technology Inc.
32.2.1 MPLAB
The MPLAB IDE Software brings an ease of software de velopment pre viously unseen in the 8-bit
microcontroller market. MPLAB is a Windows based application that contains:
A full featured editor
Three operating modes
- editor
- emulator
- simulator
A project manager
Customizable tool bar and key mapping
A status bar with project information
Extensive on-line help
MPLAB allows you to:
Edit your source files. This includes:
- MPASM assembly language
- MPLAB-C ‘C’ language
One touch assemble (or compile) and download to PIC16/17 tools
(automatically updates all project information)
Debug using:
- source files
- absolute listing file
- program memory
Run up to four emulators on the same PC
Run or Single-step
- program memory
- source file
- absolute listing
Microchip’ s simulator , MPLAB-SIM, oper ates under the same platform as the PICMASTER emu-
lator. This allows the user to learn a single tool set which functions equivalently for both the sim-
ulator and the full featured emulator.
1997 Microchip Technology Inc. DS31032A-page 32-5
Section 32. Development Tools
Development
Tools
32
Figure 32-1 shows a typical MPLAB desktop in the middle of a project. Some of the highlights
are:
Tool bars, multiple choices and user configurable
Status, mode information, and button help on footer bar
Multiple windows, such as
- Source code
- Source listing (most useful for ‘C’ programs)
- Register file window (RAM)
- Watch windows (to look at specific register)
- Stop watch window for time/cycle calculations
Programmer support (in this case PRO MATE pull down menu)
Figure 32-1: MPLAB Project Window
PICmicro MID-RANGE MCU FAMILY
DS31032A-page 32-6 1997 Microchip Technology Inc.
32.3 MPLAB Software Language Support
To make the de vice operate as desired in the application, a software progr am needs to be written
f or the microcontroller . This software progr am needs to be written in one of the programming lan-
guages for the device. Currently MPLAB supports two of Microchip’s language products:
Microchip Assembler (MPASM)
Microchip ‘C’ Compiler (MPLAB-C)
Other language products that support Common Object Description (COD) may also work
with MPLAB
32.3.1 Assembler (MPASM)
The MPASM Universal Macro Assembler is a PC-hosted symbolic assembler. It supports all
Microchip microcontroller families.
MPASM offers full f eatured Macro capabilities, conditional assemb ly, and sever al source and list-
ing for mats. It generates various object code for mats to suppor t Microchip's development tools
as well as third party programmers.
MPASM allow full symbolic debugging from the Microchip Universal Emulator System
(PICMASTER).
MPASM has the following features to assist in developing software for specific use applications.
Provides translation of Assembler source code to object code for all Microchip microcon-
trollers.
Macro assembly capability.
Produces all the files (Object, Listing, Symbol, and special) required for symbolic debug
with Microchip’s emulator systems.
Supports Hex (default), Decimal and Octal source and listing formats.
MPASM provides a rich directive language to support programming of the PICmicro. Directives
are helpful in making the de velopment of your assemb le source code shorter and more maintain-
able.
32.3.2 C Compiler (MPLAB-C)
The MPLAB-C is a complete ‘C’ compiler f or Microchip’ s PICmicro f amily of microcontrollers . The
compiler provides powerful integration capabilities and ease of use not found with other
compilers.
For easier source level debugging, the compiler provides symbol infor mation that is compatible
with the MPLAB IDE memory display, Watch windows, and File register windows.
1997 Microchip Technology Inc. DS31032A-page 32-7
Section 32. Development Tools
Development
Tools
32
32.3.3 MPLINK Linker
MPLINK is a linker f or the Microchip C compiler, MPLAB-C, and the Microchip relocatable assem-
bler, MPASM. MPLINK is introduced with MPLAB-C v2.00 and can only be used with these or
later versions.
MPLINK allows you to produce modular, re-usable code with MPLAB-C and MPASM. Control
over the linking process is accomplished through a linker “script” file and with command line
options. MPLINK ensures that all symbolic ref erences are resolved and that code and data fit into
the available PICmicro device.
MPLINK combines multiple input object modules generated by MPLAB-C or MPASM, into a sin-
gle executable file. The actual addresses of data and the location of functions will be assigned
when MPLINK is executed. This means that you will instruct MPLINK to place code and data
somewhere within the named regions of memory, not to specific physical locations.
Once the linker kno ws about the ROM and RAM memory regions a vailable in the target PICmicro
device and it analyzes all the input files, it will try to fit the application’s routines into ROM and
assign it’s data variables into available RAM. If there is too much code or too many variables to
fit, MPLINK will give an error message.
MPLINK also provides flexibility for specifying that certain blocks of data memory are re-usable ,
so that different routines (which never call each other and don’t depend on this data to be
retained between execution) can share limited RAM space.
32.3.4 MPLIB Librarian
MPLIB is a librarian for use with COFF object modules created using either MPASM v2.0,
MPASMWIN v2.0, or MPLAB-C v2.0 or later.
MPLIB manages the creation and modification of library files. A library file is a collection of object
modules that are stored in a single file. There are several reasons for creating library files:
Libraries make linking easier. Since library files can contain many object files, the name of
a library file can be used instead of the names of many separate object when linking.
Libraries help keep code small. Since a linker only uses the required object files contained
in a library, not all object files which are contained in the library necessarily wind up in the
linker’s output module.
Libraries make projects more maintainable. If a library is included in a project, the addition
or removal of calls to that library will not require a change to the link process.
Libraries help convey the purpose of a group of object modules. Since libraries can group
together several related object modules, the purpose of a library file is usually more under-
standable that the purpose of its individual object modules. For example, the purpose of a
file named “math.lib” is more apparent that the purpose of 'power.o', 'ceiling.o', and 'floor.o'.
PICmicro MID-RANGE MCU FAMILY
DS31032A-page 32-8 1997 Microchip Technology Inc.
32.4 MPLAB-SIM Simulator Software
The software simulator is a no-cost tool with which to e v aluate Microchip’ s products and designs.
The use of the simulator greatly helps deb ug software , particularly algorithms. Depending on the
complexity of a design project a time/cost benefit should be looked at comparing the simulator
with an emulator.
For projects that have multiple engineers in the development, the simulator in conjunction with
an emulator can keep costs down and will allow speedy debug of the tough problems.
MPLAB-SIM Simulator simulates the PICmicro series microcontrollers on an instruction lev el. On
any given instruction, the user may examine or modify any of the data areas or provide external
stimulus to any of the pins. The input/output radix can be set by the user and the execution can
be performed in; single step, execute until break, or in a trace mode.
MPLAB-SIM supports symbolic debugging using MPLAB-C, and MPASM. The Software Simula-
tor off ers the low cost fle xibility to de velop and deb ug code outside of the laboratory environment
making it an excellent multi-project software development tool.
1997 Microchip Technology Inc. DS31032A-page 32-9
Section 32. Development Tools
Development
Tools
32
32.5 MPLAB Emulator Hardware Support
Microchip offers two emulators, a high-end version (PICMASTER) and a low-cost version
(ICEPIC). Both versions off er a very good price/feature value, and the selection of which emula-
tor should depend on the feature set that you wish. For people looking at doing several projects
with Microchip devices (or using the high-end devices) the use of PICMASTER may offset the
additional inv estment, through time savings achie ved with the sophisticated breakpoint and tr ace
capabilities.
32.5.1 PICMASTER: High Performance Universal In-Circuit Emulator
The PICMASTER Universal In-Circuit Em ulator provides the product de v elopment engineer with
a complete microcontroller design tool set for all microcontrollers in the Baseline, Mid-Range,
and High End f amilies. PICMASTER operates in the MPLAB Integ rated Development Environ-
ment (IDE), which allows editing, “make” and download, and source debugging from a single
environment.
Interchangeable target probes allo w the system to be easily re-configured f or emulation of diff er-
ent processors. The universal architecture of the PICMASTER allows expansion to support all
new Microchip microcontrollers.
The PICMASTER Emulator System has been designed as a real-time emulation system with
advanced features that are generally found on more expensive development tools.
A CE compliant version of PICMASTER is available for European Union (EU) countries.
32.5.2 ICEPIC: Low-Cost PIC16CXXX In-Circuit Emulator
ICEPIC is a low-cost in-circuit emulator solution f or the Microchip Base-line and Mid-Range f am-
ilies of 8-bit OTP microcontrollers.
ICEPIC user interf ace operates on PC-compatible machines ranging from 286-AT through P en-
tium based machines under Windows 3.x environment. ICEPIC features real-time emulation.
ICEPIC is available under the MPLAB environment.
ICEPIC is designed by Neosoft Inc. and is manufactured under license by RF Solutions. Other
emulator solutions may be available directly from RF solutions.
PICmicro MID-RANGE MCU FAMILY
DS31032A-page 32-10 1997 Microchip Technology Inc.
32.6 MPLAB Programmer Support
Microchip off ers two lev els of de vice programmer support. F or most bench setups the PICSTART
Plus is sufficient. When true system qualification is done, the PRO MATE II should be the mini-
mum used, due to the v alidation of progr am memory at VDD min and VDD max for maxim um reli-
ability
32.6.1 PRO MATE® II: Universal Device Programmer
The PRO MATE II Universal Programmer is a full-featured programmer capable of operating in
stand-alone mode as well as PC-hosted mode. PRO MATE II operates under MPLAB or as a
DOS command driven program.
The PRO MATE II has programmab le VDD and VPP supplies which allows it to v erify programmed
memor y at VDD min and VDD max for maximum reliability. It has an LCD display for error mes-
sages, keys to enter commands and a modular detachable socket assembly to suppor t various
package types. In stand-alone mode the PRO MATE II can read, verify or program Baseline,
Mid-Range, and High End devices. It can also set configuration and code-protect bits in this
mode. The PRO MATE II programmer also supports Microchip’s Serial EEPROM and KEELOQ®
Security devices.
A separate In-Circuit Serial Programming (ICSP) module is a v ailab le f or v olume progr amming in
a manuf acturing environment. See the Programming module documentation f or specific applica-
tion requirements.
32.6.2 PICSTART® Plus Low-Cost Development Kit
The PICSTART Plus progr ammer is an easy-to-use , low-cost prototype prog rammer. It connects
to the PC via one of the COM (RS-232) ports. MPLAB Integ rated Dev elopment Environment soft-
ware mak es using the programmer simple and efficient. PICSTART Plus is not recommended f or
production programming, since it does not do program memory verification at VDDMIN and
VDDMAX.
PICSTART Plus supports all Baseline, Mid-Range, and High End devices. For devices with up
more than 40 pins an adapter socket is required. DIP packages are the form factor that are
directly supported. Other package types may be supported with adapter sockets.
1997 Microchip Technology Inc. DS31032A-page 32-11
Section 32. Development Tools
Development
Tools
32
32.7 Supplemental Tools
Microchip endeav ors to provide a broad range of solutions to our customers. Some of these prod-
ucts ma y f all outside the realm of the classic de v elopment tools and include more adv anced top-
ics such as high level languages, fuzzy logic, or visual programming aids. These tools are
considered supplemental tools and ma y be availab le directly from Microchip or from another ven-
dor. A comprehensive listing of alternate tool providers is contained in the Third Party Guide.
32.7.1
fuzzy
TECH-MP Fuzzy Logic Development System
The
fuzzy
TECH-MP fuzzy logic development tool is available in two versions - a low cost intro-
ductory v ersion, MP Explorer , f or designers to gain a comprehensive working knowledge of fuzzy
logic system design, and a full-f eatured version,
fuzzy
TECH-MP, for implementing more comple x
systems.
Both versions include Microchip’ s
fuzzy
LAB demonstration board f or hands-on experience with
fuzzy logic systems implementation.
32.7.2 MP-DriveWay – Application Code Generator
MP-DriveWay is an easy-to-use Windows-based Application Code Generator. With MP-Drive-
Way you can visually configure all the peripherals in a PIC16/17 device and, with a click of the
mouse, generate all the initialization and man y functional code modules in C language . The out-
put is fully compatible with Microchip’s MPLAB-C C compiler. The code produced is highly mod-
ular and allows easy integration of your own code.
32.7.3 Third Party Guide
Looking for something else? Microchip strongly encourages and supports it’s Third Parties.
Microchip publishes the “Third Party Guide”. It is an extensive volume that provides:
Company
Product
Contact Information
Consultants
F or over 100 companies and 200 products. These products include Emulators, Device Program-
mers, Gang Programmers, Language Products, and other tool solutions.
PICmicro MID-RANGE MCU FAMILY
DS31032A-page 32-12 1997 Microchip Technology Inc.
32.8 Development Boards
De v elopment boards giv e a quick start on a circuit that demonstrates the capabilities of a partic-
ular de vice. The de vice program can then be modified f or y our own e v aluation of the de vice func-
tionality and operation.
32.8.1 PICDEM-1 Low-Cost PIC16/17 Demonstration Board
The PICDEM-1 is a simple board which demonstrates the capabilities of several of Microchip’s
microcontrollers. The microcontrollers supported are: PIC16C5X (PIC16C54 to PIC16C58A),
PIC16C61, PIC16C62X, PIC16C71, PIC16C710, PIC16C711, PIC16C8X, PIC17C42A,
PIC17C43 and PIC17C44. All necessar y hardware and software is included to run basic demo
programs. The users can program the sample microcontrollers provided with the PICDEM-1
board, on a PRO MATE II or PICSTART-Plus programmer, and easily test firmware. The
user can also connect the PICDEM-1 board to the PICMASTER emulator and download the
firmware to the emulator f or testing. Additional prototype area is availab le to build additional hard-
ware. Some of the features include an RS-232 interface, a potentiometer for simulated analog
input, push-button switches and eight LEDs connected to PORTB.
32.8.2 PICDEM-2 Low-Cost PIC16CXXX Demonstration Board
The PICDEM-2 is a simple demonstration board that supports the PIC16C62, PIC16C63,
PIC16C64, PIC16C65, PIC16C72, PIC16C73 and PIC16C74 microcontrollers. All the neces-
sary hardware and software is included to run the basic demonstration programs. The
user can program the sample microcontrollers provided with the PICDEM-2 board, on a
PRO MATE II programmer or PICSTART-Plus, and easily test firmware. The PICMASTER
emulator ma y also be used with the PICDEM-2 board to test firmware. Additional prototype area
has been provided for additional hardware. Some of the features include a RS-232 interface,
push-button switches, a potentiometer for simulated analog input, a Serial EEPROM to demon-
strate usage of the I2C bus and separate headers for connection to an LCD module and a key-
pad.
1997 Microchip Technology Inc. DS31032A-page 32-13
Section 32. Development Tools
Development
Tools
32
32.8.3 PICDEM-3 Low-Cost PIC16CXXX Demonstration Board
The PICDEM-3 is a simple demonstration board that suppor ts the PIC16C923 and PIC16C924
in the PLCC package . It will also support future 44-pin PLCC microcontrollers that have an
LCD Module. All the necessar y hardware and software is included to run the basic dem-
onstration programs. The user can program the sample microcontrollers, provided with
the PICDEM-3 board, on a PRO MATE II programmer or PICSTART Plus with an adapter
socket, and easily test firmware. The PICMASTER emulator may also be used with the
PICDEM-3 board to test firmw are. Additional prototype area has been provided f or adding hard-
ware. Some of the features include an RS-232 interface, push-button switches, a potentiometer
f or simulated analog input, a thermistor and separate headers for connection to an e xternal LCD
module and a ke ypad. Also provided on the PICDEM-3 board is an LCD panel, with 4 commons
and 12 segments, that is capab le of displaying time, temperature and da y of the w eek. The PIC-
DEM-3 provides an additional RS-232 interface and Windows 3.1 software for showing the
de-multiple xed LCD signals on a PC . A simple serial interface allows the user to construct a hard-
ware de-multiplexer for the LCD signals.
32.8.4 PICDEM-14A Low-Cost PIC14C000 Demonstration Board
The PICDEM-14A demo board is a general purpose platform which is provided to help e valuate
the PIC14C000 mixed signal microcontroller. The board runs a PIC14C000 measur ing the volt-
age of a potentiometer and the on-chip temperature sensor. The voltages are then calibrated to
the internal bandgap voltage reference. The voltage and temperature data are then transmitted
to the RS-232 port. This data can be displa yed using a terminal emulation progr am, such as Win-
dows Terminal. This demo board also includes peripherals that allo w users to displa y data on an
LCD panel, read from and write to a serial EEPR OM, and prototype custom circuitry to interface
to the microcontroller.
PICmicro MID-RANGE MCU FAMILY
DS31032A-page 32-14 1997 Microchip Technology Inc.
32.9 Development Tools for Other Microchip Products
32.9.1 SEEVAL Evaluation and Programming System
The SEEVAL Serial EEPROM Designer’s Kit supports all Microchip 2-wire and 3-wire Serial
EEPROMs. The kit includes everything necessar y to read, wr ite, erase or program special fea-
tures of any Microchip SEEPROM product including Smart Serials and secure serials. The
Total Endurance Disk is included to aid in trade-off analysis and reliability calculations. The total
endurance kit can significantly reduce time-to-market and results in a more optimized system.
32.9.2 KEELOQ Evaluation and Programming Tools
KEELOQ evaluation and programming tools supports Microchip’s HCS Secure Data Products.
The HCS evaluation kit includes an LCD display to show changing codes, a decoder to decode
transmissions, and a programming interface to program test transmitters.
1997 Microchip Technology Inc. DS31032A-page 32-15
Section 32. Development Tools
Development
Tools
32
32.10 Related Application Notes
This section lists application notes that are related to this section of the manual. These applica-
tion notes ma y not be written specifically for the Mid-Range MCU f amily (that is they ma y be writ-
ten f or the Base-Line, or the High-End), but the concepts are pertinent, and could be used (with
modification and possible limitations). The current application notes related to Microchip’s devel-
opment tools are:
Title Application Note #
Air Flow using Fuzzy Logic AN600
PICmicro MID-RANGE MCU FAMILY
DS31032A-page 32-16 1997 Microchip Technology Inc.
32.11 Revision History
Revision A
This is the initial released revision of Microchip’s development tools description.
1997 Microchip Technology Inc. DS30133A page 33-1
M
Code
Development
33
Section 33. Code Development
HIGHLIGHTS
No material is available at this time. Please monitor the Microchip web site for the B revision of
the Code Development section of the Mid-range Reference Manual.
PICmicro MID-RANGE MCU FAMILY
DS30133A-page 33-2 1997 Microchip Technology Inc.
33.1 Revision History
Revision A
This is the initial released revision for the Code Development with a PICmicro™ description.
1997 Microchip Technology Inc. DS31034A page 34-1
M
Appendix
34
Section 34. Appendix
HIGHLIGHTS
This section of the manual contains the following major topics:
Appendix A:I2C Overview....................................................................................................34-2
Appendix B:List of LCD Glass Manufacturers......................................................................34-11
Appendix C:Device Enhancement .......................................................................................34-13
Appendix D:Revision History................................................................................................34-19
I2C is a trademark of Philips Corporation.
PICmicro MID-RANGE MCU FAMILY
DS31034A-page 34-2 1997 Microchip Technology Inc.
APPENDIX A:I2C OVERVIEW
This section provides an overview of the Inter-Integrated Circuit (I2C™) bus, with Subsection
A.2 “Addressing I2C Devices” discussing the operation of the SSP modules in I2C mode.
The I2C b us is a two-wire serial interface . The original specification, or standard mode, is f or data
transfers of up to 100 Kbps. An enhanced specification, or fast mode (400 Kbps) is supported.
Standard and F ast mode de vices will operate when attached to the same bus, if the b us operates
at the speed of the slower device.
The I2C interface employs a comprehensive protocol to ensure reliable transmission and recep-
tion of data. When transmitting data, one de vice is the “master” which initiates transf er on the bus
and generates the clock signals to permit that transfer, while the other device(s) acts as the
“slav e .” All portions of the slave protocol are implemented in the SSP module’s hardware, e xcept
general call support, while portions of the master protocol need to be addressed in the
PIC16CXX software . The MSSP module supports the full implementation of the I2C master pro-
tocol, the general call address, and data transfers upto 1 Mbps. The 1 Mbps data transfers are
suppor ted by some of Microchips Serial EEPROMs. Table A-1 defines some of the I2C bus ter-
minology.
In the I2C interf ace protocol each de vice has an address. When a master wishes to initiate a data
transf er, it first transmits the address of the de vice that it wishes to “talk” to. All devices “listen” to
see if this is their address. Within this address, a bit specifies if the master wishes to
read-from/write-to the slave device. The master and slave are always in opposite modes (trans-
mitter/receiver) of oper ation during a data transf er. That is the y can be thought of as oper ating in
either of these two relations:
Master-transmitter and Slave-receiver
Slave-transmitter and Master-receiver
In both cases the master generates the clock signal.
The output stages of the clock (SCL) and data (SD A) lines m ust hav e an open-drain or open-col-
lector in order to perform the wired-AND function of the bus. External pull-up resistors are used
to ensure a high level when no device is pulling the line down. The number of devices that may
be attached to the I 2C bus is limited only by the maximum bus loading specification of 400 pF
and addressing capability.
1997 Microchip Technology Inc. DS31034A-page 34-3
Appendix A
Appenidx
34
A.1 Initiating and Terminating Data Transfer
During times of no data transfer (idle time), both the cloc k line (SCL) and the data line (SDA) are
pulled high through the exter nal pull-up resistors. The START and STOP conditions determine
the start and stop of data transmission. The STAR T condition is defined as a high to low transition
of the SDA when the SCL is high. The STOP condition is defined as a low to high transition of
the SDA when the SCL is high. Figure A-1 shows the START and STOP conditions. The master
generates these conditions for starting and terminating data transfer. Due to the definition of the
START and ST OP conditions, when data is being transmitted, the SD A line can only change state
when the SCL line is low.
Figure A-1: Start and Stop Conditions
Table A-1: I2C Bus Terminology
Term Description
Transmitter The device that sends the data to the bus.
Receiver The device that receives the data from the bus.
Master The device which initiates the tr ansf er, generates the clock and terminates
the transfer.
Slave The device addressed by a master.
Multi-master More than one master device in a system. These masters can attempt to
control the bus at the same time without corrupting the message.
Arbitration Procedure that ensures that only one of the master devices will control the
bus. This ensure that the transfer data does not get corrupted.
Synchronization Procedure where the clock signals of two or more devices are synchro-
nized.
SDA
SCL SP
Start
Condition Change
of Data
Allowed
Change
of Data
Allowed
Stop
Condition
PICmicro MID-RANGE MCU FAMILY
DS31034A-page 34-4 1997 Microchip Technology Inc.
A.2 Addressing I2C Devices
There are two address formats. The simplest is the 7-bit address format with a R/W bit
(Figure A-2). The more complex is the 10-bit address with a R/W bit (Figure A-3). For 10-bit
address format, two bytes must be transmitted. The first five bits specify this to be a 10-bit
address f ormat. The 1st tr ansmitted byte has 5-bits which specify a 10-bit address, the tw o MSbs
of the address, and the R/W bit. The second byte is the remaining 8-bits of the address.
Figure A-2: 7-bit Address Format
Figure A-3: I2C 10-bit Address Format
SR/W ACK
Sent by
Slave
slave address
S
R/W Read/Write pulse
MSb LSb
Start Condition
ACK Acknowledge
S 1 1 1 1 0 A9 A8 R/W ACK A7 A6 A5 A4 A3 A2 A1 A0 ACK
sent by slave
= 0 for write
S
R/W
ACK
- Start Condition
- Read/Write Pulse
- Acknowledge
1997 Microchip Technology Inc. DS31034A-page 34-5
Appendix A
Appenidx
34
A.3 Transfer Acknowledge
All data must be transmitted per byte, with no limit to the number of bytes transmitted per data
transfer. After each byte, the slave-receiver generates an acknowledge bit (ACK) (Figure A-4).
When a slav e-receiver doesn’t ac knowledge the slav e address or received data, the master m ust
abort the transf er . The slave must lea ve SD A high so that the master can generate the ST OP con-
dition (Figure A-1).
Figure A-4: Slave-Receiver Acknowledge
If the master is receiving the data (master-receiver), it gener ates an acknowledge signal f or each
received byte of data, except for the last byte. To signal the end of data to the slave-transmitter,
the master does not generate an acknowledge (not acknowledge). The slave then releases the
SDA line so the master can generate the STOP condition. The master can also generate the
STOP condition during the acknowledge pulse for valid termination of data transfer.
If the slave needs to delay the transmission of the next byte, holding the SCL line low will force
the master into a wait state. Data transfer continues when the slave releases the SCL line. This
allows the slave to move the received data or fetch the data it needs to transfer before allowing
the clock to start. This wait state technique can also be implemented at the bit level, Figure A-5.
Figure A-5: Data Transfer Wait State
S
Data
Output by
Transmitter
Data
Output by
Receiver
SCL from
Master
Start
Condition Clock Pulse for
Acknowledgment
not acknowledge
acknowledge
1289
12 789 123 89 P
SDA
SCL S
Start
Condition Address R/W ACK Wait
State Data ACK
MSB acknowledgment
signal from receiver acknowledgment
signal from receiver
byte complete
interrupt with receiver
clock line held low while
interrupts are serviced
Stop
Condition
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DS31034A-page 34-6 1997 Microchip Technology Inc.
Figure A-6 and Figure A-7 show Master-transmitter and Master-receiver data transfer
sequences.
Figure A-6: Master-Transmitter Sequence
Figure A-7: Master-Receiver Sequence
For 7-bit address:
S
Slave Address
(Code + A9:A8)
S R/W A1 Slave Address
(A7:A0) A2 Data A Data P
A master transmitter addresses a slave receiver
with a 10-bit address.
A/A
Slave Address R/W A Data A Data A/A P
'0' (write) data transferred
(n bytes - acknowledge)
A master transmitter addresses a slave receiver with a
7-bit address. The transfer direction is not changed.
From master to slave
From slave to master
A = acknowledge (SDA low)
A = not acknowledge (SDA high)
S = Start Condition
P = Stop Condition
(write)
For 10-bit address:
For 7-bit address:
S
Slave Address
(Code + A9:A8)
S R/W A1 Slave Address
(A7:A0) A2
A master transmitter addresses a slave receiver
with a 10-bit address.
Slave Address R/W A Data A Data A P
'1' (read) data transferred
(n bytes - acknowledge)
A master reads a slave immediately after the first byte.
From master to slave
From slave to master
A = acknowledge (SDA low)
A = not acknowledge (SDA high)
S = Start Condition
P = Stop Condition
(write)
For 10-bit address: Slave Address
(Code + A9:A8)
Sr R/W A3 AData A PData
(read)
1997 Microchip Technology Inc. DS31034A-page 34-7
Appendix A
Appenidx
34
When a master does not wish to relinquish the bus (which occurs by generating a STOP condi-
tion), a repeated START condition (Sr) must be gener ated. This condition is identical to the start
condition (SD A goes high-to-low while SCL is high), but occurs after a data tr ansfer ac knowledge
pulse (not the bus-free state). This allows a master to send “commands” to the slave and then
receive the requested inf ormation or to address a diff erent slav e de vice . This sequence is shown
in Figure A-8.
Figure A-8: Combined Format
Combined format:
S
Combined format - A master addresses a slave with a 10-bit address, then transmits
Slave AddressR/W A Data A/A Sr P
(read) Sr = repeated
Transfer direction of data and acknowledgment bits depends on R/W bits.
From master to slave
From slave to master
A = acknowledge (SDA low)
A = not acknowledge (SDA high)
S = Start Condition
P = Stop Condition
Slave Address
(Code + A9:A8)
Sr R/W A
(write)
data to this slave and reads data from this slave.
Slave Address
(A7:A0) Data Sr Slave Address
(Code + A9:A8)R/W A Data A A PA A Data A/A Data
(read)
Slave Address R/W A Data A/A
Start Condition (write) Direction of transfer
may change at this point
(read or write)
(n bytes + acknowledge)
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DS31034A-page 34-8 1997 Microchip Technology Inc.
A.4 Multi-master
The I2C protocol allows a system to have more than one master. This is called multi-master.
When two or more masters try to transfer data at the same time , arbitr ation and synchronization
occur.
A.4.1 Arbitration
Arbitration tak es place on the SDA line, while the SCL line is high. The master which tr ansmits a
high when the other master transmits a low loses arbitration (Figure A-9), and tur ns off its data
output stage. A master which lost arbitration can generate clock pulses until the end of the data
byte where it lost arbitr ation. When the master devices are addressing the same device, arbitra-
tion continues into the data.
Figure A-9: Multi-Master Arbitration (Two Masters)
Masters that also incorporate the slave function, and have lost arbitration must immediately
switch over to slave-receiver mode. This is because the winning master-transmitter may be
addressing it.
Arbitration is not allowed between:
A repeated START condition
A STOP condition and a data bit
A repeated START condition and a STOP condition
Care needs to be taken to ensure that these conditions do not occur.
transmitter 1 loses arbitration
DATA 1 SDA
DATA 1
DATA 2
SDA
SCL
1997 Microchip Technology Inc. DS31034A-page 34-9
Appendix A
Appenidx
34
A.4.2 Clock Synchronization
Clock synchronization occurs after the devices have started arbitration. This is perfor med using
a wired-AND connection to the SCL line. A high to low transition on the SCL line causes the con-
cerned devices to start counting off their low period. Once a de vice clock has gone low, it will hold
the SCL line low until its SCL high state is reached. The low to high transition of this clock may
not change the state of the SCL line, if another de vice cloc k is still within its lo w period. The SCL
line is held low by the device with the longest lo w period. Devices with shorter low periods enter
a high wait-state , until the SCL line comes high. When the SCL line comes high, all devices start
counting off their high periods. The first device to complete its high period will pull the SCL line
low. The SCL line high time is determined by the device with the shortest high period,
Figure A-10.
Figure A-10: Clock Synchronization
Figure A-11: I2C Bus Start/Stop Bits Timing Specification
Table A-2: I2C Bus Start/Stop Bits Timing Specification
Microchip
Parameter
No. Sym Characteristic Min Typ Max Units Conditions
90 TSU:STA START condition 100 kHz mode 4700 ns Only relevant for
repeated START condi-
tion
Setup time 400 kHz mode 600
91 THD:STA START condition 100 kHz mode 4000 ns After this period the first
clock pulse is generated
Hold time 400 kHz mode 600
92 TSU:STO STOP condition 100 kHz mode 4700 ns
Setup time 400 kHz mode 600
93 THD:STO STOP condition 100 kHz mode 4000 ns
Hold time 400 kHz mode 600
CLK
1
CLK
2
SCL
wait
state start counting
HIGH period
counter
reset
91 93
SCL
SDA
START
Condition STOP
Condition
90 92
PICmicro MID-RANGE MCU FAMILY
DS31034A-page 34-10 1997 Microchip Technology Inc.
Figure A-12: I2C Bus Data Timing Specification
Table A-3: I2C Bus Data Timing Specification
Microchip
Parameter
No. Sym Characteristic Min Max Units Conditions
100 THIGH Clock high time 100 kHz mode 4.0 µs
400 kHz mode 0.6 µs
101 TLOW Clock low time 100 kHz mode 4.7 µs
400 kHz mode 1.3 µs
102 TRSDA and SCL
rise time 100 kHz mode 1000 ns
400 kHz mode 20 +
0.1Cb 300 ns Cb is specified to be from
10 to 400 pF
103 TFSD A and SCL fall
time 100 kHz mode 300 ns
400 kHz mode 20 +
0.1Cb 300 ns Cb is specified to be from
10 to 400 pF
90 TSU:STA START condition
setup time 100 kHz mode 4.7 µs Only relev ant for repeated
START condition
400 kHz mode 0.6 µs
91 THD:STA START condition
hold time 100 kHz mode 4.0 µs After this period the first
clock pulse is generated
400 kHz mode 0.6 µs
106 THD:DAT Data input hold
time 100 kHz mode 0 ns
400 kHz mode 0 0.9 µs
107 TSU:DAT Data input setup
time 100 kHz mode 250 ns Note 2
400 kHz mode 100 ns
92 TSU:STO STOP condition
setup time 100 kHz mode 4.7 µs
400 kHz mode 0.6 µs
109 TAA Output valid from
clock 100 kHz mode 3500 ns Note 1
400 kHz mode 1000 ns
110 TBUF Bus free time 100 kHz mode 4.7 µs Time the bus must be free
before a new transmis-
sion can start
400 kHz mode 1.3 µs
D102 Cb Bus capacitive loading 400 pF
Note 1: As a transmitter, the device must provide this internal minimum delay time to bridge the undefined region
(min. 300 ns) of the falling edge of SCL to avoid unintended generation of START or STOP conditions.
2: A fast-mode I2C-bus device can be used in a standard-mode I2C-bus system, but the requirement
tsu;DAT 250 ns must then be met. This will automatically be the case if the device does not stretch the
LOW period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must out-
put the next data bit to the SDA line
TR max.+tsu;DAT = 1000 + 250 = 1250 ns (according to the standard-mode I2C bus specification) before
the SCL line is released.
90
91 92
100
101
103
106 107
109 109 110
102
SCL
SDA
In
SDA
Out
1997 Microchip Technology Inc. DS31034A-page 34-11
Appendix B
Appenidx
34
APPENDIX B:LIST OF LCD GLASS MANUFACTURERS
AEG-MIS
3340 Peachtree Rd. NE Suite 500
Atlanta, GA 30326
TEL: 404-239-0277
FAX: 404-239-0383
Interstate Electronics Corp.
1001 E. Bull Rd.
Anaheim, CA 92805
TEL: 800-854-6979
FAX: 714-758-4111
All Shore INDS Inc.
1 Edgewater Plaza
Staten Island, NY 10305
TEL: 718-720-0018
FAX: 718-720-0225
Kent Display Systems
343 Portage Blvd.
Kent, OH 44240
TEL: 330-673-8784
Crystaloid
5282 Hudson Drive
Hudson, OH 44236-3769
TEL: 216-655-2429
FAX: 216-655-2176
LCD Planar Optics Corporation
2100-2 Artic Ave.
Bohemia, NY 11716
TEL: 516-567-4100
FAX: 516-567-8516
DCI Inc.
14812 W. 117th St.
Olathe, KS 66062-9304
TEL: 913-782-5672
FAX: 913-782-5766
LXD Inc.
7650 First Place
Oakwood Village, OH 44146
TEL: 216-786-8700
FAX: 216-786-8711
Excel Technology International Corporation
Unit 5, Bldg. 4, Stryker Lane
Belle Mead, NJ 08502
TEL: 908-874-4747
FAX: 908-874-3278
Nippon Sheet Glass
Tomen America Inc.
1285 Avenue of the Americas
New York, NY 10019
TEL: 212-397-4600
FAX: 212-397-3351
F-P Electronics/Mark IV Industries
6030 Ambler Drive
Mississauga, ON Canada L4W 2PI
TEL: 905-624-3020
FAX: 905-238-3141
OPTREX America
44160 Plymouth Oaks Blvd.
Plymouth, MI 48170
TEL: 313-416-8500
FAX: 313-416-8520
Hunter Components
24800 Chagrin Blvd, Suite 101
Cleveland, OH 44122
TEL: 216-831-1464
FAX: 216-831-1463
Phillips Components
LCD Business Unit
1273 Lyons Road, Bldg G
Dayton, OH 45459
TEL: 573-436-9500
FAX: 573-436-2230
PICmicro MID-RANGE MCU FAMILY
DS31034A-page 34-12 1997 Microchip Technology Inc.
Satori Electric
23717 Hawthorne Blvd. 3rd Floor
Torrance, CA 90505
TEL: 310-214-1791
FAX: 310-214-1721
Varitronix Limited Inc.
3250 Wilshire Blvd. Suite 1901
Los Angeles, CA 90010
TEL: 213-738-8700
FAX: 213-738-5340
Seiko Instruments USA Inc.
Electronic Components Division
2990 West Lomita Blvd.
Torrance, CA 90505
TEL: 213-517-7770
213-517-8113
FAX: 213-517-7792
Varitronix Limited Inc.
4/F, Liven House
61-63 King Yip Street
Kwun Tong, Ko wloon
Hong Kong
TEL: 852 2389 4317
FAX: 852 2343 9555
Standish International
European Technical Center
Am Baümstuck II
65520 Bad Camberg/Erbach
Germany
TEL: 011 49 6434 3324
FAX: 011 49 6434 377238
Varitronix (France) S.A.R.L.
13/15 Chemin De Chilly
91160 Champlain
France
TEL:(33) 1 69 09 7070
FAX:(33) 1 69 09 0535
Standish LCD
W7514 Highway V
Lake Mills, WI 53551
TEL: 414-648-1000
FAX: 414-648-1001
Varitronix Italia, S.R.L.
Via Bruno Buozzi 90
20099 Sesto San Giovanni
Milano, Italy
TEL:(39) 2 2622 2744
FAX:(39) 2 2622 2745
Truly Semiconductors Ltd. (USA)
2620 Concord Ave.
Suite 106
Alhambra, CA 91803
TEL: 818-284-3033
FAX: 818-284-6026
Varitronix (UK) Limited
Display House, 3 Milbanke Court
Milbanke W a y, Bracknell
Berkshire RG12 1BR
United Kingdom
TEL:(44) 1344 30377
FAX(44) 1344 300099
Truly Semiconductor Ltd.
2/F, Chung Shun Knitting Center
1-3 Wing Y ip Street,
Kwai Chung, N.T., Hong Kong
TEL: 852 2487 9803
FAX: 852 2480 0126
Varitronix (Canada) Limited
18 Crown Steel Drive, Suite 101
Markham, Ontario
Canada L3R 9X8
TEL:(905) 415-0023
FAX:(905) 415-0094
Vikay America Inc.
195 W. Main St.
Avon, CT 06001-3685
TEL: 860-678-7600
FAX: 860-678-7625
1997 Microchip Technology Inc. DS31034A-page 34-13
Appendix C
Appenidx
34
APPENDIX C:DEVICE ENHANCEMENT
As the Midrange architecture matured, certain modules and f eatures ha ve been enhanced. The y
are:
1. The data memory map
2. The SSP module
3. The A/D module
4. Brown-out Reset added to the core
5. MCLR Filter
6. USART
7. Device Oscillator
The following subsections discuss the implementations of these enhancements.
C.1 Data Memory Map
The Data Memory Map shows the location of the Special Function Registers (SFRs) and the
General Purpose Registers (GPRs). SFRs provide controls and give status on the operation of
the device, while the GPRs are the general purpose RAM.
Figure C-1 show the v arious memory maps that have been implemented in the midr ange family.
Memory Map A was implemented on the first midrange devices. They were 18/20-pin devices
that had limited peripheral features. When the product roadmap dictated the requirement for
de vices with increased I/O , and a richer peripheral set, memory map B was implemented. Mem-
ory map C is actually a subset of memory map B, b ut context saving (due to an interrupt) requires
additional software o verhead. This is because there is no GPR in Bank1. To minimize the conte xt
saving software, memory map D was defined. A common RAM memory map will be used for all
future devices. See the “Memory Organization” section for use and implementation of the
Midrange PICmicro’s memory.
Figure C-1: Various Data Memory Maps
Bank0 Bank1
SFR SFR
GPR (1)
Bank0 Bank1
SFR SFR
GPR (2)
Bank0 Bank1
SFR SFR
GPR GPR
80h
9Fh
A0h
FFh
00h
1Fh
20h
7Fh
80h
9Fh
A0h
FFh
80h
8Bh
8Ch
FFh
00h
1Fh
20h
7Fh
00h
0Bh
0Ch
7Fh
Bank0 Bank1
SFR SFR
GPR GPR
80h
9Fh
A0h
FFh
00h
1Fh
20h
7Fh Bank2 Bank3
SFR SFR
GPR GPR
180h
19Fh
1A0h
1FFh
100h
11Fh
120h
17Fh
(1) (1) (1)
ABC
D(3)
Note 1: Mapped in Bank0.
2: Unimplemented, read as '0'.
3: Some devices have some GPR located in the SFR region.
F0h70h 1F0h170h
PICmicro MID-RANGE MCU FAMILY
DS31034A-page 34-14 1997 Microchip Technology Inc.
C.2 SSP (Synchronous Serial Port) Module
The SSP module has two modes of operation;
SPI (Serial Peripheral Interface)
•I
2C (Inter-Integrated Circuit).
There are now three different SSP modules that exist in Microchip’s design library. The first SSP
module (now called Basic SSP) implements two of the four SPI modes, and the I2C module in
slave mode. The second SSP module (called SSP) implements all four SPI modes, and the I2C
module in slave mode. The third SSP module (called Master SSP) implements all four SPI
modes, and the I2C module in master and slave modes. Table C-1 shows the devices that have
an SSP module and denotes which version is implemented. As new devices are introduced,
either the SSP module or Master SSP module will be implemented (that is, the Basic SSP mod-
ule is being phased out). Only select de vices will be introduced with the Master SSP module due
to the size (silicon area => cost) difference in relation to the SSP module. If your application
requires I2C Master mode, then you should also check into Microchip’s high-end family,
PIC17CXXX.
Table C-1: Devices With an SSP module
Device Synchronous Serial Port Version
SSP Basic SSP Master SSP (1)
PIC16C62 Yes
PIC16C62A Yes
PIC16CR62 Yes
PIC16C63 Yes
PIC16CR63 Yes
PIC16C64 Yes
PIC16C64A Yes
PIC16CR64 Yes
PIC16C65 Yes
PIC16C65A Yes
PIC16CR65 Yes
PIC16C66 Yes
PIC16C67 Yes
PIC16C72 Yes
PIC16CR72 Yes
PIC16C73 Yes
PIC16C73A Yes
PIC16C74 Yes
PIC16C74A Yes
PIC16C76 Yes
PIC16C77 Yes
PIC16C923 Yes
PIC16C924 Yes
Future Devices with SSP
module See Device
Data Sheet See Device
Data Sheet
Note 1: At present NO midrange de vices are a v ailab le with the Master SSP module. Please
ref er to Microchip’ s Web site or BBS f or release of Product Briefs. You will be ab le to
find out the details of features for new devices.
This module is av ailable on Micr oc hip’s High End family (PIC17CXXX). Please
refer to Microchip’s Web site, BBS, Regional Sales Office, or Factory Repre-
sentatives.
1997 Microchip Technology Inc. DS31034A-page 34-15
Appendix C
Appenidx
34
C.3 A/D (Analog-to-Digital) Module
There now exists several different versions of the A/D module in Microchip’s design library. The
first A/D module (now called Basic 8-bit A/D) is an 8-bit A/D with f our input channels. The second
A/D module (called 8-bit A/D) is an 8-bit A/D with up to 8 input channels. The Third A/D module
(called 10-bit A/D) is a 10-bit A/D with up to16 input channels implemented. Table C-2 shows
which devices have an A/D module, and the version implemented. As new devices are intro-
duced, either the 8-bit A/D module or 10-bit A/D module will be implemented (that is the Basic
8-bit A/D module is being phased out). If your application requires the 10-bit A/D, y ou should refer
to Microchip’s High End Family (PIC17CXXX). This family currently has some devices that have
this module implemented.
Table C-2: Devices With A/D modules
Device 8-bit A/D Basic 8-bit A/D 10-bit A/D (1) Slope A/D
PIC16C710 Yes
PIC16C71 Yes
PIC16C711 Yes
PIC16C715 Yes
PIC16C72 Yes
PIC16CR72 Yes
PIC16C73 Yes
PIC16C73A Yes
PIC16C74 Yes
PIC16C74A Yes
PIC16C76 Yes
PIC16C77 Yes
PIC16C924 Yes
PIC14C000 Yes
Future Devices
with A/D module See Device
Data Sheet See Device
Data Sheet See Device
Data Sheet See Device
Data Sheet
Note 1: At present NO midrange devices are available with the 10-bit A/D module. Please
ref er to Microchip’ s Web site or BBS f or release of Product Briefs. You will be ab le to
find out the details of features for new devices.
This module is av ailable on Micr oc hip’s High End family (PIC17CXXX). Please
refer to Microchip’s Web site, BBS, Regional Sales Office, or Factory Repre-
sentatives.
PICmicro MID-RANGE MCU FAMILY
DS31034A-page 34-16 1997 Microchip Technology Inc.
C.4 Brown-out Reset
An internal Brown-out Reset (BOR) circuit was added as a special feature. This circuit will be
added to most new devices. The exception will be for devices whose target market will require
normal operation below the BOR trip point (handheld battery applications). Table C-3 shows the
devices that evolved into having the BOR circuitry.
Table C-3: Devices That Were Revised to Include On-chip Brown-out Reset
C.5 Comparator
If a change in the CMCON register (C1OUT or C2OUT) should occur when a read operation is
being executed (start of the Q2 cycle), then the CMIF interrupt flag bit may not get set.
Base Device
No
Brown-out Reset
Subsequent Device
with
Brown-out Reset
PIC16C62 PIC16C62A
PIC16C64 PIC16C64A
PIC16C65 PIC16C65A
PIC16C71 PIC16C711
PIC16C73 PIC16C73A
PIC16C74 PIC16C74A
1997 Microchip Technology Inc. DS31034A-page 34-17
Appendix C
Appenidx
34
C.6 MCLR Filter
The master clear (MCLR) logic has had a filter added. This filter ignores shor t duration (glitch)
low level pulses on the Master Clear pin. Table C-4 shows whether the device has the master
clear filter.
Table C-4: Devices With Master Clear Filter
Device
Master Clear
No Filter
(Fast Reset) Filter
PIC16C61 Yes
PIC16C62 Yes
PIC16C62A Yes
PIC16CR62 Yes
PIC16C63 Yes
PIC16CR63 Yes
PIC16C64 Yes
PIC16C64A Yes
PIC16CR64 Yes
PIC16C65 Yes
PIC16C65A Yes
PIC16CR65 Yes
PIC16C66 Yes
PIC16C67 Yes
PIC16C620 Yes
PIC16C621 Yes
PIC16C622 Yes
PIC16C710 Yes
PIC16C71 Yes
PIC16C711 Yes
PIC16C715 Yes
PIC16C72 Yes
PIC16CR72 Yes
PIC16C73 Yes
PIC16C73A Yes
PIC16C74 Yes
PIC16C74A Yes
PIC16C76 Yes
PIC16C77 Yes
PIC16C83 Yes
PIC16C84 Yes
PIC16F83 Yes
PIC16F84 Yes
PIC16C923 Yes
PIC16C924 Yes
All New Devices Yes
PICmicro MID-RANGE MCU FAMILY
DS31034A-page 34-18 1997 Microchip Technology Inc.
C.7 USART
The original USART/SCI module that w as offered on Midrange devices specified a “high speed”
mode (when the BRGH control bit is set). Due to the design of the sampling circuitry, the opera-
tion of this mode was not as rob ust as desired. The sampling circuitry has been changed so that
operation now meets Microchip’ s requirements . The diff erence in the sampling is described in the
“USART” section. Table C-5 shows which devices use the new and old sampling logic.
Table C-5: USART/SCI Sampling Logic
C.8 Device Oscillator
A new mode has been added into the device oscillator which allows the device to operate from
an internal RC. This is specified at time of device programming (configuration word). This mode
will be included on many future de vices . See the de vice data sheets configuration w ord to deter-
mine if the device supports this mode.
C.9 Parallel Slave Port
The control pins have changed from level sensitive to edge sensitive.
Table C-6: Parallel Slave Port Change Sensitivity
Device Sampling Logic
Old New
PIC16C63 Yes
PIC16CR63 Yes
PIC16C65 Yes
PIC16C65A Yes
PIC16CR65 Yes
PIC16C66 Yes
PIC16C67 Yes
PIC16C73 Yes
PIC16C73A Yes
PIC16C74 Yes
PIC16C74A Yes
PIC16C76 Yes
PIC16C77 Yes
New Devices with
USART/SCI module —Yes
Device Sensitivity
Level Edge
PIC16C64 Yes
PIC16C64A Yes
PIC16C65 Yes
PIC16C65A Yes
PIC16C67 Yes
PIC16C74 Yes
PIC16C74A Yes
PIC16C77 Yes
New Devices with
Parallel Slave Port —Yes
1997 Microchip Technology Inc. DS31034A-page 34-19
Appendix D
Appenidx
34
APPENDIX D:REVISION HISTORY
Revision A
This is the initial released revision of the Reference Guide Appendix.
PICmicro MID-RANGE MCU FAMILY
DS31034A-page 34-20 1997 Microchip Technology Inc.
1997 Microchip Technology Inc. DS31035A page 35-1
M
Glossary
35
Section 35. Glossary
A
A/D
See Analog to Digital.
Acquisition Time (TACQ)
This is related to Analog to Digital (A/D) conv erters . This is the time that the A/D’ s holding capac-
itor acquires the analog input voltage level connected to it. When the GO bit is set, the analog
input is disconnected from the holding capacitor and the A/D conversion is started.
ALU
Arithmetical Logical Unit. De vice logic that is responsible f or the mathematical (add, subtract, ...),
logical (and, or, ...), and shifting operations.
Analog to Digital (A/D)
The conversion of an analog input voltage to a ratiometric digital equivalent value.
Assembly Language
A symbolic language that describes the binary machine code in a readable form.
PICmicro MID-RANGE MCU FAMILY
DS31035A-page 35-2 1997 Microchip Technology Inc.
B
Bank
This is a method of addressing Data Memory. Since midrange devices have 7-bits for direct
addressing, instructions can address up to 128 bytes (including special function registers). To
allow more data memory to be present on a device, data memory is partitioned into contiguous
banks of 128 bytes each. To select the desired bank, the bank selection bits (RP1:RP0) need to
be appropriately configured. Since there are presently 2 bank selection bits, 4 banks can be
implemented.
Baud
Generally how the communication speed of serial ports is described. Equivalent to bits per sec-
ond (bps).
BCD
See Binary Coded Decimal.
Binary Coded Decimal (BCD)
Each 4-bit nibble expresses a digit from 0-9. Usually two digits are packed to a byte giving a
range of 0 - 99.
BOR
See Brown-out Reset.
Brown-out
A condition where the supply voltage of the de vice temporarily f alls below the specified minim um
operation point. This can occur when a load is s witched on and causes the system/device v oltage
to drop.
Brown-out Reset (BOR)
Circuitry which will f orce the device to the reset state if the (de vice) voltage f alls below a specified
voltage level. Some devices have an internal BOR circuit, while other devices would require an
external circuit to be created.
Bus width
This is the number of bits of inf ormation that the bus carries. For the Data Memory, the bus width
is 8-bits. For the midrange devices the Program Memory bus width is 14-bits.
1997 Microchip Technology Inc. DS31035A-page 35-3
Glossary
Glossary
35
C
Capture
A function of the CCP module in which the value of a timer/counter is “captured”, into a holding
register, when a predetermined event occurs.
CCP
Capture, Compare, Pulse Width Modulation (PWM). This module can be configured to operate
as an input capture, or a timer compare, or a PWM output.
Common RAM
This is a region of the data memor y RAM that is the same RAM location across all banks. This
common RAM ma ybe implemented between addresses 70h -7Fh (inclusiv e). This common area
is useful for the saving of required variables dur ing context switching (such as during an inter-
rupt).
Compare
A function of the CCP module in which the device will perform an action when a timer’s register
value matches the value in the compare register.
Compare Register
A 16-bit register that contains a value that is compared to the 16-bit TMR1 register . The compare
function triggers when the counter matches the contents of the compare register.
Capture Register
A 16-bit register that gets loaded with the value of the 16-bit TMR1 register when a capture ev ent
occurs.
Configuration W ord
This is a location that specifies the characteristics that the device will ha v e for oper ation (such as
oscillator mode, WDT enable, start-up timer enables). These character istics can be specified at
time of de vice programming. For EPROM memory devices, as long as the bit is a '1', it may at a
later time be programmed as a '0'. The device must be erased for a '0' to be returned to a '1'.
Conversion Time (Tconv)
This is related to Analog to Digital (A/D) converters. This is the time that the A/D converter
requires to convert the analog voltage level on the holding capacitor to a digital value.
CPU
Central Processing Unit. Decodes the instructions, and determines the operands that are
needed and the operations that need to be done. Arithmetic, logical, or shift operations will be
passed to the ALU.
PICmicro MID-RANGE MCU FAMILY
DS31035A-page 35-4 1997 Microchip Technology Inc.
D
D/A
See Digital to analog
DAC
Digital to analog converter
Data Bus
The bus which is used to transfer data to and from the data memory.
Data EEPROM
Data Electrically Erasable Progr ammable Read Only Memory. This memory has the capability to
be programmed and re-programmed by the CPU to ensure that in the case of a pow er loss critical
values/variables are retained in the non-volatile memory.
Data Memory
The memory that is on the Data Bus . This memory is volatile (SRAM) and contains both the Spe-
cial Function Registers and General Purpose Registers.
Direct Addressing
When the Data Memory Address is contained in the Instruction. The execution of this type of
instruction will always access the data at the embedded address.
Digital to Analog
E
EEPROM
Electrically Erasable Programmable Read Only Memory. This memory has the capability to be
programmed and erased in-circuit.
EPROM
Electrically Programmable Read Only Memory. This memory has the capability to be pro-
grammed in-circuit. Erasing requires that the program memory be exposed to UV light.
EXTRC
External Resistor-Capacitor (RC). Some devices have a device oscillator option that allows the
clock to come from an external RC. This is the same as RC mode on some devices.
F
Flash Memory
This memory has the capability to be progr ammed and erased in-circuit. Program Memory tech-
nology that is almost functionally equivalent to Program EEPROM Memory.
Fosc
Frequency of the device oscillator.
1997 Microchip Technology Inc. DS31035A-page 35-5
Glossary
Glossary
35
G
GIO
General Input/Output
GPIO
General Purpose Input/Output
GPR
General Purpose Register (RAM). A por tion of the data memory that can be used to store the
program’s dynamic variables.
H
Harvard Architecture
In this architecture the Program Memory and Data Memory buses are separated. This allows
concurrent accesses to Data Memor y and Program Memory, which increases the perfor mance
of the device.
Holding Capacitor
This is a capacitor in the Analog to Digital (A/D) module which “holds” to analog input lev el once
the conversion is started. During acquisition, the holding capacitor is charged/discharged b y the
voltage le v el on the analog input pin. Once the conv ersion is started, the holding capacitor is dis-
connected from the analog input and “holds” this voltage for the A/D conversion.
HS
High Speed. One of the de vice oscillator modes. The oscillator circuit is tuned to support the high
frequency operation. Used for operation from 4 MHz to 20 MHz.
PICmicro MID-RANGE MCU FAMILY
DS31035A-page 35-6 1997 Microchip Technology Inc.
I
I2C
Inter-Integrated Circuit. This is a two wire communication interface. This feature is one of the
modes of the SSP module.
Indirect Addressing
When the Data Memory Address is not contained in the Instruction. The instruction operates on
the INDF address, which causes the Data Memory Address to be the value in the FSR register.
The e xecution of the instruction will alwa ys access the data at the address pointed to b y the FSR
register.
Instruction Bus
The bus which is used to transfer instruction words from the program memory to the CPU.
Instruction Fetch
Due to the Harv ard architecture , when one instruction is to be executed, the next location in pro-
gram memory is “f etched” and ready to be decoded as soon as the currently ex ecuting instruction
is completed.
Instruction cycle
The e v ents f or an instruction to e x ecute . There are f our e vents which can generally be described
as: Decode, Read, Execute, and Write. Not all events will be done by all instr uctions. To see the
operations during the instruction cycle, please look in the description of each instr uction. Four
external clocks (Tosc) make one instruction cycle (TCY).
Interrupt
A signal to the CPU that causes the program flow to be forced to the Interrupt Vector Address
(04h in program memory). Before the program flow is changed, the contents of the Program
Counter (PC) are forced onto the hardware stack, so that program execution may retur n to the
interrupted point.
INTRC
Internal Resistor-Capacitor (RC). Some devices have a device oscillator option that allows the
clock to come from an internal RC.
1997 Microchip Technology Inc. DS31035A-page 35-7
Glossary
Glossary
35
L
LCD
Liquid Crystal Displa y. Useful for giving visual status of a system. This may require the specifica-
tion of custom LCD glass.
LED
Light Emitting Diode. Useful for giving visual status of a system.
Literal
This is a constant value that is embedded in an instruction word.
Long W ord Instruction
An instruction word that embeds all the required information (opcode and data) into a single
word. This ensures that every instruction is accessed and executed in a single instruction cycle.
LP
One of the de vice oscillator modes . Used f or lo w frequency oper ation which allo ws the oscillator
to be tuned for low power consumption. Operation is up to 200 kHz.
LSb
Least Significant Bit.
LSB
Least Significant Byte.
M
Machine cycle
This is a concept where the device clock is divided down to a unit time. For PICmicros this unit
time is 4 times the device oscillator (4TOSC), also known as TCY.
MSb
Most Significant Bit.
MSB
Most Significant Byte.
PICmicro MID-RANGE MCU FAMILY
DS31035A-page 35-8 1997 Microchip Technology Inc.
N
Non-Return to Zero
Two level encoding used to transmit data over a communications medium. A bit value of '1' indi-
cates a high voltage signal. A bit v alue of '0' indicates a low v oltage signal. The data line defaults
to a high level.
NRZ
See Non-Return to Zero
O
Opcode
The por tion of the 14-bit instruction word that specifies the operation that needs to occur. The
opcode is of variab le length depending on the instruction that needs to be ex ecuted. The opcode
varies from 4-bits to x-bits. The remainder of the instruction word contains program or data mem-
ory information.
Oscillator Start-up Timer (OST)
This timer counts 1024 cr ystal/resonator oscillator clock before releasing the inter nal reset sig-
nal.
OST
See Oscillator Start-up Timer.
1997 Microchip Technology Inc. DS31035A-page 35-9
Glossary
Glossary
35
P
Pages
Method of addressing the Program Memory. Midrange de vices ha ve 11-bit addressing for CALL
and GOTO instructions, which gives these instructions a 2-Kword reach. To allow more program
memory to be present on a de vice, prog ram memory is partitioned into contiguous pages, where
each page is 2-Kwords. To select the desired page, the page selection bits (PCLATCH<5:4>)
need to be appropriately configured. Since there are presently 2 page selection bits, 4 pages can
be implemented.
Parallel Slave Port (PSP)
A parallel communication port which is used to interface to a microprocessor’s 8-bit data bus.
POP
A termed used to refer to the action of restoring information from a stack (software and/or hard-
ware). See PUSH.
Postscaler
A circuit that slows the rate of the interrupt generation (or WDT reset) from a counter/timer by
dividing it down.
Power-on Reset POR)
Circuitry which determines if the device voltage rose from a powered down level (0V). If the
device voltage is rising from ground, a device reset occurs and the PWRT is started.
Power-up Timer (PWRT)
A timer which holds the internal reset signal low for a timed delay to allow the device voltage to
reach the valid operating voltage range. Once the timer times out, the OST circuitry is enabled
(for all crystal/resonator device oscillator modes).
Prescaler
A circuit that slows the rate of a clocking source to a counter/timer.
Program Bus
The bus which is used to transfer instruction words form the program memory to the CPU.
Program Counter
A register which specifies the address in program memory that is the next instruction to e x ecute.
Program Memory
Any memory that is one the program memory bus. Static variables ma y be contained in prog ram
memory (such as tables).
PSP
See Parallel Slave Port.
Pulse Width Modulation (PWM)
A serial signal in which the information is contained in the width of a (high) pulse of a constant
frequency signal. A PWM output, from the CCP module, of the same duty cycle requires no soft-
ware overhead.
PUSH
A termed used to refer to the action of saving infor mation onto a stack (software and/or hard-
ware). See POP.
PWM
Pulse Width Modulation.
PICmicro MID-RANGE MCU FAMILY
DS31035A-page 35-10 1997 Microchip Technology Inc.
Q
Q-cycles
This is the same as a device oscillator cycle. There are 4 Q-cycles for each instruction cycle.
R
RC
Resistor-Capacitor . The def ault configuration f or the de vice oscillator . This allo ws a “ Real-Cheap”
implementation for the device clock source. This clock source does not supply an accurate
time-base. Operation to 4 MHz is supported. (See EXTRC).
Read-Modify-Write
This is where a register is read, then modified, and then written back to the original register . This
may be done in one instruction cycle or multiple instruction cycles.
Register File
This is the Data Memory. Contains the SFRs and GPRs.
ROM
Read Only Memory. Memory that is fixed and cannot be modified.
1997 Microchip Technology Inc. DS31035A-page 35-11
Glossary
Glossary
35
S
Sampling Time
Sampling time is the complete time to get an A/D result. It includes the acquisition time and the
conversion time.
Serial Peripheral Interface (SPI)
This is one of the modes of the SSP module. This is typically a 3-wire interface, with a data out
line, a data in line, and a clock line. Since the clock is present, this is a synchronous interface.
SFR
Special Function Register. These registers contain the control bits and status information for the
device.
Single cycle instruction
An instruction that executes in a “single” machine cycle (TCY).
Sleep
This is the low power mode of the device, where the device’s oscillator is disabled.This reduces
the current the de vice consumes. Certain peripherals ma y be placed into modes where they con-
tinue to operate.
Special Function Registers (SFR)
These registers contain the control bits and status information for the device.
SPI
See Serial Peripheral Interface.
Stack
A portion of the CPU which retains the return address for program execution. The stack gets
loaded with the value in the Program Counter when a CALL instruction is ex ecuted or an interrupt
occurs.
PICmicro MID-RANGE MCU FAMILY
DS31035A-page 35-12 1997 Microchip Technology Inc.
T
TAD
In the A/D Conver ter, the time for a single bit of the analog voltage to be converted to a digital
value.
TCY
The time for an instruction to complete. This time is equal to Fosc/4 and is divided into four
Q-cycles.
Tosc
The time for the device oscillator to do a single period.
U
USART
Universal Synchronous Asynchronous Receiver Transmitter. This module can either operate as
a full duple x asynchronous communications port, or a half duplex synchronous communications
port. When operating in the asynchronous mode, this can be interfaced to a PC’s serial port.
1997 Microchip Technology Inc. DS31035A-page 35-13
Glossary
Glossary
35
V
Voltage Reference (VREF)
A voltage le v el that can be used as a ref erence point for A/D con versions (A VDD and AVSS) or the
trip point for comparators.
von Neumann Architecture
In this architecture the Program Memory and Data Memory are contained in the same area. This
means that accesses to the program memory and data memory must occur sequentially, which
affects the performance of the device.
W
W Register
See W orking Register .
Watchdog Timer (WDT)
Used to increase the robustness of a design by recovering from software flows that were not
expected in the design of the product or other system related issues. The Watchdog Timer
causes a reset if it is not cleared prior to overflow. The clock source for a PICmicro is an on-chip
RC oscillator which enhances system reliability.
WDT
W atchdog Timer .
Working Register (W)
Can also be thought of as the accumulator of the de vice. Also used as an operand in conjunction
with the ALU during two operand instructions.
X
XT
One of the device oscillator modes. Used for operation from 100 kHz to 4 MHz.
PICmicro MID-RANGE MCU FAMILY
DS31035A-page 35-14 1997 Microchip Technology Inc.
35.1 Revision History
Revision A
This is the initial released revision of the Glossary.
1997 Microchip Technology Inc. DS33023A
M
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