42129D–SAM– 08/2013
Description
The Atmel® SAM D20 is a series of low-power microcontrollers using the 32-bit
ARM®Cortex®-M0+ processor, and ranging from 32- to 64-pins with up to 256KB Flash and
32KB of SRAM. The SAM D20 devices operate at a maximum frequency of 48MHz and
reach 2.14 Coremark/MHz. They are designed for simple and intuitive migration with
identical peripheral modules, hex compatible code, identical linear address map and pin
compatible migration paths between all devices in the product series. All devices include
intelligent and flexible peripherals, Atmel Event System for inter-peripheral signaling, and
support for capacitive touch button, slider and wheel user interfaces.
The Atmel SAM D20 devices provide the following features: In-system programmable Flash,
eight-channel Event System, programmable interrupt controller, up to 52 programmable I/O
pins, 32-bit real-time clock and calendar, up to eight 16-bit Timer/Coun ters (TC), where
each TC can be configured to perform frequency and waveform generation, accurate
program execution timing or input capture with time and frequency measurement of digital
signals. The TCs can operate in 8- or 16-bit mode, and two TCs can be cascaded to form a
32-bit TC. The series provide up to six Serial Communication Modules (SERCOM) that each
can be configured to act as an USART, UART, SPI and I2C up to 400kHz; up to twenty-
channel 350ksps 12-bit ADC with pro grammable gain and optional oversampling and
decimation supporting up to 16-bit resolution, one 10-bit 350ksps DAC, two analog
comparators with window mode, Peripheral Touch Controller supporting up to 256 buttons,
sliders and wheels; programmable Watchd og Timer, brown-out detector and power-on
reset, two-pin Serial Wire Debug (SWD) prog ram and debug interface.
All devices have accurate and low-power external and internal oscillators. All oscillators can
be used as a source for the system clock. Different clock domains can be independently
configured to run at different frequencies, enabling power saving by running each peripheral
at its optimal clock frequency, and thus maintaining a high CPU frequency while reducing
power consumption.
The SAM D20 devices have two software-selectable sleep mode s, idle and standby. In idle
mode the CPU is stopped while all other functions can be kept running. In standby all clocks
and functions are stopped expect those selected to continue running. The device supports
SleepWalking, which is the module's ability to wake itself up and wake up its own clock, and
hence perform predefined tasks without waking up the CPU. The CPU can then be only
woken on a need only basis, e.g. a threshold is crossed or a result is ready. The Event
System supports synchronous and asynchronous events, allowing peripherals to receive,
react to and send events even in standby mode.
The Flash program memory can be reprogrammed in-system through the SWD interface.
The same interface can be used for non-intrusive on-chip debug of application code. A boot
loader running in the device can use any communication interface to download and upgrade
the application program in the Flash memory.
The Atmel SAM D20 devices are supported with a full suite of program and system
development tools, including C compilers, macro assemblers, program
debugger/simulators, programmers and evaluation kits.
Atmel SAM D20J / SAM D20G / SAM D20E
ARM-Based Microcontroller
PRELIMINARY DATASHEET
2
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
Features
zProcessor
zARM Cortex-M0+ CPU running at up to 48MHz
zSingle-cycle hardware multiplier
zMemories
z16/32/64/128/256KB in-system self-programmable flash
z2/4/8/16/32KB SRAM
zSystem
zPower-on reset (POR) and brown-out detection (BOD)
zInternal and external clock options with 48MHz Digital Frequency Locked Loop (DFLL48M)
zExternal Interrupt Controller (EIC)
z16 external interrupts
zOne non-maskable interrupt
zTwo-pin Serial Wire Debug (SWD) programming, test and debugging interface
zLow Power
zIdle and standby sleep modes
zSleepWalking peripherals
zPeripherals
z8-channel Event System
zUp to eight 16-bit Timer/Counters (TC), configurable as either:
zOne 16-bit TC with compare/ca pture channels
zOne 8-bit TC with compare/capture channels
zOne 32-bit TC with compare/capture channels, by using two TCs
z32-bit Real Time Counter (RTC) with clock/calendar function
zWatchdog Timer (WDT)
zCRC-32 generator
zUp to six Serial Communication Interfaces (SERCOM), each configurable to operate as either:
zUSART with full-duplex and single-wire half-duplex configuration
zI2C
zSPI
zOne 12-bit, 350ksps Analog-to-Digital Converter (ADC) with up to 20 channels
zDifferential and single-ended channels
z1/2x to 16x gain stage
zAutomatic offset and gain error compensation
zOversampling and decimation in hardware to support 13-, 14-, 15- or 16-bit resolution
z10-bit, 350ksps Digital-to-Analog Converter (DAC)
zTwo Analog Comparators (AC) with window compare function
zPeripheral Touch Controller (PTC)
z256-Channel capacitive touch and proximity sensing
zI/O
zUp to 52 programmable I/O pins
zPackages
z64-pin TQFP, QFN
z48-pin TQFP, QFN
z32-pin TQFP, QFN
zOperating Voltage
z1.62V – 3.63V
3
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
1. Configuration Summary
SAM D20J SAM D20G SAM D20E
Flash 256/128/64/32/16KB 256/128/64/32/16KB 128/64/32/16KB
SRAM 32/16/8/4/2KB 32/16/8/4/2KB 16/8/4/2KB
Timer Counter (TC) instances 8 6 6
Waveform output ch annels per
Timer Counter instance 2 2 2
Serial Communication Interface
(SERCOM) instances 6 6 4
Analog-to-Digital Converter (ADC)
channels 20 14 10
Analog Comparators (AC) 2 2 2
Digital-to-Analog Converter (DAC)
instances 1 1 1
Real-Time Counter (RTC) Yes Yes Yes
RTC alarms 1 1 1
RTC compare values 1 32-bit value or
2 16-bit values 1 32-bit value or
2 16-bit values 1 32-bit value or
2 16-bit values
General Purpose I/O-pins (GPIOs) 52 38 26
External Interrupt lines 16 16 16
Peripheral Touch Controller (PTC) X
and Y lines 16x16 12x10 10x6
Maximum frequency 48MHz
Number of pins 64 48 32
Packages QFN
TQFP QFN
TQFP QFN
TQFP
Oscillators
32.768kHz crystal oscillator (XOSC32K)
0.4-32MHz crystal oscillator (XOSC)
32.768kHzinternal oscillator (OSC32K)
32kHz ultra-low-power internal oscillator (OSCULP32K)
8MHz high-accuracy internal oscillator (OSC8M)
48MHz Digital Frequency Locked Loop (DFLL48M)
Event System channels 8 8 8
SW Debug Interface Yes Yes Yes
Watchdog T imer (WDT) Yes Yes Yes
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
2. Ordering Information
2.1 SAM D20E
SAMD20E14A‐MUT
ProductFamily
SAMD=GeneralPurposeMicrocontroller
ProductSeries
20=CortexM0+CPU,GeneralFeatureSet
FlashMemory
18=256KB
17=128KB
16=64KB
15=32KB
14=16KB
ProductVariant
A=DefaultVariant
PinCount
E=32Pins
G=48Pins
J=64Pins
PackageCarrier
Nocharacter=Tray(Default)
T=TapeandReel
PackageGrade
PackageType
A=TQFP
M=QFN
C=UBGA
U=WLCSP
U=‐40‐85°CMatteSnPlating
H=‐40‐85°CNiPdAuPlating
Ordering Code FLASH (bytes) SRAM (bytes) Package Carrier Type
SAMD20E14A-AU
16K 2K
TQFP32 Tray
SAMD20E14A-AUT Tape & Reel
SAMD20E14A-MU QFN32 Tray
SAMD20E14A-MUT Tape & Reel
SAMD20E15A-AU
32K 4K
TQFP32 Tray
SAMD20E15A-AUT Tape & Reel
SAMD20E15A-MU QFN32 Tray
SAMD20E15A-MUT Tape & Reel
SAMD20E16A-AU
64K 8K
TQFP32 Tray
SAMD20E16A-AUT Tape & Reel
SAMD20E16A-MU QFN32 Tray
SAMD20E16A-MUT Tape & Reel
SAMD20E17A-AU
128K 16K
TQFP32 Tray
SAMD20E17A-AUT Tape & Reel
SAMD20E17A-MU QFN32 Tray
SAMD20E17A-MUT Tape & Reel
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
2.2 SAM D20G
2.3 SAM D20J
Ordering Code FLASH (bytes) SRAM (bytes) Package Carrier Type
SAMD20G14A-AU
16K 2K
TQFP48 Tray
SAMD20G14A-AUT Tape & Reel
SAMD20G14A-MU QFN48 Tray
SAMD20G14A-MUT Tape & Reel
SAMD20G15A-AU
32K 4K
TQFP48 Tray
SAMD20G15A-AUT Tape & Reel
SAMD20G15A-MU QFN48 Tray
SAMD20G15A-MUT Tape & Reel
SAMD20G16A-AU
64K 8K
TQFP48 Tray
SAMD20G16A-AUT Tape & Reel
SAMD20G16A-MU QFN48 Tray
SAMD20G16A-MUT Tape & Reel
SAMD20G17A-AU
128K 16K
TQFP48 Tray
SAMD20G17A-AUT Tape & Reel
SAMD20G17A-MU QFN48 Tray
SAMD20G17A-MUT Tape & Reel
SAMD20G18A-AU
256K 32K
TQFP48 Tray
SAMD20G18A-AUT Tape & Reel
SAMD20G18A-MU QFN48 Tray
SAMD20G18A-MUT Tape & Reel
Ordering Code FLASH (bytes) SRAM (bytes) Package Carrier Type
SAMD20J14A-AU
16K 2K
TQFP64 Tray
SAMD20J14A-AUT Tape & Reel
SAMD20J14A-MU QFN64 Tray
SAMD20J14A-MUT Tape & Reel
SAMD20J15A-AU
32K 4K
TQFP64 Tray
SAMD20J15A-AUT Tape & Reel
SAMD20J15A-MU QFN64 Tray
SAMD20J15A-MUT Tape & Reel
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
SAMD20J16A-AU
64K 8K
TQFP64 Tray
SAMD20J16A-AUT Tape & Reel
SAMD20J16A-MU QFN64 Tray
SAMD20J16A-MUT Tape & Reel
SAMD20J17A-AU
128K 16K
TQFP64 Tray
SAMD20J17A-AUT Tape & Reel
SAMD20J17A-MU QFN64 Tray
SAMD20J17A-MUT Tape & Reel
SAMD20J18A-AU
256K 32K
TQFP64 Tray
SAMD20J18A-AUT Tape & Reel
SAMD20J18A-MU QFN64 Tray
SAMD20J18A-MUT Tape & Reel
Ordering Code FLASH (bytes) SRAM (bytes) Package Carrier Type
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
3. Block Diagram
Notes: 1. Some products have different number of SERCOM instances, Timer/Counter instances, PTC signals and ADC sig-
nals. Refer to “Configuration Summary” on page 3 for details.
6 x SERCOM
8 x Timer Counter
REAL TIME
COUNTER
AHB/APB
BRIDGE C
M
S
HIGH SPEED
BUS MATRIX
PORT
PORT
WATCHDOG
TIMER
SERIAL
WIRE
SWDIO
NVM
CONTROLLER
256/128/64/32/16KB
FLASH
S
ARM CORTEX-M0+
PROCESSOR
F
max
48MHz
SWCLK
DEVICE
SERVICE
UNIT
AHB/APB
BRIDGE A
ADC
AIN[19:0]
VREFA
AIN[3:0]
S
32/16/8/4/2KB
RAM
M
RESET
CONTROLLER
SLEEP
CONTROLLER
CLOCK
CONTROLLER
POWER MANAGER
RESET
8 x TIMER COUNTER
EVENT SYSTEM
S
6 x SERCOM
2 ANALOG
COMPARATORS
SYSTEM CONTROLLER
XOUT
XIN
XOUT32
XIN32
OSCULP32K
OSC32K
OSC8M
DFLL48M
BOD33
BOD12
XOSC32K
XOSC
VREFVREG
GENERIC CLOCK
X[15:0]
Y[15:0]
PERIPHERAL
TOUCH
CONTROLLER
PERIPHERAL
ACCESS CONTROLLER
AHB/APB
BRIDGE B
VREFP
VOUT
DAC
EXTERNAL INTERRUPT
CONTROLLER
PERIPHERAL
ACCESS CONTROLLER
PERIPHERAL
ACCESS CONTROLLER
EXTINT[15:0]
NMI
GCLK_IO[7:0]
S
PIN[3:0]
WO[1:0]
VREFB
(See Note1)
CMP1:0]
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
4. Pinout
4.1 SAM D20J
PA00 1
PA01 2
PA02 3
PA03 4
PB04 5
PB05 6
GNDANA 7
VDDANA 8
PB06 9
PB07 10
PB08 11
PB09 12
PA04 13
PA05 14
PA06 15
PA07 16
PA08 17
PA09 18
PA10 19
PA11 20
VDDIO 21
GND 22
PB10 23
PB11 24
PB12 25
PB13 26
PB14 27
PB15 28
PA12 29
PA13 30
PA14 31
PA15 32
VDDIO48
GND47
PA2546
PA2445
PA2344
PA2243
PA2142
PA2041
PB1740
PB1639
PA1938
PA1837
PA1736
PA1635
VDDIO34
GND33
PB22
49
PB23
50
PA27
51
RESET
52
PA28
53
GND
54
VDDCORE
55
VDDIN
56
PA30
57
PA31
58
PB30
59
PB31
60
PB0061
PB0162
PB02
63
PB03
64
DIGITAL PIN
ANALOG PIN
OSCILLATOR
GROUND
INPUT SUPPLY
REGULATED OUTPUT SUPPLY
RESET PIN
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
4.2 SAM D20G
PA21
PA00 1
PA01 2
PA02 3
PA03 4
GNDANA 5
VDDANA 6
PB08 7
PB09 8
PA04 9
PA05 10
PA06 11
PA07 12
PA08 13
PA09 14
PA10 15
PA11 16
VDDIO 17
GND 18
PB10 19
PB11 20
PA12 21
PA13 22
PA14 23
PA15 24
VDDIO36
GND35
PA2534
PA2433
PA2332
PA2231
30
PA2029
PA1928
PA1827
PA1726
PA1625
PB22
37
PB2338
PA27
39
RESET
40
PA28
41
GND
42
VDDCORE
43
VDDIN
44
PA30
45
PA31
46
PB02
47
PB03
48
DIGITAL PIN
ANALOG PIN
OSCILLATOR
GROUND
INPUT SUPPLY
REGULATED OUTPUT SUPPLY
RESET PIN
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
4.3 SAM D20E
PA00 1
PA01 2
PA02 3
PA03 4
PA04 5
PA05 6
PA06 7
PA07 8
VDDANA 9
GND 10
PA08 11
PA09 12
PA10 13
PA11 14
PA14 15
PA15 16
PA25
24
PA24
23
PA23
22
PA22
21
PA19
20
PA18
19
PA17
18
PA16
17
PA27
25
RESET
26
PA28
27
GND
28
VDDCORE
29
VDDIN
30
PA30
31
PA31
32
DIGITAL PIN
ANALOG PIN
OSCILLATOR
GROUND
INPUT SUPPLY
REGULATED OUTPUT SUPPLY
RESET PIN
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
5. I/O Multiplexing and Considerations
5.1 Multiplexed Signals
Each pin is by default controlled by the PORT as a gene ral purpose I/O and alternatively it can be assigned to one of the
peripheral functions A, B, C, D, E, F, G or H. To enable a peripheral function on a pin, the Peripheral Multiplexer Enable
bit in the Pin Configuration register corresponding to that pin (PINCFGn.PMUXEN, n = 0-31) in the PORT must be written
to one. The selection of peripheral function A to H is done by writing to the Peripheral Multiplexing Odd and Even bits in
the Peripheral Multiplexing register (PMUXn.PMUXE/O) in the PORT. Refer to “PORT” on page 284 for details on how to
configure the I/O multiplexing.
Table 5-1 describes the peripheral signals multiplexed to the PORT I/O pins.
Table 5-1. PORT Function Multiplexing
Pin
I/O
Pin Supply Type
A B(1) C D E F G H
SAM
D20E SAM
D20G SAM
D20J EIC REF ADC AC PTC DAC SERCOM(2) TC(3) AC/GCLK
1 1 1 PA00 VDDANA EXTINT[0] SERCOM1/
PAD[0] TC2/WO[0]
2 2 2 PA01 VDDANA EXTINT[1] SERCOM1/
PAD[1] TC2/WO[1]
3 3 3 PA02 VDDANA EXTINT[2] AIN[0] Y[0] VOUT
4 4 4 PA03 VDDANA EXTINT[3]
ADC/VREFA
DAC/VREFP
AIN[1] Y[1]
5PB04 VDDANA EXTINT[4] AIN[12] Y[10]
6PB05 VDDANA EXTINT[5] AIN[13] Y[11]
9PB06 VDDANA EXTINT[6] AIN[14] Y[12]
10 PB07 VDDANA EXTINT[7] AIN[15] Y[13]
711 PB08 VDDANA EXTINT[8] AIN[2] Y[14] SERCOM4/
PAD[0] TC4/WO[0]
812 PB09 VDDANA EXTINT[9] AIN[3] Y[15] SERCOM4/
PAD[1] TC4/WO[1]
5 9 13 PA04 VDDANA EXTINT[4] ADC
VREFB AIN[4] AIN[0] Y[2] SERCOM0/
PAD[0] TC0/WO[0]
610 14 PA05 VDDANA EXTINT[5] AIN[5] AIN[1] Y[3] SERCOM0/
PAD[1] TC0/WO[1]
711 15 PA06 VDDANA EXTINT[6] AIN[6] AIN[2] Y[4] SERCOM0/
PAD[2] TC1/WO[0]
812 16 PA07 VDDANA EXTINT[7] AIN[7] AIN[3] Y[5] SERCOM0/
PAD[3] TC1/WO[1]
11 13 17 PA08 VDDIO I2CNMI AIN[16] X[0] SERCOM0/
PAD[0] SERCOM2/
PAD[0] TC0/WO[0]
12 14 18 PA09 VDDIO I2CEXTINT[9] AIN[17] X[1] SERCOM0/
PAD[1] SERCOM2/
PAD[1] TC0/WO[1]
13 15 19 PA10 VDDIO EXTINT[10] AIN[18] X[2] SERCOM0/
PAD[2] SERCOM2/
PAD[2] TC1/WO[0] GCLK/IO[4]
14 16 20 PA11 VDDIO EXTINT[11] AIN[19] X[3] SERCOM0/
PAD[3] SERCOM2/
PAD[3] TC1/WO[1] GCLK/IO[5]
19 23 PB10 VDDIO EXTINT[10] SERCOM4/
PAD[2] TC5/WO[0] GCLK/IO[4]
20 24 PB11 VDDIO EXTINT[11] SERCOM4/
PAD[3] TC5/WO[1] GCLK/IO[5]
25 PB12 VDDIO I2CEXTINT[12] X[12] SERCOM4/
PAD[0] TC4/WO[0] GCLK/IO[6]
26 PB13 VDDIO I2CEXTINT[13] X[13] SERCOM4/
PAD[1] TC4/WO[1] GCLK/IO[7]
27 PB14 VDDIO EXTINT[14] X[14] SERCOM4/
PAD[2] TC5/WO[0] GCLK/IO[0]
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
Note: 1. All analog pin functions are on peripheral function B. Peripheral function B must be selected to disable the digital con-
trol of the pin.
28 PB15 VDDIO EXTINT[15] X[15] SERCOM4/
PAD[3] TC5/WO[1] GCLK/IO[1]
21 29 PA12 VDDIO I2CEXTINT[12] SERCOM2/
PAD[0] SERCOM4/
PAD[0] TC2/WO[0] AC/CMP[0]
22 30 PA13 VDDIO I2CEXTINT[13] SERCOM2/
PAD[1] SERCOM4/
PAD[1] TC2/WO[1] AC/CMP[1]
15 23 31 PA14 VDDIO EXTINT[14] SERCOM2/
PAD[2] SERCOM4/
PAD[2] TC3/WO[0] GCLK/IO[0]
16 24 32 PA15 VDDIO EXTINT[15] SERCOM2/
PAD[3] SERCOM4/
PAD[3] TC3/WO[1] GCLK/IO[1]
17 25 35 PA16 VDDIO EXTINT[0] X[4] SERCOM1/
PAD[0] SERCOM3/
PAD[0] TC2/WO[0] GCLK/IO[2]
18 26 36 PA17 VDDIO EXTINT[1] X[5] SERCOM1/
PAD[1] SERCOM3/
PAD[1] TC2/WO[1] GCLK/IO[3]
19 27 37 PA18 VDDIO EXTINT[2] X[6] SERCOM1/
PAD[2] SERCOM3/
PAD[2] TC3/WO[0] AC/CMP[0]
20 28 38 PA19 VDDIO EXTINT[3] X[7] SERCOM1/
PAD[3] SERCOM3/
PAD[3] TC3/WO[1] AC/CMP[1]
39 PB16 VDDIO I2CEXTINT[0] SERCOM5/
PAD[0] TC6/WO[0] GCLK/IO[2]
40 PB17 VDDIO I2CEXTINT[1] SERCOM5/
PAD[1] TC6/WO[1] GCLK/IO[3]
29 41 PA20 VDDIO EXTINT[4] X[8] SERCOM5/
PAD[2] SERCOM3/
PAD[2] TC7/WO[0] GCLK/IO[4]
30 42 PA21 VDDIO EXTINT[5] X[9] SERCOM5/
PAD[3] SERCOM3/
PAD[3] TC7/WO[1] GCLK/IO[5]
21 31 43 PA22 VDDIO I2CEXTINT[6] X[10] SERCOM3/
PAD[0] SERCOM5/
PAD[0] TC4/WO[0] GCLK/IO[6]
22 32 44 PA23 VDDIO I2CEXTINT[7] X[11] SERCOM3/
PAD[1] SERCOM5/
PAD[1] TC4/WO[1] GCLK/IO[7]
23 33 45 PA24 VDDIO EXTINT[12] SERCOM3/
PAD[2] SERCOM5/
PAD[2] TC5/WO[0]
24 34 46 PA25 VDDIO EXTINT[13] SERCOM3/
PAD[3] SERCOM5/
PAD[3] TC5/WO[1]
37 49 PB22 VDDIO EXTINT[6] SERCOM5/
PAD[2] TC7/WO[0] GCLK/IO[0]
38 50 PB23 VDDIO EXTINT[7] SERCOM5/
PAD[3] TC7/WO[1] GCLK/IO[1]
25 39 51 PA27 VDDIO EXTINT[15] GCLK/IO[0]
27 41 53 PA28 VDDIO EXTINT[8] GCLK/IO[0]
31 45 57 PA30 VDDIO EXTINT[10] SERCOM1/
PAD[2] TC1/WO[0] SWCLK GCLK/IO[0]
32 46 58 PA31 VDDIO EXTINT[11] SERCOM1/
PAD[3] TC1/WO[1]
59 PB30 VDDIO I2CEXTINT[14] SERCOM5/
PAD[0] TC0/WO[0]
60 PB31 VDDIO I2CEXTINT[15] SERCOM5/
PAD[1] TC0/WO[1]
61 PB00 VDDANA EXTINT[0] AIN[8] Y[6] SERCOM5/
PAD[2] TC7/WO[0]
62 PB01 VDDANA EXTINT[1] AIN[9] Y[7] SERCOM5/
PAD[3] TC7/WO[1]
47 63 PB02 VDDANA EXTINT[2] AIN[10] Y[8] SERCOM5/
PAD[0] TC6/WO[0]
48 64 PB03 VDDANA EXTINT[3] AIN[11] Y[9] SERCOM5/
PAD[1] TC6/WO[1]
Table 5-1. PORT Function Multiplexing (Continued)
Pin
I/O
Pin Supply Type
A B(1) C D E F G H
SAM
D20E SAM
D20G SAM
D20J EIC REF ADC AC PTC DAC SERCOM(2) TC(3) AC/GCLK
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Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
2. Only some pins can be used in SERCOM I2C mode. See the Type column for using a SERCOM pin in I2C mode.
Refer to the “Electrical Characteristics” on page 562 for details on the I2C pin characteristics.
3. Note that TC6 and TC7 are not supported on the SAM D20G. Refer to “Configuration Summary” on page 3 for det ails.
5.2 Other Functions
5.2.1 Oscillat o r Pino ut
The oscillators are not mapped to the normal PORT functions and their multiplexing are controlled by registers in the
System Controller (SYSCTRL). Refer to “SYSCTRL – System Controller” on page 127 for more information.
5.2.2 Serial Wire Debug Interface Pinout
Only the SWCLK pin is mapped to the normal PORT functions. A debugger cold-plugging or hot-plugging detection will
automatically switch the SWDIO port to the SWDIO function. Refer to “DSU – Device Service Unit” on page 36 for more
information.
Oscillator Supply Signal I/O Pin
XOSC VDDIO XIN PA14
XOUT PA15
XOSC32K VDDANA XIN32 PA00
XOUT32 PA01
Signal Supply I/O Pin
SWCLK VDDIO PA30
SWDIO VDDIO PA31
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Atmel SAM D20 [Preliminary DATASHEET]
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6. Signal Descriptions List
The following table gives details on signal names classified by peripheral.
Signal Name Function Type Active Level
Analog Comparators - AC
AIN[3:0] AC Analog Inputs Analog
CMP[1:0] AC Comparator Outputs Digital
Analog Digita l Converter - ADC
AIN[19:0] ADC Analog Inputs Analog
VREFP ADC Voltage External Reference Analog
Digita l Analog Converter - DAC
VOUT DAC Voltage output Analog
VREFP DAC Voltage External Reference Analog
External Interrupt Controller - EIC
EXTINT[15:0] External Interrupts Input
NMI External Non-Maskable Interrupt Input
Generic Clock Generator - GCLK
IO[7:0] Generic Clock (source clock or generic clock generator output) I/O
Power Manager - PM
RESET Reset Input Low
Serial Communication Inter f ace - SERCOMx
PAD[3:0] SERCOM I/O Pads I/O
System Control - SYSCTRL
XIN Crystal Input Analog/ Digital
XIN32 32kHz Crystal Input Analog/ Digital
XOUT Crystal Output Analog
XOUT32 32kHz Crystal Output Analog
Timer Counter - TCx
WO[1:0] Waveform Outputs Output Low
Peripheral Touch Controller - PTC
X[15:0] PTC Input Analog
Y[15:0] PTC Input Analog
General Purpose I/O - PORT
PA25 - PA00 Parallel I/O Controller I/O Port A I/O
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PA28 - PA27 Parallel I/O Controller I/O Port A I/O
PA31 - PA30 Parallel I/O Controller I/O Port A I/O
PB17 - PB00 Parallel I/O Controller I/O Port B I/O
PB23 - PB22 Parallel I/O Controller I/O Port B I/O
PB31 - PB30 Parallel I/O Controller I/O Port B I/O
Signal Name Function Type Active Level
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7. Power Supply and Start-Up Considerations
7.1 Power Domain Overview
7.2 Power Supply Considerations
7.2.1 Power Supplies
The Atmel® SAM D20 has several different power supply pins:
zVDDIO: Powers I/O lines, OSC8M and XOSC. Voltage is 1.62V to 3.63V.
zVDDIN: Powers I/O lines and the internal regulator. Voltage is 1.62V to 3.63V.
zVDDANA: Powers I/O lines and the ADC, AC, DAC, PTC, OSCULP32K, OSC32K, XOSC32K. Voltage is 1.62V to
3.63V.
zVDDCORE: Internal regulated voltage output. Powers the core, memories and peripherals. Voltage is 1.2V.
The same voltage must be applied to both VDDIN, VDDIO and VDDANA. This common voltage is referred to as VDD in
the datasheet.
The ground pins, GND, are common to VDDCORE, VDDIO and VDDIN. The ground pin for VDDANA is GNDANA.
VOLTAGE
REGULATOR
VDDIN
VDDCORE
GND
ADC
AC
DAC
PTC
XOSC32K
OSC32K
VDDANA
GNDANA
PA[7:2]
PB[9:0]
PA[1:0]
Digital Logic
(CPU, peripherals)
DFLL48M
VDDIO
OSC8M
BOD33
XOSC
OSCULP32K
PA[31:16]
PB[31:10]
PA[15:14]
BOD12
POR
PA[13:8]
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For decoupling recommendations for the different power supplies, refer to the schematic checklist.
Refer to “Schematic Checklist” on page 600 for details.
7.2.2 Voltage Regulator
The voltage regulator has two different modes:
zNormal mode: To be used when the CPU and peripherals are running
zLow Power (LP) mode: To be used when the regulator draws small static current. It can be used in standby mode
7.2.3 Typical Powering Schematics
The SAM D20 uses a single supply from 1.62V to 3.63V.
The following figure shows the recommended power supply connection.
Figure 7-1. Power Supply Connection
7.2.4 Power-Up Sequence
7.2.4.1 Minimum Rise Rate
The integrated power-on reset (POR) circuitry monitoring the VDDANA power supply requires a minimum rise rate. Refer
to the “Electrical Characteristics” on page 562 for details.
7.2.4.2 Maximum Rise Rate
The rise rate of the power supply must not exceed the values described in Electrical Characteristics. Refer to the
“Electrical Characteristics” on page 562 for details.
(1.62V — 3.63V)
Main Supply VDDIO
VDDANA
VDDIN
VDDCORE
GND
GNDANA
SAM D20
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7.3 Power-Up
This section summarizes the power-up sequence of the SAM D20. The behavior after power-up is controlled by the
Power Manager. Refer to “PM – Power Manager” on page 100 for details.
7.3.1 Starting of Clocks
After power-up, the device is set to its initial state and kept in reset, until the power has stabilized throughout the device.
Once the power has stabilized, the device will use a 1MHz clock. This clock is derived from the 8MHz Internal Oscillator
(OSC8M), which is divided by eight and used as a clock source for generic clock generator 0. Generic clock generator 0
is the main clock for the Power Manager (PM).
Some synchronous system clocks are active, allowing software execution.
Refer to the “Clock Mask Register” section in “PM – Power Manager” on page 100 for the list of default peripheral clocks
running. Synchronous system clocks that are running are by default not divided and receive a 1MHz clock through
generic clock generator 0. Other generic clocks are disabled except GCLK_WDT, which is used by the Watchdog Timer
(WDT).
7.3.2 I/O Pins
After power-up, the I/O pins are tri-stated.
7.3.3 Fetching of Initial Instructions
After reset has been released, the CPU starts fetching PC and SP values from the reset address, which is 0x00000000.
This address points to the first executable address in the internal flash. The code read from the internal flash is free to
configure the clock system and clock sources. Refer to “PM – Power Manager” on page 100, “GCLK – Generic Clock
Controller” on page 78 and “SYSCTRL – System Controller” on page 127 for details. Refer to the ARM Architecture
Reference Manual for more information on CPU startup (http://www.arm.com).
7.4 Power-On Reset and Brown-Out Detector
The SAM D20 embeds three features to monitor, warn and/or reset the device:
zPOR: Power-on reset on VDDANA
zBOD33: Brown-out detector on VDDANA
zBOD12: Brown-out detector on VDDCORE
7.4.1 Power-On Reset on VDDANA
POR monitors VDDANA. It is always activated and monitors voltage at startup and also during all the sleep modes. If
VDDANA goes below the threshold voltage, the entire chip is reset.
7.4.2 Brown-Out Detector on VDDANA
BOD33 monitors VDDANA. Refer to “SYSCTRL – System Controller” on page 127 for details.
7.4.3 Brown-Out Detector on VDDCORE
Once the device has started up, BOD12 monitors the internal VDDCORE. Refer to “SYSCTRL – System Controller” on
page 127 for details.
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8. Product Mapping
Figure 8-1. SAM D2 0 Produc t Ma pp ing
This figure represents the full configuration of the Atmel® SAM D20 with maximum flash and SRAM capabilities and a full
set of peripherals. Refer to the “Configuration Summary” on page 3 for details.
Code
SRAM
Undefined
Peripherals
Reserved
Undefined
Global Memory Space
0x00000000
0x20000000
0x20008000
0x40000000
0x43000000
0x60000000
0x60000200
0xFFFFFFFF
Internal SRAM
SRAM
0x20000000
0x20008000
Peripheral
Bridge A
Peripheral
Bridge B
Peripheral
Bridge C
Peripherals
0x40000000
0x41000000
0x42000000
0x42FFFFFF
Reserved
PAC0
PM
SYSCTRL
GCLK
WDT
RTC
EIC
Peripheral Bridge A
0x40000000
0x40000400
0x40000800
0x40000C00
0x40001000
0x40001400
0x40001800
0x40FFFFFF
0x40001C00
Peripheral Bridge B
Reserved
PAC1
DSU
NVMCTRL
PORT
0x41000000
0x41002000
0x41004000
0x41004400
0x41FFFFFF
0x41004800
Internal flash
Code
0x00000000
0x00040000
0x1FFFFFFF
Reserved
SERCOM5
PAC2
EVSYS
SERCOM0
SERCOM1
SERCOM2
SERCOM3
SERCOM4
Peripheral Bridge C
TC7
TC0
TC1
TC2
TC3
TC4
TC5
TC6
ADC
AC
0x42000000
0x42000400
0x42000800
0x42000C00
0x42001000
0x42001400
0x42001800
0x42002000
0x42001C00
0x42003000
0x42003400
0x42003800
0x42003C00
0x42004000
0x42004400
0x42004800
Reserved
0x42FFFFFF
DAC
0x42004C00
0x42002400
0x42002800
0x42002C00
PTC
0x42005000
Reserved
System
0xE0000000
SCS
Reserved
Reserved
ROM Table
Reserved
System
0xE0000000
0xE000E000
0xE000F000
0xE00FF000
0xE0100000
0xFFFFFFFF
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9. Memories
9.1 Embedded Memories
zInternal high-speed flash
zInternal high-speed RAM, single-cycle access at full speed
zDedicated flash area for EEPROM emulation
9.2 Physical Memory Map
The High-Speed bus is implemented as a Bus Matrix. Refer to “High-Speed Bus Matrix” on page 25 for details. All High-
Speed bus addresses are fixed, and they are never remapped. The 32-bit physical address space is mapped as follows:
Table 9-1. SAM D20 Physical Memory Map(1)
Note: 1. x = G, J or E. SAMD20E18 is not available. Refer to “Ordering Information” on page 4 for details.
Table 9-2. Flash Memory Parameters(1)
Notes: 1. x = G, J or E. SAMD20E18 is not available. Refer to “Ordering Information” on page 4 for details.
2. The number of pages (NVMP) and page size (PSZ) can be read from the NVM Pages and Page Size bits in
the NVM Parameter register in the NVMCTRL (PARAM.NVMP and PARAM.PSZ, respectively). Refer to
PARAM for details.
Memory Start address
Size
SAMD20x18 SAMD20x17 SAMD20x16 SAMD20x15 SAMD20x14
Embedded Flash 0x00000000 256KB 128KB 64KB 32KB 16KB
Embedded SRAM 0x20000000 32KB 16KB 8KB 4KB 2KB
Peripheral Bridge A 0x40000000 64KB 64KB 64KB 64KB 64KB
Peripheral Bridge B 0x41000000 64KB 64KB 64KB 64KB 64KB
Peripheral Bridge C 0x42000000 64KB 64KB 64KB 64KB 64KB
Device Flash Size Number of Pages (NVMP) Page Size (PSZ) Row Size
SAMD20x18 256KB 4096 64 bytes 4 pages = 256 bytes
SAMD20x17 128KB 2048 64 bytes 4 pages = 256 bytes
SAMD20x16 64KB 1024 64 bytes 4 pages = 256 bytes
SAMD20x15 32KB 512 64 bytes 4 pages = 256 bytes
SAMD20x14 16KB 256 64 bytes 4 pages = 256 bytes
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9.3 Non-Volatile Memory (NVM) User Row Mapping
The NVM User Row contains calibration data that are automatically read at device power on.
The NVM User Row can be read at address 0x804000.
To write the NVM User Row refer to “NVMCTRL – Non-Volatile Memory Controller” on page 261.
Note that when writing to the User Row the values will only be loaded at device reset.
Table 9-3. NVM User Row Mapping
Bit Position Name Description
2:0 BOOTPROT Used to select one of eight different bootloader sizes. Refer to “NVMCTRL –
Non-Volatile Memory Controller” on page 261.
3Reserved
6:4 EEPROM Used to select one of eight different EEPROM area sizes. Refer to
“NVMCTRL – Non-Volatile Memory Controller” on page 261.
7Reserved
13:8 BOD33 Level BOD33 Threshold Level (BOD33.LEVEL) at power on. Refer to BOD33
register.
14 BOD33 Enable BOD33 Enable at power on. Refer to BOD33 register.
16:15 BOD33 Action BOD33 Action at power on. Refer to BOD33 register.
21:17 BOD12 Level BOD12 Threshold Level at power on. Refer to BOD12 register.
22 BOD12 Enable BOD12 Enable at power on. Refer to BOD12 register.
24:23 BOD12 Action BOD12 Action at power on. Refer to BOD12 register.
25 WDT Enable WDT Enable at power on. Refer to WDT CTRL register .
26 WDT Always-On WDT Always-On at power on. Refer to WDT CTRL register.
30:27 WDT Period WDT Period at power on. Refer to WDT CONFIG register.
34:31 WDT Window WDT Window mode time-out at power on. Refer to WDT CONFIG register.
38:35 WDT EWOFFSET WDT Early Warning Interrupt Time Offset at power on. Refer to WDT
EWCTRL register.
39 WDT WEN WDT Timer Window Mode Enable at power on. Refer to WDT CTRL register.
40 BOD33 Hysteresis BOD33 Hysteresis configuration at power on. Refer to BOD33 register.
41 BOD12 Hysteresis BOD12 Hysteresis configuration at power on. Refer to BOD12 register.
47:42 Reserved
63:48 LOCK NVM Region Lock Bits. Refer to “NVMCTRL – Non-Volatile Memory
Controller” on page 261.
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9.4 NVM Software Calibration Row Mapping
The NVM Software Calibration Row contains calibration data that are measured and written during production test.
These calibration values should be read by the application software and written back to the corresponding register.
The NVM Software Calibration Row can be read at address 0x806020.
The NVM Software Calibration Row can not be written.
Table 9-4. NVM Software Calibration Row Mapping
Bit Position Name Description
2:0 Reserved
14:3 ADC GAINCORR ADC Gain Correction. Should be written to GAINCORR register.
26:15 ADC OFFSETCORR ADC Offset Correction. Should be written to OFFSETCORR register.
34:27 ADC LINEARITY ADC Linearity Calibration. Should be written to CALIB register.
37:35 ADC BIASCAL ADC Bias Calibration. Should be written to CALIB register.
44:38 OSC32K CAL OSC32KCalibration. Should be written to OSC32K register.
63:38 Reserved
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10. Processor and Architecture
10.1 Cortex-M0+ Processor
The Atmel® SAM D20 implements the ARM® Cortex®-M0+ processor, which is based on the ARMv6 architecture and
Thumb®-2 ISA. The Cortex M0+ is 100% instruction set compatible with its predecessor, the Cortex-M0 processor, and
upward compatible with the Cortex-M3 and Cortex-M4 processors. The ARM Cortex-M0+ implemented is revision r0p1.
For more information, refer to www.arm.com.
10.1.1 Cortex-M0+ Config uration
Note: 1. All software run in privileged mode only
The ARM Cortex-M0+ processor has two bus interfaces:
zSingle 32-bit AMBA® 3 AHB-Lite™ system interface that provides connections to peripherals and all system
memory, including flash and RAM
zSingle 32-bit I/O port bus interfacing to the PORT with one-cycle loads and stores
10.1.2 Cortex-M0+ Periph erals
zSystem Control Space (SCS)
zThe processor provides debug through registers in the SCS. Refer to the Cortex-M0+ Technical Reference
Manual for details (www.arm.com).
zSystem Timer (SysTick)
zThe System Timer is a 24-bit timer that extends the functionality of both the processor and the NVIC. Refer
to the Cortex-M0+ Tec hnical Reference Manual for details (www.arm.com).
zNested Vectored Interrupt Controller (NVIC)
Feature Configurable Option SAM D20 Configuration
Interrupts External interrupts 0-32 32
Data endianness Little-endian or big-endian Little-endian
SysTick timer Present or absent Present
Number of watchpoint comparators 0, 1, 2 2
Number of breakpoint comparators 0, 1, 2, 3, 4 4
Halting debug support Present or absent Present
Multiplier Fast or small Fast (single cycle)
Single-cycle I/O port Presen t or absent Present
Wake-up interrupt controller Supported or not supported Not supported
Vector Table Offset Register Present or absent Present
Unprivileged/Privileged support Present or absent Absent
Memory Protection Unit Not present or 8-region Not present
Reset all registers Present or absent Absent(1)
Instruction fetch width 16-bit only or mostly 32-bit 32-bit
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zExternal interrupt signals connect to the NVIC, and the NVIC prioritizes the interrupts. Software can set the
priority of each interrupt. The NVIC and the Cortex-M0+ processor core are closely coupled, providing low
latency interrupt processing and efficient processing of late arriving interrupts. Refer to “Nested Vector
Interrupt Controller” on page 24 and the Cortex-M0+ Technical Reference Manual for details
(www.arm.com).
zSystem Control Block (SCB)
zThe System Control Block provides system implementation information, and system control. This includes
configuration, control, and reporting of the system exceptions. Refer to the Cortex-M0+ Devices Generic
User Guide for details (www.arm.com).
10.1.3 Cortex-M0+ Address Map
Table 10-1. Cortex-M0+ Address Map
10.1.4 I/O Interface
10.1.4.1 Overview
Because accesses to the AMBA AHB-Lite and the single-cycle I/O interface can be made concurrently, the Cortex-M0+
processor can fetch the next instructions while accessing the I/Os. This enables single-cycle I/O accesses to be
sustained for as long as needed.
10.1.4.2 Description
Direct access to PORT registers.
10.2 Nested Vector Interrupt Controller
10.2.1 Overview
The Nested Vectored Interrupt Controller (NVIC) in the SAM D20 supports 32 interrupt lines with four different priority
levels. For more details, refer to the Cortex-M0+ Technical Reference Manual (www.arm.com).
10.2.2 Interrupt Line Mapping
Each of the 32 interrupt lines is connected to one peripheral instance, as shown in the table below. Each peripheral can
have one or more interrupt flags, located in the peripheral’s Interrupt Flag Status and Clear (INTFLAG) register. The
interrupt flag is set when the interrupt condition occurs. Each interrupt in the peripheral can be individually enabled by
writing a one to the corresponding bit in the peripheral’s Interrupt Enable Set (INTENSET) register, and disabled by
writing a one to the corresponding bit in the peripheral’s Interrupt Enable Clear (INTENCLR) register . An interrupt request
is generated from the peripheral when the interrupt flag is set and the corresponding interrupt is enabled. The interrupt
requests for one peripheral are ORed together on system level, generating one interrupt request for each peripheral. An
interrupt request will set the corresponding interrupt pending bit in the NVIC interrupt pending registers
(SETPEND/CLRPEND bits in ISPR/ICPR). For the NVIC to activate the interrupt, it must be enabled in the NVIC interrupt
enable register (SETENA/CLRENA bits in ISER/ICER). The NVIC interrupt priority registers IPR0-IPR7 provide a priority
field for each interrupt.
Address Peripheral
0xE000E000 System Control Space (SCS)
0xE000E010 System Timer (SysTick)
0xE000E100 Nested Vectored Interrupt Controller (NVIC)
0xE000ED00 System Control Block (SCB)
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10.3 High-Speed Bus Matrix
10.3.1 Features
The High-Speed Bus Matrix includes these features:
zSymmetric crossbar bus switch implementation
zAllows concurrent accesses from different masters to different slaves
z32-bit data bus
zOperation at a one-to-one clock frequency with the bus masters
Peripheral Source NVIC Line
EIC NMI – External Interrupt Controller Non Maskable Interrupt NMI
PM – Power Manager 0
SYSCTRL – System Controller 1
WDT – Watchdog Timer 2
RTC – Real Time Counter 3
EIC – External Interrupt Controller 4
NVMCTRL – Non-Volatile Memory Controller 5
EVSYS – Event System 6
SERCOM0 – Serial Communication Interface 0 7
SERCOM1 – Serial Communication Interface 1 8
SERCOM2 – Serial Communication Interface 2 9
SERCOM3 – Serial Communication Interface 3 10
SERCOM4 – Serial Communication Interface 4 11
SERCOM5 – Serial Communication Interface 5 12
TC0 – Timer/Counter 0 13
TC1 – Timer/Counter 1 14
TC2 – Timer/Counter 2 15
TC3 – Timer/Counter 3 16
TC4 – Timer/Counter 4 17
TC5 – Timer/Counter 5 18
TC6 – Timer/Counter 6 19
TC7 – Timer/Counter 7 20
ADC – Analog-to-Digital Converter 21
AC – Analog Comparator 22
DAC – Digital-to-Analog Converter 23
PTC – Peripheral Touch Controller 24
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10.3.2 Configuration
CM0+ 0
DSU 1
High-Speed Bus
Slaves
Internal Flash
0
AHB-APB bridge A
1
AHB-APB bridge B
2
AHB-APB bridge C
3
Internal SRAM
4
High-Speed Bus
Masters
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10.4 AHB-APB Bridge
The AHB-APB bridge is an AHB slave, providing an interface between the high-speed AHB domain and the low-power
APB domain. It is used to provide access to the programmable control registers of peripherals (see “Product Mapping” on
page 19).
to operate the AHB-APB bridge, the clock (CLK_HPBx_AHB) must be enabled. See “PM – Power Manager” on page 100
for details.
10.5 PAC – Peripheral Access Controller
10.5.1 Overview
There is one PAC associated with each AHB-APB bridge. The PAC can provide write protection for registers of each
peripheral connected on the same bridge.
The PAC peripheral bus clock (CLK_PACx_APB) is enabled by default, and can be enabled and disabled in the Power
Manager. Refer to “PM – Power Manager” on page 100 for details. The PAC will continue to operate in any sleep mode
where the selected clock source is running.
Write-protection does not apply for debugger access. When the debugger makes an access to a peripheral, write-
protection is ignored so that the debugger can update the register.
Write-protect registers allow the user to disable a selected peripheral’s write-protection without doing a read-modify-write
operation. These registers are mapped into two I/O memory locations, one for clearing and one for setting the register
bits. Writing a one to a bit in the Write Protect Clear register (WPCLR) will clear the corresponding bit in both registers
(WPCLR and WPSET) and disable the write-protection for the corresponding peripheral, while writing a one to a b it in the
Write Protect Set (WPSET) register will set the corresponding bit in both registers (WPCLR and WPSET) and enable the
write-protection for the corresponding peripheral. Both registers (WPCLR and WPSET) will return the same value when
read.
If a peripheral is write-protected, and if a write access is performed, data will not be written, and the peripheral will return
an access error (CPU exception).
The PAC also offers a safety feature for correct program execution, with a CPU exception generated on double write-
protection or double unprotection of a peripheral. If a peripheral n is write-protected and a write to one in WPSET[n] is
detected, the PAC returns an error. This can be used to ensure that the application follows the intended program flow by
always following a write-protect with an unprotect, and vice versa. However, in applications where a write-protected
peripheral is used in several contexts, e.g., interrupts, care should be taken so that either the interrupt can not happen
while the main application or other interrupt levels manipulate the write-protection status, or when the interrupt handler
needs to unprotect the peripheral, based on the current protection status, by reading WPSET.
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10.6 Register Description
Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters and 16-bit halves of a 32-bit register, and
the 8-bit halves of a 16-bit register can be accessed directly.
Please refer to “Product Mapping” on page 19 for PAC locations.
10.6.1 Write Protect Clear
Name: WPCLR
Offset: 0x00
Reset: 0x00000000
Property: -
zBits 31:7 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 6:1 – EIC, RTC, WDT, GCLK, SYSCTRL, PM: Write Protect Disable
0: Write-protection is disabled.
1: Write-protection is enabled.
Writing a zero to these bits has no effect.
Writing a one to these bits will clear the Write Protect bits for the corresponding peripherals.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
AccessRRRRRRRR
Reset00000000
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
EIC RTC WDT GCLK SYSCTRL PM
Access R R/W R/W R/W R/W R/W R/W R
Reset00000000
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10.6.2 Write Protect Set
Name: WPSET
Offset: 0x04
Reset: 0x00000000
Property: -
zBits 31:7 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 6:1 – EIC, RTC, WDT, GCLK, SYSCTRL, PM: Write Protect Enable
0: Write-protection is disabled.
1: Write-protection is enabled.
Writing a zero to these bits has no effect.
Writing a one to these bits will set the Write Protect bit for the corresponding peripherals.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 15 14 13 12 11 10 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
EIC RTC WDT GCLK SYSCTRL PM
Access R R/W R/W R/W R/W R/W R/W R
Reset00000000
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10.6.3 PAC1 Register Description
Write Protect Clear
Name: WPCLR
Offset: 0x00
Reset: 0x00000002
Property: -
zBits 31:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:1 – PORT, NVMCTRL, DSU: Write Protect
0: Write-protection is disabled.
1: Write-protection is enabled.
Writing a zero to these bits has no effect.
Writing a one to these bits will clear the Write Protect bit for the corresponding peripherals.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
AccessRRRRRRRR
Reset00000000
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
PORT NVMCTRL DSU
Access R R R R R/W R/W R/W R
Reset00000010
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Write Protect Set
Name: WPSET
Offset: 0x04
Reset: 0x00000002
Property: -
zBits 31:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:1 – PORT, NVMCTRL, DSU: Write Protect
0: Write-protection is disabled.
1: Write-protection is enabled.
Writing a zero to these bits has no effect.
Writing a one to these bits will set the Write Protect bit for the corresponding peripherals.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
10.6.4 PAC2 Register Description
Write Protect Clear
Name: WPCLR
Offset: 0x00
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 15 14 13 12 11 10 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
PORT NVMCTRL DSU
AccessRRRRR/WR/WR/WR
Reset00000010
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Reset: 0x00100000
Property: -
zBits 31:20 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
reset value when this register is written. These bits will always return reset value when read.
zBits 19:1 – PTC, DAC, AC, ADC, TC7, TC6, TC5, TC4, TC3, TC2, TC1, TC0, SERCOM5, SERCOM4,
SERCOM3, SERCOM2, SERCOM1, SERCOM0, EV SYS: Write Protect
0: Write-protection is disabled.
1: Write-protection is enabled.
Writing a zero to these bits has no effect.
Writing a one to these bits will clear the Write Protect bit for the corresponding peripherals.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
PTC DAC AC ADC
Access R R R R R/W R/W R/W R/W
Reset00010000
Bit151413121110 9 8
TC7TC6TC5TC4TC3TC2TC1TC0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS
Access R/W R/W R/W R/W R/W R/W R/W R
Reset00000000
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Write Protect Set
Name: WPSET
Offset: 0x04
Reset: 0x00100000
Property: -
zBits 31:20 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
reset value when this register is written. These bits will always return reset value when read.
zBits 19:1 – PTC, DAC, AC, ADC, TC7, TC6, TC5, TC4, TC3, TC2, TC1, TC0, SERCOM5, SERCOM4,
SERCOM3, SERCOM2, SERCOM1, SERCOM0, EVSYS: Write Protect Enable
0: Write-protection is disabled.
1: Write-protection is enabled.
Writing a zero to these bits has no effect.
Writing a one to these bits will set the Write Protect bit for the corresponding peripherals.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
PTC DAC AC ADC
Access R R R R R/W R/W R/W R/W
Reset00010000
Bit151413121110 9 8
TC7TC6TC5TC4TC3TC2TC1TC0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS
Access R/W R/W R/W R/W R/W R/W R/W R
Reset00000000
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11. Peripherals Configuration Overview
The following table shows an overview of all the peripherals in the device. The IRQ Line column shows the interrupt
mapping, as described in “Nested Vector Interrupt Controller” on page 24.
The AHB and APB clock indexes correspond to the bit in the AHBMASK and APBMASK (x = A, B or C) registers in the
Power Manager, while the Enabled at Reset column shows whether the peripheral clock is enabled at reset (Y) or not
(N). Refer to the Power Manager AHBMASK, APBAMASK, APBBMASK and APBCMASK registers for details.
The Generic Clock Index column corresponds to the value of the Generic Clock Selection ID bits in the Generic Clock
Control register (CLKCTRL.ID) in the Generic Clock Controller. Refer to the GCLK CLKCTRL register description for
details.
The PAC Index column corresponds to the bit in the PACi (i = 0, 1 or 2) registers, while the Prot at Reset column shows
whether the peripheral is protected at reset (Y) or not (N). Refer to “PAC – Peripheral Access Controller” on page 27 for
details.
The numbers in the Events User column correspond to the value of the User Multiplexer Selection bits in the User
Multiplexer register (USER.USER) in the Event System. See the USER register description and Table 22-6 for details.
The numbers in the Events Generator column correspond to the value of the Even t Generator bits in the Channel register
(CHANNEL.EVGEN) in the Event System. See the CHANNEL register description and Table 22-3 for details.
Table 11-1. P eripherals Configuratio n Overview
Peripheral
Name Base
Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events
Index Enabled
at Reset Index Enabled
at Reset Index Index Prot at
Reset User Generator
HPB0
Peripheral
Bridge A 0x40000000 0 Y
PAC0 0x40000000 0 Y
PM 0x40000400 0 1 Y 1 N
SYSCTRL 0x40000800 1 2 Y 0: DFLL48M
reference 2 N
GCLK 0x40000C00 3 Y 3 N
WDT 0x40001000 2 4 Y 1 4 N
RTC 0x40001400 3 5 Y 2 5 N
1: CMP0/ALARM0
2: CMP1
3: OVF
4-11: PER0-7
EIC 0x40001800 NMI,
46 Y 3 6 N 12-27: EXTINT0-15
HPB1
Peripheral
Bridge B 0x41000000 1 Y
PAC1 0x41000000 0 Y
DSU 0x41002000 3 Y 1 Y 1 Y
NVMCTRL 0x41004000 5 4 Y 2 Y 2 N
PORT 0x41004400 3 Y 3 N
HPB2
Peripheral
Bridge C 0x42000000 2 Y
PAC2 0x42000000 0 N
EVSYS 0x42000400 6 1 N 4-11: one per
CHANNEL 1 N
SERCOM0 0x42000800 7 2 N 13: CORE
12: SLOW 2 N
SERCOM1 0x42000C00 8 3 N 14: CORE
12: SLOW 3 N
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SERCOM2 0x42001000 9 4 N 15: CORE
12: SLOW 4 N
SERCOM3 0x42001400 10 5 N 16: CORE
12: SLOW 5 N
SERCOM4 0x42001800 11 6 N 17: CORE
12: SLOW 6 N
SERCOM5 0x42001C00 12 7 N 18: CORE
12: SLOW 7 N
TC0 0x42002000 13 8 N 19 8 N 0: TC 28: OVF
29-30: MC0-1
TC1 0x42002400 14 9 N 19 9 N 1: TC 31: OVF
32-33: MC0-1
TC2 0x42002800 15 10 N20 10 N2: TC 34: OVF
35-36: MC0-1
TC3 0x42002C00 16 11 N20 11 N3: TC 37: OVF
38-39: MC0-1
TC4 0x42003000 17 12 N21 12 N4: TC 40: OVF
41-42: MC0-1
TC5 0x42003400 18 13 N21 13 N5: TC 43: OVF
44-45: MC0-1
TC6 0x42003800 19 14 N22 14 N6: TC 46: OVF
47-48: MC0-1
TC7 0x42003C00 20 15 N22 15 N7: TC 49: OVF
50-51: MC0-1
ADC 0x42004000 21 16 Y23 16 N8: START
9: SYNC 52: RESRDY
53: WINMON
AC 0x42004400 22 17 N24: DIG
25: ANA 17 N10-11: COMP0-1 54-55: COMP0-1
56: WIN0
DAC 0x42004800 23 18 N26 18 N12: START 57: EMPTY
PTC 0x42004C00 24 19 N27 19 N13: STCONV 58: EOC
59: WCOMP
Table 11-1. P eripherals Configuratio n Overview
Peripheral
Name Base
Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events
Index Enabled
at Reset Index Enabled
at Reset Index Index Prot at
Reset User Generator
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12. DSU – Device Service Unit
12.1 Overview
The Device Service Unit (DSU) provides a means to detect debugger probes. This enables the ARM Debug Access Port
(DAP) to have control over multiplexed debug pads and CPU reset. The DSU also provides system-level services to
debug adapters in an ARM debug system. It implements a CoreSight Debug ROM that provides device identification as
well as identification of other debug components in the system. Hence, it complies with the ARM Peripheral Identification
specification. The DSU also provides system services to applications that need memory testing, as required for
IEC60730 Class B compliance, for example. The DSU can be accessed simultaneously by a debugger and the CPU, as
it is connected on the High-Speed Bus Matrix. For security reasons, some of the DSU features will be limited or
unavailable when the device is protected by the NVMCTRL security bit (refer to “Security Bit” on page 268).
12.2 Features
zCPU reset extension
zDebugger probe detection (Cold- and Hot-Plugging)
zChip-Erase command and status
z32-bit cyclic redundancy check (CRC32) of any memory accessible through the bus matrix
zARM® CoreSight™ compliant device identification
zTwo debug communications channels
zDebug access port security filter
zOnboard memory built-in self-test (MBIST)
12.3 Block Diagram
Figure 12-1. DSU Bock Diagram
D
SU
S
W
C
LK
CO
RE
S
I
G
HT R
OM
DAP
S
E
CU
RITY FILTE
R
C
RC-32
MBI
ST
C
HIP ERAS
E
R
E
S
ET
c
pu_reset_extens
i
o
n
CP
U
D
AP
S
WDI
O
NVM
C
TRL
DB
G
M
HIGH-SPEED
HIGH-
SPEE
BUS MATRIX
MATR
US M
M
S
d
e
b
ugger_presen
t
D
E
B
U
G
G
E
R
P
R
O
B
E
INTERFA
CE
A
HB-A
P
PORTMUX
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12.4 Signal Description
Refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral.
12.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
12.5.1 I/O Lines
The SWCLK pin is by default assign ed to the DSU module to allow debugge r probe detection and the condition to stretch
the CPU reset phase. For more information, refer to “Debugger Probe Detection” on page 38. The Hot-Plugging feature
depends on the PORT configuration. If the SWCLK pin function is changed in the PORT or if the PORT_MUX is disabled,
the Hot-Plugging feature is disabled until a power-reset or an external reset.
12.5.2 Power Management
The DSU will continue to operate in any sleep mode where the selected source clock is running.
Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
12.5.3 Clocks
The DSU bus clocks (CLK_DSU_APB and CLK_DSU_AHB) can be enabled and disabled in the Power Manager. For
more information on the CLK_DSU_APB and CLK_DSU_AHB clock masks, refer to “PM – Power Manager” on page
100.
12.5.4 Interrupts
Not applicable.
12.5.5 Events
Not applicable.
12.5.6 Register Access Protection
All registers with write access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following registers:
zDebug Communication Channel 0 register (DCC0)
zDebug Communication Channel 1 register (DCC1)
Write-protection is denoted by the Write-Protection property in the register description.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
12.5.7 Analog Connections
Not applicable.
Signal Name Type Description
RESET Digital Input External reset
SWCLK Digital Input SW clock
SWDIO Digital I/O SW bidirectional data pin
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12.6 Debug Operation
12.6.1 Principle of Operation
The DSU provides basic services to allow on-chip debug using the ARM Debug Access Port and the ARM processor
debug resources:
zCPU reset extension
zDebugger probe detection
For more details on the ARM debug components, refer to the ARM Debug Interface v5Architecture Specification.
12.6.2 CPU Reset Ex te ns ion
“CPU reset extension” refers to the extension of the reset phase of the CPU core after the external reset is released. This
ensures that the CPU is not executing code at startup while a debugger connects to the system. It is detected on a
RESET release event when SWCLK is low. At startup, SWCLK is internally pulled up to avoid false detection of a
debugger if SWCLK is left unconnected. When the CPU is held in the reset extension phase, the CPU Reset Extension
bit (CRSTEXT) of the Status A register (STATUSA.CRSTEXT) is set. To release the CPU, write a one to
STATUSA.CRSTEXT. STATUSA.CRSTEXT will then be set to zero. Writing a zero to STATUSA.CRSTEXT has no
effect. For security reasons, it is not possible to release the CPU reset extension when the device is protected by the
NVMCTRL security bit (refer to “Security Bit” on page 268). Trying to do so sets the Protection Error bit (PERR) of the
Status A register (STATUSA.PERR).
Figure 12-2. Typical CPU Re s et Ex ten s ion Set and Clear Timin g Diagram
12.6.3 Debugger Probe Detection
12.6.3.1 Cold-Plugging
Cold-Plugging is the detection of a debugger when the system is in reset. Cold-Plugging is detected when the CPU reset
extension is requested, as described above.
12.6.3.2 Hot-Plugging
Hot-Plugging is the detection of a debugger probe when the system is not in reset. Hot-Plugging is not possible under
reset because the detector is reset when POR or RESET are asserted. Hot-Plugging is active when a SWCLK falling
edge is detected. The SWCLK pad is multiplexed with other functions and the user must ensure that its default function is
assigned to the debug system. If the SWCLK function is changed, the Hot-Plugging feature is disabled until a power-
reset or external reset occurs. Availability of the Hot-Plugging feature can be read from the Hot-Plugging Enable bit of the
Status B register (STATUSB.HPE).
DSU CRSTEXT
Clear
SWCLK
CPU reset
extension
CPU_STATE reset running
RE
S
E
T
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Figure 12-3. Hot-Plugging Detection Timing Diagram
The presence of a debugger probe is detected when either Hot-Plugging or Cold-Plugging is detected. Once detected,
the Debugger Present bit of the Status B register (STATUSB.DBGPRES) is set. For security reasons, Hot-Plugging is not
available when the device is protected by the NVMCTRL security bit (refer to “Security Bit” on page 268).
This detection requires that pads are correctly powered. Thus, at cold startup, this detection cannot be done until POR is
released. If the device is protected, Cold-Plugging is the only way to detect a debugger probe, and so the external reset
timing must be longer than the POR timing. If external reset is deasserted before POR release, the user must retry the
procedure above until it gets connected to the device.
12.7 Chip-Erase
Chip-Erase consists of removing all sensitive information stored in the chip and clearing the NVMCTRL security bit (refer
to “Security Bit” on page 268). Hence, all volatile memories and the flash array (including the EEPROM emulation area)
will be erased. The flash auxiliary rows, including the user row, will not be erased. When the device is protected, the
debugger must reset the device in order to be detected. This ensures that internal registers are reset after the protected
state is removed. The Chip-Erase operation is triggered by writing a one to the Chip-Erase bit in the Control register
(CTRL.CE). This command will be discarded if the DSU is protected by the Peripheral Access Controller (PAC). Once
issued, the module clears volatile memories prior to erasing the flash array. To ensure that the Chip-Erase operation is
completed, check the Done bit of the Status A register (STATUSA.DONE). The Chip-Erase operation depends on clocks
and power management features that can be altered by the CPU. For that reason, it is recommended to issue a Chip-
Erase after a Cold-Plugging procedure to ensure that the device is in a known and safe state.
The recommended sequence is as follows:
1. Issue the Cold-Plugging procedure (refer to “Cold-Plugging” on page 38). The device then:
1. Detects the debugger probe
2. Holds the CPU in reset
2. Issue the Chip-Erase command by writing a one to CTRL.CE. The device then:
1. Clears the system volatile memories
2. Erases the whole flash array (including the EEPROM emulation area, not including auxiliary rows)
3. Erases the lock row, removing the NVMCTRL security bit protection
3. Check for completion by polling STATUSA.DONE (read as one when completed).
4. Reset the device to let the NVMCTRL update fuses.
12.8 Programming
Programming of the flash or RAM memories is available when the device is not protected by the NVMCTRL security bit
(refer to “Security Bit” on page 268).
1. At power up, RESET is driven low by a debugger. The on-chip regulator holds the system in a POR state until the
input supply is above the POR threshold (refer to “Power-On Reset (POR) Characteristics” on page 571). The sys-
SWCLK
Hot-Plugging
CPU_STATE
reset running
R
ESET
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tem continues to be held in this static state until the internally regulated supplies have reached a safe operating
state.
2. The PM starts, clocks are switched to the slow clock (Core Clock, System Clock, Flash Clock and any Bus Clocks
that do not have clock gate control). Internal resets are maintained due to the external reset.
3. The debugger maintains a low level on SWCLK. Releasing RESET results in a debugger Cold-Plugging
procedure.
4. The debugger generates a clock signal on the SWCLK pin, the Debug Access Port (DAP) receives a clock.
5. The CPU remains in reset due to the Cold-Plugging procedure; meanwhile, the rest of the system is released.
6. A Chip-Erase is issued to ensure that the flash is fully erased prior to programming.
7. Programming is available through the AHB-AP.
8. After operation is completed, the chip can be restarted e ither by asserting RESET, toggling power or writing a one
to the Status A register CPU Reset Phase Extension bit (STATUSA.CRSTEXT). Make sure that the SWCLK pin is
high when releasing RESET to prevent extending the CPU reset.
12.9 Intellectual Property Protection
Intellectual property protection consists of restricting access to internal memories from external tools when the device is
protected, and is accomplished by setting the NVMCTRL security bit (refer to “Security Bit” on page 268). This protected
state can be removed by issuing a Chip-Erase (refer to “Chip-Erase” on page 39). When the device is protected,
read/write accesses using the AHB-AP are limited to the DSU address range and DSU commands are restricted.
The DSU implements a security filter that monitors the AHB transactions generated by the ARM AHB-AP inside the DAP.
If the device is protected, then AHB-AP read/write accesses outside the DSU external address range are discarded,
causing an error response that sets the ARM AHB-AP sticky erro r bits (refer to the ARM Debug Interface v5 Architecture
Specification on http://www.arm.com).
The DSU is intended to be accessed either:
zInternally from the CPU, without any limitation, even when the device is protected
zExternally from a debug adapter, with some restrictions when the device is protected
For security reasons, DSU features have limitations when used from a debug adapter. To differentiate external accesses
from internal ones, the first 0x100 bytes of the DSU register map have been replicated at offset 0x100:
zThe first 0x100 bytes form the internal address range
zThe next 0x100 bytes form the external address range
When the device is protected, the DAP can only issue MEM-AP accesses in the DSU address range limited to the 0x100-
0x2000 offset range.
The DSU operating registers are located in the 0x00-0xFF area and remapped in 0x100-0x1FF t o differentiate accesses
coming from a debugger and the CPU. If the device is p rotected and an access is issued in the region 0x100 -0x1FF, it is
subject to security restrictions. For more information, refer to Table 12-1.
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Some features not activated by APB transactions are not available when the device is protected:
12.10 Device Identification
Device identification relies on the ARM CoreSight component identification scheme, which allows the chip to be identified
as an ATMEL device implementing a DSU. The DSU contains identification registers to differentiate the device.
12.10.1 CoreSight Identification
A system-level ARM CoreSight ROM table is present in the device to identify the vendor and the chip identification
method. Its address is provided in the MEM-AP BASE register inside the ARM Debug Access Port. The CoreSight ROM
implements a 64-bit conceptual ID composed as follows from the PID0 to PID7 CoreSight ROM Table registers:
Figure 12-5. Conceptual 64-Bit Peripheral ID
Figure 12-4. APB Memory Mapping
0x0000 DSU operati ng
registers
Internal address range
(cannot be accessed from debug tools when the device is
protected by the NVMCTRL security bit)
0x00FC
0x0100 Replicated
DSU operating
registers
External address range
(can be accessed from debug tools with some restrictions)
0x01FD
Empty
0x1000 DSU CoreSight
ROM
0x1FFC
Table 12-1. Feature Availability Under Protection
Features Availability When the Device is Protected
CPU reset extension Yes
Debugger Cold-Plugging Yes
Debugger Hot-Plugging No
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For more information, refer to the ARM Debug Interface Version 5 Architecture Specification.
12.10.2 DSU Chip Identification Method:
The DSU DID register identifies the device by implementing the following information:
zProcessor identification
zFamily identification
zSubfamily identification
zDevice select
12.11 Functional Description
12.11.1 Principle of Operation
The DSU provides memory services such as CRC32 or MBIST that require almost the same interface. Hence, the
Address, Length and Data registers are shared. They must be configured first; then a command can be issued by writing
the Control register. When a command is ongoing, other commands are discarded until the current operation is
completed. Hence, the user must wait for the STATUSA.DONE bit to be set prior to issuing another one.
12.11.2 Basic Operation
12.11.2.1 Initialization
The module is enabled by enabling its clocks. For more details, refer to “Clocks” on page 37. The DSU registers can be
write-protected. Refer to “PAC – Peripheral Access Controller” on page 27.
12.11.2.2 Operation from a debug adapter
Debug adapters should access the DSU registers in the external address range 0x100 – 0x2000. If the device is
protected by the NVMCTRL security bit (refer to “Security Bit” on page 268), accessing the first 0x100 bytes causes the
system to return an error (refer to “Intellectual Property Protection” on page 40).
12.11.2.3 Operation from the CPU
There are no restrictions when accessing DSU registers from the CPU. However, the user should access DSU registers
in the internal address range (0x0 – 0x100) to avoid external security restrictions (refer to “Intellectual Property
Protection” on page 40).
Table 12-2. Conceptual 64-Bit Peripheral ID Bit Descriptio ns
Field Size Description Location
JEP-106 CC code 4Atmel continuation code: 0x0 PID4
JEP-106 ID code 7Atmel device ID: 0x1F PID1+PID2
4KB count 4Indicates that the CoreSight component is a ROM: 0x0 PID4
RevAnd 4Not used; read as 0 PID3
CUSMOD 4Not used; re ad as 0 PID3
PARTNUM 12 Cont ains 0xCD0 to indicate that DSU is present PID0+PID1
REVISION 4
DSU revision (starts at 0x0 and increments by 1 at both major and minor
revisions). Identifies DSU identification method variants. If 0x0, this
indicates that device identification can be completed by readin g the
Device Identification register (DID)
PID3
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12.11.3 32-bit Cyclic Redundancy Check (CRC32)
The DSU unit provides support for calculating a cyclic redundancy check (CRC32) value for a memory area (including
flash and AHB RAM).
When the CRC32 command is issued from:
zThe internal range, the CRC32 can be operated at any memory location
zThe external range, the CRC32 operation is restricted; DATA, ADDR and LENGTH values are forced (see below)
The algorithm employed is the industry standard CRC32 algorithm using the generator polynomial 0xEDB88320
(reversed representation).
12.11.3.1 Starting CRC32 Calculation
CRC32 calculation for a memory range is started after writing the start address into the Address register (ADDR) and the
size of the memory range into the Length register (LENGTH). Both must be word-aligned.
The initial value used for the CRC32 calculation must be written to the Data register. This value will usually be
0xFFFFFFFF, but can be, for example, the result of a previous CRC32 calculation if generating a common CRC32 of
separate memory blocks.
Once completed, the calculated CRC32 value can be read out of the Data register. The read value must be
complemented to match standard CRC32 implementations or kept non-inverted if used as starting point for subsequent
CRC32 calculations.
If the device is in protected state by the NVMCTRL security bit (refer to “Security Bit” on page 268), it is only possible to
calculate the CRC32 of the whole flash array. In most cases, this area will be the entire onboard non-volatile memory.
The Address, Length and Data registers will be forced to predefined values once the CRC32 operation is started, and
values written by the user are ignored. This allows the user to verify the contents of a protected device.
The actual test is started by writing a one in the 32-bit Cyclic Red undancy Check bit of the Control register (CTRL.CRC).
A running CRC32 operation can be canceled by resetting the module (writing a one to CTRL.SWRST).
12.11.3.2 Interpreting the Results
The user should monitor the Status A register. When the operation is completed, STATUSA.DONE is set. Then the Bus
Error bit of the Status A register (STATUSA.BERR) must be read to ensure that no bus error occurred.
12.11.4 Debug Communication Channels
The Debug Communication Channels (DCCO and DCC1) consist of a pair of registers with associated handshake logic,
accessible by both CPU and debugger even if the device is protected by the NVMCTRL security bit (refer to “Security Bit”
on page 268). The registers can be used to exchange data between the CPU and the debugger, during run time as well
as in debug mode. This enables the user to build a custom debug protocol using only these registers. The DCC0 and
DCC1 registers are accessible when the protected state is active. When the device is protected, however, it is not
possible to connect a debugger while the CPU is running (STATUSA.CRSTEXT is not writable and the CPU is held
under reset). Dirty bits in the status registers indicate whether a new value has been written in DCC0 or DCC1. These
bits,DCC0D and DCC1D, are located in the STATUSB registers. They are automatically set on write and cleared on
Table 12-3. AMOD Bit Descriptions wh en Operating CRC32
AMOD[1:0] Short Name External Range Restrictions
0ARRAY CRC32 is restricted to the full flash array area (EEPROM emulation area not included)
DATA fo rced to 0xFFFFFFFF before calcul ation (no seed)
1EEPROM CRC32 of the whole EEPROM emulation area
DATA fo rced to 0xFFFFFFFF before calcul ation (no seed)
2-3 Reserved
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read. The DCC0 and DCC1 registers are shared with the onboard memory testing logic (MBIST). Accordingly, DCC0 and
DCC1 must not be used while performing MBIST operations.
12.11.5 Testing of Onboard Memories (MBIST)
The DSU implements a feature for automatic testing of memory also known as MBIST. This is primarily intended for
production test of onboard memories. MBIST cannot be operated from the external address range when the device is
protected by the NVMCTRL security bit (refer to “Security Bit” on page 268). If a MBIST command is issued when the
device is protected, a protection error is reported in the Protection Error bit in the Status A register (STATUSA.PERR).
1. Algorithm
The algorithm used for testing is a type of March algorithm called "March LR". This algorithm is able to detect a
wide range of memory defects, while still keeping a linear run time. The algorithm is:
1. Write entire memory to 0, in any order.
2. Bit for bit read 0, write 1, in descending order.
3. Bit for bit read 1, write 0, read 0, write 1, in ascending order.
4. Bit for bit read 1, write 0, in ascending order.
5. Bit for bit read 0, write 1, read 1, write 0, in ascending order.
6. Read 0 from entire memory, in ascending order.
The specific implementation used has a run time of O(14n) where n is the number of bits in the RAM. The detected
faults are:
zAddress decoder faults
zStuck-at faults
zTransition faults
zCoupling faults
zLinked Coupling faults
zStuck-open faults
2. Starting MBIST
To test a memory, you need to write the start address of the memory to the ADDR.ADDR bit g roup, and the size of
the memory into the Length register. See “Physical Memory Map” on page 20 to know which memories are avail-
able, and which address they are at.
For best test coverage, an entire physical memory block should be tested at once. It is possible to test only a sub-
set of a memory, but the test coverage will then be somewhat lower.
The actual test is started by writing a one to CTRL.MBIST. A running MBIST operation can be canceled by writing
a one to CTRL.SWRST.
3. Interpreting the Results
The tester should monitor the STATUSA register. When the operation is completed, STATUSA.DONE is set.
There are three different modes:
zADDR.AMOD=0: exit-on-error (default)
In this mode, the algorithm terminates either when a fault is detected or on successful completion. In both cases,
STATUSA.DONE is set. If an error was detected, STATUSA.FAIL will be set. User then can read the DATA and
ADDR registers to locate the fault. Refer to “Locating Errors” on page 44.
zADDR.AMOD=1: pause-on-error
In this mode, the MBIST algorithm is paused when an error is detected. In such a situation, only STATUSA.FAIL is
asserted. The state machine waits for user to clear STATUSA.FAIL by writing a one in STATUSA.FAIL to resume.
Prior to resuming, user can read the DATA and ADDR registers to locate the fault. Refer to “Lo cating Errors” on
page 44.
4. Locating Errors
If the test stops with STATUSA.FAIL set, one or more bits failed the test. The test stops at the first detected error.
The position of the failing bit can be found by reading the following registers:
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zADDR: Address of the word containing the failing bit.
zDATA: contains data to identify which bit failed, and during which phase of the test it failed. The DATA
register will in this case contains the following bit groups:
Table 12-4. DATA bits Description When MBIST Operation Retu rn s An Error
zbit_index: contains the bit number of the failing bit
zphase: indicates which phase of the test failed and the cause of the error. See Table 12-5 on page 45.
12.11.6 System Services Availability When Accessed Externally
External access: Access performed in the DSU address offset 0x200-0x1FFF range.
Internal access: Access performed in the DSU address offset 0x0-0x100 range.
Bit3130292827262524
Bit2322212019181716
Bit151413121110 9 8
phase
Bit76543210
bit_index
Table 12-5. MBIST Operation Phases
Phase Test Actions
0Write all bits to zero. This phase cannot fail.
1Read 0, write 1, increment address
2Read 1, write 0
3Read 0, write 1, decrement address
4Read 1, write 0, decrement address
5Read 0, write 1
6Read 1, write 0, decrement address
7Read all zeros. bit_index is not used
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Table 12-6. Available Features When Op erated From The External Addre ss Range
Features Availability From The External Address Range
Chip-Erase command and status Yes
CRC32 Yes, only full array or full EEPROM
CoreSight Compliant Device identification Yes
Debug communication channels Yes
Testing of onboard memories (MBIST) Yes
STATUSA.CRSTEXT clearing No (STATUSA.PERR is set when attempting to do so )
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12.12 Register Summary
Table 12-7. Register Summary
Offset Name Bit
Pos
0x0000 CTRL 7:0 CE MBIST CRC SWRST
0x0001 STATUSA 7:0 PERR FAIL BERR CRSTEXT DONE
0x0002 STATUSB 7:0 HPE DCCD1 DCCD0 DBGPRES PROT
0x0003 Reserved
0x0004
ADDR
7:0 ADDR[5:0]
0x0005 15:8 ADDR[13:6]
0x0006 23:16 ADDR[21:14]
0x0007 31:24 ADDR[29:22]
0x0008
LENGTH
7:0 LENGTH[5:0]
0x0009 15:8 LENGTH[13:6]
0x000A 23:16 LENGTH[21:14]
0x000B 31:24 LENGTH[29:22]
0x000C
DATA
7:0 DATA[7:0]
0x000D 15:8 DATA[15:8]
0x000E 23:16 DATA[23:16]
0x000F 31:24 DATA[31:24]
0x0010
DCC0
7:0 DATA[7:0]
0x0011 15:8 DATA[15:8]
0x0012 23:16 DATA[23:16]
0x0013 31:24 DATA[31:24]
0x0014
DCC1
7:0 DATA[7:0]
0x0015 15:8 DATA[15:8]
0x0016 23:16 DATA[23:16]
0x0017 31:24 DATA[31:24]
0x0018
DID
7:0 DEVSEL[7:0]
0x0019 15:8 DIE[3:0] REVISION[3:0]
0x001A 23:16 SUBFAMILY[7:0]
0x001C 31:24 PROCESSOR[3:0] FAMILY[3:0]
0x001D Reserved
... ...
0x00FF Reserved
0x0100-
0x01FF
External address range:
Replicates the 0x00:0x1C address range,
Gives access to the same resources but with security restrictions when the device is protected.
This address range is the only one accessible externally (using the ARM DAP) when the device is protected.
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0x1000
ENTRY0
7:0 FMT EPRES
0x1001 15:8 ADDOFF[3:0]
0x1002 23:16 ADDOFF[11:4]
0x1003 31:24 ADDOFF[19:12]
0x1004
ENTRY1
7:0 FMT EPRES
0x1005 15:8 ADDOFF[3:0]
0x1006 23:16 ADDOFF[11:4]
0x1007 31:24 ADDOFF[19:12]
0x1008
END
7:0 END[7:0]
0x1009 15:8 END[15:8]
0x100A 23:16 END[23:16]
0x100B 31:24 END[31:24]
0x1FCC
MEMTYPE
7:0 SMEMP
0x1FCD 15:8
0x1FCE 23:16
0x1FCF 31:24
0x1FD0
PID4
7:0 FKBC[3:0] JEPCC[3:0]
0x1FD1 15:8
0x1FD2 23:16
0x1FD3 31:24
0x1FD4 Reserved
… …
0x1FDF Reserved
0x1FE0
PID0
7:0 PARTNBL[7:0]
0x1FE1 15:8
0x1FE2 23:16
0x1FE3 31:24
0x1FE4
PID1
7:0 JEPIDCL[3:0] PARTNBH[3:0]
0x1FE5 15:8
0x1FE6 23:16
0x1FE7 31:24
0x1FE8
PID2
7:0 REVISION[3:0] JEPU JEPIDCH[2:0]
0x1FE9 15:8
0x1FEA 23:16
0x1FEB 31:24
0x1FEC
PID3
7:0 REVAND[3:0] CUSMOD[3:0]
0x1FED 15:8
0x1FEE 23:16
0x1FEF 31:24
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0x1FF0
CID0
7:0 PREAMBLEB0[7:0]
0x1FF1 15:8
0x1FF2 23:16
0x1FF3 31:24
0x1FF4
CID1
7:0 CCLASS[3:0] PREAMBLE[3:0]
0x1FF5 15:8
0x1FF6 23:16
0x1FF7 31:24
0x1FF8
CID2
7:0 PREAMBLEB2[7:0]
0x1FF9 15:8
0x1FFA 23:16
0x1FFB 31:24
0x1FFC
CID3
7:0 PREAMBLEB3[7:0]
0x1FFD 15:8
0x1FFE 23:16
0x1FFF 31:24
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12.13 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write protection is denoted by
the Write-Protected property in each individual register description. Please refer to “Register Access Protection” on page
37 for details.
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12.13.1 Control
Name: CTRL
Offset: 0x0000
Reset: 0x00
Property: Write-Protected
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – CE: Chip Erase
Writing a zero to this bit has no effect.
Writing a one to this bit starts the Chip-Erase operation.
zBit 3 – MBIST: Memory Built-In Self-Test
Writing a zero to this bit has no effect.
Writing a one to this bit starts the memory BIST algorithm.
zBit 2 – CRC: 32-bit Cyclic Redundancy Check
Writing a zero to this bit has no effect.
Writing a one to this bit starts the cyclic redundancy check algorithm.
zBit 1 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written.
zBit 0 – SWRST: Software Reset
Writing a zero to this bit has no effect.
Writing a one to this bit resets the module.
Bit 76543210
CE MBIST CRC SWRST
Access R R R W W W R W
Reset00000000
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12.13.2 Status A
Name: STATUSA
Offset: 0x0001
Reset: 0x00
Property: Write-Protected
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – PERR: Protection Error
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Protection Error bit.
This bit is set when a command that is not allowed in protected state is issued.
zBit 3 – FAIL: Failure
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Failure bit.
This bit is set when a DSU operation failure is detected.
zBit 2 – BERR: Bus Error
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Bus Error bit.
This bit is set when a bus error is detected.
zBit 1 – CRSTEXT: CPU Reset Phase Extension
Writing a zero to this bit has no effect.
Writing a one to this bit clears the CPU Reset Phase Extension bit.
This bit is set when a debug adapter Cold-Plugging is detected, which extends the CPU reset phase.
zBit 0 – DONE: Done
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Done bit.
This bit is set when a DSU operation is completed.
Bit 76543210
PERR FAIL BERR CRSTEXT DONE
Access R R R R/W R/W R/W R/W R/W
Reset00000000
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12.13.3 Status B
Name: STATUSB
Offset: 0x0002
Reset: 0x1X
Property: Write-Protected
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – HPE: Hot-Plugging Enable
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
This bit is set when Hot-Plugging is enabled.
This bit is cleared when Hot-Plugging is disabled. This is the case when the SWCLK function is changed. Only a
power-reset or a external reset can set it again.
zBits 3:2 – DCCDx [x=1..0]: Debug Communication Channel x Dirty
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
This bit is set when DCCx is written.
This bit is cleared when DCCx is read.
zBit 1 – DBGPRES: Debugger Present
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
This bit is set when a debugger probe is detected.
This bit is never cleared.
zBit 0 – PROT: Protected
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
This bit is set at powerup when the device is protected.
This bit is never cleared.
Bit 76543210
HPE DCCD1 DCCD0 DBGPRES PROT
AccessRRRRRRRR
Reset000100XX
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12.13.4 Address
Name: ADDR
Offset: 0x0004
Reset: 0x00000000
Property: Write-Protected
zBits 31:2 – ADDR[29:0]: Address
Initial word start address needed for memory operations.
zBits 1:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit 3130292827262524
ADDR[29:22]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
ADDR[21:14]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 151413121110 9 8
ADDR[13:6]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 76543210
ADDR[5:0]
Access R/W R/W R/W R/W R/W R/W R R
Reset00000000
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12.13.5 Length
Name: LENGTH
Offset: 0x0008
Reset: 0x00000000
Property: Write-Protected
zBits 31:2 – LENGTH[29:0]: Length
Length in words needed for memory operations.
zBits 1:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit 3130292827262524
LENGTH[29:22]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
LENGTH[21:14]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 151413121110 9 8
LENGTH[13:6]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 76543210
LENGTH[5:0]
Access R/W R/W R/W R/W R/W R/W R R
Reset00000000
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12.13.6 Data
Name: DATA
Offset: 0x000C
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – DATA[31:0]: Data
Memory operation initial value or result value.
Bit 3130292827262524
DATA[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
DATA[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 151413121110 9 8
DATA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 76543210
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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12.13.7 Debug Communication Channel n
Name: DCCn
Offset: 0x0010+n*0x4 [n=0..1]
Reset: 0x00000000
Property: -
zBits 31:0 – DATA[31:0]: Data
Data register.
Bit 3130292827262524
DATA[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
DATA[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 151413121110 9 8
DATA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 76543210
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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12.13.8 Device Identification
Name: DID
Offset: 0x0018
Reset: 0x1000XXXX
Property: Write-Protected
zBits 31:28 – PROCESSOR[3:0]: Processor
zBits 27:24 – FAMILY[3:0]: Family
Bit 3130292827262524
PROCESSOR[3:0] FAMILY[3:0]
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
SUBFAMILY[7:0]
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
DIE[3:0] REVISION[3:0]
AccessRRRRRRRR
ResetXXXXXXXX
Bit 76543210
DEVSEL[7:0]
AccessRRRRRRRR
ResetXXXXXXXX
Id Description
0x0 Reserved
0x1 Cortex-M0+
0x2-0xF Reserved
Id Description
0x0 General purpose
0x1-0xF Reserved
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zBits 23:16 – SUBFAMILY[7:0]: Sub-Family
zBits 15:12 – DIE[3:0]: Die Number
Identifies the die in the family
zBits 11:8 – REVISION[3:0]: Revision Number
Identifies the die revision number
zBits 7:0 – DEVSEL[7:0]: Device Select
The value of DEVSEL is related to the pin count and flash memory density. Refer to the “Ordering Information” on
page 4 for details, and Table 12-8.
Id Description
0x00 Baseline
0x01-0xFF Reserved
Table 12-8. DEVSEL Select
DEVSEL Flash RAM Pincount
0x0 256KB 32KB 64
0x1 128KB 16KB 64
0x2 64KB 8KB 64
0x3 32KB 4KB 64
0x4 16KB 2KB 64
0x5 256KB 32KB 48
0x6 128KB 16KB 48
0x7 64KB 8KB 48
0x8 32KB 4KB 48
0x9 16KB 2KB 48
0xA Reserved
0xB 128KB 16KB 32
0xC 64KB 8KB 32
0xD 32KB 4KB 32
0xE 16KB 2KB 32
0xF-0xFF Reserved
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12.13.9 CoreSight ROM Table Entry n
Name: ENTRYn
Offset: 0x1000+n*0x4 [n=0..1]
Reset: 0xXXXXX00X
Property: Write-Protected
zBits 31:12 – ADDOFF[19:0]: Address Offset
The base address of the component, relative to the base address of this ROM table.
zBits 11:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – FMT: Format
Always read as one, indicates a 32-bit ROM table.
zBit 0 – EPRES: Entry Present
This bit indicates whether an entry is present at this location in the ROM table.
This bit is set at powerup if the device is not protected indicating that the entry is not present.
This bit is cleared at powerup if the device is not protected indicating that the entry is present.
Bit 3130292827262524
ADDOFF[19:12]
AccessRRRRRRRR
ResetXXXXXXXX
Bit 2322212019181716
ADDOFF[11:4]
AccessRRRRRRRR
ResetXXXXXXXX
Bit 151413121110 9 8
ADDOFF[3:0]
AccessRRRRRRRR
ResetXXXX0000
Bit 76543210
FMT EPRES
AccessRRRRRRRR
Reset0000001X
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12.13.10 CoreSight ROM Table End
Name: END
Offset: 0x1008
Reset: 0x00000000
Property: -
zBits 31:0 – END[31:0]: End Marker
Indicates the end of the CoreSight ROM table entries.
Bit 3130292827262524
END[31:24]
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
END[23:16]
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
END[15:8]
AccessRRRRRRRR
Reset00000000
Bit 76543210
END[7:0]
AccessRRRRRRRR
Reset00000000
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12.13.11 Coresight ROM Table Memory Type
Name: MEMTYPE
Offset: 0x1FCC
Reset: 0x0000000X
Property: -
zBits 31:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – SMEMP: System Memory Present
This bit indicates whether system memory is present on the bus that connects to the ROM table.
This bit is set at powerup if the device is not protected indicating that the system memory is accessible from a
debug adapter.
This bit is cleared at powerup if the device is protected indicating that the system memory is not accessible from a
debug adapter.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
SMEMP
AccessRRRRRRRR
Reset0000000X
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12.13.12 Peripheral Identification 4
Name: PID4
Offset: 0x1FD0
Reset: 0x00000000
Property: -
zBits 31:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:4 – FKBC[3:0]: 4KB Count
These bits will always return zero when read, indicating that this debug component occupies one 4KB block.
zBits 3:0 – JEPCC[3:0]: JEP-106 Continuation Code
These bits will always return zero when read, indicating a Atmel device.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
FKBC[3:0] JEPCC[3:0]
AccessRRRRRRRR
Reset00000000
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12.13.13 Peripheral Identification 0
Name: PID0
Offset: 0x1FE0
Reset: 0x000000D0
Property: -
zBits 31:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:0 – PARTNBL[7:0]: Part Number Low
These bits will always return 0xD0 when read, indicating that this device implements a DSU module instance.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
PARTNBL[7:0]
AccessRRRRRRRR
Reset11010000
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12.13.14 Peripheral Identification 1
Name: PID1
Offset: 0x1FE4
Reset: 0x000000FC
Property: -
zBits 31:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:4 – JEPIDCL[3:0]: Low part of the JEP-106 Identity Code
These bits will always return 0xF when read, indicating a Atmel device (Atmel JEP-106 identity code is 0x1F).
zBits 3:0 – PARTNBH[3:0]: Part Number High
These bits will always return 0xC when read, indicating that this device implements a DSU module instance.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
JEPIDCL[3:0] PARTNBH[3:0]
AccessRRRRRRRR
Reset11111100
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12.13.15 Peripheral Identification 2
Name: PID2
Offset: 0x1FE8
Reset: 0x00000009
Property: -
zBits 31:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:4 – REVISION[3:0]: Revision Number
Revision of the peripheral. Starts at 0x0 and increments by one at both major and minor revisions.
zBit 3 – JEPU: JEP-106 Identity Code is used
This bit will always return one when read, indicating that JEP-106 code is used.
zBits 2:0 – JEPIDCH[2:0]: JEP-106 Identity Code High
These bits will always return 0x1 when read, indicating an Atmel device (Atmel JEP-106 identity code is 0x1F).
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
REVISION[3:0] JEPU JEPIDCH[2:0]
AccessRRRRRRRR
Reset00001001
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12.13.16 Peripheral Identification 3
Name: PID3
Offset: 0x1FEC
Reset: 0x00000000
Property: -
zBits 31:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:4 – REVAND[3:0]: Revision Number
These bits will always return 0x0 when read.
zBits 3:0 – CUSMOD[3:0]: ARM CUSMOD
These bits will always return 0x0 when read.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
REVAND[3:0] CUSMOD[3:0]
AccessRRRRRRRR
Reset00000000
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12.13.17 Component Identification 0
Name: CID0
Offset: 0x1FF0
Reset: 0x0000000D
Property: -
zBits 31:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:0 – PREAMBLEB0[7:0]: Preamble Byte 0
These bits will always return 0xD when read.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
PREAMBLEB0[7:0]
AccessRRRRRRRR
Reset00001101
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12.13.18 Component Identification 1
Name: CID1
Offset: 0x1FF4
Reset: 0x00000010
Property: -
zBits 31:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:4 – CCLASS[3:0]: Component Class
These bits will always return 0x1 when read indicating that this ARM CoreSight component is ROM table (refer to
the ARM Debug Interface v5 Architecture Specification at http://www.arm.com).
zBits 3:0 – PREAMBLE[3:0]: Preamble
These bits will always return 0x0 when read.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
CCLASS[3:0] PREAMBLE[3:0]
AccessRRRRRRRR
Reset00010000
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12.13.19 Component Identification 2
Name: CID2
Offset: 0x1FF8
Reset: 0x00000005
Property: -
zBits 31:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:0 – PREAMBLEB2[7:0]: Preamble Byte 2
These bits will always return 0x05 when read.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
PREAMBLEB2[7:0]
AccessRRRRRRRR
Reset00000101
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12.13.20 Component Identification 3
Name: CID3
Offset: 0x1FFC
Reset: 0x000000B1
Property: -
zBits 31:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:0 – PREAMBLEB3[7:0]: Preamble Byte 3
These bits will always return 0xB1 when read.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit 76543210
PREAMBLEB3[7:0]
AccessRRRRRRRR
Reset10110001
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13. Clock System
This chapter only aims to summarize the clock distribution and terminology in the SAM D20 device. It will not explain
every detail of its configuration. For in-depth documentation, see the referenced module chapters.
13.1 Clock Distribution
Figure 13-1. Clock distribution
The clock system on the SAM D20 consists of:
zClock sources, controlled by SYSCTRL
zA Clock source is the base clock signal used in the system. Example clock sources are the internal 8MHz
oscillator (OSC8M), External crystal oscillator (XOSC) and the Digita l frequency locked loop (DFLL48M).
zGeneric Clock Controller (GCLK) which controls the clock distribution system, made up of:
zGeneric Clock generators: A programmable prescaler, that can use any of the system clock sources as its
source clock. The Generic Clock Generator 0, also called GCLKMAIN, is the clock feeding the Power
Manager used to generate synchronous clocks.
zGeneric Clocks: Typically the clock input of a peripheral on the system. The generic clocks, through the
Generic Clock Multiplexer, can use any of the Generic Clock generators as its clock source. Multiple
instances of a peripheral will typically have a separate generic clock for each instance. The DFLL48M clock
input (when multiplying another clock source) is generic clock 0.
zPower Manager (PM)
zThe PM controls synchronous clocks on the system. This includes the CPU, bus clocks (APB, AHB) as well
as the synchronous (to the CPU) user interfaces of the peripherals. It contains clock masks that can turn
on/off the user interface of a peripheral as well as prescalers for the CPU and bus clocks.
Figure 13-2 shows an example where SERCOM0 is clocked by the DFLL48M in open loop mode. The DFLL48M is
enabled, the Generic Clock Generator 1 uses the DFLL48M as its clock source, and the generic clock 13, also called
GCLK_SERCOM0_CORE, that is connected to SERCOM0 uses generator 1 as its source. The SERCOM0 interface,
clocked by CLK_SERCOM0_APB, has been unmasked in the APBC Mask register in the PM.
GC
LK
G
enerator
0
S
Y
SC
TRL GCLK
GC
LK
G
enerator 1
GC
LK
G
enerator
x
GCLK Multi
p
lexer
0
(
DFLL48M Reference
)
GC
LK Multiplexer 1
GCLK Multiplexer
y
P
er
i
p
h
era
l
z
Peripheral
0
Sy
ncronous
C
lock
C
ontroller
PM
A
HB
/
APB
Sy
stem
C
lock
s
GC
LKMAI
N
OSC
8M
OSC
32K
OSCULP32K
XOSC32K
DFLL48M
XOSC
G
eneric
C
locks
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Figure 13-2. Example of SERCOM cl ock
13.2 Synchronous and Asynchronous Clocks
As the CPU and the peripherals can be clocked from different clock sources, possibly with widely different clock speeds,
some peripheral accesses by the CPU needs to b e synchronized between the different clock domains. In these cases the
peripheral includes a SYNCBUSY status flag that can be used to check if a sync operation is in progress. As the nature
of the synchronization might vary between different peripherals, detailed description for each peripheral can be found in
the sub-chapter “synchronization” for each peripheral where this is necessary.
In the datasheet references to synchronous clocks are referring to the CPU and bus clocks, while asynchronous clocks
are clock generated by generic clocks.
13.3 Register Synchronization
13.3.1 Overview
All peripherals are composed of one digital bus interface, which is connected to the APB or AHB bus and clocked using a
corresponding synchronous clock, and one core clock, which is clocked using a generic clock. Access between these
clock domains must be synchronized. As this mechanism is implemented in hardware the synchronization process takes
place even if the different clocks domains are clocked from the same source and on the same frequency. All registers in
the bus interface are accessible without synchronization. All core registers in the generic clock domain must be
synchronized when written. Some core registers must be synchronized when read. Registers that need synchronization
has this denoted in each individual register description. Two properties are used: write-synchronization and read-
synchronization.
A common synchronizer is used for all registers in one peripheral, as shown in Figure 13-3. Therefore, only one register
per peripheral can be synchronized at a time.
SYSCTRL
DFLL48M
G
eneric
C
lock
G
enerator
1
G
eneric
C
lock
Multiplexer
13
SERCOM 0
Syncronous Clock
Controller
PM
CLK_SERCOM0_APB
GCLK_SERCOM0_CORE
GCLK
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Figure 13-3. Synchronization
13.3.2 Write-Synchronization
The write-synchronization is triggered by a write to any generic clock core register. The Synchronization Busy bit in the
Status register (STATUS.SYNCBUSY) will be set when the write-synchronization starts and cleared when the write-
synchronization is complete. Refer to “Synchronization Delay” on page 76 for details on the synchronization delay.
When the write-synchronization is ongoing (STATUS.SYNCBUSY is one), any of the following actions will cause the
peripheral bus to stall until the synchronization is complete:
zWriting a generic clock core register
zReading a read-synchronized core register
zReading the register that is being written (and thus triggered the synchronization)
Core registers without read-synchronization will remain static once they have been written and synchronized, and can be
read while the synchronization is ongoing without causing the peripheral bus to stall. APB registers can also be read
while the synchronization is ongoing without causing the peripheral bus to stall.
Non Synced reg
INTFLAG
STATUS
READREQ
Write-Synced reg
Write-Synced reg
R/W-Synced reg
Synchronizer Sync
SYNCBUSY
Synchronous Domain
(CLK_APB)
Asynchronous Domain
(generic clock)
Peripheral bus
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13.3.3 Read-Synchronization
Reading a read-synchronized core register will cause the peripheral bus to stall immediately until the read-
synchronization is complete. STATUS.SYNCBUSY will not be set. Refer to “Synchronization Delay” on page 76 for
details on the synchronization delay. Note that reading a read-synchronized core register while STATUS.SYNCBUSY is
one will cause the peripheral bus to stall twice; first because of the ongoing synchronization, and then again because
reading a read-synchronized core register will cause the peripheral bus to stall immediately.
13.3.4 Completion of synchronization
The user can either poll STATUS.SYNCBUSY or use the Synchronisation Ready interrupt (if available) to check when
the synchronization is complete. It is also possible to perform the next read/write operation and wait, as this next
operation will be started once the previous write/read operation is synchronized and/or complete.
13.3.5 Read Request
The read request functionality is only available to peripherals that have the Read Request register (READREQ)
implemented. Refer to the register description of individual peripheral chapters for details.
To avoid forcing the peripheral bus to stall when reading read-synchronized core registers, the read request mechanism
can be used.
13.3.5.1 Basic Read Request
Writing a one to the Read Request bit in the Read Request register (READREQ.RREQ) will request read-
synchronization of the register specified in the Address bits in READREQ (READREQ.ADDR) and set
STATUS.SYNCBUSY. When read-synchronization is complete, STATUS.SYNCBUSY is cleared. The read-
synchronized value is then available for reading without delay until READREQ.RREQ is written to one again.
The address to use is the offset to the peripheral's base address of the register that should be synchronized.
13.3.5.2 Continuous Read Request
Writing a one to the Read Continuously bit in READREQ (READREQ.RCONT) will force continuous read-
synchronization of the register specified in READREQ.ADDR. The latest value is always available for reading without
stalling the bus, as the synchronization mechanism is continuously synchronizing the given value.
SYNCBUSY is set for the first synchronization, but not for the subsequent synchronizations. If another synchronization is
attempted, i.e. by executing a write-operation of a write-synchronized register, the read request will be stopped, and will
have to be manually restarted.
Note that continuous read-synchronization is paused in sleep modes where the generic clock is not running. This means
that a new read request is required if the value is needed immediately after exiting sleep.
13.3.6 Enable Write-Synchronization
Writing to the Enable bit in the Control register (CTRL.ENABLE) will also trigger write-synchronization and set
STATUS.SYNCBUSY. CTRL.ENABLE will read its new value immediately after being written. The Synchronisation
Ready interrupt (if available) cannot be used for Enable write-synchronization.
When the enable write-synchronization is ongoing (STATUS.SYNCBUSY is one), attempt to do any of the following will
cause the peripheral bus to stall until the enable synchronization is complete:
zWriting a core register
zWriting an APB register
zReading a read-synchronized core register
APB registers can be read while the enable write-synchronization is ongoing without causing the peripheral bus to stall.
13.3.7 Software Reset Write-Synchronization
Writing a one to the Software Reset bit in CTRL (CTRL.SWRST) will also trigger write-synchronization and set
STATUS.SYNCBUSY. When writing a one to the CTRL.SWRST bit it will immediately read as one. CTRL.SWRST and
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STATUS.SYNCBUSY will be cleared by hardware when the peripheral has been reset. Writing a zero to the
CTRL.SWRST bit has no effect. The Synchronisation Ready interrupt (if available) cannot be used for Software Reset
write-synchronization.
When the software reset is in progress (STATUS.SYNCBUSY and CTRL.SWRST are one), attempt to do any of the
following will cause the peripheral bus to stall until the Software Reset synchronization and the reset is complete:
zWriting a core register
zWriting an APB register
zReading a read-synchronized register
APB registers can be read while the software reset is being write-synchronized without causing the peripheral bus to
stall.
13.3.8 Synchronization Delay
The synchronization will delay the write or read access duration by a delay D, given by the equation:
Where is the period of the generic clock and is the period of the peripheral bus clock. A normal peripheral
bus register access duration is .
13.4 Enabling a Peripheral
To enable a peripheral clocked by a generic clock, the following parts of the system needs to be configured:
zA running clock source.
zA clock from the Generic Clock Generator must be configured to use one of the running clock sources, and the
generator must be enabled.
zThe generic clock, through the Generic Clock Multiplexer, that connects to the peripheral needs to be configured
with a running clock from the Generic Clock Generator, and the generic clock must be enabled.
zThe user interface of the peripheral needs to be unmasked in the PM. If this is not done the peripheral registers will
read as all 0’s and any writes to the peripheral will be discarded.
13.5 On-demand, Clock Requests
Figure 13-4. Clock request routing
All the clock sources in the system can be run in an on-d emand mode, where the clock source is in a stopped state when
no peripherals are requesting the clock source. Clock requests propagate from the peripheral, via the GCLK, to the clock
source. If one or more peripheral is using a clock source, the clock source will be started/kept running. As soon as the
clock source is no longer needed and no peripheral have an active request the clock source will be stopped until
requested again. For the clock request to reach the clock source, the peripheral, the generic clock and the clock from the
Generic Clock Generator in-between must be enabled. The time taken from a clock request being asserted to the clock
source being ready is dependent on the clock source startup time, clock source frequency as well as the divider used in
the Generic Clock Generator. The total startup time from a clock request to the clock is available for the peripheral is:
Delay_start_max = Clock source startup time + 2 * clock source periods + 2 * divided clock source periods
5PGCLK
⋅2PAPB
⋅+D6PGCLK
⋅3PAPB
⋅+<<
PGCLK
PAPB
2PAPB
⋅
DFLL48M
G
eneric
C
lock
G
enerator
Clock request
G
eneric
C
lock
M
ulti
p
lexer
Clock request
P
er
iph
era
l
Clock request
ENABLE
RUNSTDBY
ONDEMAND
CLKEN
RUNSTDBY
ENABLE
RUNSTDBY
GENEN
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Delay_start_min = Clock source startup time + 1 * clock source period + 1 * divided clock source period
The delay for shutting down the clock source when there is no longer an active request is:
Delay_stop_min = 1 * divided clock source period + 1 * clock source period
Delay_stop_max = 2 * divided clock source periods + 2 * clock source periods
The On-Demand principle can be disabled individually for each clock source by clearing the ONDEMAND bit located in
each clock source controller. The clock is always running whatever is the clock request. This has the effect to remove the
clock source startup time at the cost of the power consumption.
In standby mode, the clock request mechanism is still working if the modules are configured to run in standby mode
(RUNSTDBY bit).
13.6 Power Consumption vs Speed
Due to the nature of the asynchronous clocking of the peripherals there are some considerations that needs to be taken
if either targeting a low-power or a fast-acting system. If clocking a peripheral with a very low clock, the active power
consumption of the peripheral will be lower. At the same time the synchronization to the synchronous (CPU) clock
domain is dependent on the peripheral clock speed, and will be longer with a slower peripheral clock; giving lower
response time and more time waiting for the synchronization to complete.
13.7 Clocks after Reset
On any reset the synchronous clocks start to their initial state:
zOSC8M is enabled and divided by 8
zGCLKMAIN uses OSC8M as source
zCPU and BUS clocks are undivided
On a power reset the GCLK starts to their initial state:
zAll generic clock generators disabled except:
zthe generator 0 (GCLKMAIN) using OSC8M as source, with no division
zthe generator 2 using OSCULP32K as source, with no division
zAll generic clocks disabled except:
zthe WDT generic clock using the generator 2 as source
On a user reset the GCLK starts to their initial state, except for:
zgeneric clocks that are write-locked (WRTLOCK is written to one prior to reset or the WDT generic clock if the
WDT Always-On at power on bit set in the NVM User Row)
zThe generic clock dedicated to the RTC if the RTC generic clock is enabled
On any reset the clock sources are reset to their initial state except the 32KHz clock sources which are reset only by a
power reset.
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14. GCLK – Generic Clock Controller
14.1 Overview
Several peripherals may require specific clock frequencies to operate correctly. The GCLK provides a number of generic
clock generators that can provide a wide range of clock frequencies. The generic clock generators can be set to use
different external and internal clock sources. The clock in each generic clock generator can be divided down. The outputs
from the generic clock generators are used as clock sources for the generic clock multiplexers, which select one of the
sources to generate a generic clock (GCLK_PERIPH), as shown in Figure 14-2. The number of generic clocks, m,
depends on how many peripherals the device has.
14.2 Features
zProvides a user-defined number (max 64) of generic clocks
zWide frequency range
14.3 Block Diagram
The GCLK can be seen in the clocking diagram, which is shown in Figure 14-1 .
Figure 14-1. Device Clocking Diagram
The GCLK block diagram is shown in Figure 14-2.
G
CLK
_
I
O
G
eneric Clock Generato
r
OSC8M
OSC3
2K
OSCU
LP
3
2K
XOSC
32
K
S
YSCTRL
C
lock
D
ivider
&
Masker
C
loc
k
G
at
e
G
eneric
C
lock Multiplexe
r
GC
LK_PERIP
H
P
ERIPHERAL
S
G
ENERI
C
C
L
OC
K
CO
NTR
O
LLE
R
PM
GC
LKMAI
N
D
FLL4
8
M
XOSC
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Figure 14-2 . Generi c Clock Controller Block Diagram
14.4 Signal Description
Please refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One
signal can be mapped on several pins.
14.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
14.5.1 I/O Lines
Using the GCLK’s I/O lines requires the I/O pins to be configured. Refer to “PORT” on page 284 for details.
14.5.2 Power Management
The GCLK can operate in all sleep modes, if required. Refer to “PM – Power Manager” on page 100 for details on the
different sleep modes.
14.5.3 Clocks
The GCLK bus clock (CLK_GCLK_APB) can be enabled and disabled in the Power Manager, and the default state of
CLK_GCLK_APB can be found in the Peripheral Clock Masking section in “PM – Power Manager” on page 100.
14.5.4 Interrupts
Not applicable.
Generic Clock Generator 0
GC
LK_I
O
[0]
(
I/O input)
C
lock
D
ivider
&
Maske
r
C
lock
S
ources GCLKGEN
[
0
]
GC
LK_I
O
[1]
(
I/O input
)
GC
LK
G
EN[1]
G
CLK
_
IO
[
n
]
(
I
/O
input
)
GC
LK
G
EN[n]
Clock
G
at
e
G
eneric
C
lock Multiplexer
0
GCLK
_
PERIPH
[
0
]
Clock
G
at
e
G
eneric
C
lock Multiplexer 1
C
lock
G
at
e
G
eneric Clock Multi
p
lexer
m
GC
LK
G
EN[n:0]
GC
LKMAI
N
GC
LK_I
O
[1
]
(
I
/O
output
)
GC
LK_I
O
[0
]
(I/O output
)
GCLK
_
IO
[
n
]
(
I
/O
output
)
G
eneric
C
lock
G
enerator
1
C
lock
Divider &
Maske
r
G
eneric
C
lock
G
enerator
n
C
lock
D
ivider
&
M
as
k
er
GCLK_PERIPH[1]
GCLK_PERIPH[m]
]
Signal Name Type Description
GCLK_IO[n..0] Digital I/O Source clock when input
Generic clock when output
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14.5.5 Events
Not applicable.
14.5.6 Debug Operation
Not applicable.
14.5.7 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC).
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode or the CPU reset is extended, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
14.5.8 Analog Connections
Not applicable.
14.6 Functional Description
14.6.1 Principle of Operation
The GCLK module is comprised of eight generic clock generators sourcing m generic clock multiplexers.
A clock source selected as input to one of the generic clock generators can be used directly, or it can be prescaled in the
generic clock generator before the generator output is used as input to one or more of the generic clock multiplexers. A
generic clock multiplexer provides a generic clock to the peripherals (GCLK_PERIPHERAL). A generic clock can act as
the clock to one or several of the peripherals.
14.6.2 Basic Operation
14.6.2.1 Initialization
Before a generic clock is enabled, the clock source of its generic clock generator should be enabled. The generic clock
must be configured as outlined by the following steps:
1. The generic clock generator division factor must be set by performing a single 32-bit write to the Generic Clock
Generator Division register (GENDIV):
zThe generic clock generator that will be selected as the source of the generic clock must be written to the ID
bit group (GENDIV.ID)
zThe division factor must be written to the DIV bit group (GENDIV.DIV)
2. The generic clock generator must be enabled by performing a single 32-bit write to the Generic Clock Generator
Control register (GENCTRL):
zThe generic clock generator that will be selected as the source of the generic clock must be written to the ID
bit group (GENCTRL.ID)
zThe generic clock generator must be enabled by writing a one to the GENEN bit (GENCTRL.GENEN)
3. The generic clock must be configured by performing a single 16-bit write to the Generic Clock Control register
(CLKCTRL):
zThe generic clock that will be configured must be written to the ID bit group (CLKCTRL.ID)
zThe generic clock generator used as the source of the the generic clock must be written to the GEN bit
group (CLKCTRL.GEN).
14.6.2.2 Enabling, Disabling and Resetting
The GCLK module has no enable/disable bit to enable or disable the whole module.
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The GCLK is reset by writing a one to the Software Reset bit in the Control register (CTRL.SWRST). All registers in the
GCLK will be reset to their initial state except for generic clocks and associated generators that have their Write Lock bit
written to one. Refer to “Configuration Lock” on page 83 for details.
14.6.2.3 Generic Clock Generator
Each generic clock generator (GCLKGEN) can be set to run from one of eight different clock sources except
GCLKGEN[1] which can be set to run from one of seven sources. GCLKGEN[1] can act as source to the other generic
clock generators but can not act as source to itself.
Each generic clock generator GCLKGEN[x] can be connected to one specific GCLK_IO[x] pin. The GCLK_IO[x] can be
set to act as source to GCLKGEN[x] or GCLK_IO[x] can be set up to output the clock generated by GCLKGEN[x].
The selected source (GCLKGENSRC see Figure 14-3) can optionally be divided. Each generic clock generator can be
independently enabled and disabled.
Each GCLKGEN clock can then be used as a clock source for the generic clock multiplexers. Each generic clock is
allocated to one or several peripherals.
GCLKGEN[0], is used as GCLKMAIN for the synchronous clock controller inside the Power Manager. Refer to “PM –
Power Manager” on page 100 for details on the synchronous clock generation.
Figure 14-3. Generic Clock Generator
14.6.2.4 Enabling a Generic Clock Generator
A generic clock generator is enabled by writing a one to the Generic Clock Generator Enable bit in the Generic Clock
Generator Control register (GENCTRL.GENEN).
14.6.2.5 Disabling a Generic Clock Generator
A generic clock generator is disabled by writing a zero to GENCTRL.GENEN. When GENCTRL.GENEN is read as zero,
the GCLKGEN clock is disabled and clock gated.
14.6.2.6 Selecting a Clock Source for the Generic Clock Generator
Each generic clock generator can individually select a clock source by writing to the Source Select bit group in
GENCTRL (GENCTRL.SRC). Changing from one clock source, A, to another clock source, B, can be done on the fly. If
clock source B is not ready, the generic clock generator will continue running with clock source A. As soon as clock
source B is ready, however, the generic clock generator will switch to it. During the switching, the generic clock generator
holds clock requests to clock sources A and B and then releases the clock source A request when the switch is done.
The available clock sources are device dependent (usually the oscillators, RC oscillators, PLL and DFLL clocks).
GCLKGEN[1] can be used as a common source for all the generic clock generators except generic clock generator 1.
14.6.2.7 Changing Clock Frequency
The selected generic clock generator source, GENCLKSRC can optionally be divided by writing a division factor
GC
LK_I
O
D
IVIDE
R
C
loc
k
G
at
e
GC
LK
G
EN
C
lock
S
ource
s
0
1
GENCTRL.DIVSE
L
G
EN
C
TRL.
G
ENEN
G
ENDIV.DI
V
G
ENCTRL.SR
C
GC
LK
G
EN
S
R
C
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in the Division Factor bit group in the Generic Clock Generator Division register (GENDIV.DIV). Depending on the value
of the Divide Selection bit in GENCTRL (GENCTRL.DIVSEL), it can be interpreted in two ways by the integer divider, as
shown in Table 14-1.
Note that the number of DIV bits for each generic clock generator is device dependent. Refer to Table 14-10 for details.
If GENCTRL.DIVSEL is zero and GENDIV.DIV is zero or one, the output clock will be undivided.
14.6.2.8 Duty Cycle
When dividing a clock with an odd division factor, the duty-cycle will not be 50/50. Writing a one to the Improve Duty
Cycle bit in GENCTRL (GENCTRL.IDC) will result in a 50/50 duty cycle.
14.6.2.9 External Clock
Each generic clock generator output clock (GCLKGEN) can be output. If the Output Enable bit in GENCTRL
(GENCTRL.OE) is one and the generic clock generator is enabled (GENCTRL.GENEN is one), the generic clock
generator requests its clock source and the GCLKGEN clock is output to a GCLK_IO pin. If GENCTRL.OE is zero,
GCLK_IO is set according to the Output Off Value bit. If the Output Off Value bit in GENCTRL (GENCTRL.OOV) is zero,
the output clock will be low when turned off. If GENCTRL.OOV is one, the output clock will be high when turned off.
In standby mode, if the clock is output (GENCTRL.OE is one), the clock on the GCLK_IO pin is frozen to the OOV value
if the Run In Standby bit in GENCTRL (GENCTRL.RUNSTDBY) is zero. If GENCTRL.RUNSTDBY is one, the GCLKGEN
clock is kept running and output to GCLK_IO.
14.6.3 Generic Clock
Figure 14-4 . Generic Cl oc k
14.6.3.1 Enabling a Generic Clock
Before a generic clock is enabled, one of the generic clock generators must be selected as the source for the generic
clock by writing to CLKCTRL.GEN. The clock source selection is individually set for each generic clock.
When a generic clock generator has been selected, the generic clock is enabled by writing a one to the Clock Enable bit
in CLKCTRL (CLKCTRL.CLKEN). The CLKCTRL.CLKEN bit must be synchronized to the generic clock domain.
CLKCTRL.CLKEN will continue to read as its previous state until the synchronization is complete.
Table 14-1. Division Factor
GENCTRL.DIVSEL Division Fac tor
0GENDIV.DIV
12^(GENDIV.DIV+1)
C
loc
k
G
at
e
GCLK_PERIP
H
C
LKCTRL.GEN
C
LK
C
TRL.
C
LKEN
GCLKGEN
[
0
]
GC
LK
G
EN[1]
GC
LK
G
EN[2]
GCLKGEN
[
n
]
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14.6.3.2 Disabling a Generic Clock
A generic clock is disabled by writing a zero to CLKCTRL.CLKEN. The CLKCTRL.CLKEN bit must be synchronized to
the generic clock domain and the clock actually switched off. CLKCTRL.CLKEN will continue to read as its previous state
until the synchronization is complete. When the generic clock is disabled, the generic clock is clock gated.
14.6.3.3 Selecting a Clock Source for the Generic Clock
When changing a generic clock source by writing to CLKCTRL.GEN, the generic clock must be disabled before being re-
enabled with the new clock source setting. This prevents glitches during the transition:
a. Write a zero to CLKCTRL.CLKEN
b. Wait until CLKCTRL.CLKEN reads as zero
c. Change the source of the generic clock by writing CLKCTRL.GEN
d. Re-enable the generic clock by writing a one to CLKCTRL.CLKEN
14.6.3.4 Configuration Lock
The generic clock configuration is locked for further write accesses by writing the Write Lock bit (WRTLOCK) in the
CLKCTRL register. All writes to the CLKCTRL register will be ignored. It can only be unlocked by a power reset.
The generic clock generator sources of a “locked” generic clock are also locked. The corresponding GENCTRL and
GENDIV are locked, and can be unlocked only by a power reset.
There is one exception concerning the GCLKGEN[0]. As it is used as GCLKMAIN, it can not be locked. It is reset by any
reset to startup with a known configuration.
The SWRST can not unlock the registers.
14.6.4 Additional Features
14.6.4.1 Indirect Access
The Generic Clock Generator Control and Division registers (GENCTRL and GENDIV) and the Generic Clock Control
register (CLKCTRL) are indirectly addressed as shown in Figure 14-5.
Figure 14-5. GCLK Indirect Access
Writing these registers is done by setting the corresponding ID bit group.
To read a register, the user must write (byte access) the ID of the channel, i, in the corresponding register. The value of
the register for the corresponding ID is available in the user interface by a read access.
For example, the sequence to read the GENCTRL register of generic clock generator i is:
a. Do an 8-bit write of the i value to GENCTRL.ID
b. Read GENCTRL
GENCTR
L
G
ENDIV
C
LK
C
TR
L
G
EN
C
TRL.ID=
i
G
ENDIV.ID=
i
CLKCTRL.ID=
j
U
ser Interface
GENCTR
L
G
ENDIV
GC
LK
G
enerator [i
]
C
LK
C
TR
L
G
CLK[
j
]
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14.6.4.2 Generic Clock Enable after Reset
The Generic Clock Controller must be able to provide a generic clock to some specific peripherals after a reset. That
means that the configuration of the generic clock generators and generic clocks after reset is device-dependent.
Refer to Table 14-8 and Table 14-9 for details on GENCTRL reset.
Refer to Table 14-12 and Table 14-13 for details on GENDIV reset.
Refer to Table 14-4 and Table 14-5 for details on CLKCTRL reset.
14.6.5 Sleep Mode Operation
14.6.5.1 SleepWalking
The GCLK module supports the SleepWalking feature. During a sleep mode where the generic clocks are stopped, a
peripheral that needs its generic clock to execute a process must request it from the Generic Clock Controller.
The Generic Clock Controller will receive this request and then determine which generic clock generator is involved and
which clock source needs to be awakened. It then wakes up the clock source, enables the generic clock generator and
generic clock stages successively and delivers the generic clock to the peripheral.
14.6.5.2 Run in Standby Mode
In standby mode, the GCLK can continuously output the generic clock generator output to GCLK_IO. Refer to “External
Clock” on page 82
for details.
14.6.6 Synchronization
Due to the asynchronicity between CLK_GCLK_APB and GCLKGENSRC some registers must be synchronized when
accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete.
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following registers need synchronization when written:
zGeneric Clock Generator Control register (GENCTRL)
zGeneric Clock Generator Division register (GENDIV)
zControl register (CTRL)
Write-synchronization is denoted by the Write-Synchronization property in the register description.
Refer to the Synchronization chapter for further details.
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14.7 Register Summary
Offset Name Bit
Pos.
0x0 CTRL 7:0 SWRST
0x1 STATUS 7:0 SYNCBUSY
0x2 CLKCTRL 7:0 ID[5:0]
0x3 15:8 WRTLOCK CLKEN GEN[3:0]
0x4
GENCTRL
7:0 ID[3:0]
0x5 15:8 SRC[4:0]
0x6 23:16 RUNSTDBY DIVSEL OE OOV IDC GENEN
0x7 31:24
0x8
GENDIV
7:0 ID[3:0]
0x9 15:8 DIV[7:0]
0xA 23:16 DIV[15:8]
0xB 31:24
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14.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-protected property in each individual register description. Please refer to “Register Access Protection” on page
80 for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Write-Synchronized
or the Read-Synchronized property in each individual register description. Please refer to “Synchronization” on page 84
for details.
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14.8.1 Control
Name: CTRL
Offset: 0x0
Reset: 0x00
Property: Write-Protected, Write-Synchronized
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: There is a reset operation ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the GCLK to their initial state after a power reset, except for generic
clocks and associated generators that have their WRTLOCK bit in CLKCTRL read as one.
Refer to Table 14-8 for details on GENCTRL reset.
Refer to Table 14-12 for details on GENDIV reset.
Refer to Table 14-4 for details on CLKCTRL reset.
Due to synchronization, there is a delay from writing CTRL.SWRST until the reset is complete. CTRL.SWRST and
STATUS.SYNCBUSY will both be cleared when the reset is complete.
Bit76543210
SWRST
AccessRRRRRRRR/W
Reset00000000
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14.8.2 Status
Name: STATUS
Offset: 0x1
Reset: 0x00
Property: –
zBit 7 – SYNCBUSY: Synchronization Busy Status
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 6:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit76543210
SYNCBUSY
AccessRRRRRRRR
Reset00000000
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14.8.3 Generic Clock Control
This register allows the user to configure one of the generic clocks, as specified in the CLKCTRL.ID bit group. To write to
the CLKCTRL register, do a 16-bit write with all configurations and the ID.
To read the CLKCTRL register, first do an 8-bit write to the CLKCTRL.ID bit group with the ID of the generic clock whose
configuration is to be read, and then read the CLKCTRL register.
Name: CLKCTRL
Offset: 0x2
Reset: 0x0000
Property: Write-Protected
zBit 15 – WRTLOCK: Write Lock
When this bit is written, it will lock from further writes the generic clock pointed to by CLKCTRL.ID, the generic
clock generator pointed to in CLKCTRL.GEN and the division factor used in the generic clock ge nerator. It can
only be unlocked by a power reset.
One exception to this is generic clock generator 0, which cannot be locked.
0: The generic clock and the associated generic clock generator and division factor are not locked.
1: The generic clock and the associated generic clock generator and division factor are locked.
zBit 14 – CLKEN: Clock Enable
This bit is used to enable and disable a generic clock.
0: The generic clock is disabled.
1: The generic clock is enabled.
zBits 13:12 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 11:8 – GEN[3:0]: Generic Clock Generator
These bits select the generic clock generator to be used as the source of a generic clock. The value of the GEN bit
group versus generic clock generator is shown in Table 14-2.
Bit151413121110 9 8
WRTLOCK CLKEN GEN[3:0]
Access R/W R/W R R R/W R/W R/W R/W
Reset00000000
Bit76543210
ID[5:0]
Access R R R/W R/W R/W R/W R/W R/W
Reset00000000
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zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:0 – ID[5:0]: Generic Clock Selection ID
These bits select the generic clock that will be configured. The value of the ID bit group versus module instance is shown
in Table 14-3.
Table 14-2. Generic Clock Generator
Value Description
0x0 Generic clock generator 0
0x1 Generic clock generator 1
0x2 Generic clock generator 2
0x3 Generic clock generator 3
0x4 Generic clock generator 4
0x5 Generic clock generator 5
0x6 Generic clock generator 6
0x7 Generic clock generator 7
0x8-0xF Reserved
Table 14-3. Generic Clock Selection ID
Value Description
0x00 DFLL48M Reference
0x01 WDT
0x02 RTC
0x03 EIC
0x04 EVSYS_CHANNEL_0
0x05 EVSYS_CHANNEL_1
0x06 EVSYS_CHANNEL_2
0x07 EVSYS_CHANNEL_3
0x08 EVSYS_CHANNEL_4
0x09 EVSYS_CHANNEL_5
0x0A EVSYS_CHANNEL_6
0x0B EVSYS_CHANNEL_7
0x0C SERCOMx_SLOW
0x0D SERCOM0_CORE
0x0E SERCOM1_CORE
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A power reset will reset the CLKCTRL register for all IDs, including the RTC. If the WRTLOCK bit of the corresponding ID
is zero and the ID is not the RTC, a user reset will reset the CLKCTRL register for this ID.
After a power reset, the reset value of the CLKCTRL register versus module instance is as shown in Table 14-4.
After a user reset, the reset value of the CLKCTRL register versus module instance is as shown in Table 14-5.
0x0F SERCOM2_CORE
0x10 SERCOM3_CORE
0x11 SERCOM4_CORE
0x12 SERCOM5_CORE
0x13 TC0,TC1
0x14 TC2,TC3
0x15 TC4,TC5
0x16 TC6,TC7
0x17 ADC
0x18 AC_DIG
0x19 AC_ANA
0x1A DAC
0x1B PTC
0x1C-0x3F Reserved
Table 14-4. CLKCTRL Reset Value after a Power Reset
Module Instance Reset Value after a Power Reset
CLKCTRL.GEN CLKCTRL.CLKEN CLKCTRL.WRTLOCK
RTC 0x00 0x00 0x00
WDT 0x02
0x01 if WDT Enable bit in NVM
User Row written to one
0x00 if WDT Enable bit in NVM
User Row written to zero
0x01 if WDT Always-On bit in
NVM User Row written to one
0x00 if WDT Always-On bit in
NVM User Row written to zero
Others 0x00 0x00 0x00
Table 14-3. Generic Clock Selection ID (Continued )
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Table 14-5. CLKCTRL Reset Valu e after a User Reset
Module Instance Reset Value after a User Reset
CLKCTRL.GEN CLKCTRL.CLKEN CLKCTRL.WRTLOCK
RTC
0x00 if WRTLOCK=0 and
CLKEN=0
No change if WRTLOCK=1
or CLKEN=1
0x00 if WRTLOCK=0 and CLKEN=0
No change if WRTLOCK=1 or CLKEN=1 No change
WDT 0x02 if WRTLOCK=0
No change if WRTLOCK=1
If WRTLO CK =0
0x01 if WDT Enable bit in NVM User
Row written to one
0x00 if WDT Enable bit in NVM User
Row written to zero
If WRTLOCK=1 no change
No change
Others 0x00 if WRTLOCK=0
No change if WRTLOCK=1 0x00 if WRTLOCK=0
No change if WRTLOCK=1 No change
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14.8.4 Generic Clock Generator Control
This register allows the user to configure one of the generic clock generators, as specified in the GENCTRL.ID bit group.
To write to the GENCTRL register, do a 32-bit write with all configurations and the ID.
To read the GENCTRL register, first do an 8-bit write to the GENCTRL.ID bit group with the ID of the generic clock
generator twhose configuration is to be read, and then read the GENCTRL register.
Name: GENCTRL
Offset: 0x4
Reset: 0x00010600
Property: Write-protected, Write-Synchronized
zBits 31:22 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 21 – RUNSTDBY: Run in Standby
This bit is used to keep the generic clock generator running when it is configured to be output to its dedicated
GCLK_IO pin. If GENCTRL.OE is zero, this bit has no effect and the generic clock generator will only be running if
a peripheral requires the clock.
0: The generic clock generator is stopped in standby and the GCLK_IO pin state (one or zero) will be dependent
on the setting in GENCTRL.OOV.
1: The generic clock generator is kept running and output to its dedicated GCLK_IO pin during standby mode.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
RUNSTDBY DIVSEL OE OOV IDC GENEN
Access R R R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
SRC[4:0]
Access R R R R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
ID[3:0]
Access R R R R R/W R/W R/W R/W
Reset00000000
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zBit 20 – DIVSEL: Divide Selection
This bit is used to decide how the clock source used by the generic clock generator will be divided. If the clock
source should not be divided, the DIVSEL bit must be zero and the GENDIV.DIV value for the corresponding
generic clock generator must be zero or one.
0: The generic clock generator equals the clock source divided by GENDIV.DIV.
1: The generic clock generator equals the clock source divided by 2^(GENDIV.DIV+1).
zBit 19 – OE: Output Enable
This bit is used to enable output of the generated clock to GCLK_IO when GCLK_IO is not selected as a source in
the GENCLK.SRC bit group.
0: The generic clock generator is not output.
1: The generic clock generator is output to the corresponding GCLK_IO, unless the corresponding GCLK_IO is
selected as a source in the GENCLK.SRC bit group.
zBit 18 – OOV: Output Off Value
This bit is used to control the value of GCLK_IO when GCLK_IO is not selected as a source in the GENCLK.SRC
bit group.
0: The GCLK_IO will be zero when the generic clock generator is turned off or when the OE bit is zero.
1: The GCLK_IO will be one when the generic clock generator is turned off or when the OE bit is zero.
zBit 17 – IDC: Improve Duty Cycle
This bit is used to improve the duty cycle of the generic clock generator when odd division factors are used.
0: The generic clock generator duty cycle is not 50/50 for odd division factors.
1: The generic clock generator duty cycle is 50/50.
zBit 16 – GENEN: Generic Clock Generator Enable
This bit is used to enable and disable the generic clock generator.
0: The generic clock generator is disabled.
1: The generic clock generator is enabled.
zBits 15:13 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 12:8 – SRC[4:0]: Source Select
These bits define the clock source to be used as the source for the generic clock generator, as shown in Table 14-
6.
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zBits 7:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:0 – ID[3:0]: Generic Clock Generator Selection
These bits select the generic clock generator that will be configured or read. The value of the ID bit group versus
which generic clock generator is configured is shown in Table 14-7.
A power reset will reset the GENCTRL register for all IDs, including the generic clock gen erator used by the RTC. If a
generic clock generator ID other than generic clock generator 0 is not a source of a “locked” generic clock or a source of
the RTC generic clock, a user reset will reset the GENCTRL for this ID.
After a power reset, the reset value of the GENCTRL register is as shown in Table 14-8.
Table 14-6. Source Select
Value Name Description
0x00 XOSC XOSC oscillator output
0x01 GCLKIN Generator input pad
0x02 GCLKGEN1 Generic clock generator 1 output
0x03 OSCULP32K OSCULP32K oscillator output
0x04 OSC32K OSC32K oscillator output
0x05 XOSC32K XOSC32K oscill ator output
0x06 OSC8M OSC8M oscillator output
0x07 DFLL48M DFLL48M output
0x08-0x1F Reserved Reserved for future use
Table 14-7. Generic Clock Generator Selection
Value Description
0x0 Generic clock generator 0
0x1 Generic clock generator 1
0x2 Generic clock generator 2
0x3 Generic clock generator 3
0x4 Generic clock generator 4
0x5 Generic clock generator 5
0x6 Generic clock generator 6
0x7 Generic clock generator 7
0x8-0xF Reserved
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After a user reset, the reset value of the GENCTRL register is as shown in Table 14-9
.
.
Table 14-8. GENCTRL Reset Value after a Power Reset
GCLK Generator ID Reset Value after a Power Reset
0x00 0x00010600
0x01 0x00000001
0x02 0x00010302
0x03 0x00000003
0x04 0x00000004
0x05 0x00000005
0x06 0x00000006
0x07 0x00000007
Table 14-9. GENCTRL Reset Value after a User Reset
GCLK Generator ID Reset Value after a User Reset
0x00 0x00010600
0x01 0x00000001 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x02 0x00010302 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x03 0x00000003 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x04 0x00000004 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x05 0x00000005 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x06 0x00000006 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x07 0x00000007 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
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14.8.5 Generic Clock Generator Division
This register allows the user to configure one of the generic clock generators, as specified in the GENDIV.ID bit group.
To write to the GENDIV register, do a 32-bit write with all configurations and the ID.
To read the GENDIV register, first do an 8-bit write to the GENDIV.ID bit group with the ID of the generic clock generator
whose configuration is to be read, and then read the GENDIV register.
Name: GENDIV
Offset: 0x8
Reset: 0x00000000
Property: Write-protected, Write-Synchronized
zBits 31:24 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 23:8 – DIV[15:0]: Division Factor
These bits apply a division on each selected generic clock generator. The number of DIV bits each generator has
can be seen in Table 14-10. Writes to bits above the specified number will be ignored.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
DIV[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
DIV[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
ID[3:0]
Access R R R R R/W R/W R/W R/W
Reset00000000
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zBits 7:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:0 – ID[3:0]: Generic Clock Generator Selection
These bits select the generic clock generator on which the division factor will be applied, as shown in Table 14-11.
A power reset will reset the GENDIV register for all IDs, including the generic clock generator used by the RTC. If a
generic clock generator ID other than generic clock generator 0 is not a source of a “locked” genericclock or a source of
the RTC generic clock, a user reset will reset the GENDIV for this ID.
After a power reset, the reset value of the GENDIV register is as shown in Table 14-12.
Table 14-10. Division Factor
Generator Division Factor Bits
Generic clock generator 0 5 division factor bits - DIV[4:0]
Generic clock generator 1 16 division factor bits - DIV[15:0]
Generic clock generators 2 5 division factor bits - DIV[4:0]
Generic clock generators 3 - 7 8 division factor bits - DIV[7:0]
Table 14-11. Generic Clock Generator Se lection
Value Description
0x0 Generic clock generator 0
0x1 Generic clock generator 1
0x2 Generic clock generator 2
0x3 Generic clock generator 3
0x4 Generic clock generator 4
0x5 Generic clock generator 5
0x6 Generic clock generator 6
0x7 Generic clock generator 7
0x8-0xF Reserved
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After a user reset, the reset value of the GENDIV register is as shown in Table 14-13.
Table 14-12. GENDI V Re se t va lu e a fter a Power Reset
GCLK Generator ID Reset Value after a Power Reset
0x00 0x00000000
0x01 0x00000001
0x02 0x00000002
0x03 0x00000003
0x04 0x00000004
0x05 0x00000005
0x06 0x00000006
0x07 0x00000007
Table 14-13. GENDIV Reset Value after a User Reset
GCLK Generator ID Reset Value after a User Reset
0x00 0x00000000
0x01 0x00000001 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x02 0x00000002 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x03 0x00000003 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x04 0x00000004 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x05 0x00000005 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x06 0x00000006 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
0x07 0x00000007 if the generator is not used by the RTC
No change if the generator is used by the RTC or used by a GCLK with a WRTLOCK as one
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15. PM – Power Manager
15.1 Overview
The Power Manager (PM) controls the reset, clock generation and power save modes of the microcontroller.
Utilizing a main clock chosen from a large number of clock sources from the GCLK, the clock controller provides
synchronous system clocks to the CPU and the modules connected to the AHB and the APBx bus. The synchronous
system clocks are divided into a number of clock domains; one for the CPU and AHB and one for each APBx. Any
synchronous system clock can be changed at run-time during normal operation. The clock domains can run at different
speeds, enabling the user to save power by running peripherals at a relatively low clock frequency, while maintaining
high CPU performance. In addition, the clock can be masked for individual modules, enabling the user to minimize power
consumption. If for some reason the main clock stops oscillating, the clock failure detector allows switching the main
clock to the safe OSC8M clock.
Before entering the STANDBY sleep mode the user must make sure that a significant amount of clocks and peripherals
are disabled, so that the voltage regulator is not overloaded.
Various sleep modes and clock gating are provided in order to fit power consumption requirements. This enables the
microcontroller to stop unused modules to save power. In ACTIVE mode, the CPU is executing application code. When
the device enters a sleep mode, program execution is stopped and some modules and clock domains are automatically
switched off by the PM according to the sleep mode. The application code decides which sleep mode to enter and when.
Interrupts from enabled peripherals and all enabled reset sources can restore the microcontroller from a sleep mode to
ACTIVE mode.
The PM also contains a reset controller, which collects all possible reset sources. It issues a microcontroller reset and
sets the device to its initial state, and allows the reset source to be identified by software.
15.2 Features
zReset control
zReset the microcontroller and set it to an initial state according to the reset source
zMultiple reset sources
zPower reset sources: POR, BOD12, BOD33
zUser reset sources: External reset (RESET), Watchdog Timer reset, software reset
zReset status register for reading the reset source from the application code
zClock control
zGenerates CPU, AHB and APB system clocks
zMultiple clock sources and division factor from GCLK
zClock prescaler with 1x to 128x division
zSafe run-time clock switching from GCLK
zModule-level clock gating through maskable peripheral clocks
zClock failure detector
zPower management control
zSleep modes: IDLE, STANDBY
zSleepWalking support on APB and GCLK clocks
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15.3 Block Diagram
Figure 15-1. PM Block Diagram
15.4 Signal Description
Please refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One
signal can be mapped on several pins.
15.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
15.5.1 I/O Lines
Not applicable.
15.5.2 Power Management
Not applicable.
SYNCHRONOUS
CLOCK CONTROLLER
SLEEP MODE
CONTROLLER
RESET
CONTROLLER
CPU
BOD12
BOD33
POR
WDT
OSC8M
GCLK
RESET SOURCES
PERIPHERALS
RESET
CLK_APB
CLK_AHB
CLK_CPU
USER RESET
POWER RESET
POWER MANAGER
CPU
Signal Name Type Description
RESET Digital input External reset
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15.5.3 Clocks
The PM bus clock (CLK_PM_APB) can be enabled and disabled in the power manager, and the default state of
CLK_PM_APB can be found in Table 15-1. If this clock is disabled in the Power Manager, it can only be re-enabled by a
reset.
A generic clock (GCLK_MAIN) is required to generate the main clock. This clock is configured by default in the Generic
Clock Controller, and can be re-configured by the user if needed. Please refer to “GCLK – Generic Clock Controller” on
page 78 for details.
15.5.3.1 Main Clock
The main clock (CLK_MAIN) is the common source for the synchronous clocks. This is fed into the common 8-bit
prescaler that is used to generate synchronous clocks to the CPU, AHB and APBx modules.
15.5.3.2 CPU Clock
The CPU clock (CLK_CPU) is routed to the CPU. Halting the CPU clock inhibits the CPU from executing instructions.
15.5.3.3 AHB Clock
The AHB clock (CLK_AHB) is the root clock source used by peripherals requiring an AHB clock. The AHB clock is always
synchronous to the CPU clock and has the same frequency, but may run even when the CPU clock is turned off. A clock
gate is inserted from the common AHB clock to any AHB clock of a peripheral.
15.5.3.4 APBx Clocks
The APBx clock (CLK_APBX) is the root clock source used by modules requiring a clock on the APBx bus. The APBx
clock is always synchronous to the CPU clock, but can be divided by a prescaler, and will run even when the CPU clock
is turned off. A clock gater is inserted from the common APB clock to any APBx clock of a module on APBx bus.
15.5.4 Interrupts
The interrupt request line is connected to the Interrup t Controller. Using the PM interrupt requires the Interrupt Controller
to be configured first.
15.5.5 Events
Not applicable.
15.5.6 Debug Operation
When the CPU is halted in debug mode, the PM continues normal operation. In sleep mode, the clocks generated from
the PM are kept running to allow the debugger accessing any modules. As a consequence, power measurements are not
possible in debug mode.
15.5.7 Register Access Protection
All registers with write access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following registers:
zInterrupt Flag register (INTFLAG)
zReset Cause register (RCAUSE)
Write-protection is denoted by the Write-Protection property in the register description.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
15.5.8 Analog Connections
Not applicable.
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15.6 Functional Description
15.6.1 Principle of Operation
15.6.1.1 Synchronous Clocks
The GCLK_MAIN clock from GCLK module provides the source for the main clock, which is the common root for the
synchronous clocks for the CPU and APBx modules. The main clock is divided by an 8-bit prescaler, and each of the
derived clocks can run from any tapping off this prescaler or the undivided main clock, as long as fCPU ≥ fAPBx. The
synchronous clock source can be changed on the fly to respond to varying load in the application. The clocks for each
module in each synchronous clock domain can be individually masked to avoid power consumption in inactive modules.
Depending on the sleep mode, some clock domains can be turned off.
15.6.1.2 Reset Controller
The Reset Controller collects the various reset sources and generates resets for the device. The device contains a
power-on-reset (POR) detector, which keeps the system reset until power is stable. This eliminates the need for external
reset circuitry to guarantee stable operation when powering up the device.
15.6.1.3 Sleep Mode Controller
In ACTIVE mode, all clock domains are active, allowing software execution and peripheral operation. The PM Sleep
Mode Controller allows the user to choose between different sleep modes depending on application requirements, to
save power.
15.6.2 Basic Operation
15.6.2.1 Initialization
After a power-on reset, the PM is enabled and the Reset Cause (RCAUSE) register indicates the POR source. The
default clock source of the GCLK_MAIN clock is started and calibrated before the CPU st arts running. The GCLK_MAIN
clock is selected as the main clock without any division on the prescaler. The device is in the ACTIVE mode.
By default, only the necessary clocks are enabled (see Table 15-1).
15.6.2.2 Enabling, Disabling and Resetting
The PM module is always enabled and can not be reset.
15.6.2.3 Selecting the Main Clock Source
Refer to “GCLK – Generic Clock Controller” on page 78 for details on how to configure the main clock source.
15.6.2.4 Selecting the Synchronous Clock Division Ratio
The main clock feeds an 8-bit prescaler, which can be used to generate the synchronous clocks. By default, the
synchronous clocks run on the undivided main clock. The user can select a prescaler division for the CPU clock by
writing the CPU Prescaler Selection bits in the CPU Select register (CPUSEL.CPUDIV), resulting in a CPU clock
frequency determined by this equation:
Similarly, the clock for the APBx can be divided by writing their respective registers. To ensure correct operation,
frequencies must be selected so that fCPU ≥ fAPBx. Also, frequencies must never exceed the specified maximum frequency
for each clock domain.
Note that the AHB clock is always equal to the CPU clock.
fCPU fmain
2CPUDIV
----------------------=
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CPUSEL and APBxSEL can be written without halting or disabling peripheral modules. Writing CPUSEL and APBxSEL
allows a new clock setting to be written to all synchronous clocks at the same time. It is possible to keep one or more
clocks unchanged. This way, it is possible to, for example, scale the CPU speed according to the required performance,
while keeping the APBx frequency constant.
Figure 15-2. Synchronous Clock Selection and Prescaler
15.6.2.5 Clock Ready Flag
There is a slight delay from when CPUSEL and APBxSEL are written until the new clock setting becomes effective.
During this interval, the Clock Ready flag in the Interrupt Flag Status and Clear register (INTFLAG.CKRDY) will read as
zero. If CKRDY in the INTENSET register is written to one, the Power Manager interrupt can be triggered when the new
clock setting is effective. CKSEL must not be re-written while CKRDY is zero, or the system may become unstable or
hang.
15.6.2.6 Peripheral Clock Masking
It is possible to disable or enable the clock for a peripheral in the AHB or APBx clock domain by writing the corresponding
bit in the Clock Mask register (APBxMASK) to zero or one. Refer to Table 15-1 for the default state of each of the
peripheral clocks.
Clock gate
Clock gate
Prescaler
Sleep Controller
Sleep mode
CLK_AHB
Clock gate
Clock gate
CLK_APBA
Clock gate
Clock gate
CLK_APBC
Clock gate
Clock gate
CLK_APBB
APBCDIV
APBBDIV
APBADIV
clk_ahb_ip0
clk_ahb_ip1
clk_ahb_ipn
clk_apba_ip0
clk_apba_ip1
clk_apba_ipn
clk_apbb_ip0
clk_apbb_ip1
clk_apbb_ipn
clk_apbc_ip0
clk_apbc_ip1
clk_apbc_ipn
APBCMASK
APBBMASK
APBAMASK
CPUDIV
AHBMASK
CLK_CPU
GCLK
OSC8M
GCLKMAIN
BKUPCLK
Clock
gate
Clock
gate
Clock
gate
Clock
gate
Clock
gate
Clock
gate
Clock
gate
Clock
gate
Clock
gate
Clock
Failure
Detector
CLK_MAIN
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When a module is not clocked, it will cease operation, and its registers cannot be read or written. The module can be re-
enabled later by writing the corresponding mask bit to one.
A module may be connected to several clock domains (for instance, AHB and APB), in which case it will have several
mask bits.
Note that clocks should only be switched off if it is certain that the module will not be used. Switching off the clock for the
NVM Controller (NVMCTRL) will cause a problem if the CPU needs to read from the flash memory. Switching off the
clock to the Power Manager (PM), which contains the mask registers, or the corresponding APBx bridge, will make it
impossible to write the mask registers again. In this case, they can only be re-enabled by a system reset.
15.6.2.7 Clock Failure Detector
This mechanism allows the main clock to be switched automatically to the safe OSC8M clock when the main clock
source is considered off. This may happen for instance when an external crystal oscillator is selected as the clock source
for the main clock and the crystal fails. The mechanism is to designed to detect, during a OSCULP32K clock period, at
least one rising edge of the main clock. If no rising edge is seen, the clock is considered failed.
The clock failure detector is enabled by writing a one to the Clock Failure Detector Enable bit in CTRL (CFDEN.CTRL).
As soon as the Clock Failure Detector Enable bit (CTRL.CFDEN) is one, the clock failure detector (CFD) will monitor the
divided main clock. When a clock failure is detected, the main clock automatically switches to the OSC8M clock and the
Clock Failure Detector flag in the interrupt Flag Status and Clear register (INTFLAG.CFD) is generated, if enabled. The
BKUPCLK bit in the CTRL register is set by hardware to indicate that the main clock comes from OSC8M. The
Table 15-1. Peripheral Clock Default State
Peripheral Clock Default State
CLK_PAC0_APB Enabled
CLK_PM_APB Enabled
CLK_SYSCTRL_APB Enabled
CLK_GCLK_APB Enabled
CLK_WDT_APB Enabled
CLK_RTC_APB Enabled
CLK_EIC_APB Enabled
CLK_PAC1_APB Enabled
CLK_DSU_APB Enabled
CLK_NVMCTRL_APB Enabled
CLK_PORT_APB Enabled
CLK_PAC2_APB Disabled
CLK_SERCOMx_APB Disabled
CLK_TCx_APB Disabled
CLK_ADC_APB Enabled
CLK_AC_APB Disabled
CLK_DAC_APB Disabled
CLK_PTC_APB Disabled
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GCLKMAIN clock source can be selected again by writing a zero to the CTRL.BKUPCLK bit. Writing the bit does not fix
the failure, however.
Note 1: The detector does not monitor while the main clock is temporarily unavailable (startup time after a wake-up, etc.)
or in sleep mode.
Note 2: The clock failure detector must not be enabled if the source of the main clock is not significantly faster than the
OSCULP32K clock. For instance, if GCLKMAIN is the internal 32kHz RC, then the clock failure detector must be
disabled.
15.6.2.8 Reset Controller
The latest reset cause is available in RCAUSE, and can be read during the application boot sequence in order to
determine proper action.
There are two groups of reset sources:
zPower Reset: Resets caused by an electrical issue.
zUser Reset: Resets caused by the application.
The table below lists the parts of the device that are reset, depending on the reset type.
The external reset is generated when pulling the RESET pin low. This pin has an internal pull-up, and does not need to
be driven externally during normal operation.
The POR, BOD12 and BOD33 reset sources are generated by their corresponding module in the System Controller
Interface (SYSCTRL).
The WDT reset is generated by the Watchdog Timer.
The System Reset Request (SysResetReq) is a software reset generated by the CPU when asserting the
SYSRESETREQ bit located in the Reset Control register of the CPU (please see the ARM® Cortex® Technical Reference
Manual on http://www.arm.com).
Table 15-2. Effects of the Different Reset Events
Power Reset User Reset
POR, BOD12, BOD33 External Reset WDT Reset,
SysResetReq
RTC
All the 32kHz sources
WDT with ALWAYSON feature
GCLK with WRTLOCK feat ure
Y N N
Debug logic Y Y N
Others Y Y Y
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Figure 15-3. Reset Controller
15.6.2.9 Sleep Mode Controller
Sleep mode is activated by the Wait For Interrupt instruction (WFI). The Idle bits in the Sleep Mode register
(SLEEP.IDLE) and the SLEEPDEEP bit of the System Control register of the CPU should be used as argument to select
the level of the sleep mode.
There are two main types of sleep mode:
zIDLE mode: The CPU is stopped. Optionally, some synchronous clock domains are stopped, depending on the
IDLE argument. Regulator operates in normal mode
zSTANDBY mode: All clock sources are stopped, except those where the RUNSTDBY bit is set. Regulator operates
in low-power mode
RESET CONTROLLER
BOD12
BOD33
POR
WDT
RESET
RESET SOURCES
RTC
32kHz clock sources
WDT with ALWAYSON
GCLK with WRTLOCK
Debug Logic
Others
CPU
RCAUSE
Table 15-3. Sleep Mode Entry and Ex it Table
Mode Level Mode Entry Wake-Up Sources
IDLE
0SCR.SLEEPDEEP = 0
SLEEP.IDLE=Level
WFI
Synchronous (APB, AHB), asynchronous
1Synchronous (APB), asynchronous
2Asynchronous
STANDBY SCR.SLEEPDEEP = 1
WFI Asynchronous
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Notes: 1. Refer to “SYSCTRL – System Controller” on page 127 to determine the clock sources.
2. Refer to “On-demand, Clock Requests” on pa ge 76 .
IDLE Mode
The IDLE mode allows power optimization with the fastest wake-up time.
The CPU is stopped. To further reduce power consumption, the user can disable the clocking of modules and clock
sources by configuring the SLEEP.IDLE bit group. The module will be halted regardless of the bit settings of the mask
registers in the Power Manager (PM.AHBMASK, PM.APBxMASK).
Regulator operates in normal mode.
zEntering IDLE mode: The IDLE mode is entered by executing the WFI instruction. Additionally, if the
SLEEPONEXIT bit in the ARM Cortex System Control register (SCR) is set, the IDLE mode will also be entered
when the CPU exits the lowest priority ISR. This mechanism can be useful for applications that only require the
processor to run when an interrupt occurs. Before entering the IDLE mode, the user must configure the IDLE mode
configuration bit group and must write a zero to the SCR.SLEEPDEEP bit.
zExiting IDLE mode: The processor wakes the system up when it detects any non-masked interrupt with sufficient
priority to cause exception entry. The system goes back to the ACTIVE mode. The CPU and af fected modules are
restarted.
STANDBY Mode
The STANDBY modes allow achieving very low power consumption.
In this mode, all clocks are stopped except those which are kept running if requested by a running module or have the
ONDEMAND bit set to zero. For example, the RTC can operate in STANDBY mode. In this case, its GCLK clock source
will also be enabled.
The regulator and the RAM operate in low-power mode.
A SLEEPONEXIT feature is also available.
zEntering STANDBY mode: This mode is entered by executing the WFI instruction with the SCR.SLEEPDEEP bit of
the CPU is written to 1.
zExiting STANDBY mode: Any peripheral able to generate an asynchronous interrupt can wake up the system. For
example, a module running on a GCLK clock can trigger an interrupt. When the enabled asynchronous wake-up
event occurs and the system is woken up, the device will either execute the interrupt service routine or continue
the normal program execution according to the Priority Mask Register (PRIMASK) configuration of the CPU.
15.6.3 Additional Features
15.6.4 Interrupts
The peripheral has the following interrupt sources:
Table 15-4. Sleep Mode Overview
SLEEP
Mode SLEEP.
IDLE CPU
Clock AHB
Clock APB
Clock Clock
Sources(1)(2) Main
Clock Regulator
Mode RAM
Mode
IDLE
0Stop Run Run Run if
(ONDEMAND == 0) |
((ONDEMAND == 1)
& (Module request))
Run
Normal Normal1Stop Stop Run Run
2Stop Stop Stop Run
STANDBY Stop Stop Stop
Run if
RUNSTDBY &
((ONDEMAND == 0) |
((ONDEMAND == 1)
& (Module request)))
Stop Low power Low power
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zClock Ready flag
zClock failure detector
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
(INTFLAG) register is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set (INTENSET) register, and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear (INTENCLR) register. An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the peripheral is reset. An interrupt flag is cleared by writing a one to the
corresponding bit in the INTFLAG register. Each peripheral can have one interrupt request line per interrupt source or
one common interrupt request line for all the interrupt sources. Refer to “Nested Vector Interrupt Controller” on page 24
for details. If the peripheral has one common interrupt request line for all the interrupt sources, the user must read the
INTFLAG register to determine which interrupt condition is present.
15.6.5 Events
Not applicable.
15.6.6 Sleep Mode Operation
In all IDLE sleep modes, the power manager is still running on the selected main clock.
In STANDDBY sleep mode, the power manager is frozen and is able to go back to ACTIVE mode upon any
asynchronous interrupt.
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15.7 Register Summary
Offset Name Bit Pos.
0x00 CTRL 7:0 BKUPCLK CFDEN
0x01 SLEEP 7:0 IDLE[1:0]
0x02 Reserved
0x03 Reserved
… … … … … … … … … … …
0x06 Reserved
0x07 Reserved
0x08 CPUSEL 7:0 CPUDIV[2:0]
0x09 APBASEL 7:0 APBADIV[2:0]
0x0A APBBSEL 7:0 APBBDIV[2:0]
0x0B APBCSEL 7:0 APBCDIV[2:0]
0x0C Reserved
0x0D Reserved
…
0x12 Reserved
0x13 Reserved
0x14
AHBMASK
7:0 NVMCTRL DSU HPB2 HPB1 HPB0
0x15 15:8
0x16 23:16
0x17 31:24
0x18
APBAMASK
7:0 EIC RTC WDT GCLK SYSCTRL PM PAC0
0x19 15:8
0x1A 23:16
0x1B 31:24
0x1C
APBBMASK
7:0 PORT NVMCTRL DSU PAC1
0x1D 15:8
0x1E 23:16
0x1F 31:24
0x20
APBCMASK
7:0 SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS PAC2
0x21 15:8 TC7 TC6 TC5 TC4 TC3 TC2 TC1 TC0
0x22 23:16 PTC DAC AC ADC
0x23 31:24
0x24 Reserved
0x25 Reserved
… … … … … … … … … … …
0x32 Reserved
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15.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be accessed directly.
Exception for APBASEL, APBBSEL and APBCSEL: These registers must only be accessed with 8-bit access.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Please refer to “Register Access Protection” on page
102 for details.
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15.8.1 Control
Name: CTRL
Offset: 0x00
Reset: 0x00
Property: Write-Protected
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – BKUPCLK: Backup Clock Select
This bit is set by hardware when a clock failure is detected.
0: The GCLKMAIN clock is selected for the main clock.
1: The OSC8M backup clock is selected for the main clock.
zBit 3 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 2 – CFDEN: Clock Failure Detector Enable
0: The clock failure detector is disabled.
1: The clock failure detector is enabled.
zBits 1:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit 7 6 5 4 3 2 1 0
BKUPCLK CFDEN
Access R R R R/W R R/W R R
Reset 0 0 0 0 0 0 0 0
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15.8.2 Sleep Mode
Name: SLEEP
Offset: 0x01
Reset: 0x00
Property: Write-Protected
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – IDLE[1:0]: Idle Mode Configuration
These bits select the Idle mode configuration after a WFI instruction.
Bit76543210
IDLE[1:0]
AccessRRRRRRR/WR/W
Reset00000000
Table 15-5. Idle Mode Configuration
IDLE[1:0] Description
0x0 The CPU clock domain is stopped
0x1 The CPU and AHB clock domains are stopped
0x2 The CPU, AHB and APB clock domains are sto pped
0x3 Reserved
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15.8.3 CPU Clock Select
Name: CPUSEL
Offset: 0x08
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 2:0 – CPUDIV[2:0]: CPU Prescaler Selection
These bits define the division ratio of the main clock prescaler (2n).
Bit76543210
CPUDIV[2:0]
AccessRRRRRR/WR/WR/W
Reset00000000
Table 15-6. CPU Clock Frequency Ratio
CPUDIV[1:0] Description
0x0 Divide by 1
0x1 Divide by 2
0x2 Divide by 4
0x3 Divide by 8
0x4 Divide by 16
0x5 Divide by 32
0x6 Divide by 64
0x7 Divide by 128
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15.8.4 APBA Clock Select
Name: APBASEL
Offset: 0x09
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 2:0 – APBADIV[2:0]: APBA Prescaler Selection
These bits define the division ratio of the APBA clock prescaler (2n).
Bit76543210
APBADIV[2:0]
Access R R R R R R/W R/W R/W
Reset00000000
Table 15-7. APBA Prescaler Selection
APBADIV[1:0] Description
0x0 Divide by 1
0x1 Divide by 2
0x2 Divide by 4
0x3 Divide by 8
0x4 Divide by 16
0x5 Divide by 32
0x6 Divide by 64
0x7 Divide by 128
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15.8.5 APBB Clock Select
Name: APBBSEL
Offset: 0x0A
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 2:0 – APBBDIV[2:0]: APBB Prescaler Selection
These bits define the division ratio of the APBB clock prescaler (2n).
Bit76543210
APBBDIV[2:0]
AccessRRRRRR/WR/WR/W
Reset00000000
Table 15-8. APBB Prescaler Selection
APBBDIV[1:0] Description
0x0 Divide by 1
0x1 Divide by 2
0x2 Divide by 4
0x3 Divide by 8
0x4 Divide by 16
0x5 Divide by 32
0x6 Divide by 64
0x7 Divide by 128
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15.8.6 APBC Clock Select
Name: APBCSEL
Offset: 0x0B
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 2:0 – APBCDIV[2:0]: APBC Prescaler Selection
These bits define the division ratio of the APBC clock prescaler (2n).
Bit76543210
APBCDIV[2:0]
Access R R R R R R/W R/W R/W
Reset00000000
Table 15-9. APBC Prescaler Selection
APBCDIV[1:0] Description
0x0 Divide by 1
0x1 Divide by 2
0x2 Divide by 4
0x3 Divide by 8
0x4 Divide by 16
0x5 Divide by 32
0x6 Divide by 64
0x7 Divide by 128
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15.8.7 AHB Mask
Name: AHBMASK
Offset: 0x14
Reset: 0x0000001F
Property: Write-Protected
zBits 31:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:0 – NVMCTRL, DSU, HPB2, HPB1, HPB0: AH B Clock Enable
For any bit:
0: The AHB clock for the corresponding module is stopped.
1: The AHB clock for the corresponding module is enabled.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
AccessRRRRRRRR
Reset00000000
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
NVMCTRL DSU HPB2 HPB1 HPB0
Access R R R R/W R/W R/W R/W R/W
Reset00011111
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15.8.8 APBA Mask
Name: APBAMASK
Offset: 0x18
Reset: 0x0000007F
Property: Write-Protected
zBits 31:7 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 6:0 – EIC, RTC, WDT, GCLK, SYSCTRL, PM, PAC0: APB Clock Enable
For any bit:
0: The APBA clock for the corresponding module is stopped.
1: The APBA clock for the corresponding module is enabled.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
AccessRRRRRRRR
Reset00000000
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
EIC RTC WDT GCLK SYSCTRL PM PAC0
Access R R/W R/W R/W R/W R/W R/W R/W
Reset01111111
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15.8.9 APBB Mask
Name: APBBMASK
Offset: 0x1C
Reset: 0x0000001F
Property: Write-Protected
zBits 31:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:0 – PORT, NVMCTRL, DSU, PAC1: APB Clock Enable
For any bit:
0: The APBB clock for the corresponding module is stopped.
1: The APBB clock for the corresponding module is enabled.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
AccessRRRRRRRR
Reset00000000
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
PORT NVMCTRL DSU PAC1
Access R R R R R/W R/W R/W R/W
Reset00011111
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15.8.10 APBC Mask
Name: APBCMASK
Offset: 0x20
Reset: 0x00010000
Property: Write-Protected
zBits 31:20 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 19:0 – PTC, DAC, AC, ADC, TC7, TC6, TC5, TC4, TC3, TC2, TC1, TC0, SERCOM5, SERCOM4,
SERCOM3, SERCOM2, SERCOM1, SERCOM0, EVSYS, PAC2: APB Clock Enable
For any bit:
0: The APBC clock for the corresponding module is stopped.
1: The APBC clock for the corresponding module is enabled.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
PTC DAC AC ADC
Access R R R R R/W R/W R/W R/W
Reset00000001
Bit151413121110 9 8
TC7 TC6 TC5 TC4 TC3 TC2 TC1 TC0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS PAC2
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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15.8.11 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set (INTENSET) register.
Name: INTENCLR
Offset: 0x34
Reset: 0x00
Property: Write-Protected
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – CFD: Clock Failure Detector Interrupt Enable
0: The Clock Failure Detector interrupt is disabled.
1: The Clock Failure Detector interrupt is enabled and an interrupt request will be generated when the Clock Fail-
ure Detector Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Clock Failure Detector Interrupt Enable bit and the corresponding interrupt
request.
zBit 0 – CKRDY: Clock Ready Interrupt Enable
0: The Clock Ready interrupt is disabled.
1: The Clock Ready interrupt is enabled an d will generate an interrupt request when the Clock Ready Interrupt flag
is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Clock Ready Interrupt Enable bit and the corresponding interrupt request.
Bit76543210
CFD CKRDY
AccessRRRRRRR/WR/W
Reset00000000
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15.8.12 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Name: INTENSET
Offset: 0x35
Reset: 0x00
Property: Write-Protected
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – CFD: Clock Failure Detector Interrupt Enable
0: The Clock Failure Detector interrupt is disabled.
1: The Clock Failure Detector interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Clock Failure Detector Interrupt Enable bit and enable the Clock Failure Detec-
tor interrupt.
zBit 0 – CKRDY: Clock Ready Interrupt Enable
0: The Clock Ready interrupt is disabled.
1: The Clock Ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Clock Ready Interrupt Enable bit and enable the Clock Ready interrupt.
Bit76543210
CFD CKRDY
AccessRRRRRRR/WR/W
Reset00000000
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15.8.13 Interrupt Flag Status and Clear
Name: INTFLAG
Offset: 0x36
Reset: 0x00
Property: –
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – CFD: Clock Failure Detector
This flag is cleared by writing a one to the flag.
This flag is set on the next cycle after a clock failure detector occurs and will generate an interrupt request if
INTENCLR/SET.CFD is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Clock Failure Detector Interrupt flag.
zBit 0 – CKRDY: Clock Ready
This flag is cleared by writing a one to the flag.
This flag is set when the synchronous CPU and APBx clocks have frequencies as indicated in the CPUSEL and
APBxSEL registers, and will generate an interrupt if INTENCLR/SET.CKRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Clock Ready Interrupt flag.
Bit76543210
CFD CKRDY
AccessRRRRRRR/WR/W
Reset00000000
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15.8.14 Reset Cause
Name: RCAUSE
Offset: 0x38
Reset: Latest Reset Source
Property: –
zBit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 6 – SYST: System Reset Request
This bit is set if a system reset request has been performed. Refer to the Cortex processor documentation for more
details.
zBit 5 – WDT: Watchdog Reset
This flag is set if a Watchdog Timer reset occurs.
zBit 4 – EXT: External Reset
This flag is set if an external reset occurs.
zBit 3 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 2 – BOD33: Brown Out 33 Detector Reset
This flag is set if a BOD33 reset occurs.
zBit 1 – BOD12: Brown Out 12 Detector Reset
This flag is set if a BOD12 reset occurs.
zBit 0 – POR: Power-On Reset
This flag is set if a POR occurs.
Bit76543210
SYST WDT EXT BOD33 BOD12 POR
AccessRRRRRRRR
Reset0XXX0XXX
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16. SYSCTRL – System Controller
16.1 Overview
The System Controller (SYSCTRL) provides a user interface to the XOSC, XOSC32K, OSC32K, OSCULP32K, OSC8M,
DFLL48M, BOD33, BOD12, VREG and VREF.
Through the interface registers, it is possible to enable, disable, calibrate and monitor the SYSCTRL sub-peripherals.
All sub-peripheral statuses are collected in the Power and Clocks Status register (PCLKSR). They can additionally trigger
interrupts upon status changes via the INTENSET, INTENCLR and INTFLAG registers.
Additionally, BOD33 and BOD12 interrupts can be used to wake up the device from standby mode upon a programmed
brown-out detection.
16.2 Features
z0.4-32MHz Crystal Oscillator (XOSC)
zTunable gain control
zProgrammable start-up time
zCrystal or external input clock on XIN I/O
z32.768kHz Crystal Oscillator (XOSC32K)
zAutomatic or manual gain control
zProgrammable start-up time
zCrystal or ext e rnal input clock on XIN3 2 I/O
z32.768kHz High Accuracy Internal Oscillator (OSC32K)
zFrequency fine tuning
zProgrammable start-up time
z32.768kHz Ultra Low Power Internal Oscillator (OSCULP32K)
zUltra low power, always-on oscillator
zFrequency fine tuning
zCalibration value loaded from Flash Factory Calibration at reset
z8MHz Internal Oscillator (OSC8M)
zFast startup
zOutput frequency fine tuning
z4/2/1MHz divided output frequencies available
zCalibration value loaded from Flash Factory Calibration at reset
zDigital Frequency Locked Loop (DFLL48M)
zInternal oscillator with no external components
z48MHz output frequency
zOperates standalone as a high-frequency programmable oscillator in open loop mode
zOperates as an accurate frequency multiplier ag ainst a known frequency in closed loop mode
z3.3V Brown-Out Detector (BOD33)
zProgrammable threshold
zThreshold value loaded from Flash User Calibration at startup
zTriggers resets or interrupts
zOperating modes:
zContinuous mode
zSampled mode for low power applications (prog ramma ble refresh frequency)
zHysteresis
z1.2V Brown-Out Detector (BOD12)
zProgrammable threshold
zThreshold value loaded from Flash User Calibration at startup
zTriggers resets or interrupts
zOperating modes:
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zContinuous mode
zSampled mode for low power applications (prog ramma ble refresh frequency)
zHysteresis
zVoltage Reference System (VREF)
zBandgap voltage generator with programmable calibration value
zTemperature sensor
zBandgap calibration value loaded from Flash Factory Calibration at startup
zVoltage Regulator System (VREG)
zTr imable core supply voltage level
zVoltage regulator trim value loaded from Flash Factory Calibration at startup
16.3 Block Diagram
Figure 16-1. SYSCTRL Block Diagram
XOSC
X
OSC
32
K
OSC3
2
K
OSCU
LP
3
2K
O
SC8
M
DFLL48M
BO
D12
BO
D
33
VO
LTA
G
E
R
EFEREN
CE
S
Y
S
TE
M
VO
LTA
GE
R
EGULATOR
S
YSTE
M
OSC
ILLAT
O
R
S
CO
NTR
OL
PO
WER
M
O
NIT
OR
CO
NTR
OL
VO
LTA
G
E
R
EFEREN
CE
CO
NTR
OL
VO
LTA
G
E
R
EGULATOR
CONTRO
L
S
TAT
US
(
PCLKSR re
g
ister
)
INTERRUPT
S
G
ENERAT
OR
I
nterrupt
s
SYSCTRL
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16.4 Signal Description
The I/O lines are automatically selected when XOSC or XOSC32K are enabled.
16.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
16.5.1 I/O Lines
I/O lines are configured by SYSCTRL when either XOSC or XOSC32K are enabled, and need no user configuration.
16.5.2 Power Management
The SYSCTRL can continue to operate in any sleep mode where the selected source clock is running. The SYSCTRL
interrupts can be used to wake up the device from sleep modes. The events can trigger other operations in the system
without exiting sleep modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
16.5.3 Clocks
The SYSCTRL gathers controls for all device oscillators and provides clock sources to the Generic Clock Controller
(GCLK). The available clock sources are: XOSC, XOSC32K, OSC32K, OSCULP32K, OSC8M and DFLL48M.
The SYSCTRL bus clock (CLK_SYSCTRL_APB) can be enabled and disabled in the Power Manager, and the default
state of CLK_SYSCTRL_APB can be found in the Peripheral Clock Masking section in the “PM – Power Manager” on
page 100.
The clock used by BOD33 and BOD12 in sampled mode is asynchronous to the user interface clock
(CLK_SYSCTRL_APB). Likewise, the DFLL48M control logic uses the DFLL oscillator output, which is also
asynchronous to the user interface clock (CLK_SYSCTRL_APB). Due to this asynchronicity, writes to certain registers
will require synchronization between the clock domains. Refer to “Synchronization” on page 138 for further details.
16.5.4 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the SYSCTRL interrupts requires the interrupt
controller to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
16.5.5 Debug Operation
When the CPU is halted in debug mode, the SYSCTRL continues normal operation. If the SYSCTRL is configured in a
way that requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss
may result during debugging.
If a debugger connection is detected by the system, BOD33 and BOD12 resets will be blocked.
Signal Name Type Description
XIN Analog Input Multipurpose Crystal Oscillator or external
clock generator input
XOUT Analog Output External Multipurpose Crystal Oscillator
output
XIN32 Analog Input 32kHz Crystal Oscillator or external clock
generator input
XOUT32 Analog Output 32kHz Crystal Oscillator output
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16.5.6 Register Access Protection
All registers with write-access are optionally write-protected by the peripheral access controller (PAC), except the
following registers:
zInterrupt Flag Status and Clear register (INTFLAG)
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
16.5.7 Analog Connections
The 32.768kHz crystal must be connected between the XIN32 and XOUT32 pins, and the 0.4-32MHz crystal must be
connected between the XIN and XOUT pins, along with any required load capacitors. For details on recommended
oscillator characteristics and capacitor load. Refer to the “Electrical Characteristics” on page 562 for details.
16.6 Functional Description
16.6.1 Principle of Operation
XOSC, XOSC32K, OSC32K, OSCULP32K, OSC8M, DFLL48M, BOD33, BOD12, VREG and VREF are configured via
SYSCTRL control registers. Through this interface, the sub-peripherals are enabled, disabled or have their calibration
values updated.
The Power and Clocks Status register gathers different status signals coming from the sub-peripherals controlled by the
SYSCTRL. The status signals can be used to generate system interrupts, and in some cases wake up the system from
standby mode, provided the corresponding interrupt is enabled.
16.6.2 External Multipurpose Crystal Oscillator (XOSC) Operation
The XOSC can operate in two different modes:
zExternal clock, with an external clock signal connected to the XIN pin
zCrystal oscillator, with an external 0.4-32MHz crystal
The XOSC can be used as a clock source for generic clock generators, as described in the “GCLK – Generic Clock
Controller” on page 78.
At reset, the XOSC is disabled, and the XIN/XOUT pins can be used as General Purpose I/O (GPIO) pins or by other
peripherals in the system. When XOSC is enabled, the operating mode determines the GPIO usage. When in crystal
oscillator mode, the XIN and XOUT pins are controlled by the SYSCTRL, and GPIO functions are overridden on both
pins. When in external clock mode, the only XIN pin will be overridden and controlled by the SYSCTRL, while the XOUT
pin can still be used as a GPIO pin.
The XOSC is enabled by writing a one to the Enable bit in the External Multipurpose Crystal Oscillator Control register
(XOSC.ENABLE). To enable the XOSC as a crystal oscillator, the XTAL Enable bit (XOSC.XTALEN) must written to one.
If XOSC.XTALEN is zero, external clock input will be enabled.
When in crystal oscillator mode (XOSC.XTALEN is one), the External Multipurpose Crystal Oscillator Gain (XOSC.GAIN)
must be set to match the external crystal oscillator frequency. If the External Multipurpose Crystal Oscillator Automatic
Amplitude Gain Control (XOSC.AMPGC) is one, the oscillator amplitude will be automatically adjusted, and in most
cases result in a lower power consumption.
The XOSC will behave differently in different sleep modes based on the settings of XOSC.RUNSTDBY,
XOSC.ONDEMAND and XOSC.ENABLE:
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After a hard reset, or when waking up from a sleep mode where the XOSC was disabled, the XOSC will need a certain
amount of time to stabilize on the correct frequency. This start-up time can be configured by changing the Oscillator
Start-Up Time bit group (XOSC.STARTUP) in the External Multipurpose Crystal Oscillator Control register. During the
start-up time, the oscillator output is masked to ensure that no unstable clock propagates to the digital logic. The External
Multipurpose Crystal Oscillator Ready bit in the Power and Clock Status register (PCLKSR.XOSCRDY) is set when the
external clock or crystal oscillator is stable and ready to be used as a clock source. An interrupt is generated on a zero-
to-one transition on PCLKSR.XOSCRDY if the External Multipurpose Crystal Oscillator Ready bit in the Interrupt Enable
Set register (INTENSET.XOSCRDY) is set.
16.6.3 32kHz External Crystal Oscillator (XOSC32K) Operation
The XOSC32K can operate in two different modes:
zExternal clock, with an external clock signal connected to XIN32
zCrystal oscillator, with an external 32.768kHz crystal connected between XIN32 and XOUT32
The XOSC32K can be used as a source for generic clock generators, as described in the “GCLK – Generic Clock
Controller” on page 78.
At power-on, reset the XOSC32K is disabled, and the XIN32/XOUT32 pins can be used as General Purpose I/O (GPIO)
pins or by other peripherals in the system. When XOSC32K is enabled, the operating mode determines the GPIO usage.
When in crystal oscillator mode, XIN32 and XOUT32 are controlled by the SYSCTRL, an d GPIO functions are overridden
on both pins. When in external clock mode, only the XIN32 pin will be overridden and controlled by the SYSCTRL, while
the XOUT32 pin can still be used as a GPIO pin.
The external clock or crystal oscillator is enabled by writing a one to the Enable bit (XOSC32K.ENABLE) in the 32kHz
External Crystal Oscillator Control register. To enable the XOSC32K as a crystal oscillator, a one must be written to the
XTAL Enable bit (XOSC32K.XTALEN). If XOSC32K.XTALEN is zero, external clock input will be enabled.
The oscillator is disabled by writing a zero to the Enable bit (XOSC32K.ENABLE) in the 32kHz External Crystal Oscillator
Control register while keeping the other bits unchanged. Writing to the XOSC32K.ENABLE bit while writing to other bits
may result in unpredictable behavior. The oscillator remains enabled in all sleep modes if it has been enabled
beforehand. The start-up time of the 32kHz External Crystal Oscillator is selected by writing to the Oscillator Start-Up
Time bit group (XOSC32K.STARTUP) in the in the 32kHz External Crystal Oscillator Control register. The SYSCTRL
masks the oscillator output during the start-up time to ensure that no unstable clock propagates to the digital logic. The
32kHz External Crystal Oscillator Ready bit (PCLKSR.XOSC32KRDY) in the Power and Clock Status register is set
when the oscillator is stable and ready to be used as a clock source. An interrupt is generated on a zero-to-one transition
XOSC.RUNSTDBY XOSC.ONDEMAND XOSC.ENABLE Sleep Behavior
- - 0 Disabled
0 0 1 Always run in IDLE sleep
modes. Disabl ed in
STANDBY sleep mode.
0 1 1
Only run in IDLE sleep
modes if requested by a
peripheral. Disabled in
STANDBY sleep mode.
1 0 1 Always run in IDLE and
STANDBY sleep modes.
1 1 1 Only run in IDLE or
STANDBY sleep modes if
requested by a peripheral.
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of PCLKSR.XOSC32KRDY if the 32kHz External Crystal Oscillator Ready bit (INTENSET.XOSC32KRDY) in the
Interrupt Enable Set Register is set.
As a crystal oscillator usually requires a very long start-up time (up to one second), the 32kHz External Crystal Oscillator
will keep running across resets, except for power-on reset (POR).
The XOSC32K has a 32.768kHz output enabled by writing a one to the 32kHz External Crystal Oscillator 32kHz Output
Enable bit (XOSC32K.EN32K) in the 32kHz External Crystal Oscillator Control register. The XOSC32K also has a
1.024kHz clock output enabled by writing a one to the 32kHz External Crystal Oscillator 1kHz Output Enable bit
(XOSC32K.EN1K) in the External 32kHz Crystal Oscillator Control register. XOSC32K.EN32K and XOSC32K.EN1K are
only usable when XIN32 is connected to a crystal, and not when an external digital clock is applied on XIN32.
16.6.4 32kHz Internal Oscillator (OSC32K) Operation
The OSC32K provides a tunable, low-speed and low-power clock source.
The OSC32K can be used as a source for the generic clock generators, as described in the “GCLK – Generic Clock
Controller” on page 78.
The OSC32K is disabled by default. The OSC32K is enabled by writing a one to the 32kHz Internal Oscillator Enable bit
(OSC32K.ENABLE) in the 32kHz Internal Oscillator Control register. It is disabled by writing a zero to OSC32K.ENABLE.
The OSC32K has a 32.768kHz output enabled by writing a one to the 32kHz Internal Oscillator 32kHz Output Enab le bit
(OSC32K.EN32K). The OSC32K also has a 1.024kHz clock output enabled by writing a one to the 32kHz Internal
Oscillator 1kHz Output Enable bit (OSC32K.EN1K).
The frequency of the OSC32K oscillator is controlled by the value in the 32kHz Internal Oscillator Calibration bits
(OSC32K.CALIB) in the 32kHz Internal Oscillator Control register. The CALIB value must be written by the user. Flash
Factory Calibration values are stored in the non-volatile memory. When writing to the Calibration bits, the user must wait
for the PCLKSR.OSC32KRDY bit to go high before the value is committed to the oscillator.
16.6.5 32kHz Ultra Low Power Internal Oscillator (OSCULP32K) Operation
The OSCULP32K provides a tunable, low-speed and ultra-low-power clock source. The OSCULP32K is factory-
calibrated under typical voltage and temperature conditions. The OSCULP32K should be preferred to the OSC32K
whenever the power requirements are prevalent over frequency stability and accuracy.
The OSCULP32K can be used as a source for the generic clock generators, as described in the “GCLK – Generic Clock
Controller” on page 78.
The OSCULP32K is enabled by default after a power-on reset (POR) and will always run except during POR. The
OSCULP32K has a 32.768kHz output and a 1.024kHz output that are always running.
The frequency of the OSCULP32K oscillator is controlled by the value in the 32kHz Ultra Low Power Internal Oscillator
Calibration bits (OSCULP32K.CALIB) in the 32kHz Ultra Low Power Internal Oscillator Control register.
OSCULP32K.CALIB is automatically loaded from Flash Factory Calibration during startup, and is used to compensate for
process variation, as described in the “Electrical Characteristics” on page 562. The calibration value can be overridden
by the user by writing to OSCULP32K.CALIB.
16.6.6 8MHz Internal Oscillator (OSC8M) Operation
OSC8M is an internal oscillator operating in open-loop mode and generating an 8MHz frequency. The OSC8M is factory-
calibrated under typical voltage and temperature conditions.
OSC8M is the default clock source that is used after a power-on reset (POR). The OSC8M can be used as a source for
the generic clock generators, as described in the “GCLK – Generic Clock Controller” on page 78, as well as function as
the backup clock if a main clock failure is detected.
OSC8M is enabled by writing a one to the Oscillator Enable bit (OSC8M.ENABLE) in the OSC8M Control register, and
disabled by writing a zero to this bit. When enabling OSC8M, OSC8M.ENABLE must be read back until it reads one. The
user must ensure that the OSC8M is fully disabled before enabling it, and that the OSC8M is fully enabled before
disabling it by reading OSC8M.ENABLE.
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The frequency of the OSC8M oscillator is controlled by the value in the calibration bits (OSC8M.CALIB) in the OSC8M
Control register. CALIB is automatically loaded from Flash Factory Calibration during startup, and is used to compensate
for process variation, as described in the “Electrical Characteristics” on page 562.
The user can control the oscillation frequency by writing to the Frequency Range (FRANGE) and Calibration (CALIB) bit
groups in the 8MHz RC Oscillator Control register (OSC8M). The FRANGE and CALIB bit groups should only be updated
when the OSC8M is disabled. As this is in open-loop mode, the frequency will be voltage, temperature and process
dependent. Refer to the “Electrical Characteristics” on page 562 for details.
OSC8M is automatically switched off in certain sleep modes to reduce power consumption, as described in the “PM –
Power Manager” on page 100.
16.6.7 Digital Frequency Locked Loop (DFLL48M) Operation
The DFLL48M can operate in both open-loop mode and closed-loop mode. In closed-loop mode, a low-frequency clock
with high accuracy can be used as the reference clock to get high accuracy on the output clock (CLK_DFLL48M).
The DFLL48M can be used as a source for the generic clock generators, as described in the “GCLK – Generic Clock
Controller” on page 78.
16.6.7.1 Basic Operation
Open-Loop Operation
After any reset, the open-loop mode is selected. When operating in open-loop mode, the output frequency of the
DFLL48M will be determined by the values written to the DFLL Coarse Value bit group and the DFLL Fine Value bit
group (DFLLVAL.COARSE and DFLLVAL.FINE) in the DFLL Value register.
It is possible to change the values of DFLLVAL.COARSE and DFLLVAL.FINE and thereby the output frequency of the
DFLL48M output clock, CLK_DFLL48M, while the DFLL48M is enabled and in use. CLK_DFLL48M is ready to be used
when PCLKSR.DFLLRDY is set after enabling the DFLL48M.
Closed-Loop Operation
In closed-loop operation, the output frequency is continuously regulated against a reference clock. Once the
multiplication factor is set, the oscillator fine tuning is automatically adjusted. The DFLL48M must be correctly configured
before closed-loop operation can be enabled. After enabling the DFLL48M, it must be configured in the following way:
1. Enable and select a reference clock (CLK_DFLL48M_REF). CLK_DFLL48M_REF is Generic Clock Channel 0
(DFLL48M_Reference). Refer to “GCLK – Generic Clock Controller” on page 78 for details.
2. Select the maximum step size allowed in finding the Coarse and Fine values by writing the appropriate values to
the DFLL Coarse Maximum Step and DFLL Fine Maximum Step bit groups (DFLLMUL.CSTEP and DFLL-
MUL.FSTEP) in the DFLL Multiplier register. A small step size will ensure low overshoot on the output frequency,
but will typically result in longer lock times. A high value might give a large overshoot, but will typically provide
faster locking. DFLLMUL.CSTEP and DFLLMUL.FSTEP should not be higher than 50% of the maximum value of
DFLLVAL.COARSE and DFLLVAL.FINE, respectively.
3. Select the multiplication factor in the DFLL Multiply Factor bit group (DFLLMUL.MUL) in the DFLL Multiplier regis-
ter. Care must be taken when choosing DFLLMUL.MUL so that the output frequency does not exceed the
maximum frequency of the device. If the target frequency is below the minimum frequency of the DFLL48M, the
output frequency will be equal to the DFLL minimum frequency.
4. Start the closed loop mode by writing a one to the DFLL Mode Selection bit (DFLLCTRL.MODE) in the DFLL Con-
trol register.
The frequency of CLK_DFLL48M (Fclkdfll48m) is given by:
Fclkdfll48mDFLLMUL MUL Fclkdfll48mref
×⋅=
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where Fclkdfll48mref is the frequency of the reference clock (CLK_DFLL48M_REF). DFLLVAL.COARSE and
DFLLVAL.FINE are read-only in closed-loop mode, and are controlled by the frequency tuner shown in Figure 16-1 to
meet user specified frequency. In closed-loop mode, the value in DFLLVAL.COARSE is used by the frequency tuner as
a starting point for Coarse. Writing DFLLVAL.COARSE to a value close to the final value before entering closed-oop
mode will reduce the time needed to get a lock on Coarse.
Frequency Locking
The locking of the frequency in closed-loop mode is divided into two stages. In the first, coarse stage, the control logic
quickly finds the correct value for DFLLVAL.COARSE and sets the output frequency to a value close to the correct
frequency. On coarse lock, the DFLL Locked on Coarse Value bit (PCLKSR.DFLLLOCKC) in the Power and Clocks
Status register will be set.
In the second, fine stage, the control logic tunes the value in DFLLVAL.FINE so that the output fre quency is very close to
the desired frequency. On fine lock, the DFLL Locked on Fine Value bit (PCLKSR.DFLLLOCKF) in the Power and Clocks
Status register will be set.
Interrupts are generated by both PCLKSR.DFLLLOCKC and PCLKSR.DFLLLOCKF if INTENSET.DFLLOCKC or
INTENSET.DFLLOCKF are written to one.
CLK_DFLL48M is ready to be used when the DFLL Ready bit (PCLKSR.DFLLRDY) in the Power and Clocks Status
register is set, but the accuracy of the output frequency depends on which locks are set. For lock times, refer to the
“Electrical Characteristics” on page 562.
Frequency Error Measurement
The ratio between CLK_DFLL48M_REF and CLK48M_DFLL is measured automatically when the DFLL48M is in closed-
loop mode. The difference between this ratio and the value in DFLLMUL.MUL is stored in the DFLL Multiplication Ratio
Difference bit group(DFLLVAL.DIFF) in the DFLL Value register. The relative error on CLK_DFLL48M compared to the
target frequency is calculated as follows:
Drift Compensation
If the Stable DFLL Frequency bit (DFLLCTRL.STABLE) in the DFLL Control register is zero, the frequency tuner will
automatically compensate for drift in the CLK_DFLL48M without losing either of the locks. This means that
DFLLVAL.FINE can change after every measurement of CLK_DFLL48M. If the DFLLVAL.FINE value overflows or
underflows due to large drift in temperature and/or voltage, the DFLL Out Of Bounds bit (PCLKSR.DFLLOOB) in the
Power and Clocks Status register will be set. After an Out of Bounds error condition, the user must rewrite
DFLLMUL.MUL to ensure correct CLK_DFLL48M frequency. An interrupt is generated on a zero-to-one transition on
PCLKSR.DFLLOOB if the DFLL Out Of Bounds bit (INTENSET.DFLLOOB) in the Interrupt Enable Set register is set.
This interrupt will also be set if the tuner is not able to lock on the correct Coarse value.
Reference Clock Stop Detection
If CLK_DFLL48M_REF stops or is running at a very low frequency (slower than CLK_DFLL48M/(2 * MULMAX)), the DFLL
Reference Clock Stopped bit (PCLKSR.DFLLRCS) in the Power and Clocks Status register will be set. Detecting a
stopped reference clock can take a long time, on the order of 217 CLK_DFLL48M cycles. When the reference clock is
stopped, the DFLL48M will operate as if in open-loop mode. Closed-loop mode operation will automatically resume if the
CLK_DFLL48M_REF is restarted. An interrupt is generated on a zero-to-one transition on PCLKSR.DFLLRCS if the
DFLL Reference Clock Stopped bit (INTENSET.DFLLRCS) in the Interrupt Enable Set register is set.
16.6.7.2 Additional Features
Dealing with Delay in the DFLL in Closed-Loop Mode
The time from selecting a new CLK_DFLL48M frequency until this frequency is output by the DFLL48M can be up to
several microseconds. If the value in DFLLMUL.MUL is small, this can lead to instability in the DFLL48M locking
mechanism, which can prevent the DFLL48M from achieving locks. To avoid this, a chill cycle, during which the
CLK_DFLL48M frequency is not measured, can be enabled. The chill cycle is enabled by default, but can be disabled by
ERROR DIFF
MUL
--------------=
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writing a one to the DFLL Chill Cycle Disable bit (DFLLCTRL.CCDIS) in the DFLL Control register. Enabling chill cycles
might double the lock time.
Another solution to this problem consists of using less strict lock requirements. This is called Quick Lock (QL), which is
also enabled by default, but it can be disabled by writing a one to the Quick Lock Disable bit (DFLLCTRL.QLDIS) in the
DFLL Control register. The Quick Lock might lead to a larger spread in the output frequency than chill cycles, but the
average output frequency is the same.
Wake from Sleep Modes
DFLL48M can optionally reset its lock bits when it is disabled. This is configured by the Lose Lock After Wake bit
(DFLLCTRL.LLAW) in the DFLL Control register. If DFLLCTRL.LLAW is zero, the DFLL48M will be re-enabled and start
running with the same configuration as before being disabled, even if the reference clock is not available. The locks will
not be lost. When the reference clock has restarted, the Fine tracking will quickly compensate for any frequency drift
during sleep if DFLLCTRL.STABLE is zero. If DFLLCTRL.LLAW is one when disabling the DFLL48M, the DFLL48M will
lose all its locks, and needs to regain these through the full lock sequence.
Accuracy
There are three main factors that determine the accuracy of Fclkdfll48m. These can be tuned to obtain maximum accuracy
when fine lock is achieved.
zFine resolution: The frequency step between two Fine values. This is relatively smaller for high output frequencies.
zResolution of the measurement: If the resolution of the measured Fclkdfll48m is low, i.e., the ratio between the
CLK_DFLL48M frequency and the CLK_DFLL48M_REF frequency is small, then the DFLL48M might lock at a
frequency that is lower than the targeted frequency. It is recommended to use a reference clock frequency of
32kHz or lower to avoid this issue for low target frequencies.
zThe accuracy of the reference clock.
16.6.8 Brown-Out Detect o r Ope r at io n
The SYSCTRL provides user control to two Brown-Out Detectors (BOD) monitoring two supply domains. One BOD
monitors the 3.3V VDDANA supply (BOD33), and a second BOD monitors the 1.2V VDDCORE supply (BOD12).
Both Brown-Out Detectors support continuous or sampling modes.
For each BOD, the threshold value action (reset the device or generate an interrupt), th e Hysteresis configuration, as well
as the enable/disable settings are loaded from Flash User Calibration at startup, and can be overridden by writing to the
corresponding user register bit groups.
16.6.8.1 3.3V Brown-Out Detector (BOD33)
The 3.3V Brown-Out Detector (BOD33) monitors the VDDANA supply and compares the voltage with the brown-out
threshold level set in the BOD33 Level bit group (BOD33.LEVEL) in the BOD33 register. The Brown-Out Detector can
generate either an interrupt or a reset when VDDANA crosses below the brown-out threshold level. The BOD33
detection status can be read from the BOD33 Detection bit (PCLKSR.BOD33DET) in the Power and Clocks Status
register.
At startup or at power-on reset (POR), the BOD33 register values are loaded from the Flash User Row. Refer to “Non-
Volatile Memory (NVM) User Row Mapping” on page 21 for more details.
16.6.8.2 1.2V Brown-Out Detector (BOD12)
The 1.2V Brown-Out Detector (BOD12) monitors the VDDCORE supply and compares the voltage with the brown-out
threshold level set in the BOD12 Level bit group (BOD12.LEVEL) in the BOD12 register. The BOD12 can generate either
an interrupt or a reset when VDDCORE crosses below the brown-out threshold level. The BOD12 detection status can
be read from the BOD12 Detection bit (PCLKSR.BOD12DET) in the Power and Clocks Status register.
At startup or at power-on reset (POR), the BOD12 register values are loaded from the Flash User Row. Refer to “Non-
Volatile Memory (NVM) User Row Mapping” on page 21 for more details.
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16.6.8.3 Continuous Mode
When the BOD33 Mode bit (BOD33.MODE) in the BOD33 register is written to zero and the BOD33 is enabled, the
BOD33 operates in continuous mode. In this mode, the BOD33 is continuously monitoring the VDDANA supply voltage.
When the BOD12 Mode bit (BOD12.MODE) in the BOD12 register is written to zero and the BOD12 is enabled, the
BOD12 operates in continuous mode. In this mode, the BOD12 is continuously monitoring the VDDCORE supply
voltage. Continues mode is not available for BOD12 when running in standby sleep mode.
Continuous mode is the default mode for both BOD12 and BOD33.
16.6.8.4 Sampling Mode
The sampling mode is a low-power mode where the BOD33 or BOD12 is being repeatedly e nabled on a sampling clock’s
ticks. The BOD33 or BOD12 will monitor the supply voltage for a short period of time and then go to a low-power disabled
state until the next sampling clock tick.
Sampling mode is enabled by writing one to BOD33.MODE for BOD33, and by writing one to BOD12.MODE for BOD12.
The frequency of the clock ticks (Fclksampling) is controlled by the BOD33 Prescaler Select bit group (BOD33.PSEL) in the
BOD33 register and Prescaler Select bit group(BOD12.PSEL) in the BOD12 BOD12 register for BOD33 and BOD12,
respectively.
The prescaler signal (Fclkprescaler) is a 1kHz clock, output from the32kHz Ultra Low Power Oscillator, OSCULP32K.
As the sampling mode clock is different from the APB clock domain, synchronization among the clocks is necessary.
Figure 16-2 shows a block diagram of the sampling mode. The BOD33 and BOD12 Synchronization Ready bits
(PCLKSR.B33SRDY and PCLKSR.B12SRDY, respectively) in the Power and Clocks Status register show the
synchronization ready status of the synchronizer. Writing attempts to the BOD33 register are ignored while
PCLKSR.B33SRDY is zero. Writing attempts to the BOD12 register are ignored while PCLKSR.B12SRDY is zero.
Figure 16-2. Sampling Mode Block diagram
The BOD33 Clock Enable bit (BOD33.CEN) in the BOD33 register and the BOD12 Clock Enable bit (BOD12.CEN) in the
BOD12 register should always be disabled before changing the prescaler value. To change the prescaler value for the
BOD33 or BOD12 during sampling mode, the following steps need to be taken:
1. Wait until the PCLKSR.B33SRDY bit or the PCLKSR.B12SRDY bit is set.
2. Write the selected value to the BOD33.PSEL or BOD12.PSEL bit group.
16.6.8.5 Hysteresis
The hysteresis functionality can be used in both continuous and sampling mode. Writing a one to the BOD33 Hysteresis
bit (BOD33.HYST) in the BOD33 register will add hysteresis to the BOD33 threshold level. Writing a one to the BOD12
Hysteresis bit (BOD12.HYST) in the BOD12 register will add hysteresis to the BOD12 threshold level.
Fclksampling Fclkprescaler
2PSEL 1+()
------------------------------=
US
ER INTERFA
CE
R
E
G
I
S
TER
S
(
APB clock domain
)
P
RE
SC
ALE
R
(
clk_prescale
r
domain
)
S
YN
C
HR
O
NIZER
P
S
EL
C
EN
MO
DE
ENABL
E
C
LK_APB
C
LK_PRE
SC
ALER
C
LK
_
SAMPLIN
G
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16.6.9 Voltage Regulator System Operation
The embedded Voltage Regulator (VREG) is an internal voltage regulator that provides the core logic supply
(VDDCORE).
16.6.9.1 User Control of the Voltage Regulator System
The Voltage Regulator output supply level is determined by the LEVEL bit group (VREG.LEVEL) value in the VREG
register. At reset, the VREG.LEVEL register value is loaded from Flash Factory Calibration.
The device is allowed to restart executing code only after the core supply voltage is restored to an acceptable level. The
threshold at which this system triggers is significantly lower than the 1.2V Brown-Out Detector's own threshold (BOD12).
This can, therefore, be seen as a complementary voltage monitoring feature.
16.6.10 Voltage Reference System Operation
The Voltage Reference System (VREF) consists of a Bandgap Reference Voltage Generator and a temperature sensor.
The Bandgap Reference Voltage Generator is factory-calibrated under typical voltage and temperature conditions.
At reset, the VREF.CAL register value is loaded from Flash Factory Calibration.
The temperature sensor can be used to get an absolute temperature in the temperature range of CMIN to CMAX
degrees Celsius. The sensor will output a linear voltage proportional to the temperature. The output voltage and
temperature range are located in the “Electrical Characteristics” on page 562. To calculate the temperature from a
measured voltage, the following formula can be used:
16.6.10.1 User Control of the Voltage Regulator System
To enable the temperature sensor, write a one the Temperature Sensor Enable bit (VREF.TSEN) in the VREF register.
The temperature sensor can be redirected to the ADC for conversion. The Bandgap Reference Voltage Generator output
can also be routed to the ADC if the Bandgap Output Enable bit (VREF.BGOUTEN) in the VREF register is set.
The Bandgap Reference Voltage Generator output level is determined by the CALIB bit group (VREF.CALIB) value in the
VREF register.The default calibration value can be overridden by the user by writing to the CALIB bit group.
16.6.11 Interrupts
The SYSCTRL has the following interrupt sources:
zXOSCRDY - Multipurpose Crystal Oscillator Ready: A “0-to-1” transition on the PCLKSR.XOSCRDY bit is detected
zXOSC32KRDY - 32kHz Crystal Oscillator Ready: A “0-to-1” transition on the PCLKSR.XOSC32KRDY bit is detected
zOSC32KRDY - 32kHz Internal Oscillator Ready: A “0-to-1” transition on the PCLKSR.OSC32KRDY bit is detected
zOSC8MRDY - 8MHz Internal Oscillator Ready: A “0-to-1” transition on the PCLKSR.OSC8MRDY bit is detected
zDFLLRDY - DFLL48M Ready: A “0-to-1” transition on the PCLKSR.DFLLRDY bit is detected
zDFLLOOB - DFLL48M Out Of Boundaries: A “0-to-1” transition on the PCLKSR.DFLLOOB bit is detected
zDFLLLOCKF - DFLL48M Fine Lock: A “0-to-1” transition on the PCLKSR.DFLLLOCKF bit is detected
zDFLLLOCKC - DFLL48M Coarse Lock: A “0-to-1” transition on the PCLKSR.DFLLLOCKC bit is detected
zDFLLRCS - DFLL48M Reference Clock has Stopped: A “0-to-1” transition on the PCLKSR.DFLLRCS bit is detected
zBOD33RDY - BOD33 Ready: A “0-to-1” transition on the PCLKSR.BOD33RDY bit is detected
zBOD33DET - BOD33 Detection: A “0-to-1” transition on the PCLKSR.BOD33DET bit is detected
zB33SRDY - BOD33 Synchronization Ready: A “0-to-1” transition on the PCLKSR.B33SRDY bit is detected
zBOD12RDY - BOD12 Ready: A “0-to-1” transition on the PCLKSR.BOD12RDY bit is detected
zBOD12DET - BOD12 Detection: A “0-to-1” transition on the PCLKSR.BOD12DET bit is detected
zB12SRDY - BOD12 Synchronization Ready: A “0-to-1” transition on the PCLKSR.B12SRDY bit is detected
CMIN Vmes VoutMAX
–()
Δtemperature
Δvoltage
------------------------------------
+
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Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the SYSCTRL is reset. See the INTFLAG re gister for details on ho w to clear interrupt
flags.
The SYSCTRL has one common interrupt request line for all the interrupt sources.The user must read the INTFLAG
register to determine which interrupt condition is present. Refer to the INTFLAG register for details.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to the “Nested Vector Interrupt
Controller” on page 24 for details.
16.6.12 Synchronization
Due to the multiple clock domains, values in the DFLL48M control registers need to be synchronized to other clock
domains. The status of this synchronization can be read from the Power and Clocks Status register (PCLKSR). Before
writing to any of the DFLL48M control registers, the user must check that the DFLL Ready bit (PCLKSR.DFLLRDY) in
PCLKSR is set to one. When this bit is set, the DFLL48M can be configured and CLK_DFLL48M is ready to be used. Any
write to any of the DFLL48M control registers while DFLLRDY is zero will be ignored. An interrupt is generated on a zero-
to-one transition of DFLLRDY if the DFLLRDY bit (INTENSET.DFLLDY) in the Interrupt Enable Set register is set.
In order to read from any of the DFLL48M configuration registers, the user must request a read synchronization by
writing a one to DFLLSYNC.READREQ. The registers can be read only when PCLKSR.DFLLRDY is set. If
DFLLSYNC.READREQ is not written before a read, a synchronization will be started, and the bus will be halted until the
synchronization is complete. Reading the DFLL48M registers when the DFLL48M is disabled will not halt the bus.
The prescaler counter used to trigger one-shot brown-out detections also operates asynchronously from the peripheral
bus. As a consequence, the prescaler registers require synchronization when written or read. The synchronization
results in a delay from when the initialization of the write or read operation begins until the operation is complete.
The write-synchronization is triggered by a write to the BOD12 or BOD33 control register. The Synchronization Ready bit
(PCLKSR.B12SRDY or PCLKSR.B33SRDY) in the PCLKSR register will be cleared when the write-synchronization
starts and set when the write-synchronization is complete. When the write-synchronization is ongoing
(PCLKSR.B33SRDY or PCLKSR.B12SRDY is zero), an attempt to do any of the following will cause the peripheral bus
to stall until the synchronization is complete:
zWriting to the BOD33 or BOD12 control register
zReading the BOD33 or BOD12 control register that was written
The user can either poll PCLKSR.B12SRDY or PCLKSR.B33SRDY or use the INTENSET.B12SRDY or
INTENSET.B33SRDY interrupts to check when the synchronization is complete. It is also possible to perform the next
read/write operation and wait, as this next operation will be completed after the ongoing read/write operation is
synchronized.
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16.7 Register Summary
Table 16-1. SYSCTRL Register Summary
Offset Name Bit
Pos.
0x00
INTENCLR
7:0 DFLLLCKC DFLLLCKF DFLLOOB DFLLRDY OSC8MRDY OSC32KRDY XOSC32KRDY XOSCRDY
0x01 15:8 B12SRDY BOD12DET BOD12RDY B33SRDY BOD33DET BOD33RDY DFLLRCS
0x02 23:16
0x03 31:24
0x04
INTENSET
7:0 DFLLLCKC DFLLLCKF DFLLOOB DFLLRDY OSC8MRDY OSC32KRDY XOSC32KRDY XOSCRDY
0x05 15:8 B12SRDY BOD12DET BOD12RDY B33SRDY BOD33DET BOD33RDY DFLLRCS
0x06 23:16
0x07 31:24
0x08
INTFLAG
7:0 DFLLLCKC DFLLLCKF DFLLOOB DFLLRDY OSC8MRDY OSC32KRDY XOSC32KRDY XOSCRDY
0x09 15:8 B12SRDY BOD12DET BOD12RDY B33SRDY BOD33DET BOD33RDY DFLLRCS
0x0A 23:16
0x0B 31:24
0x0C
PCLKSR
7:0 DFLLLCKC DFLLLCKF DFLLOOB DFLLRDY OSC8MRDY OSC32KRDY XOSC32KRDY XOSCRDY
0x0D 15:8 B12SRDY BOD12DET BOD12RDY B33SRDY BOD33DET BOD33RDY DFLLRCS
0x0E 23:16
0x0F 31:24
0x10 XOSC 7:0 ONDEMAND RUNSTDBY XTALEN
0x11 15:8 STARTUP[3:0] AMPGC GAIN[2:0]
0x12 Reserved
0x13 Reserved
0x14 XOSC32K 7:0 ONDEMAND RUNSTDBY AAMPEN EN1K EN32K XTALEN
0x15 15:8 WRTLOCK STARTUP[2:0]
0x16 Reserved
0x17 Reserved
0x18
OSC32K
7:0 ONDEMAND RUNSTDBY EN1K EN32K
0x19 15:8 WRTLOCK STARTUP[2:0]
0x1A 23:16 CALIB[6:0]
0x1B 31:24
0x1C OSCULP32K 7:0 WRTLOCK CALIB[4:0]
0x1D Reserved
0x1E Reserved
0x1F Reserved
0x20
OSC8M
7:0 ONDEMAND RUNSTDBY
0x21 15:8 PRESC[1:0]
0x22 23:16 CALIB[7:0]
0x23 31:24 FRANGE[1:0] CALIB[11:8]
0x24 DFLLCTRL 7:0 ONDEMAND RUNSTDBY LLAW STABLE MODE
0x25 15:8 QLDIS CCDIS
0x26 Reserved
0x27 Reserved
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0x28
DFLLVAL
7:0 FINE[7:0]
0x29 15:8 COARSE[5:0] FINE[9:8]
0x2A 23:16 DIFF[7:0]
0x2B 31:24 DIFF[15:8]
0x2C
DFLLMUL
7:0 MUL[7:0]
0x2D 15:8 MUL[15:8]
0x2E 23:16 FSTEP[7:0]
0x2F 31:24 CSTEP[5:0] FSTEP[9:8]
0x30 DFLLSYNC 7:0 READREQ
0x31 Reserved
0x32 Reserved
0x33 Reserved
0x34
BOD33
7:0 RUNSTDBY ACTION[1:0] HYST
0x35 15:8 PSEL[3:0] CEN MODE
0x36 23:16 LEVEL[5:0]
0x37 31:24
0x38
BOD12
7:0 ACTION[1:0] HYST
0x39 15:8 PSEL[3:0] CEN MODE
0x3A 23:16 LEVEL[4:0]
0x3B 31:24
0x3C VREG 7:0 RUNSTDBY
0x3D 15:8 CALIB[2:0] LEVEL[2:0]
0x3E Reserved
0x3F Reserved
0x40
VREF
7:0 BGOUTEN TSEN
0x41 15:8
0x42 23:16 CALIB[7:0]
0x43 31:24 CALIB[10:8]
Table 16-1. SYSCTRL Register Summary (Continued)
Offset Name Bit
Pos.
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16.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Please refer to the Register Access Protection
section and the PAC chapter for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Synchronized
property in each individual register description. Refer to “Synchronization” on page 138 for details.
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16.8.1 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x00
Reset: 0x00000000
Property: Write-Protected
zBits 31:15 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 14 – B12SRDY: BOD12 Synchronization Ready Interrupt Enable
0: The BOD12 Synchronization Ready interrupt is disabled.
1: The BOD12 Synchronization Ready interrupt is enabled, and an interrupt request will be generated when the
BOD12 Synchronization Ready Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the BOD12 Synchronization Ready Interrupt Enable bit, which disables the
BOD12 Synchronization Ready interrupt.
zBit 13 – BOD12DET: BOD12 Detection Interrupt Enable
0: The BOD12 Detection interrupt is disabled.
1: The BOD12 Detection interrupt is enabled, and an interrupt request will be generated when the BOD12 Detec-
tion Interrupt flag is set.
Bit313029282726 25 24
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit232221201918 17 16
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit151413121110 9 8
B12SRDY BOD12DET BOD12RDY B33SRDY BOD33DET BOD33RDY DFLLRCS
Access R R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DFLLLCKC DFLLLCKF DFLLOOB DFLLRDY OSC8MRDY OSC32KRDY XOSC32KRDY XOSCRDY
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
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Writing a zero to this bit has no effect.
Writing a one to this bit will clear the BOD12 Detection Interrupt Enable bit, which disables the BOD12 Detection
interrupt.
zBit 12 – BOD12RDY: BOD12 Ready Interrupt Enable
0: The BOD12 Ready interrupt is disabled.
1: The BOD12 Ready interrupt is enabled and an interrupt request will be generated when the BOD12 Ready Inter-
rupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the BOD12 Ready Interrupt Enable bit, which disables the BOD12 Ready
interrupt.
zBit 11 – B33SRDY: BOD33 Synchronization Ready Interrupt Enable
0: The BOD33 Synchronization Ready interrupt is disabled.
1: The BOD33 Synchronization Ready interrupt is enabled, and an interrupt request will be generated when the
BOD33 Synchronization Ready Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the BOD33 Synchronization Ready Interrupt Enable bit, which disables the
BOD33 Synchronization Ready interrupt.
zBit 10 – BOD33DET: BOD33 Detection Interrupt Enable
0: The BOD33 Detection interrupt is disabled.
1: The BOD33 Detection interrupt is enabled, and an interrupt request will be generated when the BOD33 Detec-
tion Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the BOD33 Detection Interrupt Enable bit, which disables the BOD33 Detection
interrupt.
zBit 9 – BOD33RDY: BOD33 Ready Interrupt Enable
0: The BOD33 Ready interrupt is disabled.
1: The BOD33 Ready interrupt is enabled, and an interrupt request will be generated when the BOD33 Ready
Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the BOD33 Ready Interrupt Enable bit, which disables the BOD33 Ready
interrupt.
zBit 8 – DFLLRCS: DFLL Reference Clock Stopped Interrupt Enable
0: The DFLL Reference Clock Stopped interrupt is disabled.
1: The DFLL Reference Clock Stopped interrupt is enabled, and an interrupt request will be generated when the
DFLL Reference Clock Stopped Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the DFLL Reference Clock Stopped Interrupt Enable bit, which disables the DFLL
Reference Clock Stopped interrupt.
zBit 7 – DFLLLCKC: DFLL Lock Coarse Interrupt Enable
0: The DFLL Lock Coarse interrupt is disabled.
1: The DFLL Lock Coarse interrupt is enabled, and an interrupt request will be generated when the DFLL Lock
Coarse Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the DFLL Lock Coarse Interrupt Enable bit, which disables the DFLL Lock Coarse
interrupt.
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zBit 6 – DFLLLCKF: DFLL Lock Fine Interrupt Enable
0: The DFLL Lock Fine interrupt is disabled.
1: The DFLL Lock Fine interrupt is enabled, and an interrupt request will be generated when the DFLL Lock Fine
Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the DFLL Lock Fine Interrupt Enable bit, which disables the DFLL Lock Fine
interrupt.
zBit 5 – DFLLOOB: DFLL Out Of Bounds Interrupt Enable
0: The DFLL Out Of Bounds interrupt is disabled.
1: The DFLL Out Of Bounds interrupt is enabled, and an interrupt request will be generated when the DFLL Out Of
Bounds Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the DFLL Out Of Bounds Interrupt Enable bit, which disables the DFLL Out Of
Bounds interrupt.
zBit 4 – DFLLRDY: DFLL Ready Interrupt Enable
0: The DFLL Ready interrupt is disabled.
1: The DFLL Ready interrupt is enabled, and an interrupt request will be generated when the DFLL Ready Interrupt
flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the DFLL Ready Interrupt Enable bit, which disables the DFLL Ready interrupt.
zBit 3 – OSC8MRDY: OSC8M Ready Interrupt Enable
0: The OSC8M Ready interrupt is disabled.
1: The OSC8M Ready interrupt is enabled, and an interrupt request will be generated when the OSC8M Ready
Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the OSC8M Ready Interrupt Enable bit, which disables the OSC8M Ready
interrupt.
zBit 2 – OSC32KRDY: OSC32K Ready Interrupt Enable
0: The OSC32K Ready interrupt is disabled.
1: The OSC32K Ready interrupt is enabled, and an interrupt request will be generated when the OSC32K Ready
Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the OSC32K Ready Interrupt Enable bit, which disables the OSC32K Ready
interrupt.
zBit 1 – XOSC32KRDY: XOSC32K Ready Interrupt Enable
0: The XOSC32K Ready interrupt is disabled.
1: The XOSC32K Ready interrupt is enabled, and an interrupt request will be generated when the XOSC32K
Ready Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the XOSC32K Ready Interrupt Enable bit, which disables the XOSC32K Ready
interrupt.
zBit 0 – XOSCRDY: XOSC Ready Interrupt Enable
0: The XOSC Ready interrupt is disabled.
1: The XOSC Ready interrupt is enabled, and an interrupt request will be generated when the XOSC Ready Inter-
rupt flag is set.
Writing a zero to this bit has no effect.
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Writing a one to this bit will clear the XOSC Ready Interrupt Enable bit, which disables the XOSC Ready interrupt.
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16.8.2 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x04
Reset: 0x00000000
Property: Write-Protected
zBits 31:15 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 14 – B12SRDY: BOD12 Synchronization Ready Interrupt Enable
0: The BOD12 Synchronization Ready interrupt is disabled.
1: The BOD12 Synchronization Ready interrupt is enabled, and an interrupt request will be generated when the
BOD12 Synchronization Ready Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the BOD12 Synchronization Ready Interrupt Enable bit, which enables the BOD12
Synchronization Ready interrupt.
zBit 13 – BOD12DET: BOD12 Detection Interrupt Enable
0: The BOD12 Detection interrupt is disabled.
1: The BOD12 Detection interrupt is enabled, and an interrupt request will be generated when the BOD12 Detec-
tion Interrupt flag is set.
Bit3130292827 26 25 24
Access R R R R R R R R
Reset00000 0 0 0
Bit2322212019 18 17 16
Access R R R R R R R R
Reset00000 0 0 0
Bit1514131211 10 9 8
B12SRDY BOD12DET BOD12RDY B33SRDY BOD33DET BOD33RDY DFLLRCS
Access RR/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DFLLLCKC DFLLLCKF DFLLOOB DFLLRDY OSC8MRDY OSC32KRDY XOSC32KRDY XOSCRDY
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000 0 0 0
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Writing a zero to this bit has no effect.
Writing a one to this bit will set the BOD12 Detection Interrupt Enable bit, which enables the BOD12 Detection
interrupt.
zBit 12 – BOD12RDY: BOD12 Ready Interrupt Enable
0: The BOD12 Ready interrupt is disabled.
1: The BOD12 Ready interrupt is enabled, and an interrupt request will be generated when the BOD12 Ready
Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the BOD12 Ready Interrupt Enable bit, which enables the BOD12 Ready interrupt.
zBit 11 – B33SRDY: BOD33 Synchronization Ready Interrupt Enable
0: The BOD33 Synchronization Ready interrupt is disabled.
1: The BOD33 Synchronization Ready interrupt is enabled, and an interrupt request will be generated when the
BOD33 Synchronization Ready Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the BOD33 Synchronization Ready Interrupt Enable bit, which enables the BOD33
Synchronization Ready interrupt.
zBit 10 – BOD33DET: BOD33 Detection Interrupt Enable
0: The BOD33 Detection interrupt is disabled.
1: The BOD33 Detection interrupt is enabled, and an interrupt request will be generated when the BOD33 Detec-
tion Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the BOD33 Detection Interrupt Enable bit, which enables the BOD33 Detection
interrupt.
zBit 9 – BOD33RDY: BOD33 Ready Interrupt Enable
0: The BOD33 Ready interrupt is disabled.
1: The BOD33 Ready interrupt is enabled, and an interrupt request will be generated when the BOD33 Ready
Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the BOD33 Ready Interrupt Enable bit, which enables the BOD33 Ready interrupt.
zBit 8 – DFLLRCS: DFLL Reference Clock Stopped Interrupt Enable
0: The DFLL Reference Clock Stopped interrupt is disabled.
1: The DFLL Reference Clock Stopped interrupt is enabled, and an interrupt request will be generated when the
DFLL Reference Clock Stopped Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the DFLL Reference Clock Stopped Interrupt Enable bit, which enables the DFLL
Reference Clock Stopped interrupt.
zBit 7 – DFLLLCKC: DFLL Lock Coarse Interrupt Enable
0: The DFLL Lock Coarse interrupt is disabled.
1: The DFLL Lock Coarse interrupt is enabled, and an interrupt request will be generated when the DFLL Lock
Coarse Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the DFLL Lock Coarse Interrupt Enable bit, which enables the DFLL Lock Coarse
interrupt.
zBit 6 – DFLLLCKF: DFLL Lock Fine Interrupt Enable
0: The DFLL Lock Fine interrupt is disabled.
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1: The DFLL Lock Fine interrupt is enabled, and an interrupt request will be generated when the DFLL Lock Fine
Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the DFLL Lock Fine Interrupt Disable/Enable bit, disable the DFLL Lock Fine inter-
rupt and set the corresponding interrupt request.
zBit 5 – DFLLOOB: DFLL Out Of Bounds Interrupt Enable
0: The DFLL Out Of Bounds interrupt is disabled.
1: The DFLL Out Of Bounds interrupt is enabled, and an interrupt request will be generated when the DFLL Out Of
Bounds Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the DFLL Out Of Bounds Interrupt Enable bit, which enables the DFLL Out Of
Bounds interrupt.
zBit 4 – DFLLRDY: DFLL Ready Interrupt Enable
0: The DFLL Ready interrupt is disabled.
1: The DFLL Ready interrupt is enabled, and an interrupt request will be generated when the DFLL Ready Interrupt
flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the DFLL Ready Interrupt Enable bit, which enables the DFLL Ready interrupt and
set the corresponding interrupt request.
zBit 3 – OSC8MRDY: OSC8M Ready Interrupt Enable
0: The OSC8M Ready interrupt is disabled.
1: The OSC8M Ready interrupt is enabled, and an interrupt request will be generated when the OSC8M Ready
Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the OSC8M Ready Interrupt Enable bit, which enables the OSC8M Ready interrupt.
zBit 2 – OSC32KRDY: OSC32K Ready Interrupt Enable
0: The OSC32K Ready interrupt is disabled.
1: The OSC32K Ready interrupt is enabled, and an interrupt request will be generated when the OSC32K Ready
Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the OSC32K Ready Interrupt Enable bit, which enables the OSC32K Ready
interrupt.
zBit 1 – XOSC32KRDY: XOSC32K Ready Interrupt Enable
0: The XOSC32K Ready interrupt is disabled.
1: The XOSC32K Ready interrupt is enabled, and an interrupt request will be generated when the XOSC32K
Ready Interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the XOSC32K Ready Interrupt Enable bit, which enables the XOSC32K Ready
interrupt.
zBit 0 – XOSCRDY: XOSC Ready Interrupt Enable
0: The XOSC Ready interrupt is disabled.
1: The XOSC Ready interrupt is enabled, and an interrupt request will be generated when the XOSC Ready Inter-
rupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the XOSC Ready Interrupt Enable bit, which enables the XOSC Ready interrupt.
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16.8.3 Interrupt Flag S tatus and Clear
Name: INTFLAG
Offset: 0x08
Reset: 0x00000000
Property: -
zBits 31:15 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 14 – B12SRDY: BOD12 Synchronization Ready
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the BOD12 Synchronization Ready bit in the Status register
(PCLKSR.B12SRDY) and will generate an interrupt request if INTENSET.B12SRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the BOD12 Synchronization Ready interrupt flag.
zBit 13 – BOD12DET: BOD12 Detection
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the BOD12 Detection bit in the Status register (PCLKSR.BOD12 DET)
and will generate an interrupt request if INTENSET.BOD12DET is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the BOD12 Detection interrupt flag.
Bit313029282726 25 24
Access R R R R R R R R
Reset000000 0 0
Bit232221201918 17 16
Access R R R R R R R R
Reset000000 0 0
Bit151413121110 9 8
B12SRDY BOD12DET BOD12RDY B33SRDY BOD33DET BOD33RDY DFLLRCS
Access R R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DFLLLCKC DFLLLCKF DFLLOOB DFLLRDY OSC8MRDY OSC32KRDY XOSC32KRDY XOSCRDY
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset000000 0 0
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zBit 12 – BOD12RDY: BOD12 Ready
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the BOD12 Ready bit in the Status register (PCLKSR.BOD12RDY)
and will generate an interrupt request if INTENSET.BOD12RDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the BOD12 Ready interrupt flag.
zBit 11 – B33SRDY: BOD33 Synchronization Ready
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the BOD33 Synchronization Ready bit in the Status register
(PCLKSR.B33SRDY) and will generate an interrupt request if INTENSET.B33SRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the BOD33 Synchronization Ready interrupt flag
zBit 10 – BOD33DET: BOD33 Detection
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the BOD33 Detection bit in the Status register (PCLKSR.BOD33 DET)
and will generate an interrupt request if INTENSET.BOD33DET is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the BOD33 Detection interrupt flag.
zBit 9 – BOD33RDY: BOD33 Ready
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the BOD33 Ready bit in the Status register (PCLKSR.BOD33RDY)
and will generate an interrupt request if INTENSET.BOD33RDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the BOD33 Ready interrupt flag.
zBit 8 – DFLLRCS: DFLL Reference Clock Stopped
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the DFLL Reference Clock Stopped bit in the Status register
(PCLKSR.DFLLRCS) and will generate an interrupt request if INTENSET.DFLLRCS is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the DFLL Reference Clock Stopped interrupt flag.
zBit 7 – DFLLLCKC: DFLL Lock Coarse
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the DFLL Lock Coarse bit in the Status register (PCLKSR.DFLLL-
CKC) and will generate an interrupt request if INTENSET.DFLLLCKC is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the DFLL Lock Coarse interrupt flag.
zBit 6 – DFLLLCKF: DFLL Lock Fine
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the DFLL Lock Fine bit in the Status register (PCLKSR.DFLLLCKF)
and will generate an interrupt request if INTENSET.DFLLLCKF is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the DFLL Lock Fine interrupt flag.
zBit 5 – DFLLOOB: DFLL Out Of Bounds
This flag is cleared by writing a one to it.
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This flag is set on a zero-to-one transition of the DFLL Out Of Bounds bit in the Status register (PCLKSR.DFL-
LOOB) and will generate an interrupt request if INTENSET.DFLLOOB is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the DFLL Out Of Bounds interrupt flag.
zBit 4 – DFLLRDY: DFLL Ready
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the DFLL Ready bit in the Status register (PCLKSR.DFLLRDY) and
will generate an interrupt request if INTENSET.DFLLRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the DFLL Ready interrupt flag.
zBit 3 – OSC8MRDY: OSC8M Ready
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the OSC8M Ready bit in the Status register (PCLKSR.OSC8MRDY)
and will generate an interrupt request if INTENSET.OSC8MRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the OSC8M Ready interrupt flag.
zBit 2 – OSC32KRDY: OSC32K Ready
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the OSC32K Ready bit in the Status register (PCL KSR.OSC32KRDY)
and will generate an interrupt request if INTENSET.OSC32KRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the OSC32K Ready interrupt flag.
zBit 1 – XOSC32KRDY: XO SC32K Ready
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the XOSC32K Ready bit in the Status register
(PCLKSR.XOSC32KRDY) and will generate an interrupt request if INTENSET.XOSC32KRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the XOSC32K Ready interrupt flag.
zBit 0 – XOSCRDY: XOSC Ready
This flag is cleared by writing a one to it.
This flag is set on a zero-to-one transition of the XOSC Ready bit in the Status register (PCLKSR.XOSCRDY) and
will generate an interrupt request if INTENSET.XOSCRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the XOSC Ready interrupt flag.
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16.8.4 Power and Clocks Status
Name: PCLKSR
Offset: 0x0C
Reset: 0x00000000
Property: -
zBits 31:15 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 14 – B12SRDY: BOD12 Synchronization Ready
0: BOD12 synchronization is ongoing.
1: BOD12 synchronization is complete.
zBit 13 – BOD12DET: BOD12 Detection
0: No BOD12 detection.
1: BOD12 has detected that the core power supply is going below the BOD12 reference value.
zBit 12 – BOD12RDY: BOD12 Ready
0: BOD12 is not ready.
1: BOD12 is ready.
zBit 11 – B33SRDY: BOD33 Synchronization Ready
0: BOD33 synchronization is ongoing.
1: BOD33 synchronization is complete.
Bit313029282726 25 24
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit232221201918 17 16
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit151413121110 9 8
B12SRDY BOD12DET BOD12RDY B33SRDY BOD33DET BOD33RDY DFLLRCS
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DFLLLCKC DFLLLCKF DFLLOOB DFLLRDY OSC8MRDY OSC32KRDY XOSC32KRDY XOSCRDY
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
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zBit 10 – BOD33DET: BOD33 Detection
0: No BOD33 detection.
1: BOD33 has detected that the I/O power supply is going below the BOD33 reference value.
zBit 9 – BOD33RDY: BOD33 Ready
0: BOD33 is not ready.
1: BOD33 is ready.
zBit 8 – DFLLRCS: DFLL Reference Clock Stopped
0: DFLL reference clock is running.
1: DFLL reference clock has stopped.
zBit 7 – DFLLLCKC: DFLL Lock Coarse
0: No DFLL coarse lock detected.
1: DFLL coarse lock detected.
zBit 6 – DFLLLCKF: DFLL Lock Fine
0: No DFLL fine lock detected.
1: DFLL fine lock detected.
zBit 5 – DFLLOOB: DFLL Out Of Bounds
0: No DFLL Out Of Bounds detected.
1: DFLL Out Of Bounds detected.
zBit 4 – DFLLRDY: DFLL Ready
0: DFLL is not ready.
1: DFLL is stable and ready to be used as a clock source.
zBit 3 – OSC8MRDY: OSC8M Ready
0: OSC8M is not ready.
1: OSC8M is stable and ready to be used as a clock source.
zBit 2 – OSC32KRDY: OSC32K Ready
0: OSC32K is not ready.
1: OSC32K is stable and ready to be used as a clock source.
zBit 1 – XOSC32KRDY: XO SC32K Ready
0: XOSC32K is not ready.
1: XOSC32K is stable and ready to be used as a clock source.
zBit 0 – XOSCRDY: XOSC Ready
0: XOSC is not ready.
1: XOSC is stable and ready to be used as a clock source.
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16.8.5 External Multipurpose Crystal Oscillator (XOSC) Control
Name: XOSC
Offset: 0x10
Reset: 0x0080
Property: Write-Protected
zBits 15:12 – STARTUP[3:0]: Start-Up Time
These bits select start-up time for the oscillator according to Table 16-2.
The OSCULP32K oscillator is used to clock the start-up counter.
Bit151413121110 9 8
STARTUP[3:0] AMPGC GAIN[2:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
ONDEMAND RUNSTDBY XTALEN ENABLE
Access R/W R/W R R R R/W R/W R
Reset10000000
Table 16-2. Start-UpTime for External Multipu rpo se Crystal Oscillator
STARTUP[3:0]
Number of
OSCULP32K Clock
Cycles Number of XOSC
Clock Cycles Approximate Equivalent Time(1)(2)
0x0 1 3 31µs
0x1 2 3 61µs
0x2 4 3 122µs
0x3 8 3 244µs
0x4 16 3488µs
0x5 32 3977µs
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Notes: 1. Actual startup time is 1 OSCULP32K cycle + 3 XOSC cycles.
2. The given time neglects the 3 XOSC cycles before OSCULP32K cycle.
zBit 11 – AMPGC: Automatic Amplitude Gain Control
0: The automatic amplitude gain control is disabled.
1: The automatic amplitude gain control is enabled. Amplitude gain will be automatically adjusted during Crystal
Oscillator operation.
zBits 10:8 – GAIN[2:0]: Oscillator Gain
These bits select the gain for the oscillator, given in table Table 16-3. The listed maximum frequencies are recom-
mendations, and might vary based on capacitive load and crystal characteristics. Setting this bit group has no
effect when the Automatic Amplitude Gain Control is active.
zBit 7 – ONDEMAND: On Demand Control
The On Demand operation mode allows an oscillator to be enabled or disabled, depending on peripheral clock
requests.
In On Demand operation mode, i.e., if the XOSC.ONDEMAND bit has been previously written to one, the oscillator
will be running only when requested by a peripheral. If there is no peripheral requesting the oscillator’s clock
source, the oscillator will be in a disabled state.
If On Demand is disabled, the oscillator will always be running when enabled.
In standby sleep mode, the On Demand operation is still active if the XOSC.RUNSTDBY bit is one. If
XOSC.RUNSTDBY is zero, the oscillator is disabled.
0: The oscillator is always on, if enabled.
0x6 64 31953µs
0x7 128 33906µs
0x8 256 37813µs
0x9 512 315625µs
0xA 1024 331250µs
0xB 2048 362500µs
0xC 4096 3125000µs
0xD 8192 3250000µs
0xE 16384 3500000µs
0xF 32768 31000000µs
Table 16-2. Start-UpTime for External Multipu rpo se Crystal Oscillator
Table 16-3. External Multipur pose Crystal Oscillator Gain Settings
GAIN[2:0] Recommended Max Frequency
0x0 2MHz
0x1 4MHz
0x2 8MHz
0x3 16MHz
0x4 30MHz
0x5-0x7 Reserved
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1: The oscillator is enabled when a peripheral is requesting the oscillator to be used as a clock source. The oscilla-
tor is disabled if no peripheral is requesting the clock source.
zBit 6 – RUNSTDBY: Run in Standby
This bit controls how the XOSC behaves during standby sleep mode:
0: The oscillator is disabled in standby sleep mode.
1: The oscillator is not stopped in standby sleep mode. If XOSC.ONDEMAND is one, the clock source will be run-
ning when a peripheral is requesting the clock. If XOSC.ONDEMAND is zero, the clock source will always be
running in standby sleep mode.
zBits 5:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – XTALEN: Crystal Oscillator Enable
This bit controls the connections between the I/O pads and the external clock or crystal oscillator:
0: External clock connected on XIN. XOUT can be used as general-purpose I/O.
1: Crystal connected to XIN/XOUT.
zBit 1 – ENABLE: Oscillator Enable
0: The oscillator is disabled.
1: The oscillator is enabled.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
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16.8.6 32kHz External Crystal Oscillator (XOSC32K) Control
Name: XOSC32K
Offset: 0x14
Reset: 0x0080
Property: Write-Protected
zBits 15:13 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 12 – WRTLOCK: Write Lock
This bit locks the XOSC32K register for futur writes to fix the XOSC32K configuration.
0: The XOSC32K configuration is not locked.
1: The XOSC32K configuration is locked.
zBit 11 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 10:8 – STARTUP[2:0]: Oscillator Start-Up Time
These bits select the start-up time for the oscillator according to Table 16-4
The OSCULP32K oscillator is used to clock the start-up counter.
Bit151413121110 9 8
WRTLOCK STARTUP[2:0]
Access R R R R/W R R/W R/W R/W
Reset00000000
Bit76543210
ONDEMAND RUNSTDBY AAMPEN EN1K EN32K XTALEN ENABLE
Access R/W R/W R/W R/W R/W R/W R/W R
Reset10000000
Table 16-4. Start-Up Time for 32kHz External Crystal Oscillator
STARTUP[2:0]
Number of
OSCULP32K Clock
Cycles
Number of
XOSC32K Clock
Cycles Approximate Equivalent Time
(OSCULP = 32kHz)(1)(2)
0x0 1 3 122µs
0x1 32 31068µs
0x2 2048 362592µs
0x3 4096 3125092µs
0x4 16384 3500092µs
0x5 32768 31000092µs
0x6 65536 32000092µs
0x7 131072 34000092µs
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Notes: 1. Actual startup time is 1 OSCULP32K cycle + 3 XOSC32K cycles.
2. The given time assumes an XTAL frequency of 32768Hz.
zBit 7 – ONDEMAND: On Demand Control
The On Demand operation mode allows an oscillator to be enabled or disabled depending on peripheral clock
requests.
In On Demand operation mode, i.e., if the ONDEMAND bit has been previously written to one, the oscillator will
only be running when requested by a peripheral. If there is no peripheral requesting the oscillator’s clock source,
the oscillator will be in a disabled state.
If On Demand is disabled the oscillator will always be running when enabled.
In standby sleep mode, the On Demand operation is still active if the XOSC32K.RUNSTDBY bit is one. If
XOSC32K.RUNSTDBY is zero, the oscillator is disabled.
0: The oscillator is always on, if enabled.
1: The oscillator is enabled when a peripheral is requesting the oscillator to be used as a clock source. The oscilla-
tor is disabled if no peripheral is requesting the clock source.
zBit 6 – RUNSTDBY: Run in Standby
This bit controls how the XOSC32K behaves during standby sleep mode:
0: The oscillator is disabled in standby sleep mode.
1: The oscillator is not stopped in standby sleep mode. If XOSC32K.ONDEMAND is one, the clock source will be
running when a peripheral is requesting the clock. If XOSC32K.ONDEMAND is zero, the clock source will always
be running in standby sleep mode.
zBit 5 – AAMPEN: Automatic Amplitude Control Enable
0: The automatic amplitude control for the crystal oscillator is disabled.
1: The automatic amplitude control for the crystal oscillator is enabled.
zBit 4 – EN1K: 1kHz Output Enable
0: The 1kHz output is disabled.
1: The 1kHz output is enabled.
zBit 3 – EN32K: 32kHz Output Enable
0: The 32kHz output is disabled.
1: The 32kHz output is enabled.
zBit 2 – XTALEN: Crystal Oscillator Enable
This bit controls the connections between the I/O pads and the external clock or crystal oscillator:
0: External clock connected on XIN32. XOUT32 can be used as general-purpose I/O.
1: Crystal connected to XIN32/XOUT32.
zBit 1 – ENABLE: Oscillator Enable
0: The oscillator is disabled.
1: The oscillator is enabled.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
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16.8.7 32kHz Internal Oscillator (OSC32K) Control
Name: OSC32K
Offset: 0x18
Reset: 0x00000080
Property: Write-Protected
zBits 31:23 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 22:16 – CALIB[6:0]: Oscillator Calibration
These bits control the oscillator calibration.
This value must be written by the user.
Factory calibration values can be loaded from the non-volatile memory. Refer to “Non-Volatile Memory (NVM)
User Row Mapping” on page 21.
zBits 15:13 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 12 – WRTLOCK: Write Lock
This bit locks the OSC32K register for futur writes to fix the OSC32K configuration.
0: The OSC32K configuration is not locked.
1: The OSC32K configuration is locked.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
CALIB[6:0]
AccessR R/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit151413121110 9 8
WRTLOCK STARTUP[2:0]
Access R R R R/W R R/W R/W R/W
Reset00000000
Bit76543210
ONDEMAND RUNSTDBY EN1K EN32K ENABLE
Access R/W R/W R R R/W R/W R/W R
Reset10000000
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zBit 11 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 10:8 – STARTUP[2:0]: Oscillator Start-Up Time
These bits select start-up time for the oscillator according to Table 16-5.
The OSCULP32K oscillator is used as input clock to the startup counter.
Notes: 1. Start-up time is given by STARTUP + 3 OSC32K cycles.
2. The given time assumes an XTAL frequency of 32.768kHz.
zBit 7 – ONDEMAND: On Demand Control
The On Demand operation mode allows an oscillator to be enabled or disabled depending on peripheral clock
requests.
In On Demand operation mode, i.e., if the ONDEMAND bit has been previously written to one, the oscillator will
only be running when requested by a peripheral. If there is no peripheral requesting the oscillator’s clock source,
the oscillator will be in a disabled state.
If On Demand is disabled the oscillator will always be running when enabled.
In standby sleep mode, the On Demand operation is still active if the OSC32K.RUNSTDBY bit is one. If
OSC32K.RUNSTDBY is zero, the oscillator is disabled.
0: The oscillator is always on, if enabled.
1: The oscillator is enabled when a peripheral is requesting the oscillator to be used as a clock source. The oscilla-
tor is disabled if no peripheral is requesting the clock source.
zBit 6 – RUNSTDBY: Run in Standby
This bit controls how the OSC32K behaves during standby sleep mode:
0: The oscillator is disabled in standby sleep mode.
1: The oscillator is not stopped in standby sleep mode. If OSC32K.ONDEMAND is one, the clock source will be
running when a peripheral is requesting the clock. If OSC32K.ONDEMAND is zero, the clock source will always be
running in standby sleep mode.
zBits 5:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 3 – EN1K: 1kHz Output Enable
0: The 1kHz output is disabled.
Table 16-5. Start-Up Time for 32kHz Internal Oscillator
STARTUP[2:0] Number of OSC32K
clock cycles Appro ximate Equ iv alent Time (OSCULP= 32 kHz)(1)(2)
0x0 392µs
0x1 4122µs
0x2 6183µs
0x3 10 305µs
0x4 18 549µs
0x5 34 1038µs
0x6 66 2014µs
0x7 130 3967µs
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1: The 1kHz output is enabled.
zBit 2 – EN32K: 32kHz Output Enable
0: The 32kHz output is disabled.
1: The 32kHz output is enabled.
zBit 1 – ENABLE: Oscillator Enable
0: The oscillator is disabled.
1: The oscillator is enabled.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
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16.8.8 32kHz Ultra Low Power Internal Oscillator (OSCULP32K) Control
Name: OSCULP32K
Offset: 0x1C
Reset: 0xXX
Property: Write-Protected
zBit 7 – WRTLOCK: Write Lock
This bit locks the OSCULP32K register for futur writes to fix the OSCULP32K configuration.
0: The OSCULP32K configuration is not locked.
1: The OSCULP32K configuration is locked.
zBits 6:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:0 – CALIB[4:0]: Oscillator Calibration
These bits control the oscillator calibration.
These bits are loaded from Flash Calibration at startup.
Bit76543210
WRTLOCK CALIB[4:0]
Access R/W R R R/W R/W R/W R/W R/W
Reset000XXXXX
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16.8.9 8MHz Internal Oscillator (OSC8M) Control
Name: OSC8M
Offset: 0x20
Reset: 0x0XXX0082
Property: Write-Protected
zBits 31:30 – FRANGE[1:0]: Oscillator Frequency Range
These bits control the oscillator frequency range according to Table 16-6.
zBits 29:28 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 27:16 – CALIB[11:0]: Oscillator Calibration
These bits control the oscillator calibration. The calibration field is split in two:
Bit3130292827262524
FRANGE[1:0] CALIB[11:8]
AccessR/WR/W R R R/WR/WR/WR/W
Reset0000XXXX
Bit2322212019181716
CALIB[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
ResetXXXXXXXx
Bit151413121110 9 8
PRESC[1:0]
AccessRRRRRRR/WR/W
Reset00000000
Bit76543210
ONDEMAND RUNSTDBY ENABLE
Access R/W R/W R R R R R/W R
Reset10000010
Table 16-6. Oscillator Frequency Range
FRANGE[1:0] Description
0x0 4 to 6MHz
0x1 6 to 8MHz
0x2 8 to 11MHz
0x3 11 to 15MHz
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CALIB[11:7] is for temperature calibration
CALIB[6:0] is for overall process calibration
These bits are loaded from Flash Calibration at startup.
zBits 15:10 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 9:8 – PRESC[1:0]: Oscillator Prescaler
These bits select the oscillator prescaler factor setting according to the Table 16-7.
zBit 7 – ONDEMAND: On Demand Control
The On Demand operation mode allows an oscillator to be enabled or disabled depending on peripheral clock
requests.
In On Demand operation mode, i.e., if the ONDEMAND bit has been previously written to one, the oscillator will
only be running when requested by a peripheral. If there is no peripheral requesting the oscillator’s clock source,
the oscillator will be in a disabled state.
If On Demand is disabled the oscillator will always be running when enabled.
In standby sleep mode, the On Demand operation is still active if the OSC8M.RUNSTDBY bit is one. If
OSC8M.RUNSTDBY is zero, the oscillator is disabled.
0: The oscillator is always on, if enabled.
1: The oscillator is enabled when a peripheral is requesting the oscillator to be used as a clock source. The oscilla-
tor is disabled if no peripheral is requesting the clock source.
zBit 6 – RUNSTDBY: Run in Standby
This bit controls how the OSC8M behaves during standby sleep mode:
0: The oscillator is disabled in standby sleep mode.
1: The oscillator is not stopped in standby sleep mode. If OSC8M.ONDEMAND is one, the clock source will be run-
ning when a peripheral is requesting the clock. If OSC8M.ONDEMAND is zero, the clock source will always be
running in standby sleep mode.
zBits 5:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – ENABLE: Oscillator Enable
0: The oscillator is disabled.
1: The oscillator is enabled.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Table 16-7. Oscillator Prescaler
PRESC[1:0] Description
0x0 1
0x1 2
0x2 4
0x3 8
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16.8.10 DFLL48M Control
Name: DFLLCTRL
Offset: 0x24
Reset: 0x0080
Property: Write-Protected
zBits 15:10 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 9 – QLDIS: Quick Lock Disable
0: Quick Lock is enabled.
1: Quick Lock is disabled.
zBit 8 – CCDIS: Chill Cycle Disable
0: Chill Cycle is enabled.
1: Chill Cycle is disabled.
zBit 7 – ONDEMAND: On Demand Control
The On Demand operation mode allows an oscillator to be enabled or disabled depending on peripheral clock
requests.
In On Demand operation mode, i.e., if the ONDEMAND bit has been previously written to one, the oscillator will
only be running when requested by a peripheral. If there is no peripheral requesting the oscillator’s clock source,
the oscillator will be in a disabled state.
If On Demand is disabled the oscillator will always be running when enabled.
In standby sleep mode, the On Demand operation is still active if the DFLLCTRL.RUNSTDBY bit is one. If
DFLLCTRL.RUNSTDBY is zero, the oscillator is disabled.
0: The oscillator is always on, if enabled.
1: The oscillator is enabled when a peripheral is requesting the oscillator to be used as a clock source. The oscilla-
tor is disabled if no peripheral is requesting the clock source.
zBit 6 – RUNSTDBY: Run in Standby
This bit controls how the DFLL behaves during standby sleep mode:
0: The oscillator is disabled in standby sleep mode.
1: The oscillator is not stopped in standby sleep mode. If DFLLCTRL.ONDEMAND is one, the clock source will be
running when a peripheral is requesting the clock. If DFLLCTRL.ONDEMAND is zero, the clock source will always
be running in standby sleep mode.
Bit151413121110 9 8
QLDIS CCDIS
AccessRRRRRRR/WR/W
Reset00000000
Bit76543210
ONDEMAND RUNSTDBY LLAW STABLE MODE ENABLE
Access R/W R/W R R/W R/W R/W R/W R
Reset10000000
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zBit 5 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 4 – LLAW: Lose Lock After Wake
0: Locks will not be lost after waking up from sleep modes if the DFLL clock has been stopped.
1: Locks will be lost after waking up from sleep modes if the DFLL clock has been stopped.
zBit 3 – STABLE: Stable DFLL Frequency
0: FINE calibration tracks changes in output frequency.
1: FINE calibration register value will be fixed after a fine lock.
zBit 2 – MODE: Operating Mode Selection
0: The DFLL operates in open-loop operation.
1: The DFLL operates in closed-loop operation.
zBit 1 – ENABLE: DFLL Enable
0: The DFLL oscillator is disabled.
1: The DFLL oscillator is enabled.
Due to synchronization, there is delay from updating the register until the peripheral is enabled/disabled. The value
written to DFLLCTRL.ENABLE will read back immediately after written.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
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16.8.11 DFLL48M Value
Name: DFLLVAL
Offset: 0x28
Reset: 0x00000000
Property: Write-Protected
zBits 31:16 – DIFF: Multiplication Ratio Difference
In closed-loop mode (DFLLCTRL.MODE is written to one), this bit group indicates the difference between the ideal
number of DFLL cycles and the counted number of cycles. This value is not updated in open-loop mode, and
should be considered invalid in that case.
zBits 15:10 – COARSE: Coarse Value
Set the value of the Coarse Calibration register. In closed-loop mode, this field is read-only.
zBits 9:0 – FINE: Fine Value
Set the value of the Fine Calibration register. In closed-loop mode, this field is read-only.
Bit3130292827262524
DIFF[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit2322212019181716
DIFF[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
COARSE[5:0] FINE[9:8]
Access R R R R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
FINE[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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16.8.12 DFLL48M Multiplier
Name: DFLLMUL
Offset: 0x2C
Reset: 0x00000000
Property: Write-Protected
zBits 31:26 – CSTEP: Coarse Maximum Step
This bit group indicates the maximum step size allowed during coarse adjustment in closed-loop mode. When
adjusting to a new frequency, the expected output frequency overshoot depends on this step size.
zBits 25:16 – FSTEP: Fine Maximum Step
This bit group indicates the maximum step size allowed during fine adjustment in closed-loop mode. When adjust-
ing to a new frequency, the expected output frequency overshoot depends on this step size.
zBits 15:0 – MUL: DFLL Multiply Factor
This field determines the ratio of the CLK_DFLL output frequency to the CLK_DFLL_REF input frequency. Writing
to the MUL bits will cause locks to be lost and the fine calibration value to be reset to its midpoint.
Bit3130292827262524
CSTEP[5:0] FSTEP[9:8]
Access R R R R/W R/W R/W R/W R/W
Reset00000000
Bit2322212019181716
FSTEP[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit151413121110 9 8
MUL[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
MUL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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16.8.13 DFLL48M Synchronization
Name: DFLLSYNC
Offset: 0x30
Reset: 0x00
Property: Write-Protected
zBit 7 – READREQ: Read Request
To be able to read the current value of DFLLVAL in closed-loop mode, this bit should be written to one. The
updated value is available in DFLLVAL when PCLKSR.DFLLRDY is set.
zBits 6:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit76543210
READREQ
AccessWRRRRRRR
Reset00000000
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16.8.14 3.3V Brown-Out Detector (BOD3 3 ) C on t ro l
Name: BOD33
Offset: 0x34
Reset: 0x00XX00XX
Property: Synchronized, Write-Protected
zBits 31:22 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 21:16 – LEVEL[5:0]: BOD33 Threshold Level
This field sets the triggering voltage threshold for the BOD33. See the “Electrical Characteristics” on page 562 for
actual voltage levels. Note that any change to the LEVEL field of the BOD33 register should be done when the
BOD33 is disabled in order to avoid spurious resets or interrupts.
These bits are loaded from Flash User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping”
on page 21 for more details.
zBits 15:12 – PSEL[3:0]: Prescaler Select
Selects the prescaler divide-by output for the BOD33 sampling mode, as given in Table 16-8. The input clock
comes from the OSCULP32K 1kHz output.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
LEVEL[5:0]
Access R R R/W R/W R/W R/W R/W R/W
Reset00XXXXXX
Bit151413121110 9 8
PSEL[3:0] CEN MODE
Access R/W R/W R/W R/W R R R/W R/W
Reset00000000
Bit76543210
RUNSTDBY ACTION[1:0] HYST ENABLE
Access R R/W R R/W R/W R/W R/W R
Reset000XXXX0
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zBits 11:10 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 9 – CEN: Clock Enable
0: The BOD33 sampling clock is eith er disabled and stopped, or enabled but not yet stable.
1: The BOD33 sampling clock is either enabled and stable, or disabled but not yet stopped.
Writing a zero to this bit will stop the BOD33 sampling clock.
Writing a one to this bit will start the BOD33 sampling clock.
zBit 8 – MODE: Operation Mode
0: The BOD33 operates in continuous mode.
1: The BOD33 operates in sampling mode.
zBit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 6 – RUNSTDBY: Run in Standby
0: The BOD33 is disabled in standby sleep mode.
1: The BOD33 is enabled in standby sleep mode.
zBit 5 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Table 16-8. BOD33 Prescaler Select
PSEL[3:0] Name Description
0x0 DIV2 Divide clock by 2
0x1 DIV4 Divide clock by 4
0x2 DIV8 Divide clock by 8
0x3 DIV16 Divide clock by 16
0x4 DIV32 Divide clock by 32
0x5 DIV64 Divide clock by 64
0x6 DIV128 Divide clock by 128
0x7 DIV256 Divide clock by 256
0x8 DIV512 Divide clock by 512
0x9 DIV1K Divide clock by 1024
0xA DIV2K Divide clock by 2048
0xB DIV4K Divide clock by 4096
0xC DIV8K Divide clock by 8192
0xD DIV16K Divide clock by 16384
0xE DIV32K Divide clock by 32768
0xF DIV64K Divide clock by 65536
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zBits 4:3 – ACTION: BOD33 Action
These bits are used to select the BOD33 action when the supply voltage crosses below the BOD33 threshold, as
shown in Table 16-9.
These bits are loaded from Flash User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping”
on page 21 for more details.
zBit 2 – HYST: Hysteresis
This bit indicates whether hysteresis is enabled for the BOD33 threshold voltage:
0: No hysteresis.
1: Hysteresis enabled.
This bit is loaded from Flash User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping” on
page 21 for more details.
zBit 1 – ENABLE: Enable
0: BOD33 is disabled.
1: BOD33 is enabled.
This bit is loaded from Flash User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping” on
page 21 for more details.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Table 16-9. BOD33 Action
ACTION[1:0] Name Description
0x0 NONE No action
0x1 RESET The BOD33 generates a reset
0x2 INTERRUPT The BOD33 generates an interrupt
0x3 -Reserved
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16.8.15 1.2V Brown-Out Detector (BOD1 2 ) C on t ro l
Name: BOD12
Offset: 0x38
Reset: 0x00XX00XX
Property: Synchronized, Write-Protected
zBits 31:21 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 20:16 – LEVEL[4:0]: BOD12 Threshold Level
This field sets the triggering voltage threshold for the BOD12. See the “Electrical Characteristics” on page 562 for
actual voltage levels. Note that any change to the LEVEL field of the BOD12 register should be done when the
BOD12 is disabled in order to avoid spurious resets or interrupts.
These bits are loaded from Flash User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping”
on page 21 for more details.
zBits 15:12 – PSEL[3:0]: Prescaler Select
Selects the prescaler divide-by output for the BOD12 Sampling mode, as given in Table 16-10. The input clock
comes from the OSCULP32K 1kHz output.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
LEVEL[4:0]
Access R R R R/W R/W R/W R/W R/W
Reset000XXXXX
Bit151413121110 9 8
PSEL[3:0] CEN MODE
Access R/W R/W R/W R/W R R R/W R/W
Reset00000000
Bit76543210
ACTION[1:0] HYST ENABLE
Access R R R R/W R/W R/W R/W R
Reset000XXXX0
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zBits 11:10 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 9 – CEN: Clock Enable
0: The BOD12 sampling clock is eith er disabled and stopped, or enabled but not yet stable.
1: The BOD12 sampling clock is either enabled and stable, or disabled but not yet stopped.
Writing a zero to this bit will stop the BOD12 sampling clock.
Writing a one to this bit will start the BOD12 sampling clock.
zBit 8 – MODE: Operation mode
0: The BOD12 operates in continuous mode.
1: The BOD12 operates in sampling mode.
zBit 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:3 – ACTION: BOD12 Action
These bits are used to select the BOD12 action when the supply voltage crosses below the BOD12 threshold, as
shown in Table 16-11.
These bits are loaded from Flash User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping”
on page 21 for more details.
Table 16-10. BOD12 Prescaler Select
PSEL[3:0] Name Description
0x0 DIV2 Divide clock by 2
0x1 DIV4 Divide clock by 4
0x2 DIV8 Divide clock by 8
0x3 DIV16 Divide clock by 16
0x4 DIV32 Divide clock by 32
0x5 DIV64 Divide clock by 64
0x6 DIV128 Divide clock by 128
0x7 DIV256 Divide clock by 256
0x8 DIV512 Divide clock by 512
0x9 DIV1K Divide clock by 1024
0xA DIV2K Divide clock by 2048
0xB DIV4K Divide clock by 4096
0xC DIV8K Divide clock by 8192
0xD DIV16K Divide clock by 16384
0xE DIV32K Divide clock by 32768
0xF DIV64K Divide clock by 65536
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zBit 2 – HYST: Hysteresis
This bit indicates whether hysteresis is enabled for the BOD12 threshold voltage:
0: No hysteresis.
1: Hysteresis enabled.
This bit is loaded from Flash User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping” on
page 21 for more details.
zBit 1 – ENABLE: Enable
0: BOD12 is disabled.
1: BOD12 is enabled.
This bit is loaded from Flash User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping” on
page 21 for more details.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Table 16-11. BOD12 Action
ACTION[1:0] Name Description
0x0 NONE No action
0x1 RESET The BOD12 generates a reset
0x2 INTERRUPT The BOD12 generates an interrupt
0x3 -Reserved
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16.8.16 Voltage Regulator System (VREG) Control
Name: VREG
Offset: 0x3C
Reset: 0x0X02
Property: Write protected
zBit 15 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 14:12 – CALIB[2:0]: Voltage Regulator Calibration
These bits are used for voltage regulator calibration.
zBit 11 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 10:8 – LEVEL[2:0]: Voltage Regulator Level
These bits are used to set the voltage level of the regulator. Refer to “Electrical Characteristics” on page 562 for
details. These bits are loaded from Flash Calibration Row at startup. Refer to “Non-Volatile Memory (NVM) User
Row Mapping” on page 21 for more details
zBit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 6 – RUNSTDBY: Run in Standby
0: The voltage regulator is in low-power configuration in standby sleep mode.
1: The voltage regulator is not in low-power configuration in standby sleep mode.
zBits 5:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit151413121110 9 8
CALIB[2:0] LEVEL[2:0]
Access R R/W R/W R/W R R/W R/W R/W
Reset 0 0 0 0 0 X X X
Bit 76543210
RUNSTDBY
Access R R/W R R R R R R
Reset 00000000
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16.8.17 Voltage References System (VREF) Control
Name: VREF
Offset: 0x40
Reset: 0x0XXX0000
Property: Write-Protected
zBits 31:27 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 26:16 – CALIB[10:0]: Bandgap Voltage Generator Calibration
These bits are used to calibrate the output level of the bandgap voltage reference. These bits are loaded from
Flash Calibration Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping” on page 21 for more
details.
zBits 15:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – BGOUTEN: Bandgap Output Enable
0: The bandgap output is not available as an ADC input channel.
1: The bandgap output is routed to an ADC input channel.
zBit 1 – TSEN: Temperature Sensor Enable
0: Temperature sensor is disabled.
Bit3130292827262524
CALIB[10:8]
AccessRRRRRR/WR/WR/W
Reset00000XXX
Bit2322212019181716
CALIB[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
ResetXXXXXXXX
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
BGOUTEN TSEN
AccessRRRRRR/WR/WR
Reset00000000
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1: Temperature sensor is enabled and routed to an ADC input channel.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
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17. WDT – Watchdog Timer
17.1 Overview
The Watchdog Timer (WDT) is a system function for monitoring correct progra m operation. It makes it possible to recover
from error situations such as runaway or deadlocked code. The WDT is configured to a predefined time-out period, and is
constantly running when enabled. If the WDT is not cleared within the time-out period, it will issue a system reset. An
early-warning interrupt is available to indicate an upcoming watchdog time-out condition.
The window mode makes it possible to define a time slot (or window) inside the total time-out period during which the
WDT must be cleared. If the WDT is cleared outside this window, either too early or too late, a system reset will be
issued. Compared to the normal mode, this can also catch situations where a code error causes the WDT to be cleared
frequently.
When enabled, the WDT will run in active mode and all sleep modes. It is asynchronous and runs from a CPU-
independent clock source.The WDT will continue operation and issue a system reset or interrupt even if the main clocks
fail.
17.2 Features
zIssues a system reset if the Watchdog Timer is not cleared before its time-out period
zEarly Warning interrupt generation
zAsynchronous operation from dedicated oscillator
zTwo types of operation:
zNormal mode
zWindow mode
zSelectable time-out periods, from 8 cycles to 16,000 cycles in normal mode or 16 cycles to 32,000 cycles in window
mode
zAlways-on capability
17.3 Block Diagram
Figure 17-1. WDT Block Diagram
GCLK_WDT COUNT
Reset
PER/WINDOW/EWOFFSET
0
CLEAR
0xA5
Ea rly Warning In te rrupt
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17.4 Signal Description
Not applicable.
17.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
17.5.1 I/O Lines
Not applicable.
17.5.2 Power Management
The WDT can continue to operate in any sleep mode where the selected source clock is running. The WDT interrupts
can be used to wake up the device from sleep modes. The events can trigger other operations in the system without
exiting sleep modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
17.5.3 Clocks
The WDT bus clock (CLK_WDT_APB) is enabled by default, and can be enabled and disabled in the Power Manager.
Refer to “PM – Power Manager” on page 100 for details.
A generic clock (GCLK_WDT) is required to clock the WDT. This clock must be configured and enabled in the Generic
Clock Controller before using the WDT. Refer to “GCLK – Generic Clock Controller” on page 78 for details.
This generic clock is asynchronous to the user interface clock (CLK_WDT_APB). Due to this asynchronicity, accessing
certain registers will require synchronization between the clock domains. Refer to “Synchronization” on page 185 for
further details.
GCLK_WDT is intended to be sourced from the clock of the internal ultra-low-power (ULP) oscillator. Due to the ultra-
low-power design, the oscillator is not very accurate, and so the exact time-out period may vary from device to device.
This variation must be kept in mind when designing software that uses the WDT to ensure that the time-out periods used
are valid for all devices. For more information on ULP oscillator accuracy, consult the “Ultra Low Power Internal 32kHz
RC Oscillator (OSCULP32K) Characteristics” on page 585.
GCLK_WDT can also be clocked from other sources if a more accurate clock is needed, but at the cost of higher power
consumption.
17.5.4 DMA
Not applicable.
17.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the WDT interrupts requires the interrupt
controller to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
17.5.6 Events
Not applicable.
17.5.7 Debug Operation
When the CPU is halted in debug mode, the WDT will halt normal operation. If the WDT is configured in a way that
requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss may result
during debugging. The WDT can be forced to halt operation during debugging.
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17.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the peripheral access controller (PAC), except the
following registers:
zInterrupt Flag Status and Clear register (INTFLAG)
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
17.5.9 Analog Connections
Not applicable.
17.6 Functional Description
17.6.1 Principle of Operation
The Watchdog Timer (WDT) is a system for monitoring correct program operation, making it possible to recover from
error situations such as runaway code by issuing a reset. When enabled, the WDT is a constantly running timer that is
configured to a predefined time-out period. Before the end of the time-out period, the WDT should be reconfigured.
The WDT has two modes of operation, normal and window. Additionally, the user can enable Early Warning interrupt
generation in each of the modes. The description for each of the basic mod es is given below. The settings in the Control
register (CTRL) and the Interrupt Enable register (INTENCLR/SET) determine the mode of operation, as illustrated in
Table 17-1.
17.6.2 Basic Operation
17.6.2.1 Initialization
The following registers are enable-protected:
zControl register (CTRL), except the Enable bit (CTRL.ENABLE)
zConfiguration register (CONFIG)
zEarly Warning Interrupt Control register (EWCTRL)
Any writes to these bits or registers when the WDT is enabled or is being enabled (CTRL.ENABLE is one) will be
discarded. Writes to these registers while the WDT is being disabled will be completed after the disabling is complete.
Enable-protection is denoted by the Enable-Protected property in the register description.
Initialization of the WDT can be done only while the WDT is disabled. The WDT is configured by defining the required
Time-Out Period bits in the Configuration register (CONFIG.PER). If window-mode operation is required, the Window
Table 17-1. WDT Opera ting Modes
ENABLE WEN Interrupt
Enable Mode
0 x x Stopped
100Normal
101Normal with Early Warning interrupt
110Window
111Window with Early Warning interrupt
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Enable bit in the Control register (CTRL.WEN) must be written to one and the Window Period bits in the Configuration
register (CONFIG.WINDOW) must be defined.
17.6.2.2 Configurable Reset Values
On a power-on reset, some registers will be loaded with initial values from the NVM User Row. Refer to “Non-Volatile
Memory (NVM) User Row Mapping” on page 21 for more details.
This encompasses the following bits and bit groups:
zEnable bit in the Control register (CTRL.ENABLE)
zAlways-On bit in the Control register (CTRL.ALWAYSON)
zWatchdog Timer Windows Mode Enable bit in the Control register (CTRL.WEN)
zWatchdog Timer Windows Mode Time-Out Period bits in the Configuration register (CONFIG.WINDOW)
zTime-Out Period in the Configuration register (CONFIG.PER)
zEarly Warning Interrupt Time Offset bits in the Early Warning Interrupt Control register (EWCTRL.EWOFFSET)
For more information about fuse locations, see “Non-Volatile Memory (NVM) User Row Mapping” on page 21.
17.6.2.3 Enabling and Disabling
The WDT is enabled by writing a one to the Enable bit in the Control register (CTRL.ENABLE). The WDT is disabled by
writing a zero to CTRL.ENABLE.
The WDT can be disabled only while the Always-On bit in the Control register (CTRL.ALWAYSON) is zero.
17.6.2.4 Normal Mode
In normal-mode operation, the length of a time-out period is configured in CONFIG.PER. The WDT is enabled by writing
a one to the Enable bit in the Control register (CTRL.ENABLE). Once enabled, if the WDT is not cleared from the
application code before the time-out occurs, the WDT will issue a system reset. There are 12 possible WDT time-out
(TOWDT) periods, selectable from 8ms to 16s, and the WDT can be cleared at any time during the time-out p eriod. A new
WDT time-out period will be started each time the WDT is cleared by writing 0xA5 to the Clear register (CLEAR). Writing
any value other than 0xA5 to CLEAR will issue an immediate system reset.
By default, WDT issues a system reset upon a time-out, and the early warning interrupt is disabled. If an early warning
interrupt is required, the Early Warning Interrupt Enable bit in the Interrupt Enable register (INTENSET.EW) must be
enabled. Writing a one to the Early Warning Interrupt bit in the Interrupt Enable Set register (INTENSET.EW) enables the
interrupt, and writing a one to the Early Warning Interrupt bit in the Interrupt Enable Clear register (INTENCLR.EW)
disables the interrupt. If the Early Warning Interrupt is enabled, an interrupt is generated prior to a watchdog time-out
condition. In normal mode, the Early Warning Offset bits in the Early Warning Interrupt Control register
(EWCTRL.EWOFFSET) define the time where the early warning interrupt occurs. The normal-mode operation is
illustrated in Figure 17-2.
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Figure 17-2. Normal-Mode Operation
17.6.2.5 Window Mode
In window-mode operation, the WDT uses two different time-out periods, a closed window time-out period (TOWDTW) and
the normal, or open, time-out period (TOWDT). The closed window time-out period defines a duration from 8ms to 16s
where the WDT cannot be reset. If the WDT is cleared during this period, the WDT will issue a system reset. The normal
WDT time-out period, which is also from 8ms to 16s, defines the duration of the open period during which the WDT can
be cleared. The open period will always follow the closed period, and so the total duration of the time-out period is the
sum of the closed window and the open window time-out periods. The closed window is defined by the Window Period
bits in the Configuration register (CONFIG.WINDOW), and the open window is defined by the Period bits in the
Configuration register (CONFIG.PER).
By default, the WDT issues a system reset upon a time-out and the Early Warning interrupt is disabled. If an Early
Warning interrupt is required, INTENCLR/SET.EW must be set. Writing a one to INTENSET.EW enables the interrupt,
and writing a one to INTENCLR.EW disables the interrupt. If the Early Wa rning interrupt is enabled in window mode, t he
interrupt is generated at the start of the open window period.
The window mode operation is illustrated in Figure 17-3.
Figure 17-3. Window-Mode Operation
t [ms]
WDT Count
510
15 20 25 30 35
PER[3:0]=1 Timely W DT Clear
TO
WDT
WDT Timeout
System Reset
EWOFFSET[3:0]=0 Early Wa rning In te rrupt
t [ms]
WDT Count
510
15 20 25 30 35
WINDOW[3:0]=0
PER[3:0]=0 Timely WDT Cle ar
Closed
TO
WDTW
Open
TO
WDT
Early WDT Clear
WDT Timeout
Early Warning Interrupt
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17.6.3 Additional Features
17.6.3.1 Always-On Mode
The always-on mode is enabled by writing a one to the Always-On bit in the Control register (CTRL.ALWAYSON). When
the always-on mode is enabled, the WDT runs continuously, regardless of the state of CTRL.ENABLE. Once written, the
Always-On bit can only be cleared by a power-on reset. The Configuration (CONFIG) and Early Warning Control
(EWCTRL) registers are read-only registers while the CTRL.ALWAYSON bit is set. Thus, the time period configuration
bits (CONFIG.PER, CONFIG.WINDOW, EWCTRL.EWOFFSET) of the WDT cannot be changed.
Enabling or disabling window-mode operation by writing the Window Enable bit (CTRL.WEN) is allowed while in the
always-on mode, but note that CONFIG.PER cannot be changed.
The Interrupt Clear and Interrupt Set registers are accessible in the always-on mode. The Early Warning interrupt can still
be enabled or disabled while in the always-on mode, but note that EWCTRL.EWOFFSET cannot be changed.
Table 17-2 shows the operation of the WDT when CTRL.ALWAYSON is set.
Table 17-2. WDT Operating Mod es With Always-On
17.6.4 Interrupts
The WDT has the following interrupt sources:
zEarly Warning
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the WDT is reset. See INTFLAG for details on how to clear interrupt flags.
The WDT has one common interrupt request line for all the interrupt sources. The user must read INTFLAG to determine
which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to “Nested Vector Interrupt
Controller” on page 24 for details.
The Early Warning interrupt behaves differently in normal mode and in window mode. In normal mode, the Early Warning
interrupt generation is defined by the Early Warning Offset in the Early Warning Control register (EWCTRL.EWOFFSET).
The Early Warning Offset bits define the number of GCLK_WDT clocks before the interrupt is generated, relative to the
start of the watchdog time-out period. For example, if the WDT is operating in normal mode with CONFIG.PER = 0x2 and
EWCTRL.EWOFFSET = 0x1, the Early Warning interrupt is generated 16 GCLK_WDT clock cycles from the start of the
watchdog time-out period, and the watchdog time-out system reset is generated 32 GCLK_WDT clock cycles from the
start of the watchdog time-out period. The user must take caution when programming the Early Warning Offset bits. If
these bits define an Early Warning interrupt generation time greater than the watchdog time-out period, the watchdog
time-out system reset is generated prior to the Early Warning interrupt. Thus, the Early Warning interrupt will never be
generated.
WEN Interrupt enable Mode
0 0 Always-on and normal mode
0 1 Always-on and normal mode with Early Warning interrupt
1 0 Always-on and window mode
1 1 Always-on and window mode with Early Warning interrupt
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In window mode, the Early Warning interrupt is generated at the start of the open window period. In a typical application
where the system is in sleep mode, it can use this interrupt to wake up and clear the Watchdog Timer, after which the
system can perform other tasks or return to sleep mode.
17.6.5 Synchronization
Due to the asynchronicity between CLK_WDT_APB and GCLK_WDT some registers must be synchronized when
accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status
register(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronizati on is complete. The
synchronization Ready interrupt can be used to signal when sync is complete. This can be accessed via the
Synchronization Ready Interrupt Flag in the Interrupt Flag Status and Clear register (INTFLAG.SYNCRDY).
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following registers need synchronization when written:
zControl register (CTRL)
zClear register (CLEAR)
Write-synchronization is denoted by the Write-Synchronized property in the register description.
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17.7 Register Summary
Register summary
Offset Name Bit
Pos.
0x0 CTRL 7:0 ALWAYSON WEN ENABLE
0x1 CONFIG 7:0 WINDOW[3:0] PER[3:0]
0x2 EWCTRL 7:0 EWOFFSET[3:0]
0x3 Reserved
0x4 INTENCLR 7:0 EW
0x5 INTENSET 7:0 EW
0x6 INTFLAG 7:0 EW
0x7 STATUS 7:0 SYNCBUSY
0x8 CLEAR 7:0 CLEAR[7:0]
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17.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Refer to “Register Access Protection” on page 181
for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Write-Synchronized
or the Read-Synchronized property in each individual register description. Refer to “Synchronization” on page 185 for
details.
Some registers are enable-protected, meaning they can be written only when the WDT is disabled. Enable-protection is
denoted by the Enable-Protected property in each individual register description.
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17.8.1 Control
Name: CTRL
Offset: 0x0
Reset: N/A - Loaded from NVM User Row at startup
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBit 7 – ALWAYSON: Always-On
This bit allows the WDT to run continuously. After being written to one, this bit cannot be written to zero, and the
WDT will remain enabled until a power-on reset is received. When this bit is one, the Control register (CTRL), the
Configuration register (CONFIG) and the Early Warning Control register (EWCTRL) will be read-only, and any
writes to these registers are not allowed. Writing a zero to this bit has no effect.
0: The WDT is enabled and disabled through the ENABLE bit.
1: The WDT is enabled and can only be disabled by a power-on reset (POR).
This bit is not enable-protected.
These bits are loaded from NVM User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping”
on page 21 for more details.
zBits 6:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – WEN: Watchdog Timer Window Mode Enable
This bit enables window mode. Can be written only while CTRL.ALWAYSON is zero. The initial value of this bit is
loaded from Flash Calibration.
0: Window mode is disabled (normal operation).
1: Window mode is enabled.
This bit is loaded from NVM User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping” on
page 21 for more details.
zBit 1 – ENABLE: Enable
This bit enables or disables the WDT. Can only be written while CTRL.ALWAYSON is zero.
0: The WDT is disabled.
1: The WDT is enabled.
Due to synchronization, there is delay from writing CTRL.ENABLE until the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately, and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY will be cleared when the operation is complete.
This bit is not enable-protected.
This bit is loaded from NVM User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping” on
page 21 for more details.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Bit76543210
ALWAYSON WEN ENABLE
Access R/W1 R/W R/W R/W R/W R/W R/W R/W
ResetX0000XX0
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17.8.2 Configuration
Name: CONFIG
Offset: 0x1
Reset: N/A - Loaded from NVM User Row at startup
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBits 7:4 – WINDOW[3:0]: Window Mode Time-Out Period
In window mode, these bits determine the watchdog closed window period as a number of oscillator cycles. The
closed window periods are defined in Table 17-3.
These bits are loaded from NVM User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping”
on page 21 for more details.
zBits 3:0 – PER[3:0]: Time-Out Period
These bits determine the watchdog time-out period as a number of GCLK_WDT clock cycles. In window mode
operation, these bits define the open window period. The different typical time-out periods are fo und in Table 17-4.
These bits are loaded from NVM User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping”
on page 21 for more details.
Bit76543210
WINDOW[3:0] PER[3:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
ResetXXXXXXXX
Table 17-3. Windo w Mode Time-Out Period
Value Description
0x0 8 clock cycles
0x1 16 clock cycles
0x2 32 clock cycles
0x3 64 clock cycles
0x4 128 clock cycles
0x5 256 clocks cycles
0x6 512 clocks cycles
0x7 1024 clock cycles
0x8 2048 clock cycles
0x9 4096 clock cycles
0xA 8192 clock cycles
0xB 16384 clock cycles
0xC-0xF Reserved
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Table 17-4. Time-Out Period
Value Description
0x0 8 clock cycles
0x1 16 clock cycles
0x2 32 clock cycles
0x3 64 clock cycles
0x4 128 clock cycles
0x5 256 clocks cycles
0x6 512 clocks cycles
0x7 1024 clock cycles
0x8 2048 clock cycles
0x9 4096 clock cycles
0xA 8192 clock cycles
0xB 16384 clock cycles
0xC-0xF Reserved
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17.8.3 Early Warning Interrupt Control
Name: EWCTRL
Offset: 0x2
Reset: N/A - Loaded from NVM User Row at startup
Property: Write-Protected, Enable-Protected
zBits 7:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:0 – EWOFFSET[3:0]: Early Warning Interrupt Time Offset
These bits determine the number of GCLK_WDT clocks in the offset from the start of the watchdog time-out period
to when the Early Warning interrupt is generated. The Early Warning Offset is defined in Table 17-5. These bits
are loaded from NVM User Row at startup. Refer to “Non-Volatile Memory (NVM) User Row Mapping” on page 21
for more details.
Bit76543210
EWOFFSET[3:0]
Acces
sRRRRR/WR/WR/WR/W
Reset0000XXXX
Table 17-5. Early Warning Interrupt Time Offset
Value Description
0x0 8 clock cycles
0x1 16 clock cycles
0x2 32 clock cycles
0x3 64 clock cycles
0x4 128 clock cycles
0x5 256 clocks cycles
0x6 512 clocks cycles
0x7 1024 clock cycles
0x8 2048 clock cycles
0x9 4096 clock cycles
0xA 8192 clock cycles
0xB 16384 clock cycles
0xC-0xF Reserved
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17.8.4 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x4
Reset: 0x00
Property: Write-Protected
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – EW: Early Warning Interrupt Enable
0: The Early Warning interrupt is disabled.
1: The Early Warning interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit disables the Early Warning interrupt.
Bit76543210
EW
AccessRRRRRRRR/W
Reset00000000
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17.8.5 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x5
Reset: 0x00
Property: Write-Protected
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – EW: Early Warning Interrupt Enable
0: The Early Warning interrupt is disabled.
1: The Early Warning interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit enables the Early Warning interrupt.
Bit76543210
EW
AccessRRRRRRRR/W
Reset00000000
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17.8.6 Interrupt Flag S tatus and Clear
Name: INTFLAG
Offset: 0x6
Reset: 0x00
Property: –
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these
bits to zero when this register is written. These bits will always return zero when read.
zBit 0 – EW: Early Warning
This flag is set when an Early Warning interrupt occurs, as defined by the EWOFFSET bit group in
EWCTRL.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Early Warning interrupt flag.
Bit76543210
EW
AccessRRRRRRRR/W
Reset00000000
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17.8.7 Status
Name: STATUS
Offset: 0x7
Reset: 0x00
Property: –
zBit 7 – SYNCBUSY: Synchronization Busy
This bit is cleared when the synchronization of registers between clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 6:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit 76543210
SYNCBUSY
AccessRRRRRRRR
Reset00000000
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17.8.8 Clear
Name: CLEAR
Offset: Offset: 0x8
Reset: 0x00
Property: Write-Protected, Write-Synchronized
zBits 7:0 – CLEAR: Watchdog Clear
Writing 0xA5 to this register will clear the Watchdog Timer and the watchdog time-out period is restarted. Writing
any other value will issue an immediate system reset.
Bit76543210
CLEAR[7:0]
AccessWWWWWWWW
Reset00000000
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17.9 Asynchronous Watchdog Clock Characterization
The source intended for the asynchronous watchdog clock (OSCULP32K) has a variance of +/- 15%. In a typical
application with GCLK_WDT = 1kHz or GCLK_WDT = 32kHz, the time period is illustrated in Table 17-6.
Table 17-6. Typica l Time-Out Period
Typical Time-Out Periods
GCLK_WDT = 1kHz GCLK_WDT = 32kHz
Min Typ Max Min Typ Max
8 clock cycles 6.64ms 7.81ms 8.98ms 0.20ms 0.24ms 0.28ms
16 clock cycles 13.28ms 15.62ms 17.97ms 0.41ms 0.48ms 0.56ms
32 clock cycles 26.56ms 31.25ms 39.94ms 0.83ms 0.97ms 1.12ms
64 clock cycles 53.12ms 62.50ms 71.87ms 1.66ms 1.95ms 2.24ms
128 clock cycles 0.10s 0.12s 0.14s 3.32ms 3.90ms 4.49ms
256 clocks cycles 0.21s 0.25s 0.28s 6.64ms 7.81ms 8.98ms
512 clocks cycles 0.42s 0.50s 0.57s 13.28ms 15.62ms 17.96ms
1024 clock cycles 0.85s 1.00s 1.15s 26.56ms 31.25ms 35.93ms
2048 clock cycles 1.70s 2.00s 2.30s 53.12ms 62.50ms 71.87ms
4096 clock cycles 3.40s 4.00s 4.60s 0.10s 0.12s 0.14s
8192 clock cycles 6.80s 8.00s 9.20s 0.21s 0.25s 0.28s
16384 clock cycles 13.60s 16.00s 18.40s 0.42s 0.50s 0.57s
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18. RTC – Real-Time Counter
18.1 Overview
The Real-Time Counter (RTC) is a 32-bit counter with a 10-bit programmable prescaler that typically runs continuously to
keep track of time. The RTC can wake up the device from sleep modes using the alarm/compare wake up, periodic wake
up or overflow wake up mechanisms.
The RTC is typically clocked by the 1.024kHz output from the 32.768kHz High-Accuracy Internal Crystal
Oscillator(OSC32K) and this is the configuration optimized for the lowest power consumption. The faster 32.768kHz
output can be selected if the RTC needs a resolution higher than 1ms. The RTC can also be clocked from other sources,
selectable through the Generic Clock module (GCLK).
The RTC can generate periodic peripheral events from outputs of the prescaler, as well as alarm/compare interrupts and
peripheral events, which can trigger at any counter value. Additionally, the timer can trigger an overflow interrupt and
peripheral event, and be reset on the occurrence of an alarm/compare match. This allows periodic interrupts and
peripheral events at very long and accurate intervals.
The 10-bit programmable prescaler can scale down the clock source, and so a wide range of resolutions and time-out
periods can be configured. With a 32.768kHz clock source, the minimum counter tick interval is 30.5µs, and time-out
periods can range up to 36 hours. With the counter tick interval configured to 1s, the maximum time-out period is more
than 136 years.
18.2 Features
z32-bit counter with 10-bit prescaler
zMultiple clock sources
z32-bit or 16-bit Counter mode
zOne 32-bit or two 16-bit compare values
zClock/Calendar mode
zTime in seconds, minutes and hours (12 /24 )
zDate in day of month, month and year
zLeap year correction
zDigital prescaler correction/tuning for increased accuracy
zOverflow, alarm/compare match and prescaler interrupts and events
zOptional clear on alarm/compare match
18.3 Block Diagram
Figure 18-1. RTC Block Diagram (Mode 0 — 32-Bit Counter)
COUNT
COMPn
=Compare n
Overflow
0
MATCHCLR
10-bit
Prescaler
GCLK_RTC CLK_RTC_CNT
32
Periodic
Events
32
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Figure 18-2. RTC Block Diagram (Mode 1 — 16-Bit Counter)
Figure 18-3. RTC Block Diagram (Mode 2 — Clock/Calend ar)
18.4 Signal Description
Not applicable.
18.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
18.5.1 I/O Lines
Not applicable.
18.5.2 Power Management
The RTC can continue to operate in any sleep mode. The RTC interrupts can be used to wake up the device from sleep
modes. The events can trigger other operations in the system without exiting sleep modes. Refer to “PM – Power
Manager” on page 100 for details on the different sleep modes.
The RTC will be reset only at power-on (POR) or by writing a one to the Software Reset bit in the Control register
(CTRL.SWRST).
10-bit
Prescaler
GCLK_RTC
COUNT
PER
Overflow
0
COMPn
Compar e n
CLK_RTC_CNT
16
Periodic
Events
16
16
=
=
CLOCK
ALARMn
=Alarm n
Overflow
0
MATCHCLR
10-bit
Prescaler
GCLK_RTC CLK_RTC_CNT
32
Periodic
Events
32
MASKn
Y/M/D H:M: S
Y/M/D H:M: S
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18.5.3 Clocks
The RTC bus clock (CLK_RTC_APB) can be enabled and disabled in the Power Manager, and the default state of
CLK_RTC_APB can be found in the Peripheral Clock Masking section in the “PM – Power Manager” on page 100.
A generic clock (GCLK_RTC) is required to clock the RTC. This clock must be configured and enabled in the Generic
Clock Controller before using the RTC. Refer to “GCLK – Generic Clock Controller” on page 78 for details.
This generic clock is asynchronous to the user interface clock (CLK_RTC_APB). Due to this asynchronicity, accessing
certain registers will require synchronization between the clock domains. Refer to “Synchronization” on page 204 for
further details.
18.5.4 DMA
Not applicable.
18.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the RTC interrupts requires the interrupt
controller to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
18.5.6 Events
To use the RTC event functionality, the corresponding events need to be configured in the event system. Refer to
“EVSYS – Event System” on page 309 for details.
18.5.7 Debug Operation
When the CPU is halted in debug mode the RTC will halt normal operation. The RTC can be forced to continue operation
during debugging. Refer to the DBGCTRL register for details.
18.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the peripheral access controller (PAC), except the
following registers:
zInterrupt Flag Status and Clear register (INTFLAG)
zRead Request register (READREQ)
zStatus register (STATUS)
zDebug register (DBGCTRL)
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
18.5.9 Analog Connections
A 32.768kHz crystal can be connected to the TOSC1 and TOSC2 pins, along with any required load capacitors. For
details on recommended crystal characteristics and load capacitors, refer to “Electrical Characteristics” on page 562 for
details.
18.6 Functional Description
18.6.1 Principle of Operation
The RTC keeps track of time in the system and enables periodic events, as well as interrupts and events at a specified
time. The RTC consists of a 10-bit prescaler that feeds a 32-bit counter. The actual format of the 32-bit counter depends
on the RTC operating mode.
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18.6.2 Basic Operation
18.6.2.1 Initialization
The following bits are enable-protected, meaning that they can only be written when the RTC is disabled (CTRL.ENABLE
is zero):
zOperating Mode bits in the Control register (CTRL.MODE)
zPrescaler bits in the Control register (CTRL.PRESCALER)
zClear on Match bit in the Control register (CTRL.MATCHCLR)
zClock Representation bit in the Control register (CTRL.CLKREP)
The following register is enable-protected:
zEvent Control register (EVCTRL)
Any writes to these bits or registers when the RTC is enabled or being disabled (CTRL.ENABLE is one) will be discarded.
Writes to these bits or registers while the RTC is being disabled will be completed after the disabling is complete.
Enable-protection is denoted by the Enable-Protection property in the register description.
Before the RTC is enabled, it must be configured, as outlined by the following steps:
zRTC operation mode must be selected by writing the Operating Mode bit group in the Control register
(CTRL.MODE)
zClock representation must be selected by writing the Clock Representation bit in the Control register
(CTRL.CLKREP)
zPrescaler value must be selected by writing the Prescaler bit group in the Control register (CTRL.PRESCALER)
The RTC prescaler divides down the source clock for the RTC counter. The frequency of the RTC clock
(CLK_RTC_CNT) is given by the following formula:
The frequency of the generic clock, GCLK_RTC, is given by fGCLK_RTC, and fCLK_RTC_CNT is the frequency of the internal
prescaled RTC clock, CLK_RTC_CNT.
Note that in the Clock/Calendar mode, the prescaler must be configured to provide a 1Hz clock to the counter for correct
operation.
18.6.2.2 Enabling, Disabling and Resetting
The RTC is enabled by writing a one to the Enable bit in the Control register (CTRL.ENABLE). The RTC is disabled by
writing a zero to CTRL.ENABLE.
The RTC should be disabled before resetting it.
The RTC is reset by writing a one to the Software Reset bit in the Control register (CTRL.SWRST). All registers in the
RTC, except DBGCTRL, will be reset to their initial state, and the RTC will be disabled.
Refer to the CTRL register for details.
18.6.3 Operating Modes
The RTC counter supports three RTC operating modes: 32-bit Counter, 16-bit Counter and Clock/Calendar. The
operating mode is selected by the Operating Mode bit group in the Control register (CTRL.MODE).
18.6.3.1 32-Bit Counter (Mode 0)
When the RTC Operating Mode bits in the Control register (CTRL.MODE) are zero, the counter operates in 32-bit
Counter mode. The block diagram of this mode is shown in Figure 18-1. When the RTC is enabled, the counter will
increment on every 0-to-1 transition of CLK_RTC_CNT. The counter will increment until it reaches the top value of
fCLK_RTC_CNT fGCLK_RTC
2PRESCALER
-----------------------------=
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0xFFFFFFFF, and then wrap to 0x00000000. This sets the Overflow Interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG.OVF).
The RTC counter value can be read from or written to the Counter Value register (COUNT) in 32-bit format.
The counter value is continuously compared with the 32-bit Compare register (COMP0). When a compare match occurs,
the Compare 0Interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.CMP0) is set on the next 0-to-1
transition of CLK_RTC_CNT.
If the Clear on Match bit in the Control register (CTRL.MATCHCLR) is one, the counter is cleared on the next counter
cycle when a compare match with COMP0 occurs. This allows the RTC to generate periodic interrupts or events with
longer periods than are possible with the prescaler events. Note that when CTRL.MATCHCLR is one, INTFLAG.CMP0
and INTFLAG.OVF will both be set simultaneously on a compare match with COMP0.
18.6.3.2 16-Bit Counter (Mode 1)
When CTRL.MODE is one, the counter operates in 16-bit Counter mode as shown in Figure 18-2. When the RTC is
enabled, the counter will increment on every 0-to-1 transition of CLK_RTC_CNT. In 16-bit Counter mode, the 16-bit
Period register (PER) holds the maximum value of the counter. The counter will increment until it reaches the PER value,
and then wrap to 0x0000. This sets the Overflow Interrupt flag in the Interrupt Flag Status and Clear register
(INTFLAG.OVF).
The RTC counter value can be read from or written to the Counter Value register (COUNT) in 16-bit format.
The counter value is continuously compared with the 16-bit Compare registers (COMPn, n=0–1). When a compare
match occurs, the Compare n Interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.CMPn, n=0–1) is set
on the next 0-to-1 transition of CLK_RTC_CNT.
18.6.3.3 Clock/Calendar (Mode 2)
When CTRL.MODE is two, the counter operates in Clock/Calendar mode, as shown in Figure 18-3. When the RTC is
enabled, the counter will increment on every 0-to-1 transition of CLK_RTC_CNT. The selected clock source and RTC
prescaler must be configured to provide a 1Hz clock to the counter for correct operation in this mode.
The time and date can be read from or written to the Clock Value register (CLOCK) in a 32-bit time/date format. Time is
represented as:
zSeconds
zMinutes
zHours
Hours can be represented in either 12- or 24-hour format, selected by the Clock Representation bit in the Control register
(CTRL.CLKREP). This bit can be changed only while the RTC is disabled.
Date is represented as:
zDay as the numeric day of the month (starting at 1)
zMonth as the numeric month of the year (1 = January, 2 = February, etc.)
zYear as a value counting the offset from a reference value that must be defined in software
The date is automatically adjusted for leap years, assuming every year divisible by 4 is a leap year. Therefore, the
reference value must be a leap year, e.g. 2000. The RTC will increment until it reaches the top value of 23:59:59
December 31 of year 63, and then wrap to 00:00:00 January 1 of year 0. This will set the Overflow Interrupt flag in the
Interrupt Flag Status and Clear registers (INTFLAG.OVF).
The clock value is continuously compared with the 32-bit Alarm register (ALARM0). When an alarm match occurs, the
Alarm 0 Interrupt flag in the Interrupt Flag Status and Clear registers (INTFLAG.ALARMn0) is set on the next 0-to-1
transition of CLK_RTC_CNT.
A valid alarm match depends on the setting of the Alarm Mask Selection bits in the Alarm 0 Mask register (MASK0.SEL).
These bits determine which time/date fields of the clock and alarm values are valid for comparison and which are
ignored.
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If the Clear on Match bit in the Control register (CTRL.MATCHCLR) is one, the counter is cleared on the next counter
cycle when an alarm match with ALARM0 occurs. This allows the RTC to generate periodic interrupts or events with
longer periods than are possible with the prescaler events (see “Periodic Events” on page 203). Note that when
CTRL.MATCHCLR is one, INTFLAG.ALARM0 and INTFLAG.OVF will both be set simultaneously on an alarm match
with ALARM0.
18.6.4 Additional Features
18.6.4.1 Periodic Events
The RTC prescaler can generate events at periodic intervals, allowing flexible system tick creation. Any of the upper
eight bits of the prescaler (bits 2 to 9) can be the source of an event. When one of the Periodic Event Output bits in the
Event Control register (EVCTRL.PEREOm) is one, an event is generated on the 0-to1 transition of the related bit in the
prescaler, resulting in a periodic event frequency of:
fGCLK_RTC is the frequency of the internal prescaler clock, GCLK_RTC, and n is the position of the EVCTRL.PERnEO bit.
For example, PER0 will generate an event every 8 GCLK_RTC cycles, PER1 every 16 cycles, etc. This is shown in
Figure 18-4. Periodic events are independent of the prescaler setting used by the RTC counter, except if
CTRL.PRESCALER is zero. Then, no periodic events will be generated.
Figure 18-4. Example Periodic Events
18.6.4.2 Frequency Correction
The RTC Frequency Correction module employs periodic counter corrections to compensate for a too-slow or too-fast
oscillator. Frequency correction requires that CTRL.PRESCALER is greater than 1.
The digital correction circuit adds or subtracts cycles from the RTC prescaler to adjust the frequency in approximately
1PPM steps. Digital correction is achieved by adding or skipping a single count in the prescaler once every 1024
GCLK_RTC cycles. The Value bit group in the Frequency Correction register (FREQCORR.VALUE) determines the
number of times the adjustment is applied over 976 of these periods. The resulting correction is as follows:
This results in a resolution of 1.0006PPM.
The Sign bit in the Frequency Correction register (FREQCORR.SIGN) determines the direction of the correction. A
positive value will speed up the frequency, and a negative value will slow down the frequency.
Digital correction also affects the generation of the periodic events from the prescaler. When the correction is applied at
the end of the correction cycle period, the interval between the previous periodic event and the next occurrence may also
be shortened or lengthened depending on the correction value.
3
_
2+
=n
RTCGCLK
PERIODIC
f
f
GCLK_RTC
PER0
PER1
PER2
PER3
PER4
Correction in PPM FREQCORR.VALUE
1024 976⋅
----------------------------------------------------- 106PPM⋅=
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18.6.5 DMA Operation
Not applicable.
18.6.6 Interrupts
The RTC has the following interrupt sources:
zOverflow
zCompare m
zAlarm m
zSynchronization Ready
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the RTC is reset. See INTFLAG for details on how to clear interrupt flags. The RTC
has one common interrupt request line for all the interrupt sources. The user must read INTFLAG to determine which
interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to “Nested Vector Interrupt
Controller” on page 24 for details.
18.6.7 Events
The RTC can generate the following output events, which are generated in the same way as the corresponding
interrupts:
zOverflow (OVF)
zPeriod n (PERn)
zCompare n (CMPn)
zAlarm n (ALARMn)
Output events must be enabled to be generated. Writing a one to an Event Output bit in the Event Control register
(EVCTRL.xxEO) enables the corresponding output event. Writing a zero to this bit disables the corresponding output
event. Refer to “EVSYS – Event System” on page 309 for details.
18.6.8 Sleep Mode Operation
The RTC will continue to operate in any sleep mode where the source clock is active. The RTC interrupts can be used to
wake up the device from a sleep mode, or the RTC events can trigger other operations in the system without exiting the
sleep mode.
An interrupt request will be generated after the wake-up if the Interrupt Controller is configured accordingly. Otherwise
the CPU will wake up directly, without triggering an interrupt. In this case, the CPU will continue executing from the
instruction following the entry into sleep.
The periodic events can also wake up the CPU through the interrupt function of the Event System. In this case, the event
must be enabled and connected to an event channel with its interrupt enabled. See “EVSYS – Event System” on page
309 for more information.
18.6.9 Synchronization
Due to the asynchronicity between CLK_RTC_APB and GCLK_RTC some registers must be synchronized when
accessed. A register can require:
zSynchronization when written
zSynchronization when read
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zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status
register(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronizati on is complete. The
synchronization Ready interrupt can be used to signal when sync is complete. This can be accessed via the
Synchronization Ready Interrupt Flag in the Interrupt Flag Status and Clear register (INTFLAG.SYNCRDY).
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following bits need synchronization when written:
zSoftware Reset bit in the Control register (CTRL.SWRST)
zEnable bit in the Control register (CTRL.ENABLE)
The following registers need synchronization when written:
zThe Counter Value register (COUNT)
zThe Clock Value register (CLOCK)
zThe Counter Period register (PER)
zThe Compare n Value registers (COMPn)
zThe Alarm n Value registers (ALARMn)
zThe Frequency Correction register (FREQCORR)
zThe Alarm n Mask register (MASKn)
Write-synchronization is denoted by the Write-Synchronization property in the register description.
The following registers need synchronization when read:
zThe Counter Value register (COUNT)
zThe Clock Value register (CLOCK)
Read-synchronization is denoted by the Read-Synchronization property in the register description.
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18.7 Register Summary
The register mapping depends on the Operating Mode bits in the Control register (CTRL.MODE). The register summary
is presented for each of the three modes.
Table 18-1. Register Summary - Mode 0 Registers
Offset Name Bit Pos.
0x00 CTRL 7:0 MATCHCLR CLKREP MODE[1:0] ENABLE SWRST
0x01 15:8 PRESCALER[3:0]
0x02 READREQ 7:0 ADDR[5:0]
0x03 15:8 RREQ RCONT
0x04 EVCTRL 7:0 PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
0x05 15:8 OVFEO CMPEO0
0x06 INTENCLR 7:0 OVF SYNCRDY CMP0
0x07 INTENSET 7:0 OVF SYNCRDY CMP0
0x08 INTFLAG 7:0 OVF SYNCRDY CMP0
0x09 Reserved
0x0A STATUS 7:0 SYNCBUSY
0x0B DBGCTRL 7:0 DBGRUN
0x0C FREQCORR 7:0 SIGN VALUE[6:0]
0x0D Reserved
0x0E Reserved
0x0F Reserved
0x10
COUNT
7:0 COUNT[7:0]
0x11 15:8 COUNT[15:8]
0x12 23:16 COUNT[23:16]
0x13 31:24 COUNT[31:24]
0x14 Reserved
0x15 Reserved
0x16 Reserved
0x17 Reserved
0x18
COMP0
7:0 COMP[7:0]
0x19 15:8 COMP[15:8]
0x1A 23:16 COMP[23:16]
0x1B 31:24 COMP[31:24]
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Table 18-2. Register Summary - Mode 1 Registers
Offset Name Bit Pos.
0x00 CTRL 7:0 MATCHCLR CLKREP MODE[1:0] ENABLE SWRST
0x01 15:8 PRESCALER[3:0]
0x02 READREQ 7:0 ADDR[5:0]
0x03 15:8 RREQ RCONT
0x04 EVCTRL 7:0 PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
0x05 15:8 OVFEO CMPEO1 CMPEO0
0x06 INTENCLR 7:0 OVF SYNCRDY CMP1 CMP0
0x07 INTENSET 7:0 OVF SYNCRDY CMP1 CMP0
0x08 INTFLAG 7:0 OVF SYNCRDY CMP1 CMP0
0x09 Reserved
0x0A STATUS 7:0 SYNCBUSY
0x0B DBGCTRL 7:0 DBGRUN
0x0C FREQCORR 7:0 SIGN VALUE[6:0]
0x0D Reserved
0x0E Reserved
0x0F Reserved
0x10 COUNT 7:0 COUNT[7:0]
0x11 15:8 COUNT[15:8]
0x12 Reserved
0x13 Reserved
0x14 PER 7:0 PER[7:0]
0x15 15:8 PER[15:8]
0x16 Reserved
0x17 Reserved
0x18 COMP0 7:0 COMP[7:0]
0x19 15:8 COMP[15:8]
0x1A COMP1 7:0 COMP[7:0]
0x1B 15:8 COMP[15:8]
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Table 18-3. Register Summary - Mode 2 Registers
Offset Name Bit Pos.
0x00 CTRL 7:0 MATCHCLR CLKREP MODE[1:0] ENABLE SWRST
0x01 15:8 PRESCALER[3:0]
0x02 READREQ 7:0 ADDR[5:0]
0x03 15:8 RREQ RCONT
0x04 EVCTRL 7:0 PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
0x05 15:8 OVFEO ALARMEO0
0x06 INTENCLR 7:0 OVF SYNCRDY ALARM0
0x07 INTENSET 7:0 OVF SYNCRDY ALARM0
0x08 INTFLAG 7:0 OVF SYNCRDY ALARM0
0x09 Reserved
0x0A STATUS 7:0 SYNCBUSY
0x0B DBGCTRL 7:0 DBGRUN
0x0C FREQCORR 7:0 SIGN VALUE[6:0]
0x0D Reserved
0x0E Reserved
0x0F Reserved
0x10
CLOCK
7:0 MINUTE[1:0] SECOND[5:0]
0x11 15:8 HOUR[3:0] MINUTE[5:2]
0x12 23:16 MONTH[1:0] DAY[4:0] HOUR[4]
0x13 31:24 YEAR[5:0] MONTH[3:2]
0x14 Reserved
0x15 Reserved
0x16 Reserved
0x17 Reserved
0x18
ALARM0
7:0 MINUTE[1:0] SECOND[5:0]
0x19 15:8 HOUR[3:0] MINUTE[5:2]
0x1A 23:16 MONTH[1:0] DAY[4:0] HOUR[4]
0x1B 31:24 YEAR[5:0] MONTH[3:2]
0x1C MASK0 7:0 SEL[2:0]
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18.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Please refer to “Register Access Protection” on page
200 for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Write-Synchronized
or the Read-Synchronized property in each individual register description. Please refer to “Synchronization” on page 204
for details.
Some registers are enable-protected, meaning they can only be written when the RTC is disabled. Enable-protection is
denoted by the Enable-Protected property in each individual register description.
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18.8.1 Control
18.8.1.1 Mode 0
Name: CTRL
Offset: 0x00
Reset: 0x0000
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBits 15:12 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 11:8 – PRESCALER[3:0]: Prescaler
These bits define the prescaling factor for the RTC clock source (GCLK_RTC) to generate the counter clock
(CLK_RTC_CNT).
These bits are not synchronized.
Bit151413121110 9 8
PRESCALER[3:0]
Access R R R R R/W R/W R/W R/W
Reset00000000
Bit76543210
MATCHCLR MODE[1:0] ENABLE SWRST
Access R/W R/W R R R/W R/W R/W R/W
Reset00000000
Table 18-4. Prescaler
PRESCALER[3:0] Prescaler Description
0x0 DIV1 CLK_RTC_CNT = GCLK_R TC/1
0x1 DIV2 CLK_RTC_CNT = GCLK_R TC/2
0x2 DIV4 CLK_RTC_CNT = GCLK_R TC/4
0x3 DIV8 CLK_RTC_CNT = GCLK_R TC/8
0x4 DIV16 CLK_RTC_CNT = GCLK_R TC/16
0x5 DIV32 CLK_RTC_CNT = GCLK_R TC/32
0x6 DIV64 CLK_RTC_CNT = GCLK_R TC/64
0x7 DIV128 CLK_RTC_CNT = GCLK_RTC/128
0x8 DIV256 CLK_RTC_CNT = GCLK_RTC/256
0x9 DIV512 CLK_RTC_CNT = GCLK_RTC/512
0xA DIV1024 CLK_RTC_CNT = GCLK_RTC/1024
0xB-0xF -Reserved
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zBit 7 – MATCHCLR: Clear on Match
This bit is valid only in Mode 0 and Mode 2. This bit can be written only when the peripheral is disabled.
0: The counter is not cleared on a Compare/Alarm 0 match.
1: The counter is cleared on a Compare/Alarm 0 match.
This bit is not synchronized.
zBits 6:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:2 – MODE[1:0]: Operating Mode
These bits define the operating mode of the RTC.
These bits are not synchronized.
zBit 1 – ENABLE: Enable
0: The peripheral is disabled or being disabled.
1: The peripheral is enabled or being enabled.
Due to synchronization, there is delay from writing CTRL.ENABLE until the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately, and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY will be cleared when the operation is complete.
This bit is not enable-protected.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the RTC, except DBGCTRL, to their initial state, and the RTC will be
disabled.
Writing a one to CTRL.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Due to synchronization, there is a delay from writing CTRL.SWRST until the reset is complete. CTRL.SWRST and
STATUS.SYNCBUSY will both be cleared when the reset is complete.
This bit is not enable-protected.
Table 18-5. Peripheral Operating Mode
MODE[1:0] Operating Mode Description
0x0 COUNT32 Mode 0: 32-bit Counter
0x1 COUNT16 Mode 1: 16-bit Counter
0x2 CLOCK Mode 2: Clock/Calendar
0x3 -Reserved
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18.8.1.2 Mode 1
Name: CTRL
Offset: 0x00
Reset: 0x0000
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBits 15:12 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 11:8 – PRESCALER[3:0]: Prescaler
These bits define the prescaling factor for the RTC clock source (GCLK_RTC) to generate the counter clock
(CLK_RTC_CNT).
These bits are not synchronized.
Bit151413121110 9 8
PRESCALER[3:0]
Access R R R R R/W R/W R/W R/W
Reset00000000
Bit76543210
MODE[1:0] ENABLE SWRST
Access R/W R/W R R R/W R/W R/W R/W
Reset00000000
Table 18-6. Prescaler
PRESCALER[3:0] Prescaler Description
0x0 DIV1 CLK_RTC_CNT = GCLK_R TC/1
0x1 DIV2 CLK_RTC_CNT = GCLK_R TC/2
0x2 DIV4 CLK_RTC_CNT = GCLK_R TC/4
0x3 DIV8 CLK_RTC_CNT = GCLK_R TC/8
0x4 DIV16 CLK_RTC_CNT = GCLK_R TC/16
0x5 DIV32 CLK_RTC_CNT = GCLK_R TC/32
0x6 DIV64 CLK_RTC_CNT = GCLK_R TC/64
0x7 DIV128 CLK_RTC_CNT = GCLK_RTC/128
0x8 DIV256 CLK_RTC_CNT = GCLK_RTC/256
0x9 DIV512 CLK_RTC_CNT = GCLK_RTC/512
0xA DIV1024 CLK_RTC_CNT = GCLK_RTC/1024
0xB-0xF -Reserved
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zBits 7:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:2 – MODE[1:0]: Operating Mode
These bits define the operating mode of the RTC.
These bits are not synchronized.
zBit 1 – ENABLE: Enable
0: The peripheral is disabled or being disabled.
1: The peripheral is enabled or being enabled.
Due to synchronization, there is delay from writing CTRL.ENABLE until the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately, and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY will be cleared when the operation is complete.
This bit is not enable-protected.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the RTC, except DBGCTRL, to their initial state, and the RTC will be
disabled.
Writing a one to CTRL.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Due to synchronization, there is a delay from writing CTRL.SWRST until the reset is complete. CTRL.SWRST and
STATUS.SYNCBUSY will both be cleared when the reset is complete.
This bit is not enable-protected.
Table 18-7. Peripheral Operating Mode
MODE[1:0] Operating Mode Description
0x0 COUNT32 Mode 0: 32-bit Counter
0x1 COUNT16 Mode 1: 16-bit Counter
0x2 CLOCK Mode 2: Clock/Calendar
0x3 -Reserved
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18.8.1.3 Mode 2
Name: CTRL
Offset: 0x00
Reset: 0x0000
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBits 15:12 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 11:8 – PRESCALER[3:0]: Prescaler
These bits define the prescaling factor for the RTC clock source (GCLK_RTC) to generate the counter clock
(CLK_RTC_CNT).
These bits are not synchronized.
Bit151413121110 9 8
PRESCALER[3:0]
Access R R R R R/W R/W R/W R/W
Reset00000000
Bit76543210
MATCHCLR CLKREP MODE[1:0] ENABLE SWRST
Access R/W R/W R R R/W R/W R/W R/W
Reset00000000
Table 18-8. Prescaler
PRESCALER[3:0] Prescaler Description
0x0 DIV1 CLK_RTC_CNT = GCLK_R TC/1
0x1 DIV2 CLK_RTC_CNT = GCLK_R TC/2
0x2 DIV4 CLK_RTC_CNT = GCLK_R TC/4
0x3 DIV8 CLK_RTC_CNT = GCLK_R TC/8
0x4 DIV16 CLK_RTC_CNT = GCLK_R TC/16
0x5 DIV32 CLK_RTC_CNT = GCLK_R TC/32
0x6 DIV64 CLK_RTC_CNT = GCLK_R TC/64
0x7 DIV128 CLK_RTC_CNT = GCLK_RTC/128
0x8 DIV256 CLK_RTC_CNT = GCLK_RTC/256
0x9 DIV512 CLK_RTC_CNT = GCLK_RTC/512
0xA DIV1024 CLK_RTC_CNT = GCLK_RTC/1024
0xB-0xF -Reserved
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zBit 7 – MATCHCLR: Clear on Match
This bit is valid only in Mode 0 and Mode 2. This bit can be written only when the peripheral is disabled.
0: The counter is not cleared on a Compare/Alarm 0 match.
1: The counter is cleared on a Compare/Alarm 0 match.
This bit is not synchronized.
zBit 6 – CLKREP: Clock Representation
This bit is valid only in Mode 2 and determines how the hours are represented in the Clock Value (CLOCK) regis-
ter. This bit can be written only when the peripheral is disabled.
0: 24 Hour
1: 12 Hour (AM/PM)
This bit is not synchronized.
zBits 5:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:2 – MODE[1:0]: Operating Mode
These bits define the operating mode of the RTC.
These bits are not synchronized.
zBit 1 – ENABLE: Enable
0: The peripheral is disabled or being disabled.
1: The peripheral is enabled or being enabled.
Due to synchronization, there is delay from writing CTRL.ENABLE until the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately, and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY will be cleared when the operation is complete.
This bit is not enable-protected.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the RTC, except DBGCTRL, to their initial state, and the RTC will be
disabled.
Writing a one to CTRL.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Due to synchronization, there is a delay from writing CTRL.SWRST until the reset is complete. CTRL.SWRST and
STATUS.SYNCBUSY will both be cleared when the reset is complete.
This bit is not enable-protected.
Table 18-9. Peripheral Operating Mode
MODE[1:0] Operating Mode Description
0x0 COUNT32 Mode 0: 32-bit Counter
0x1 COUNT16 Mode 1: 16-bit Counter
0x2 CLOCK Mode 2: Clock/Calendar
0x3 -Reserved
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18.8.2 Read Request
Name: READREQ
Offset: 0x02
Reset: 0x0010
Property: –
-
zBit 15 – RREQ: Read Request
Writing a zero to this bit has no effect.
Writing a one to this bit requests synchronization of the register pointed to by the Address bit group (READ-
REQ.ADDR) and sets the Synchronization Busy bit in the Status register (STATUS.SYNCBUSY).
zBit 14 – RCONT: Read Continuously
Writing a zero to this bit disables continuous synchronization.
Writing a one to this bit enables continuous synchronization of the register pointed to by READREQ.ADDR. The
register value will be synchronized automatically every time the register is updated. READREQ.RCONT prevents
READREQ.RREQ from clearing automatically.
This bit is cleared when the register pointed to by READREQ.ADDR is written.
zBits 13:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:0 – ADDR: Address
These bits select the offset of the register that needs read synchronization. In the RTC only the COUNT and
CLOCK registers, which share the same address, are available for read synchronization. Therefore, the ADDR bit
group is a read-only constant of 0x10.
Bit151413121110 9 8
RREQ RCONT
AccessWR/WRRRRRR
Reset00000000
Bit76543210
ADDR[5:0]
AccessRRRRRRRR
Reset00010000
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18.8.3 Event Control
18.8.3.1 Mode 0
Name: EVCTRL
Offset: 0x04
Reset: 0x0000
Property: Write-Protected, Enable-Protected
zBit 15 – OVFEO: Overflow Event Output Enable
0: Overflow event is disabled and will not be generated.
1: Overflow event is enabled and will be generated for every overflow.
zBits 14:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 8 – CMPEO0: Compare 0 Event Output Enable
0: Compare 0 event is disabled and will not be generated.
1: Compare 0 event is enabled and will be generated for every compare match.
zBits 7:0 – PEREOx: Periodic Interval x Event Output Enable
0: Periodic Interval m event is disabled and will not be generated.
1: Periodic Interval m event is enabled and will be generated.
Bit151413121110 9 8
OVFEO CMPEO0
AccessR/WRRRRRRR/W
Reset00000000
Bit76543210
PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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18.8.3.2 Mode 1
Name: EVCTRL
Offset: 0x04
Reset: 0x0000
Property: Write-Protected, Enable-Protected
zBit 15 – OVFEO: Overflow Event Output Enable
0: Overflow event is disabled and will not be generated.
1: Overflow event is enabled and will be generated for every overflow.
zBits 14:10 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 9 – CMPEO1: Compare Event Output Enable 1
0: Compare 1 event is disabled and will not be generated.
1: Compare 1 event is enabled and will be generated for every compare match.
zBit 8 – CMPEO0: Compare Event Output Enable 0
0: Compare 0 event is disabled and will not be generated.
1: Compare 0 event is enabled and will be generated for every compare match.
zBits 7:0 – PEREOx: Periodic Interval x Event Output Enable
0: Periodic Interval m event is disabled and will not be generated.
1: Periodic Interval m event is enabled and will be generated.
Bit151413121110 9 8
OVFEO CMPEO1 CMPEO0
AccessR/WRRRRRR/WR/W
Reset00000000
Bit76543210
PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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18.8.3.3 Mode 2
Name: EVCTRL
Offset: 0x04
Reset: 0x0000
Property: Write-Protected, Enabled-Protected
zBit 15 – OVFEO: Overflow Event Output Enable
0: Overflow event is disabled and will not be generated.
1: Overflow event is enabled and will be generated for every overflow.
zBits 14:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 8 – ALARMEO0: Alarm 0 Event Output Enable
0: Alarm 0 event is disabled and will not be generated.
1: Alarm 0 event is enabled and will be generated for every alarm.
zBits 7:0 – PEREOx: Periodic Interval x Event Output Enable
0: Periodic Interval n event is disabled and will not be generated.
1: Periodic Interval n event is enabled and will be generated.
Bit 151413121110 9 8
OVFEO ALARMEO0
AccessR/WRRRRRRR/W
Reset00000000
Bit76543210
PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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18.8.4 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
18.8.4.1 Mode 0
Name: INTENCLR
Offset: 0x06
Reset: 0x00
Property: Write-Protected
zBit 7 – OVF: Overflow Interrupt Enable
0: The Overflow interrupt is disabled.
1: The Overflow interrupt is enabled, and an interrupt request will be generated when the Overflow inte rrupt flag is
set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overflow Interrupt Enable bit and disable the corresponding interrupt.
zBit 6 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The Synchronization Ready interrupt is disabled.
1: The Synchronization Ready interrupt is enabled, and an interrupt request will be generated when the Synchroni-
zation Ready interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Synchronization Ready Interrupt Enable bit and disable the corresponding
interrupt.
zBits 5:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – CMP0: Compare 0 Interrupt Enable
0: The Compare 0 interrupt is disabled.
1: The Compare 0 interrupt is enabled, and an interrupt request will be generated when the Compare 0 interrupt
flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Compare 0 Interrupt Enable bit and disable the corresponding interrupt.
Bit76543210
OVF SYNCRDY CMP0
AccessR/WR/WRRRRRR/W
Reset00000000
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18.8.4.2 Mode 1
Name: INTENCLR
Offset: 0x06
Reset: 0x00
Property: Write-Protected
zBit 7 – OVF: Overflow Interrupt Enable
0: The Overflow interrupt is disabled.
1: The Overflow interrupt is enabled, and an interrupt request will be generated when the Overflow inte rrupt flag is
set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overflow Interrupt Enable bit and disable the corresponding interrupt.
zBit 6 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The Synchronization Ready interrupt is disabled.
1: The Synchronization Ready interrupt is enabled, and an interrupt request will be generated when the Synchroni-
zation Ready interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Synchronization Ready Interrupt Enable bit and disable the corresponding
interrupt.
zBits 5:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – CMP1: Compare 1 Interrupt Enable
0: The Compare 1 interrupt is disabled.
1: The Compare 1 interrupt is enabled, and an interrupt request will be generated when the Compare 1 interrupt
flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Compare 1 Interrupt Enable bit and disable the corresponding interrupt.
zBit 0 – CMP0: Compare 0 Interrupt Enable
0: The Compare 0 interrupt is disabled.
1: The Compare 0 interrupt is enabled, and an interrupt request will be generated when the Compare 0 interrupt
flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Compare 0 Interrupt Enable bit and disable the corresponding interrupt.
Bit76543210
OVF SYNCRDY CMP1 CMP0
Access R/W R/W R R R R R/W R/W
Reset00000000
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18.8.4.3 Mode 2
Name: INTENCLR
Offset: 0x06
Reset: 0x00
Property: Write-protected
zBit 7 – OVF: Overflow Interrupt Enable
0: The Overflow interrupt is disabled.
1: The Overflow interrupt is enabled, and an interrupt request will be generated when the Overflow inte rrupt flag is
set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overflow Interrupt Enable bit and disable the corresponding interrupt.
zBit 6 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The synchronization ready interrupt is disabled.
1: The synchronization ready interrupt is enabled, and an interrupt request will be generated when the Synchroni-
zation Ready interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Synchronization Ready Interrupt Enable bit and disable the corresponding
interrupt.
zBits 5:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – ALARM0: Alarm 0 Interrupt Enable
0: The Alarm 0 interrupt is disabled.
1: The Alarm 0 interrupt is enabled, and an interrupt request will be generated when the Alarm 0 interrupt flag is
set.
Writing a zero to this bit has no effect.
Writing a one to this bit disables the Alarm 0 interrupt.
Bit76543210
OVF SYNCRDY ALARM0
AccessR/WR/WRRRRRR/W
Reset00000000
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18.8.5 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
18.8.5.1 Mode 0
Name: INTENSET
Offset: 0x07
Reset: 0x00
Property: Write-Protected
zBit 7 – OVF: Overflow Interrupt Enable
0: The overflow interrupt is disabled.
1: The overflow interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Overflow Interrupt Enable bit and enable the Overflow interrupt.
zBit 6 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The synchronization ready interrupt is disabled.
1: The synchronization ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Synchronization Ready Interrupt Enable bit and enable the Synchronization
Ready interrupt.
zBits 5:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – CMP0: Compare 0 Interrupt Enable
0: The compare 0 interrupt is disabled.
1: The compare 0 interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Compare 0 Interrupt Enable bit and enable the Compare 0 interrupt.
Bit76543210
OVF SYNCRDY CMP0
AccessR/WR/WRRRRRR
Reset00000000
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18.8.5.2 Mode 1
Name: INTENSET
Offset: 0x07
Reset: 0x00
Property: Write-Protected
zBit 7 – OVF: Overflow Interrupt Enable
0: The overflow interrupt is disabled.
1: The overflow interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Overflow interrupt bit and enable the Overflow interrupt.
zBit 6 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The synchronization ready interrupt is disabled.
1: The synchronization ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Synchronization Ready Interrupt Enable bit and enable the Synchronization
Ready interrupt.
zBits 5:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – CMP1: Compare 1 Interrupt Enable
0: The compare 1 interrupt is disabled.
1: The compare 1 interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Compare 1 Interrupt Enable bit and enable the Compare 1 interrupt.
zBit 0 – CMP0: Compare 0 Interrupt Enable
0: The compare 0 interrupt is disabled.
1: The compare 0 interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Compare 0 Interrupt Enable bit and enable the Compare 0 interrupt.
Bit76543210
OVF SYNCRDY CMP1 CMP0
Access R/W R/W R R R R R/W R/W
Reset00000000
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18.8.5.3 Mode 2
Name: INTENSET
Offset: 0x07
Reset: 0x00
Property: Write-Protected
zBit 7 – OVF: Overflow Interrupt Enable
0: The overflow interrupt is disabled.
1: The overflow interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Overflow Interrupt Enable bit and enable the Overflow interrupt.
zBit 6 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The synchronization ready interrupt is disabled.
1: The synchronization ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Synchronization Ready Interrupt bit and enable the Synchronization Ready
interrupt.
Reading this bit returns the state of the synchronization ready interrupt enable.
zBits 5:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – ALARM0: Alarm0 Interrupt Enable
0: The alarm 0 interrupt is disabled.
1: The alarm 0 interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Alarm 0 Interrupt Enable bit and enable the Alarm 0 interrupt.
Bit76543210
OVF SYNCRDY ALARM0
AccessR/WR/WRRRRRR/W
Reset00000000
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18.8.6 Interrupt Flag S tatus and Clear
18.8.6.1 Mode 0
Name: INTFLAG
Offset: 0x08
Reset: 0x00
Property: -
zBit 7 – OVF: Overflow
This flag is cleared by writing a one to the flag.
This flag is set on the next CLK_RTC_CNT cycle after an overflow condition occurs, and an interrupt request will
be generated ifINTENCLR/SET.OVF is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Overflow interrupt flag.
zBit 6 – SYNCRDY: Synchronization Ready
This flag is cleared by writing a one to the flag.
This flag is set on a 1-to-0 transition of the Synchronization Busy bit in the Status register (STATUS.SYNCBUSY),
except when caused by Enable or software Reset, and an interrupt request will be generated if INTEN-
CLR/SET.SYNCRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Synchronization Ready interrupt flag.
z, and an interrupt request will be generated Bits 5:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – CMP0: Compare 0
This flag is cleared by writing a one to the flag.
This flag is set on the next CLK_RTC_CNT cycle after a match with the compare condition, and an interrupt
request will be generated if INTENCLR/SET.COMP0 is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Compare 0 interrupt flag.
Bit76543210
OVF SYNCRDY CMP0
Access R/W R/W R R R R R R/W
Reset00000000
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18.8.6.2 Mode 1
Name: INTFLAG
Offset: 0x08
Reset: 0x00
Property: -
zBit 7 – OVF: Overflow
This flag is cleared by writing a one to the flag.
This flag is set on the next CLK_RTC_CNT cycle after an overflow condition occurs, and an interrupt request will
be generated ifINTENCLR/SET.OVF is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Overflow interrupt flag.
zBit 6 – SYNCRDY: Synchronization Ready
This flag is cleared by writing a one to the flag.
This flag is set on a 1-to-0 transition of the Synchronization Busy bit in the Status register (STATUS.SYNCBUSY),
except when caused by Enable or software Reset, and an interrupt request will be generated if INTEN-
CLR/SET.SYNCRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Synchronization Ready interrupt flag.
z, and an interrupt request will be generatedBits 5:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – CMP1: Compare 1
This flag is cleared by writing a one to the flag.
This flag is set on the next CLK_RTC_CNT cycle after a match with the compare condition, and an interrupt
request will be generated if INTENCLR/SET.COMP1 is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Compare 1 interrupt flag.
zBit 0 – CMP0: Compare 0
This flag is cleared by writing a one to the flag.
This flag is set on the next CLK_RTC_CNT cycle after a match with the compare condition, and an interrupt
request will be generated if INTENCLR/SET.COMP0 is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Compare 0 interrupt flag.
Bit76543210
OVF SYNCRDY CMP1 CMP0
Access R/W R/W R R R R R/W R/W
Reset00000000
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18.8.6.3 Mode 2
Name: INTFLAG
Offset: 0x08
Reset: 0x00
Property: –
zBit 7 – OVF: Overflow
This flag is cleared by writing a one to the flag.
This flag is set on the next CLK_RTC_CNT cycle after an overflow condition occurs, and an interrupt request will
be generated ifINTENCLR/SET.OVF is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Overflow interrupt flag.
zBit 6 – SYNCRDY: Synchronization Ready
This flag is cleared by writing a one to the flag.
This flag is set on a 1-to-0 transition of the Synchronization Busy bit in the Status register (STATUS.SYNCBUSY),
except when caused by Enable or software Reset, and an interrupt request will be generated if INTEN-
CLR/SET.SYNCRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Synchronization Ready interrupt flag.
z, and an interrupt request will be generatedBits 5:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – ALARM0: Alarm 0
This flag is cleared by writing a one to the flag.
This flag is set on the next CLK_RTC_CNT cycle after a match with ALARM0 condition occurs, and an interrupt
request will be generated if INTENCLR/SET.ALARM0 is also one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Alarm 0 interrupt flag.
Bit76543210
OVF SYNCRDY ALARM0
AccessR/WR/WRRRRRR/W
Reset00000000
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18.8.7 Status
Name: STATUS
Offset: 0x0A
Reset: 0x00
Property: –
zBit 7 – SYNCBUSY: Synchronization Busy
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 6:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit76543210
SYNCBUSY
AccessRRRRRRRR
Reset00000000
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18.8.8 Debug Control
Name: DBGCTRL
Offset: 0x0B
Reset: 0x00
Property: –
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – DBGRUN: Run During Debug
This bit is not reset by a software reset.
Writing a zero to this bit causes the RTC to halt during debug mode.
Writing a one to this bit allows the RTC to continue normal operation during debug mode.
Bit76543210
DBGRUN
AccessRRRRRRRR/W
Reset00000000
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18.8.9 Frequency Correction
Name: FREQCORR
Offset: 0x0C
Reset: 0x00
Property: Write-Protected, Write-Synchronized
zBit 7 – SIGN: Correction Sign
0: The correction value is positive, i.e., frequency will be increased.
1: The correction value is negative, i.e., frequency will be decreased.
zBits 6:0 – VALUE[6:0]: Correction Value
These bits define the amount of correction applied to the RTC prescaler.
0: Correction is disabled and the RTC frequency is unchanged.
1–127: The RTC frequency is adjusted according to the value.
Bit76543210
SIGN VALUE[6:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
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18.8.10 Counter Value
18.8.10.1 Mode 0
Name: COUNT
Offset: 0x10
Reset: 0x00000000
Property: Write-Protected, Write-Synchronized, Read-Synchronized
zBits 31:0 – COUNT[31:0]: Counter Value
These bits define the value of the 32-bit RTC counter.
Bit 3130292827262524
COUNT[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
COUNT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 151413121110 9 8
COUNT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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18.8.10.2 Mode 1
Name: COUNT
Offset: 0x10
Reset: 0x0000
Property: Write-Protected, Write-Synchronized, Read-Synchronized
zBits 15:0 – COUNT[15:0]: Counter Value
These bits define the value of the 16-bit RTC counter.
Bit151413121110 9 8
COUNT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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18.8.11 Clock Value
18.8.11.1 Mode 2
Name: CLOCK
Offset: 0x10
Reset: 0x00000000
Property: Write-Protected, Write-Synchronized, Read-Synchronized
zBits 31:26 – YEAR[5:0]: Year
The year offset with respect to the reference year (defined in software).
The year is considered a leap year if YEAR[1:0] is zero.
zBits 25:22 – MONTH[3:0]: Month
1 – January
2 – February
…
12 – December
zBits 21:17 – DAY[4:0]: Day
Day starts at 1 and ends at 28, 29, 30 or 31, depending on the month and year.
zBits 16:12 – HOUR[4:0]: Hour
When CTRL.CLKREP is zero, the Hour bit group is in 24-hour format, with values 0-23. When CTRL.CLKREP is
one, HOUR[3:0] has values 1-12 and HOUR[4] represents AM (0) or PM (1).
zBits 11:6 – MINUTE[5:0]: Minute
0 – 59.
Bit 3130292827262524
YEAR[5:0] MONTH[3:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
MONTH[1:0] DAY[4:0] HOUR[4]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 151413121110 9 8
HOUR[3:0] MINUTE[5:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
MINUTE[1:0] SECOND[5:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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zBits 5:0 – SECOND[5:0]: Second
0– 59.
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18.8.12 Counter Period
18.8.12.1 Mode 1
Name: PER
Offset: 0x14
Reset: 0x0000
Property: Write-Protected, Write-Synchronized
zBits 15:0 – PER[15:0]: Counter Period
These bits define the value of the 16-bit RTC period.
Bit 151413121110 9 8
PER[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
PER[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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18.8.13 Compare n Value
18.8.13.1 Mode 0
Name: COMPn
Offset: 0x18 + n*0x4 [n=0..3]
Reset: 0x00000000
Property: Write-Protected, Write-Synchronized
zBits 31:0 – COMP[31:0]: Compare Value
The 32-bit value of COMPn is continuously compared with the 32-bit COUNT value. When a match occurs, the
Compare n interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.CMPn) is set on the next counter
cycle, and the counter value is cleared if CTRL.MATCHCLR is one.
Bit 3130292827262524
COMP[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
COMP[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
COMP[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
COMP[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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18.8.13.2 Mode 1
Name: COMPn
Offset: 0x18 + n*0x2 [n=0..5]
Reset: 0x0000
Property: Write-Protected, Write-Synchronized
zBits 15:0 – COMP[15:0]: Compare Value
The 16-bit value of COMPn is continuously compared with the 16-bit COUNT value. When a match occurs, the
Compare n interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.CMPn) is set on the next counter
cycle.
Bit151413121110 9 8
COMP[15:8]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit76543210
COMP[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
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18.8.14 Alarm n Value
18.8.14.1 Mode 2
Name: ALARMn
Offset: 0x18 + n*0x8 [n=0..3]
Reset: 0x00000000
Property: Write-Protected, Write-Synchronized
The 32-bit value of ALARMn is continuously compared with the 32-bit CLOCK value, based on the masking set by
MASKn.SEL. When a match occurs, the Alarm n interrupt flag in the Interrupt Flag Status and Clear register
(INTFLAG.ALARMn) is set on the next counter cycle, and the counter is cleared if CTRL.MATCHCLR is one.
zBits 31:26 – YEAR[5:0]: Year
The alarm year. Years are only matched if MASKn.SEL is 6.
zBits 25:22 – MONTH[3:0]: Month
The alarm month. Months are matched only if MASKn.SEL is greater than 4.
zBits 21:17 – DAY[4:0]: Day
The alarm day. Days are matched only if MASKn.SEL is greater than 3.
zBits 16:12 – HOUR[4:0]: Hour
The alarm hour. Hours are matched only if MASKn.SEL is greater than 2.
zBits 11:6 – MINUTE[5:0]: Minute
The alarm minute. Minutes are matched only if MASKn.SEL is greater than 1.
Bit 3130292827262524
YEAR[5:0] MONTH[3:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
MONTH[1:0] DAY[4:0] HOUR[4]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
HOUR[3:0] MINUTE[5:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
MINUTE[1:0] SECOND[5:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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zBits 5:0 – SECOND[5:0]: Second
The alarm second. Seconds are matched only if MASKn.SEL is greater than 0.
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18.8.15 Alarm n Mask
18.8.15.1 Mode 2
Name: MASKn
Offset: 0x1C + n*0x8 [n=0..3]
Reset: 0x00
Property: Write-Protected, Write-Synchronized
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 2:0 – SEL[2:0]: Alarm Mask Selection
These bits define which bit groups of Alarm n are valid.
Bit76543210
SEL[2:0]
Access R R R R R R/W R/W R/W
Reset00000000
Table 18-10. Alarm Mask Selection
SEL[2:0] Alarm Mask Selection Description
0x0 OFF Alarm Disabled
0x1 SS Match seconds only
0x2 MMSS Match seconds and minutes only
0x3 HHMMSS Match seconds, minutes and hours only
0x4 DDHHMMSS Match seconds, minutes, hours and days only
0x5 MMDDHHMMSS Match seconds, minutes, hours, days and months only
0x6 YYMMDDHHMMSS Match seconds, minutes, hours, days, months and years
0x7 -Reserved
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19. EIC – External Interrupt Controller
19.1 Overview
The External Interrupt Controller (EIC) allows external pins to be configured as interrupt lines. Each interrupt line can be
individually masked and can generate an interrupt on rising, falling or both edges, or on high or low levels. Each external
pin has a configurable filter to remove spikes. Each external pin can also be configured to be asynchronous in order to
wake up the device from sleep modes where all clocks have been disabled. External pins can also generate an event.
A separate non-maskable interrupt (NMI) is also supported. It has properties similar to the other external interrupts, but is
connected to the NMI request of the CPU, enabling it to interrupt any other interrupt mode.
19.2 Features
z16 external pins, plus 1 non-maskable pin
zDedicated interrupt line for each pin
zIndividually maskable interrupt lines
zInterrupt on rising, falling or both edges
zInterrupt on high or low levels
zAsynchronous interrupts for sleep modes without clock
zFiltering of external pins
zEvent generation
zConfigurable wake-up for sleep modes
19.3 Block Diagram
Figure 19-1. EIC Block Diagram
Fil
ter Ed
g
e
/
Level
Detection
I
nterru
pt
W
ake
E
vent
FILTENx
EXTINTx
intre
q_
extint
[
x
]
inwake
_
extint
[
x
]
e
vt
_
extint
[
x
]
Fil
t
e
rEdge/Level
De
t
ec
t
io
n
I
nterrup
t
Wa
k
e
NMIFILTEN NMI
S
EN
S
E[2:0]
NMI
intre
q_
nm
i
inwake_nmi
SENSEx
[
2:0
]
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19.4 Signal Description
Please refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One
signal can be mapped on several pins.
19.5 Product Dependencies
In order to use this EIC, other parts of the system must be configured correctly, as described below.
19.5.1 I/O Lines
Using the EIC’s I/O lines requires the I/O pins to be configured. Refer to “PORT” on page 284 for details.
19.5.2 Power Management
All interrupts are available in all sleep modes, but the EIC can be configured to automatically mask some interrupts in
order to prevent device wake-up.
The EIC will continue to operate in any sleep mode where the sele cted source clock is running. The EIC’s interrupts can
be used to wake up the device from sleep modes. Events connected to the Event System can trigger other operations in
the system without exiting sleep modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep
modes.
19.5.3 Clocks
The EIC bus clock (CLK_EIC_APB) can be enabled and disabled in the Power Manager, and the default state of
CLK_EIC_APB can be found in the Peripheral Clock Masking section in “PM – Power Manager” on page 100.
A generic clock (GCLK_EIC) is required to clock the peripheral. This clock must be configured and enabled in the
Generic Clock Controller before using the peripheral. Please refer to “GCLK – Generic Clock Controller” on page 78 for
details.
This generic clock is asynchronous to the user interface clock (CLK_EIC_APB). Due to this asynchronicity, writes to
certain registers will require synchronization between the clock domains. Please refer to “Synchronization” on page 247
for further details.
19.5.4 Interrupts
There are two interrupt request lines, one for the external interrupts (EXTINT) and one for non-maskable interrup t (NMI).
The EXTINT interrupt request line is connected to the interrupt controller. Using the EIC interrupt requires the interrupt
controller to be configured first. Please refer to “Nested Vector Interrupt Controller” on page 24 for details.
The NMI interrupt request line is also connected to the interrupt controller, but does not require the interrupt to be
configured.
19.5.5 Events
The events are connected to the Event System. Using the events requires the Event System to be configured first.
Please refer to “EVSYS – Event System” on page 309 for details.
Signal Name Type Description
EXTINT[15..0] Digital Input External interrupt pin
NMI Digital Input Non-maskab l e i nt errupt pin
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19.5.6 Debug Operation
When the CPU is halted in debug mode, the EIC continues normal operation. If the EIC is configured in a way that
requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss may result
during debugging.
19.5.7 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following registers:
zInterrupt Flag Status and Clear register (INTFLAG)
zNon-Maskable Interrupt Flag Status and Clear register (NMIFLAG)
Write-protection is denoted by the Write-Protected property in the register description.
Write-protection does not apply to accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
19.5.8 Analog Connections
Not applicable.
19.6 Functional Description
19.6.1 Principle of Operation
The EIC detects edge or level condition to generate interrupts to the CPU Interrupt Controller or events to the Event
System. Each external interrupt pin (EXTINT) can be filtered using majority vote filtering, clocked by generic clock
GCLK_EIC.
19.6.2 Basic Operation
19.6.2.1 Initialization
The EIC must be initialized in the following order:
1. Enable CLK_EIC_APB
2. If edge detection or filtering is required, GCLK_EIC must be enabled
3. Write the EIC configuration registers (NMICTRL, EVCTRL, WAKEUP, CONFIGy)
4. Enable the EIC
When NMI is used, GCLK_EIC must be enabled after EIC configuration
19.6.2.2 Enabling, Disabling and Resetting
The EIC is enabled by writing a one to the Enable bit in the Control register (CTRL.ENABLE). The EIC is disabled by
writing a zero to CTRL.ENABLE.
The EIC is reset by writing a one to the Software Reset bit in the Control register (CTRL.SWRST). All registers in the EIC
will be reset to their initial state, and the EIC will be disabled.
Refer to CTRL register for details.
19.6.3 External Pin Processing
Each external pin can be configured to generate an interrupt/event on edge detection (rising, falling or both edges) or
level detection (high or low). The sense of external pins is configured by writing the Interrupt Sense x bits in the Config y
register (CONFIGy.SENSEx). The corresponding interrupt flag (INTFLAG.EXTINT[x]) in the Interrupt Flag Status and
Clear register (INTFLAG) is set when the interrupt condition is met (CONFIGy.SENSEx must be different from zero).
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When the interrupt has been cleared in edge-sensitive mode, INTFLAG.EXTINT[x] will only be set if a new interrupt
condition is met. In level-sensitive mode, when interrupt has been cleared, INTFLAG.EXTINT[x] will be set immediately if
the EXTINTx pin still matches the interrupt condition.
Each external pin can be filtered by a majority vote filtering, clocked by GCLK_EIC. Filtering is enabled if bit Filter Enable
x in the Configuration y register (CONFIGy.FILTENx) is written to one. The majority vote filter samples the external pin
three times with GCLK_EIC and outputs the value when two or more samples are equal.
When an external interrupt is configured for level detection, or if filtering is disabled, detection is made asynchronously,
and GCLK_EIC is not required.
If filtering or edge detection is enabled, the EIC automatically requests the GCLK_EIC to operate (GCLK_EIC must be
enabled in the GCLK module, see “GCLK – Generic Clock Controller” on page 78 for details). If level detection is
enabled, GCLK_EIC is not required, but interrupt and events can still be generated.
Figure 19-2. Interrupt detections
The detection delay depends on the detection mode.
Table 19-1. Majority Vote Filter
Samples [0, 1, 2] Filter Outp ut
[0,0,0] 0
[0,0,1] 0
[0,1,0] 0
[0,1,1] 1
[1,0,0] 0
[1,0,1] 1
[1,1,0] 1
[1,1,1] 1
G
CLK
_
EI
C
C
LK_EI
C
_APB
E
XTINT
x
i
ntreq_ext
i
nt
[
x
]
(level detection / no filter)
i
ntre
q_
extint
[
x
]
(level detection / filter
)
i
ntre
q_
extint
[
x
]
(
edge detection
/
no
f
ilter
)
i
ntre
q_
extint
[
x
]
(edge detection / filter
)
N
o interru
p
t
N
o interru
p
t
c
lear INTFLAG.EXTINT
[
x
]
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19.6.4 Additional Features
The non-maskable interrupt pin can also generate an interrupt on edge or level detection, but it is configured with the
dedicated NMI Control register (NMICTRL). To select the sense for NMI, write to the NMISENSE bit group in the NMI
Control register (NMICTRL.NMISENSE). NMI filtering is enabled by writing a one to the NMI Filter Enable bit
(NMICTRL.NMIFILTEN).
NMI detection is enabled only by the NMICTRL.NMISENSE value, and the EIC is not required to be enabled.
After reset, NMI is configured to no detection mode.
When an NMI is detected, the non-maskable interrupt flag in the NMI Flag Status and Clear register is set
(NMIFLAG.NMI). NMI interrupt generation is always enabled, and NMIFLAG.NMI generates an interrupt request when
set.
19.6.5 Interrupts
The EIC has the following interrupt sources:
zExternal interrupt pins (EXTINTx). See “Basic Operation” on page 244
zNon-maskable interrupt pin (NMI). See “Additional Features” on page 246
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when an interrupt condition occurs (NMIFLAG for NMI). Each interrupt, except NMI, can be
individually enabled by writing a one to the corresponding bit in the Interrupt Enable Set register (INTENSET), and
disabled by writing a one to the corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request
is generated when the interrupt flag is set and the corresponding interrupt is enabled. The interrupt request remains
active until the interrupt flag is cleared, the interrupt is disabled or the EIC is reset. See the INTFLAG register for details
on how to clear interrupt flags. The EIC has one common interrupt request line for all the interrupt sources (except the
NMI interrupt request line). Refer to “Processor and Architecture” on page 23 for details. The user must read the
INTFLAG (or NMIFLAG) register to determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to “Processor and
Architecture” on page 23 for details.
19.6.6 Events
The EIC can generate the following output events:
zExternal event from pin (EXTINTx).
Writing a one to an Event Output Control register (EVCTRLEXTINTEO) enables the corresponding output event. Writing
a zero to this bit disables the corresponding output event. Refer to “EVSYS – Event System” on page 309 for details on
configuring the Event System.
When the condition on pin EXTINTx matches the configuration in the CONFIGy register, the corresponding event is
generated, if enabled.
Ta ble 19-2. Interrupt Latency
Detection Mode Latency (Worst Case)
Level without filter 3 CLK_EIC_APB periods
Level with filter 4 GCLK_EIC periods + 3 CLK_EIC_APB periods
Edge without filter 4 GCLK_EIC periods + 3 CLK_EIC_APB periods
Edge with filter 6 GCLK_EIC periods + 3 CLK_EIC_APB periods
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19.6.7 Sleep Mode Operation
In sleep modes, an EXTINTx pin can wake up the device if the corresponding condition matches the configuration in
CONFIGy register. Writing a one to a Wake-Up Enable bit (WAKEUP.WAKEUPEN[x]) enables the wake-up from pin
EXTINTx. Writing a zero to a Wake-Up Enable bit (WAKEUP.WAKEUPEN[x]) disables the wake-up from pin EXTINTx.
Figure 19-3. Wake-Up Operation Example (High-Level Detection, No Filter, WAKEUPEN[x]=1)
19.6.8 Synchronization
Due to the asynchronicity between CLK_EIC_APB and GCLK_EIC, some registers must be synchronized when
accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete. The synchronization
Ready interrupt can be used to signal when sync is complete. This can be accessed via the Synchronization Ready
interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.SYNCRDY).
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled, and interrupts will be pending as long as the bus is
stalled.
The following bits need synchronization when written:
zSoftware Reset bit in the Control register (CTRL.SWRST)
zEnable bit in the Control register (CTRL.ENABLE)
No register needs synchronization when written.
No register needs synchronization when read.
CLK
_
EIC
_
APB
EXTINTx
intwake_extint[x]
intre
q_
extint
[
x
]
c
lear INTFLAG.EXTINT
[
x
]
r
eturn to slee
p
mode
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19.7 Register Summary
Table 19-3. Register Summary
Offset Name Bit
Pos.
0x00 CTRL 7:0 ENABLE SWRST
0x01 STATUS 7:0 SYNCBUSY
0x02 NMICTRL 7:0 NMIFILTEN NMISENSE[2:0]
0x03 NMIFLAG 7:0 NMI
0x04
EVCTRL
7:0 EXTINTEO[7:0]
0x05 15:8 EXTINTEO[15:8]
0x06 23:16
0x07 31:24
0x08
INTENCLR
7:0 EXTINT[7:0]
0x09 15:8 EXTINT[15:8]
0x0A 23:16
0x0B 31:24
0x0C
INTENSET
7:0 EXTINT[7:0]
0x0D 15:8 EXTINT[15:8]
0x0E 23:16
0x0F 31:24
0x10
INTFLAG
7:0 EXTINT[7:0]
0x11 15:8 EXTINT[15:8]
0x12 23:16
0x13 31:24
0x14
WAKEUP
7:0 WAKEUPEN[7:0]
0x15 15:8 WAKEUPEN[15:8]
0x16 23:16
0x17 31:24
0x18
CONFIG0
7:0 FILTEN1 SENSE1[2:0] FILTEN0 SENSE0[2:0]
0x19 15:8 FILTEN3 SENSE3[2:0] FILTEN2 SENSE2[2:0]
0x1A 23:16 FILTEN5 SENSE5[2:0] FILTEN4 SENSE4[2:0]
0x1B 31:24 FILTEN7 SENSE7[2:0] FILTEN6 SENSE6[2:0]
0x1C
CONFIG1
7:0 FILTEN9 SENSE9[2:0] FILTEN8 SENSE8[2:0]
0x1D 15:8 FILTEN11 SENSE11[2:0] FILTEN10 SENSE10[2:0]
0x1E 23:16 FILTEN13 SENSE13[2:0] FILTEN12 SENSE12[2:0]
0x1F 31:24 FILTEN15 SENSE15[2:0] FILTEN14 SENSE14[2:0]
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19.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-protected property in each individual register description. Please refer to “Register Access Protection” on page
244 for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Synchronized
property in each individual register description. Please refer to “Synchronization” on page 247 for details.
Some registers are enable-protected, meaning they can be written only when the EIC is disabled. Enable-protection is
denoted by the Enabled-Protected property in each individual register description.
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19.8.1 Control
Name: CTRL
Offset: 0x00
Reset: 0x00
Property: Write-Protected,Write-Synchronized
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – ENABLE: Enable
0: The EIC is disabled.
1: The EIC is enabled.
Due to synchronization, there is delay from writing CTRL.ENABLE until the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately, and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY will be cleared when the operation is complete.
zBit 0 – SWRST: Software Reset
0: There is no ongoing reset operation.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the EIC to their initial state, and the EIC will be disabled.
Writing a one to CTRL.SWRST will always take precedence, meaning that all other writes in the same write opera-
tion will be discarded.
Due to synchronization, there is a delay from writing CTRL.SWRST until the reset is complete. CTRL.SWRST and
STATUS.SYNCBUSY will both be cleared when the reset is complete.
Bit 76543210
ENABLE SWRST
AccessRRRRRRR/WR/W
Reset00000000
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19.8.2 Status
Name: STATUS
Offset: 0x01
Reset: 0x00
Property: -
zBit 7 – SYNCBUSY: Synchronization Busy
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 6:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit 76543210
SYNCBUSY
AccessRRRRRRRR
Reset00000000
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19.8.3 Non-Maskable Interrupt Control
Name: NMICTRL
Offset: 0x02
Reset: 0x00
Property: Write-Protected
zBits 7:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 3 – NMIFILTEN: Non-Maskable Interrupt Filter Enable
0: NMI filter is disabled.
1: NMI filter is enabled.
zBits 2:0 – NMISENSE: Non-Maskable Interrupt Sense
These bits define on which edge or level the NMI triggers.
Bit 76543210
NMIFILTEN NMISENSE[2:0]
AccessRRRRR/WR/WR/WR/W
Reset00000000
Table 19-4. NMI Sense Configuration
NMISENSE Name Description
0x0 NONE No detection
0x1 RISE Rising-edge detection
0x2 FALL Falling-edge detection
0x3 BOTH Both-edges detection
0x4 HIGH High-level detection
0x5 LOW Low-level detection
0x6-0x7 -Reserved
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19.8.4 Non-Maskable Interrupt Flag Status and Clear
Name: NMIFLAG
Offset: 0x03
Reset: 0x00
Property: -
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – NMI: Non-Maskable Interrupt
This flag is cleared by writing a one to it.
This flag is set when the NMI pin matches the NMI sense configuration, and will generate an interrupt request.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the non-maskable interrupt flag.
Bit 76543210
NMI
AccessRRRRRRRR/W
Reset00000000
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19.8.5 Event Control
Name: EVCTRL
Offset: 0x04
Reset: 0x00000000
Property: Write-Protected
zBits 31:16 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 15:0 – EXTINTEO: External Interrupt x Event Output Enable
These bits indicate whether the event associated with the EXTINTx pin is enabled or not to generated for every
detection.
0: Event from pin EXTINTx is disabled.
1: Event from pin EXTINTx is enabled.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
EXTINTEO[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 76543210
EXTINTEO[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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19.8.6 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x08
Reset: 0x00000000
Property: Write-Protected
zBits 31:16 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 15:0 – EXTINT: External Interrupt x Enable
0: The external interrupt x is disabled.
1: The external interrupt x is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the External Interrupt x Enable bit, which enables the external interrupt.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
EXTINT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 76543210
EXTINT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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19.8.7 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Name: INTENSET
Offset: 0x0C
Reset: 0x00000000
Property: Write-Protected
zBits 31:16 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 15:0 – EXTINT: External Interrupt x Enable
0: The external interrupt x is disabled.
1: The external interrupt x is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the External Interrupt x Enable bit, which enables the external interrupt.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
EXTINT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 76543210
EXTINT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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19.8.8 Interrupt Flag S tatus and Clear
Name: INTFLAG
Offset: 0x10
Reset: 0x00000000
Property: -
zBits 31:16 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 15:0 – EXTINT: External Interrupt x
This flag is cleared by writing a one to it.
This flag is set when EXTINTx pin matches the external interrupt sense configuration and will generate an interrupt
request if INTENCLR/SET.EXTINT[x] is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the External Interrupt x flag.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
EXTINT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 76543210
EXTINT[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
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19.8.9 Wake-Up Enable
Name: WAKEUP
Offset: 0x14
Reset: 0x00000000
Property: Write-Protected
zBits 31:16 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 15:0 – WAKEUPEN: External Interrupt x Wake-up Enable
This bit enables or disables wake-up from sleep modes when the EXTINTx pin matches the external interrupt
sense configuration.
0: Wake-up from the EXTINTx pin is disabled.
1: Wake-up from the EXTINTx pin is enabled.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
WAKEUPEN[15:8]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit 76543210
WAKEUPEN[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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19.8.10 Configuration n
Name: CONFIGn
Offset: 0x18+n*0x4 [n=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31, 27, 23, 19, 15, 11, 7, 3 – FILTENx [x=7..0]: Filter x Enable
0: Filter is disabled for EXTINT[n*8+x] input.
1: Filter is enabled for EXTINT[n*8+x] input.
zBits 30:28, 26:24, 22:20, 18:16, 14:12, 10:8, 6:4, 2:0 – SENSEx[2:0] [x=7..0]: Input Sense x Configuration
These bits define on which edge or level the interrupt or event for EXTINT[n*8+x] will be generated.
Bit 3130292827262524
FILTEN7 SENSE7[2:0] FILTEN6 SENSE6[2:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
FILTEN5 SENSE5[2:0] FILTEN4 SENSE4[2:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 151413121110 9 8
FILTEN3 SENSE3[2:0] FILTEN2 SENSE2[2:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit 76543210
FILTEN1 SENSE1[2:0] FILTEN0 SENSE0[2:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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Table 19-5. Sense Configuration
SENSE Name Description
0x0 NONE No detection
0x1 RISE Rising-edge detection
0x2 FALL Falling-edge detection
0x3 BOTH Both-edges detection
0x4 HIGH High-level detection
0x5 LOW Low-level detection
0x6-0x7 -Reserved
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20. NVMCTRL – Non-Volatile Memory Controller
20.1 Overview
Non-volatile memory (NVM) is a reprogrammable flash memory that retains program and data storage even with power
off. The NVM Controller (NVMCTRL) connects to the AHB and APB bus interfaces for system access to the NVM block.
The AHB interface is used for reads and writes to the NVM block, while the APB interface is used for commands and
configuration.
20.2 Features
z32-bit AHB interface for reads and writes
zAll NVM sections are memory mapped to the AHB, including calibration and system configuration
z32-bit APB interface for commands and control
zProgrammable wait states for read optimization
z16 regions can be individually protected or unprotected
zAdditional protection for boot loader
zSupports device protection through a security bit
zInterface to Power Manager for power-down of flash blocks in sleep modes
zCan optionally wake up on exit from sleep or on first access
zDirect-mapped cache
20.3 Block Diagram
Figure 20-1 . Block Diag r am
20.4 Signal Description
Not applicable
Command and
Control
NVM Interface
Cache
NVM Block
NVMCTRL
AHB
APB
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20.5 Product Dependencies
In order to use this module, other parts of the system must be configured correctly, as described below.
20.5.1 Power Management
The NVMCTRL will continue to operate in any sleep mode where the selected source clock is runn ing. The NVMCTRL’s
interrupts can be used to wake up the device from sleep modes. Refer to “PM – Power Manager” on page 100 for details
on the different sleep modes.
The Power Manager will automatically put the NVM block into a low-power state when entering sleep mode. This is
based on the Control B register (CTRLB) SLEEPPRM bit setting. Read the CTRLB register description for more details.
20.5.2 Clocks
Two synchronous clocks are used by the NVMCTRL. One is provided by the AHB bus (CLK_NVMCTRL_AHB) and the
other is provided by the APB bus (CLK_NVMCTRL_APB). For higher system frequencies, a programmable number of
wait states can be used to optimize performance. When changing the AHB bus frequency, the user must ensure that the
NVM Controller is configured with the proper number of wait states. Refer to the “Electrical Characteristics” on page 562
for the exact number of wait states to be used for a particular frequency range. -
20.5.3 Interrupts
The NVM Controller interrupt request line is connected to the interrupt controller. Using the NVMCTRL interrupt requires
the interrupt controller to be programmed first.
20.5.4 Debug Operation
When an external debugger forces the CPU into debug mode, the peripheral continues normal operation.
Access to the NVM block can be protected by the security bit. In this case, the NVM block will not be accessible. See
“Security Bit” on page 268 for details.
20.5.5 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following registers:
zInterrupt Flag Status and Clear register (INTFLAG)
zStatus register (STATUS)
Write-protection is denoted by the Write-Protected property in the register description. Write-protection does not apply for
accesses through an external debugger.
When the CPU is halted in debug mode, all write-protection is automatically disabled. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
20.5.6 Analog Connections
Not applicable.
20.6 Functional Description
20.6.1 Principle of Operation
The NVM Controller is a slave on the AHB and APB buses. It responds to commands, read requests and write requests,
based on user configuration.
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20.6.1.1 Initialization
After power up, the NVM Controller goes through a power-up sequence. During this time, access to the NVM Controller
from the AHB bus is halted. Upon power-up completion, the NVM Controller is operational without any need for user
configuration.
20.6.2 Memory Organization
Refer to “Product Mapping” on page 19 for memory sizes and addresses for each device.
The NVM is organized into rows, where each row contains four pages, as shown in Figure 20-2. The NVM has a row-
erase granularity, while the write granularity is by page. In other words, a single row erase will erase all four pages in t he
row, while four write operations are used to write the complete row.
Figure 20-2. Row Organization
zr rows
zp pages
zwr words per row
zhw half words (16-bit) in each page and in the page buffer
zpw words in total
zaw words reserved for auxiliary space
The NVM block contains an auxiliary space that is memory mapped, as shown in Table 20-1.
The auxiliary space contains factory calibration and system configuration information. This space can be read from the
AHB bus in the same way as the main NVM main address space.
In addition, a boot section can be allocated at the beginning of the main array, and an EEPROM section can be allocated
at the end of the NVM main address space.
Table 20-1. Memory Orga nization
Memory Section Start byte address Size
Main address space 0pw words = 4pw bytes
Calibration and auxiliary space 0x0080_0000 aw words = 8 bytes
User row 0x0080_4000 1 row
Page (n * 4) + 0Row n Page (n * 4) + 1Page (n * 4) + 2Page (n * 4) + 3
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Figure 20-3. Memory Organization
The lower rows in the NVM main address space can be allocated as a boot section by using the BOOTPROT fuses, and
the upper rows can be allocated to EEPROM, as shown in Figure 20-4. The boot sections are protected by the lock bit(s)
corresponding to this address space and by the BOOTPROT[2:0] fuse. The EEPROM rows can be written, regardless of
the region lock status. The number of rows protected by BOOTPROT and the number of rows allocated to the EEPROM
are given in Table 20-4 and Table 20-5, respectively.
Figure 20-4. EEPROM and BOOT Allocation
20.6.3 Region Lock Bits
The NVM block is grouped into 16 equally sized regions. The region size is dependent on the flash memory size, and is
given in the table below. Each region has a dedicated lock bit preventing writing and erasing pages in the region. After
production, all regions will be unlocked.
0NVM Base Address
Calibration and
auxillary space
NVM Main
Address Space
Addresses are word addresses
pw-1
pw
2^21
2^21+aw
0NVM Base Address
EEPROM
allocation
Program
allocation
NVM Memory Address Space
pw-1
BOOT
allocation
pw-1-(EEPROM rows) x wr
(BOOTPROT rows) x wr
pw-(EEPROM rows) x wr
(BOOTPROT rows) x wr - 1
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Table 20-2. Region Size
To lock or unlock a region, the Lock Region and Unlock Region commands are provided. Writing one of these commands
will temporarily lock/unlock the region containing the address loaded in the ADDR register. ADDR can be written by
software, or the automatically loaded value from a write operation can be used. The new setting will stay in effect until the
next reset, or the setting can be changed again using the lock and unlock commands. The current status of the lock can
be determined by reading the LOCK register.
To change the default lock/unlock setting for a region, the user configuration section of the auxiliary space must be
written using the Write Auxiliary Page command. Writing to the auxiliary space will take effect after the next reset.
Therefore, a boot of the device is needed for changes in the lock/unlock setting to take effect. See “Product Mapping” on
page 19 for auxiliary space address mapping.
20.6.4 Command and Data Interface
The NVM Controller is addressable from the APB bus, while the NVM main address space is addressable from the AHB
bus. Read and automatic page write operations are performed by addressing the NVM main address space directly,
while other operations such as manual page writes and row erase must be performed by issuing commands through the
NVM Controller.
To issue a command, the CTRLA.CMD bits must be written along with the CTRLA.CMDEX value. When a command is
issued, INTFLAG.READY will be cleared until the command has completed. Any commands written while
INTFLAG.READY is low will be ignored. Read the CTRLA register description for more details.
The CTRLB register must be used to control the power reduction mode, read wait states and the write mode.
20.6.4.1 NVM Read
Reading from the NVM main address space is performed via the AHB bus by addressing the NVM main address space
or auxiliary address space directly. Read data is available after the configured number of read wait states (CTRLB.RWS)
set in the NVM Controller.
The number of cycles data are delayed to the AHB bus is determined by the read wait states. Examples of using zero
and one wait states are shown in Figure 20-5.
Memory Size [KB] Region Size [KB]
256 16
128 8
64 4
32 2
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Figure 20-5. Read Wait State Examples
20.6.4.2 NVM Write
The NVM Controller requires that an erase must be done before programming. The entire NVM main address space can
be erased by a debugger Chip Erase command. Alternatively, rows can be individually erased by the Erase Row
command.
After programming, the region that the page resides in can be locked to prevent spurious write or erase sequences.
Locking is performed on a per-region basis, and so locking a region locks all pages inside the region.
Data to be written to the NVM block are first written and stored in an internal buffer called the page buffer. The page
buffer contains hw half words. Writes to the page buffer must be 16 or 32 bits. 8-bit writes to the page buffer is not
allowed, and will cause a system exception.
Writing to the NVM block via the AHB bus is performed by a load operation to the page buffer. For each AHB bus write,
the address is stored in the ADDR register. After the page buffer has bee n loaded with the required number of words, the
page can be written to the addressed location by setting CMD to Write Page and setting the key value to CMDEX. The
LOAD bit in the STATUS register indicates whether the page buffer has been loaded or not. Before writing the page to
memory, the accessed row must be erased.
By default, automatic page writes are enabled (MANW=0). This will trigger a write operation to the page addressed by
ADDR when the last location of the page is written.
Because the address is automatically stored in ADDR during the I/O bus write operation, the last given address will be
present in the ADDR register. There is no need to load the ADDR register manually, unless a different page in memory is
to be written.
Procedure for Manual Page Writes (MANW=1)
The row to be written must be erased before the write command is given.
zWrite to the page buffer by addressing the NVM main address space directly
zWrite the page buffer to memory: CMD=Write Page and CMDEX
zThe READY bit in the INTFLAG register will be low while programming is in progress, and access through the AHB
will be stalled
Procedure for Automatic Page Writes (MANW=0)
The row to be written must be erased before the last write to the page buffer is performed.
Note that partially written pages must be written with a manual write.
zWrite to the page buffer by addressing the NVM main address space directly.
Rd 0 Rd 1 Id le
Data 0 Data 1
1 Wait S tate
Rd 0 Rd 1 Idle
Data 0 Da ta 1
0 Wait States
A HB Command
AHB Slave Ready
AHB Slave Data
AH B C omm and
AHB Slave Ready
A HB Sl a v e Da t a
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zWhen the last location in the page buffer is written, the page is automatically written to NVM main address
space.
zINTFLAG.READY will be zero while programming is in progress and access through the AHB will be stalled.
20.6.4.3 Page Buffer Clear
The page buffer is automatically cleared to all ones after a page write is performed. If a partial page has been written and
it is desired to clear the contents of the page buffer, the Page Buffer Clear command can be used.
20.6.4.4 Erase Row
Before a page can be written, the row that contains the page must be erased. The Erase Row command can be used to
erase the desired row. Erasing the row sets all bits to one. If the row resides in a region that is locked, the erase will not
be performed and the Lock Error bit in the Status register (STATUS.LOCKE) will be set.
Procedure for Erase Row
zWrite the address of the row to erase ADDR. Any address within the row can be used.
zIssue an Erase Row command.
20.6.4.5 Lock and Unlock Region
These commands are used to lock and unlock regions as detailed in section “Region Lock Bits” on page 264.
20.6.4.6 Set and Clear Power Reduction Mode
The NVM Controller and block can be taken in and out of power reduction mode through the set and clear power
reduction mode commands. When the NVM Controller and block are in power reduction mode, the Power Reduction
Mode bit in the Status register (STATUS.PRM) is set.
20.6.5 User Row
Table 20-3. User Row Organization
The boot loader resides in the main array starting at offset zero. The allocated boot loader section is protected against
write.
Bit Position Name Usage
2:0 BOOTPROT
Used to select one of eight different boot loader sizes (see Table 20-4.)
Rows included in the boot loader area can not be erased or programmed,
except by a debugger chip erase. BOOTPROT can be changed only when
the security bit is cleared.
3Reserved
6:4 EEPROM Used to select one of eight different EEPROM sizes. EEPROM can be
changed only when the security bit is cleared.
7Reserved
47:8 Device dependant Refer to “Non-Volatile Memory (NVM) User Row Mapping” on page 21.
63:48 LOCK Region lock bits.
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Table 20-4. Boot Loader Size
The EEPROM bits indicates the EEPROM size according to the Table 20-5. EEPROM resides in the upper rows of the
NVM main address space and are writable, regardless of the region lock status.
Table 20-5. EEPROM Size
20.6.6 Security Bit
The security bit allows the entire chip to be locked from external access for code security. The security bit can be written
by a dedicated command, Set Security Bit (SSB). Once set, the only way to clear the security bit is through a debugger
Chip Erase command. After issuing the SSB command, the PROGE error bit can be checked. Refer to “DSU – Device
Service Unit” on page 36 for details.
20.6.7 Cache
The NVM Controller cache reduces the device power consumption and improves system performance when wait states
are required. It is a direct-mapped cache that implements 8 lines of 64 bits (i.e., 64 bytes). NVM Controller cache can be
enabled by writing a zero in the CACHEDIS bit in the CTRLB register (CTRLB.CACHEDIS). Cache can be configured t o
three different modes using the READMODE bit group in the CTRLB register. Refer to CTRLB register description for
more details. The INVALL command can be issued through the CTRLA register to invalidate all cache lines. Commands
affecting NVM content automatically invalidate cache lines.
BOOTPROT [2:0] Rows Protected by BOOTPROT Boot Size in Bytes
7None 0
6 2 512
5 4 1024
4 8 2048
316 4096
232 8192
164 16384
0128 32768
EEPROM[2:0] Rows Allocated to EEPROM EEPROM Size in Bytes
7None 0
6 1 256
5 2 512
4 4 1024
3 8 2048
216 4096
132 8192
064 16384
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20.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 CMD[6:0]
0x01 15:8 CMDEX[7:0]
0x2 Reserved
0x3 Reserved
0x04
CTRLB
7:0 MANW RWS[3:0]
0x05 15:8 SLEEPPRM[1:0]
0x06 23:16 CACHEDIS READMODE[1:0]
0x07 31:24
0x08
PARAM
7:0 NVMP[7:0]
0x09 15:8 NVMP[15:8]
0x0A 23:16 PSZ[2:0]
0x0B 31:24
0x0C INTENCLR 7:0 ERROR READY
0x0D Reserved
0x0E Reserved
0x0F Reserved
0x10 INTENSET 7:0 ERROR READY
0x11 Reserved
0x12 Reserved
0x13 Reserved
0x14 INTFLAG 7:0 ERROR READY
0x15 Reserved
0x16 Reserved
0x17 Reserved
0x18 STATUS 7:0 NVME LOCKE PROGE LOAD PRM
0x19 15:8 SB
0x1A Reserved
0x1B Reserved
0x1C
ADDR
7:0 ADDR[7:0]
0x1D 15:8 ADDR[15:8]
0x1E 23:16 ADDR[21:16]
0x1F 31:24
0x20 LOCK 7:0 LOCK[7:0]
0x21 15:8 LOCK[15:8]
0x22 Reserved
0x23 Reserved
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20.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Please refer to the Register Access Protection
section and the PAC chapter for details.
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20.8.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x0000
Property: Write-Protected
zBits 15:8 – CMDEX: Command Execution
This bit group should be written with the key value 0xA5 to enable the command written to CMD to be executed. If
the bit group is written with a different key value, the write is not performed and the PROGE status bit is set.
PROGE is also set if the a previously written command is not complete.
The key value must be written at the same time as CMD. If a command is issued through the APB bus on the
same cycle as an AHB bus access, the AHB bus access will be given priority. The command will then be executed
when the NVM block and the AHB bus are idle.
The READY status must be one when the command is issued.
Bit 0 of the CMDEX bit group will read back as one until the command is issued.
zBit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 6:0 – CMD: Command
These bits define the command to be executed when the CMDEX key is written, as shown in Table 20-6.
Bit151413121110 9 8
CMDEX[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
CMD[6:0]
Access R R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Table 20-6. Command Bit Descriptio n
CMD[4:0] Group Configuration Description
0x00-0x01 -Reserved
0x02 ER Erase Row - Erases the row addressed by the ADDR register.
0x03 -Reserved
0x04 WP Write Page - Writes the contents of the page buffer to the page addressed
by the ADDR register.
0x05 EAR Erase Auxiliary Row - Erases the auxiliary row add ressed by the ADDR
register. This command can be given only when the security bit is not set
and only to the user configuration row.
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0x06 WAP Write Auxiliary Page - Writes the contents of the page buffer to the page
addressed by the ADDR register . This command can be given only when the
security bit is not set and only to the user configuration row.
0x07-0x3F -Reserved
0x40 LR Lock Region - Locks the region containing the address location in the ADDR
register.
0x41 UR Unlock Region - Unlocks the region containing the address location in the
ADDR register.
0x42 SPRM Sets the power reduction mode.
0x43 CPRM Clears the power reduction mode.
0x44 PBC Pag e Buffer Clear - Clears the page buffer.
0x45 SSB Set Security Bit - Sets the security bit by writing 0x00 to the first byte in the
lockbit row.
0x46 INVALL Invalidates all cache lines.
0x46-0x7F -Reserved
Table 20-6. Command Bit Description (Co ntinu ed)
CMD[4:0] Group Configuration Description
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20.8.2 Control B
Name: CTRLB
Offset: 0x04
Reset: 0x00000000
Property: Write-Protected
zBits 31:19 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 18 – CACHEDIS: Cache Disable
This bit is used to disable the cache.
0: The cache is enabled.
1: The cache is disabled.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
CACHEDIS READMODE[1:0]
Access R R R R R R/W R/W R/W
Reset00000000
Bit151413121110 9 8
SLEEPPRM[1:0]
AccessRRRRRRR/WR/W
Reset00000000
Bit76543210
MANW RWS[3:0]
AccessRRRRRRR/WR/W
Reset00000000
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zBits 17:16 – READMODE: NVMCTRL Read Mode
zBits 15:10 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 9:8 – SLEEPPRM: Power Reduction Mode during Sleep
Indicates the power reduction mode during sleep.
Table 20-7. Table 1-7. Power Reducti on Mode during Sleep
zBit 7 – MANW: Manual Write
0: Writing to the last word in the page buffer will initiate a write operation to the page addressed by the last write
operation. This includes writes to memory and auxiliary rows.
1: Write commands must be issued through the CMD register.
zBits 6:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:1 – RWS: NVM Read Wait States
These bits give the number of wait states for a read operation. Zero indicates zero wait states, one indicates one
wait state, etc., up to 15 wait states.
This register is initialized to 0 wait states. Software can change this value based on the NVM access time and sys-
tem frequency.
zBit 0 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
READMODE Name Description
0x0 NO_MISS_PENALTY The NVM Controller (cache system) does not insert wait states on
a cache miss. Gives the best system performance.
0x1 LOW_POWER
Reduces power consumption of the cache system, but inserts a
wait stat e ea ch time there is a cache mis s . Th is mo de may not be
relevant if CPU performance is required, as th e application will be
stalled and may lead to increase run time.
0x2 DETERMINISTIC
The cache system ensures that a cache hit or miss takes the same
amount of time, determined by the number of programmed flash
wait states. This mode can be used for real-time applications that
require deterministic exec ution timings.
0x3 Reserved
SLEEPPRM[1:0] Name Description
0x0 WAKEONACCESS NVM block enters low-power mode when entering sleep.
NVM block exits low-power mode upon first access.
0x1 WAKEUPINSTANT NVM block enters low-power mode when enteri ng sleep.
NVM block exits low-power mode when exiting sleep.
0x2 Reserved
0x3 DISABLED Auto power reduction disabled.
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20.8.3 NVM Parameter
Name: PARAM
Offset: 0x08
Reset: 0x000XXXXX
Property: –
zBits 31:19 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 18:16 – PSZ: Page Size
Indicates the page size. Not all device families will provide all the page sizes indicated in the table.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
PSZ[2:0]
AccessRRRRRRRR
Reset00000XXX
Bit151413121110 9 8
NVMP[15:8]
AccessRRRRRRRR
ResetXXXXXXXX
Bit76543210
NVMP[7:0]
Access R R R R R R R
ResetXXXXXXXX
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zBits 15:0 – NVMP: NVM Pages
Indicates the number of pages in the NVM main address space.
Table 20-8. Page Size
PSZ[2:0] Name Description
0x0 88 bytes
0x1 16 16 bytes
0x2 32 32 bytes
0x3 64 64 bytes
0x4 128 128 bytes
0x5 256 256 bytes
0x6 512 512 bytes
0x7 1024 1024 bytes
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20.8.4 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x0C
Reset: 0x00
Property: Write-Protected
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – ERROR: Error Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit clears the ERROR interrupt enable.
This bit will read as the current value of the ERROR interrupt enable.
zBit 0 – READY: NVM Ready Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit clears the READY interrupt enable.
This bit will read as the current value of the READY interrupt enable.
Bit76543210
ERROR READY
AccessRRRRRRR/WR/W
Reset00000000
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20.8.5 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x10
Reset: 0x00
Property: Write-Protected
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – ERROR: Error Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit sets the ERROR interrupt enable.
This bit will read as the current value of the ERROR interrupt enable.
zBit 0 – READY: NVM Ready Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit sets the READY interrupt enable.
This bit will read as the current value of the READY interrupt enable.
Bit76543210
ERROR READY
AccessRRRRRRR/WR/W
Reset00000000
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20.8.6 Interrupt Flag S tatus and Clear
Name: INTFLAG
Offset: 0x14
Reset: 0x00
Property: –
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – ERROR: Error
This flag is set on the occurrence of an NVME, LOCKE or PROGE error.
0: No errors have been received since the last clear.
1: At least one error has occurred since the last clear.
This bit can be cleared by writing a one to its bit location.
zBit 0 – READY: NVM Ready
0: The NVM controller is busy programming or erasing.
1: The NVM controller is ready to accept a new command.
Bit76543210
ERROR READY
AccessRRRRRRR/WR
Reset00000000
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20.8.7 Status
Name: STATUS
Offset: 0x18
Reset: 0x0X00
Property: –
zBits 15:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 8 – SB: Security Bit Status
0: The Security bit is inactive.
1: The Security bit is active.
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – NVME: NVM Error
0: No programming or erase errors have been received from the NVM controller since this bit was last cleared.
1: At least one error has been registered from the NVM Controller since this bit was last cleared.
This bit can be cleared by writing a one to its bit location.
zBit 3 – LOCKE: Lock Error Status
0: No programming of any locked lock region has happened since this bit was last cleared.
1: Programming of at least one locked lock region has happened since this bit was last cleared.
This bit can be cleared by writing a one to its bit location.
zBit 2 – PROGE: Programming Error Status
0: No invalid commands or bad keywords were written in the NVM Command register since this bit was last
cleared.
1: An invalid command and/or a bad keyword was/were written in the NVM Command register since this bit was
last cleared.
This bit can be cleared by writing a one to its bit location.
zBit 1 – LOAD: NVM Page Buffer Active Loading
This bit indicates that the NVM page buffer has been loaded with one or more words. Immediately after an NVM
load has been performed, this flag is set, and it remains set until a page write or a page buffe r clear (PBCLR) com-
mand is given.
Bit151413121110 9 8
SB
AccessRRRRRRRR
Reset0000000X
Bit76543210
NVME LOCKE PROGE LOAD PRM
Access R R R R/W R/W R/W R/W R
Reset00000000
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This bit can be cleared by writing a one to its bit location.
zBit 0 – PRM: Power Reduction Mode
This bit indicates the current NVM power reduction state. The NVM block can be set in power reduction mode in
two ways: through the command interface or automatically when entering sleep with SLEEPPRM set accordingly.
PRM can be cleared in three ways: through AHB access to the NVM block, through the command interface (SPRM
and CPRM) or when exiting sleep with SLEEPPRM set accordingly.
0: NVM is not in power reduction mode.
1: NVM is in power reduction mode.
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20.8.8 Address
Name: ADDR
Offset: 0x1C
Reset: 0x00000000
Property: Write-Protected
zBits 31:22 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 21:0 – ADDR: NVM Address
ADDR drives the hardware (16-bit) address to the NVM when a command is executed using CMDEX. This register
is also automatically updated when writing to the page buffer.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
ADDR[21:16]
Access R R R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
ADDR[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
ADDR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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20.8.9 Lock Section
Name: LOCK
Offset: 0x20
Reset: 0xXXXX
Property: –
zBits 15:0 – LOCK: Region Lock Bits
In order to set or clear these bits, the CMD register must be used.
0: The corresponding lock region is locked.
1: The corresponding lock region is not locked.
Bit151413121110 9 8
LOCK[15:8]
AccessRRRRRRRR
ResetXXXXXXXX
Bit76543210
LOCK[7:0]
AccessRRRRRRRR
ResetXXXXXXXX
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21. PORT
21.1 Overview
The Port (PORT) controls the I/O pins of the microcontroller. The I/O pins are organized in a series of groups, collectively
referred to as a line bundle, and each group can have up to 32 pins that can be configured and controlled individually or
as a group. Each pin may either be used for general-purpose I/O under direct application control or assigned to an
embedded device peripheral. When used for general-purpose I/O, each pin can be configured as input or output, with
highly configurable driver and pull settings.
All I/O pins have true read-modify-write functionality when used for general-purpose I/O; the direction or the output value
of one or more pins may be changed (set, reset or toggled) without unintentionally changing the state of any other pins in
the same line bundle via a single, atomic 8-, 16- or 32-bit write.
The PORT is connected to the high-speed bus matrix through an AHB/APB bridge. The Pin Direction, Data Output Value
and Data Input Value registers may also be accessed using the low-latency CPU local bus (IOBUS; ARM® single-cycle
I/O port).
21.2 Features
zSelectable input and output configuration individually for each pin
zSoftware-controlled multiplexing of peripheral functions on I/O pins
zFlexible pin configuration through a dedicated Pin Configuration register
zConfigurable output driver and pull settings:
zTotem-pole (push-pull)
zPull configuration
z Configurable input buffer and pull settings:
zInternal pull-up or pull-down
zInput sampling criteria
zInput buffer can be disabled if not needed for lower power consumption
zRead-modify-write support for pin configuration, output value and pin direction
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21.3 Block Diagram
Figure 21-1. PORT Block Diagram
21.4 Signal Description
Refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
21.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
21.5.1 I/O Lines
The I/O lines of the PORT are mapped to pins of the physical device package according to a simple naming scheme.
Each line bundle of up to 32 pins is assigned a letter identifier, starting with A, that monotonically increases through the
alphabet for each subsequent line bundle. Within each line bundle, each pin is assigned a numerical identifier according
to its bit position.
The resulting PORT pins are mapped as Pxy, where x=A, B, C,… and y=00, 01, …, 31 to uniquely identify each pin in the
device, e.g., PA24, PC03, etc.
Each pin may have one or more peripheral multiplexer settings, which allow the pad to be routed internally to a dedicated
peripheral function. When enabled, the selected peripheral is given control over the output state of the pad, as well as the
ability to read the current physical pad state. Refer to “I/O Multiplexing and Considerations” on page 11 for details.
Device-specific configurations may result in some pins (and the corresponding Pxy pin) not being implemented.
PORTMUX
ANALOG
BLOCKS
PERIPHERALS
Digital Controls of Analog Blocks
Analog Pad
Connections
I/O
PADS
Port Line
Bundles
IP Line Bundles
Peripheral Mux Select
PORT
Control
and
Status
Pad Line
Bundles
Signal Name Type Description
Pxy Digital I/O General-purpose I/O pin y
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21.5.2 Power Management
During reset, all PORT lines are configured as inputs with input buffers, output buffers and pull disabled.
If the PORT peripheral is shut down, the latches contained in the pad will retain their current configuration, such as the
output value and pull settings. However, the PORT configuration registers and input synchronizers will lose their
contents, and these will not be restored when PORT is powered up again. The user must, therefore, reconfigure the
PORT peripheral at power up to ensure it is in a well-defined state before use.
The PORT will continue to operate in any sleep mode where the selected module source clock is running.
21.5.3 Clocks
The PORT bus clock (CLK_PORT_APB) can be enabled and disabled in the Power Manager, and the default state of
CLK_PORT_APB can be found in the Peripheral Clock Masking section in the “PM – Power Manager” on page 100.
The PORT is fed by two different clocks: a CPU main clock, which allows the CPU to access the PORT through the low-
latency CPU local bus (IOBUS), and an APB clock, which is a divided clock of the CPU main clock and allows the CPU to
acces the PORT registers through the high-speed matrix and the AHB/APB bridge.
IOBUS accesses have priority over APB accesses. The latter must insert wait states in the event of concurrent PORT
accesses.
The PORT input synchronizers use the CPU main clock so that the resynchronization delay is minimized with respect to
the APB clock.
21.5.4 DMA
Not applicable.
21.5.5 Interrupts
Not applicable.
21.5.6 Events
Not applicable.
21.5.7 Debug Operation
When the CPU is halted in debug mode, the PORT continues normal operation. If the PORT is configured in a way that
requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss may result
during debugging.
21.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC).
Write-protection is denoted by the Write-Protected property in the register description.
When the CPU is halted in debug mode, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
21.5.9 Analog Connections
Analog functions are connected directly between the analog blocks and the I/O pads using analog buses. However,
selecting an analog peripheral function for a given pin will disable the corresponding digital features of the pad.
21.5.10 CPU Local Bus
The CPU local bus (IOBUS) is an interface that connects the CPU directly to the PORT. It is a single-cycle bus interface,
and does not support wait states. It supports byte, half word and word sizes.
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The CPU accesses the PORT module through the IOBUS when it performs read or write from address 0x60000000. The
PORT register map is equivalent to the one described in the register description section.
This bus is generally used for low latency. The Data Direction (DIR) and Data Output Value (OUT) registers can be read,
written, set, cleared or toggled using this bus, and the Data Input Value (IN) registers can be read.
Since the IOBUS cannot wait for IN register resynchronization, the Control register (CTRL) must be configured to enable
continuous sampling of all pins that will need to be read via the IOBUS to prevent stale data from being read.
21.6 Functional Description
Figure 21-2. Overvie w of the PORT
21.6.1 Principle of Operation
The I/O pins of the device are controlled by reads and writes of the PORT peripheral registers. For each port pin, a
corresponding bit in the Data Direction (DIR) and Data Output Value (OUT) registers are used to enable that pin as an
output and to define the output state.
The direction of each pin in a port bundle is configured via the DIR register. If a bit in DIR is written to one, the
corresponding pin is configured as an output pin. If a bit in DIR is written to zero, the corresponding pin is configured as
an input pin.
When the direction is set as output, the corresponding bit in the OUT register is used to set the level of the pin. If bit y of
OUT is written to one, pin y is driven high. If bit y of OUT is written to zero, pin y is driven low.
Additional pin configuration can be set by writing to the Pin Configuration (PINCFGy) registers.
The Data Input Value bit (IN) is used to read the port pin with resynchronization to the PORT clock. By default, these
input synchronizers are clocked only when an input value read is requested in order to reduce power consumption. Input
value can always be read, whether the pin is configured as input or output, except if digital input is disabled by writing a
zero to the INEN bit in the Pin Configuration registers (PINCFGy).
PULLENy
OUTy
DIRy
INENy
PORTx PADy
3.3V
INEN
OE
OUT
PULLEN
PADy
Pull
Resistor
PG
NG
Input to Other Modules Analog Input/Output
IN
INy
APB Bus
Synchronizer
Port_Mux
...
...
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The PORT also allows peripheral functions to be connected to individual I/O pins by writing a one to the corresponding
PMUXEN bit in the PINCFGy registers and by writing the chosen selection to the Peripheral Multiplexing registers
(PMUXn) for that pin. This will override the connection between the PORT and that I/O pin, and connect the selected
peripheral line bundle to the pad instead of the PORT line bundle.
Each group of up to 32 pins is controlled by a set of registers, as described in Figure 21-3. This set of registers is
duplicated for each group of pins, with increasing base addresses.
Figure 21-3. Overview of the Peripheral Functions Multiplexing
21.6.2 Basic Operation
21.6.2.1 Initialization
After reset, all standard-function device I/O pads are connected to the PORT with outputs tri-stated and input buffers
disabled, even if no clocks are running. Specific pins, such as the ones used for connection to a debugger, may be
configured differently, as required by their special function.
21.6.3 Basic Operation
Each I/O pin y can be configured and accessed by reading or writing PORT registers. Because PORT registers are
grouped into sets of registers for each group of up to 32 pins, the base address of the register set for pin y is at byte
address PORT + (y / 32) * 0x80. (y / 32) will be used as the index within that register set.
To use pin y as an output, configure it as output by writing the (y / 32) bit in the DIR register to one. To avoid disturbing
the configuration of other pins in that group, this can also be done by writing the (y / 32) bit in the DIRSET register to one.
The desired output value can be set by writing the (y / 32) bit to that value in register OUT.
Similarly, writing an OUTSET bit to one will set the corresponding bit in the OUT register to one, while writing an
OUTCLR bit to one will set it to zero, and writing an OUTTGL bit to one will toggle that bit in OUT.
To use pin y as an input, configure it as input by writing the (y / 32) bit in the DIR register to zero. To avoid disturbing the
configuration of other pins in that group, this can also be done by writing the (y / 32) bit in DIRCLR register to one. The
desired input value can be read from the (y / 32) bit in register IN as soon as the INEN bit in the Pin Configuration register
(PINCFGy) is written to one. Refer to “I/O Multiplexing and Considerations” on page 11 for details on pin configuration.
Port y PINCFG
Port y
Periph Line 0
PORT bit y
PMUXEN
Data+Config
Periph Line 1
Periph Line 15
Port y
PMUX[3:0]
Port y PMUX Select
PORTMUX
Port y Line Bundle
PAD y
Pad y
Peripheral Line Bundles
to be muxed to Pad y
Port y Peripheral
Mux Enable
15
1
0
0
1
Line Bundle
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By default, the input synchronizer is clocked only when an input read is requested, which will delay the read operation by
two CLK_PORT cycles. To remove that delay, the input synchronizers for each group of eight pins can be configured to
be always active, but this comes at the expense of higher power consumption. This is controlled by writing a one to the
corresponding SAMPLINGn bit group of the CTRL register, where n = (y / 32) / 8.
To use pin y as one of the available peripheral functions for that pin, configure it by writing a one to the corresponding
PMUXEN bit of the PINCFGy register. The PINCFGy register for pin y is at byte offset (PINCFG0 + (y / 32)).
The peripheral function can be selected by writing to the PMUXO or PMUXE bit group in the PMUXn register. The
PMUXO/PMUXE bit group is at byte offset (PMUX0 + (y / 32) / 2), in bits 3:0 if y is even and in bits 7:4 if y is odd.
The chosen peripheral must also be configured and enabled.
21.6.4 I/O Pin Configuration
The Pin Configuration register (PINCFGy) is used for additional I/O pin configuration. A pin can be set in a totem-pole,
open-drain or pull configuration.
Because pull configuration is done through the Pin Configuration register, all intermediate PORT states during switching
of pin direction and pin values are avoided.
The I/O pin configurations are described further in this chapter, and summarized in Table 21-1.
21.6.4.1 Pin Configurations Summary
Table 21-1. Pin Configurations Summary
21.6.4.2 Input Configuration
Figure 21-4. I/O Configuration - Standard Input
DIR INEN PULLEN OUT Configuration
0 0 0 X Reset or analog I/O; all digital disabled
0 0 1 0 Pull-down; input disabled
0 0 1 1 Pull-up; input disabled
0 1 0 X Input
0 1 1 0 Input with pull-down
0 1 1 1 Input with pull-up
1 0 X X Output; input disabled
1 1 X X Output; input enabled
PULLEN
DIR
OU
T
IN
INEN
PULLEN
I
NEN
DIR
0
1
0
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Figure 21-5. I/O Configuration - Input with Pull
Note that when pull is enabled, the pull value is defined by the OUTx value.
21.6.4.3 Totem-Pole Output
When configured for totem-pole (push-pull) output, the pin is driven low or high according to the corresponding bit setting
in the OUT register. In this configuration, there is no current limitation for sink or source other than what the pin is capable
of. If the pin is configured for input, the pin will float if no external pull is connected. Note, that enabling the output driver
automatically disables pull.
Figure 21-6. I/O Configuration - Totem-Pole Output with Disabled Input
Figure 21-7. I/O Configuration - Totem-Pole Output with Enabled I nput
PULLEN
DIR
OU
T
IN
INEN
PULLEN
I
NEN
DIR
11
0
PULLEN
DIR
OU
T
IN
INEN
PULLEN
I
NEN
DIR
0
0
1
PULLEN
DIR
OU
T
IN
INEN
PULLEN
I
NEN
DIR
0
1
1
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Figure 21-8. I/O Configuration - Ou tput with Pull
21.6.4.4 Digital Functionality Disabled
Figure 21-9. I/O Con figuration - Reset or Analog I/O: Digi tal Output, Input and Pull Disabled
PULLEN
DIR
OU
T
IN
INEN
PULLEN
I
NEN
DIR
1
0
0
PULLEN
DIR
OU
T
IN
INEN
PULLEN
I
NEN
DIR
0
0
0
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21.7 Register Summary
The I/O pins are organized in groups with up to 32 pins. Group 0 consists of the PA pins, group 1 the PB pins, etc. Each
group has its own set of registers. For example, the register address offset for the Data Direction (DIR) register for group
0 (PA00 to PA31) is 0x00, while the register address offset for the DIR register for group 1 (PB00 to PB31) is 0x80.
Offset Name Bit
Pos.
0x00
DIR
7:0 DIR[7:0]
0x01 15:8 DIR[15:8]
0x02 23:16 DIR[23:16]
0x03 31:24 DIR[31:24]
0x04
DIRCLR
7:0 DIRCLR[7:0]
0x05 15:8 DIRCLR[15:8]
0x06 23:16 DIRCLR[23:16]
0x07 31:24 DIRCLR[31:24]
0x08
DIRSET
7:0 DIRSET[7:0]
0x09 15:8 DIRSET[15:8]
0x0A 23:16 DIRSET[23:16]
0x0B 31:24 DIRSET[31:24]
0x0C
DIRTGL
7:0 DIRTGL[7:0]
0x0D 15:8 DIRTGL[15:8]
0x0E 23:16 DIRTGL[23:16]
0x0F 31:24 DIRTGL[31:24]
0x10
OUT
7:0 OUT[7:0]
0x11 15:8 OUT[15:8]
0x12 23:16 OUT[23:16]
0x13 31:24 OUT[31:24]
0x14
OUTCLR
7:0 OUTCLR[7:0]
0x15 15:8 OUTCLR[15:8]
0x16 23:16 OUTCLR[23:16]
0x17 31:24 OUTCLR[31:24]
0x18
OUTSET
7:0 OUTSET[7:0]
0x19 15:8 OUTSET[15:8]
0x1A 23:16 OUTSET[23:16]
0x1B 31:24 OUTSET[31:24]
0x1C
OUTTGL
7:0 OUTTGL[7:0]
0x1D 15:8 OUTTGL[15:8]
0x1E 23:16 OUTTGL[23:16]
0x1F 31:24 OUTTGL[31:24]
0x20
IN
7:0 IN[7:0]
0x21 15:8 IN[15:8]
0x22 23:16 IN[23:16]
0x23 31:24 IN[31:24]
0x24
CTRL
7:0 SAMPLING[7:0]
0x25 15:8 SAMPLING[15:8]
0x26 23:16 SAMPLING[23:16]
0x27 31:24 SAMPLING[31:24]
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0x28
WRCONFIG
7:0 PINMASK[7:0]
0x29 15:8 PINMASK[15:8]
0x2A 23:16 PULLEN INEN PMUXEN
0x2B 31:24 HWSEL WRPINCFG WRPMUX PMUX[3:0]
0x2C
Reserved
0x2D
0x2E
0x2F
0x30 PMUX0 7:0 PMUXO[3:0] PMUXE[3:0]
0x31 PMUX1 7:0 PMUXO[3:0] PMUXE[3:0]
………
0x3E PMUX14 7:0 PMUXO[3:0] PMUXE[3:0]
0x3F PMUX15 7:0 PMUXO[3:0] PMUXE[3:0]
0x40 PINCFG0 7:0 PULLEN INEN PMUXEN
0x41 PINCFG1 7:0 PULLEN INEN PMUXEN
………
0x5E PINCFG30 7:0 PULLEN INEN PMUXEN
0x5F PINCFG31 7:0 PULLEN INEN PMUXEN
Offset Name Bit
Pos.
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21.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Please refer to “Register Access Protection” on page
286 for details.
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21.8.1 Data Direction
Name: DIR
Offset: 0x00+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – DIR[31:0]: Port Data Direction
These bits set the data direction for the individual I/O pins in the PORT group.
0: The corresponding I/O pin in the group is configured as an input.
1: The corresponding I/O pin in the group is configured as an output.
Bit3130292827262524
DIR[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit2322212019181716
DIR[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
DIR[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
DIR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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21.8.2 Data Direction Clear
This register allows the user to set one or more I/O pins as an input, without doing a read-modify-write operation.
Changes in this register will also be reflected in the Data Direction (DIR), Data Direction Toggle (DIRTGL) and Data
Direction Set (DIRSET) registers.
Name: DIRCLR
Offset: 0x04+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – DIRCLR[31:0]: Port Data Direction Clear
0: The I/O pin direction is cleared.
1: The I/O pin direction is set.
Writing a zero to a bit has no effect.
Writing a one to a bit will clear the corresponding bit in the DIR register, which configures the I/O pin as an input.
Bit 3130292827262524
DIRCLR[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit2322212019181716
DIRCLR[23:16]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit151413121110 9 8
DIRCLR[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
DIRCLR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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21.8.3 Data Direction Set
This register allows the user to set one or more I/O pins as an output, without doing a read-modify-write operation.
Changes in this register will also be reflected in the Data Direction (DIR), Data Direction Toggle (DIRTGL) and Data
Direction Clear (DIRCLR) registers.
Name: DIRSET
Offset: 0x08+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – DIRSET[31:0]: Port Data Direction Set
0: The I/O pin direction is cleared.
1: The I/O pin direction is set.
Writing a zero to a bit has no effect.
Writing a one to a bit will set the corresponding bit in the DIR register, which configures the I/O pin as an output.
Bit 3130292827262524
DIRSET[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
DIRSET[23:16]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit 151413121110 9 8
DIRSET[15:8]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit76543210
DIRSET[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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21.8.4 Data Direction Toggle
This register allows the user to toggle the direction of one or more I/O pins, without doing a read-modify-write operation.
Changes in this register will also be reflected in the Data Direction (DIR), Data Direction Set (DIRSET) and Data Direction
Clear (DIRCLR) registers.
Name: DIRTGL
Offset: 0x0C+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – DIRTGL[31:0]: Port Data Direction Toggle
0: The I/O pin direction is cleared.
1: The I/O pin direction is set.
Writing a zero to a bit has no effect.
Writing a one to a bit will toggle the corresponding bit in the DIR register, which reverses the direction of the I/O
pin.
Bit3130292827262524
DIRTGL[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit2322212019181716
DIRTGL[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
DIRTGL[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
DIRTGL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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21.8.5 Data Output Value
This register sets the data output drive value for the individual I/O pins in the PORT.
Name: OUT
Offset: 0x10+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – OUT[31:0]: Port Data Output Value
These bits set the logical output drive level of I/O pins configured as outputs via the Data Direction register (DIR).
For pins configured as inputs via the Data Direction register (DIR) with pull enabled via the Pull Enable register
(PULLEN), these bits will set the input pull direction.
0: The I/O pin output is driven low, or the input is connected to an internal pull-down.
1: The I/O pin output is driven high, or the input is connected to an internal pull-up.
Bit 3130292827262524
OUT[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
OUT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
OUT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
OUT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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21.8.6 Data Output Value Clear
This register allows the user to set one or more output I/O pin drive levels low, without doing a read-modify-write
operation. Changes in this register will also be reflected in the Data Output Value (OUT), Data Output Value Toggle
(OUTTGL) and Data Output Value Set (OUTSET) registers.
Name: OUTCLR
Offset: 0x14+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – OUTCLR[31:0]: Port Data Output Value Clear
0: The I/O pin output is driven low.
1: The I/O pin output is driven high.
Writing a zero to a bit has no effect.
Writing a one to a bit will clear the corresponding bit in the OUT register, which sets the output drive level low for
I/O pins configured as outputs via the Data Direction register (DIR). For pins configured as inputs via the Data
Direction register (DIR) with pull enabled via the Pull Enable register (PULLEN), these bits will set the input pull
direction to an internal pull-down.
Bit 3130292827262524
OUTCLR[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
OUTCLR[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
OUTCLR[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
OUTCLR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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21.8.7 Data Output Value Set
This register allows the user to set one or more output I/O pin drive levels high, without doing a read-modify-write
operation. Changes in this register will also be reflected in the Data Output Value (OUT), Data Output Value Toggle
(OUTTGL) and Data Output Value Clear (OUTCLR) registers.
Name: OUTSET
Offset: 0x18+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – OUTSET[31:0]: Port Data Output Value Set
0: The I/O pin output is driven low.
1: The I/O pin output is driven high.
Writing a zero to a bit has no effect.
Writing a one to a bit will set the corresponding bit in the OUT register, which sets the output drive level high for I/O
pins configured as outputs via the Data Direction register (DIR). For pins configured as inputs via the Data Direc-
tion register (DIR) with pull enabled via the Pull Enable register (PULLEN), these bits will set the input pull d irection
to an internal pull-up.
Bit 3130292827262524
OUTSET[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
OUTSET[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 151413121110 9 8
OUTSET[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
OUTSET[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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21.8.8 Data Output Value Toggle
This register allows the user to toggle the drive level of one or more output I/O pins, without doing a read-modify-write
operation. Changes in this register will also be reflected in the Data Output Value (OUT), Data Output Value Set
(OUTSET) and Data Output Value Clear (OUTCLR) registers.
Name: OUTTGL
Offset: 0x1C+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – OUTTGL[31:0]: Port Data Output Value Toggle
0: The I/O pin output is driven low.
1: The I/O pin output is driven high.
Writing a zero to a bit has no effect.
Writing a one to a bit will toggle the corresponding bit in the OUT register, which inverts the output drive level for
I/O pins configured as outputs via the Data Direction register (DIR). For pins configured as inputs via the Data
Direction register (DIR) with pull enabled via the Pull Enable register (PULLEN), these bits will toggle the input pull
direction.
Bit3130292827262524
OUTTGL[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
OUTTGL[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 151413121110 9 8
OUTTGL[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
OUTTGL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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21.8.9 Data Input Value
Name: IN
Offset: 0x20+x*0x80 [x=0..1]
Reset: 0x00000000
Property: -
zBits 31:0 – IN[31:0]: Port Data Input Value
These bits are cleared when the corresponding I/O pin input sampler detects a logical low level on the input pin.
These bits are set when the corresponding I/O pin input sampler detects a logical high level on the input pin.
Bit 3130292827262524
IN[31:24]
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
IN[23:16]
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
IN[15:8]
AccessRRRRRRRR
Reset00000000
Bit76543210
IN[7:0]
AccessRRRRRRRR
Reset00000000
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21.8.10 Control
Name: CTRL
Offset: 0x24+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBits 31:0 – SAMPLING[31:0]: Input Sampling Mode
Configures the input sampling functionality of the I/O pin input samplers for pins configured as inputs via the Data
Direction register (DIR).
0: The I/O pin input synchronizer is disabled.
1: The I/O pin input synchronizer is enabled.
The input samplers are enabled and disabled in sub-groups of eight. Thus, if any pins within a byte request contin-
uous sampling, all pins in that eight pin sub-group will be continuously sampled.
Bit 3130292827262524
SAMPLING[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit 2322212019181716
SAMPLING[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
SAMPLING[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
SAMPLING[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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21.8.11 Write Configuration
This write-only register is used to configure several pins simultaneously with the same configuration and/or peripheral
multiplexing.
In order to avoid the side effect of non-atomic access, 8-bit or 16-bit writes to this register will have no effect. Reading this
register always returns zero.
Name: WRCONFIG
Offset: 0x28+x*0x80 [x=0..1]
Reset: 0x00000000
Property: Write-Protected
zBit 31 – HWSEL: Half-Word Select
This bit selects the half-word field of a 32-pin group to be reconfigured in the atomic write operation.
0: The lower 16 pins of the PORT group will be configured.
1: The upper 16 pins of the PORT group will be configured.
This bit will always read as zero.
zBit 30 – WRPINCFG: Write PINCFG
This bit determines whether the atomic write operation will update the Pin Configuration register (PINCFGy) or not
for all pins selected by the WRCONFIG.PINMASK and WRCONFIG.HWSEL bits.
0: The PINCFGy registers of the selected pins will not be updated.
1: The PINCFGy registers of the selected pins will be updated.
Writing a zero to this bit has no effect.
Bit3130292827262524
HWSEL WRPINCFG WRPMUX PMUX[3:0]
AccessWWRWWWWW
Reset00000000
Bit2322212019181716
PULLEN INEN PMUXEN
AccessRWRWWWWW
Reset00000000
Bit151413121110 9 8
PINMASK[15:8]
AccessWWWWWWWW
Reset00000000
Bit76543210
PINMASK[7:0]
AccessWWWWWWWW
Reset00000000
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Writing a one to this bit updates the configuration of the selected pins with the written WRCONFIG.PULLEN,
WRCONFIG.INEN, WRCONFIG.PMUXEN and WRCONFIG.PINMASK values.
This bit will always read as zero.
zBit 29 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 28 – WRPMUX: Write PMUX
This bit determines whether the atomic write operation will update the Peripheral Multiplexing register (PMUXn) or
not for all pins selected by the WRCONFIG.PINMASK and WRCONFIG.HWSEL bits.
0: The PMUXn registers of the selected pins will not be updated.
1: The PMUXn registers of the selected pins will be updated.
Writing a zero to this bit has no effect.
Writing a one to this bit updates the pin multiplexer configuration of the selected pins with the written WRCON-
FIG.PMUX value.
This bit will always read as zero.
zBits 27:24 – PMUX[3:0]: Peripheral Multiplexing
These bits determine the new value written to the Peripheral Mu ltiplexing register (PMUXn) for all pins selected by
the WRCONFIG.PINMASK and WRCONFIG.HWSEL bits, when the WRCONFIG.WRPMUX bit is set.
These bits will always read as zero.
zBits 23:19 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 18 – PULLEN: Pull Enable
This bit determines the new value written to PINCFGy.PULLEN for all p ins selected by the WRCONFIG.PINMASK
and WRCONFIG.HWSEL bits when the WRCONFIG.WRPINCFG bit is set.
This bit will always read as zero.
zBit 17 – INEN: Input Enable
This bit determines the new value written to PINCFGy.DRVSTR for all pins selected by the WRCONFIG.PINMASK
and WRCONFIG.HWSEL bits when the WRCONFIG.WRPINCFG bit is set.
This bit will always read as zero.
zBit 16 – PMUXEN: Peripheral Multiplexer Enable
This bit determines the new value written to PINCFGy.PMUXEN for all pins selected by the WRCONFIG.PIN-
MASK and WRCONFIG.HWSEL bits when the WRCONFIG.WRPINCFG bit is set.
This bit will always read as zero.
zBits 15:0 – PINMASK[15:0]: Pin Mask for Multiple Pin Configuration
These bits select the pins to be configured within the half-word group selected by the WRCONFIG.HWSEL bit.
0: The configuration of the corresponding I/O pin in the half-word group will be left unchanged.
1: The configuration of the corresponding I/O pin in the half-word pin group will be updated.
These bits will always read as zero.
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21.8.12 Peripheral Multiplexing n
There are up to 16 Peripheral Multiplexing registers in each group, one for every set of two subsequent I/O lines. The n
denotes the number of the set of I/O lines, while the m denotes the number of the group.
Name: PMUXn
Offset: 0x30+n*0x1+x*0x80 [n=0..15] [x=0..1]
Reset: 0x00
Property: Write-Protected
zBits 7:4 – PMUXO[3:0]: Peripheral Multiplexing Odd
These bits select the peripheral function for odd-numbered pins (2*n + 1) of a PORT group, if the corresponding
PINCFGy.PMUXEN bit is one.
Not all possible values for this selection may be valid. For more details, refer to “I/O Multiplexing and Consider-
ations” on page 11.
zBits 3:0 – PMUXE[3:0]: Peripheral Multiplexing Even
These bits select the peripheral function for even-numbered pins (2*n) of a PORT group, if the corresponding
PINCFGy.PMUXEN bit is one.
Not all possible values for this selection may be valid. For more details, refer to “I/O Multiplexing and Consider-
ations” on page 11.
Bit76543210
PMUXO[3:0] PMUXE[3:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Value Name Description
0x0 APeripheral function A selected
0x1 BPeripheral function B selected
0x2 CPeripheral function C selected
0x3 DPeripheral function D selected
0x4 EPeripheral function E selected
0x5 FPeripheral function F selected
0x6 GPeripheral function G selected
0x7 HPeripheral function H selected
0x8-0xF Reserved
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21.8.13 Pin Configuration y
There are up to 32 Pin Configuration registers in each group, one for each I/O line. The y denotes the number of the I/O
line, while the x denotes the number of the group.
Name: PINCFGy
Offset: 0x40+y*0x1+x*0x80 [y=0..31] [x=0..1]
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – PULLEN: Pull Enable
This bit enables the internal pull-up or pull-down resistor of an I/O pin configured as an input.
0: Internal pull resistor is disabled, and the input is in a high-impedance configuration.
1: Internal pull resistor is enabled, and the input is driven to a defined logic level in the absence of external input.
zBit 1 – INEN: Input Enable
This bit controls the input buffer of an I/O pin configured as either an input or output.
0: Input buffer for the I/O pin is disabled, and the input value will not be sampled.
1: Input buffer for the I/O pin is enabled, and the input value will be sampled when required.
Writing a zero to this bit disables the input buffer completely, preventing read-back of the physical pin state when
the pin is configured as either an input or output.
zBit 0 – PMUXEN: Peripheral Multiplexer Enable
This bit enables or disables the peripheral multiplexer selection set in the Peripheral Multiplexing register (PMUXn)
to enable or disable alternative peripheral control over an I/O pin direction and output drive value.
0: The peripheral multiplexer selection is disabled, and the PORT registers control the direction and output drive
value.
1: The peripheral multiplexer selection is enabled, and the selected peripheral controls the direction and output
drive value.
Writing a zero to this bit allows the PORT to control the pad direction via the Data Direction register (DIR) and out-
put drive value via the Data Output Value register (OUT). The peripheral multiplexer value in PMUXn is ignored.
Writing a one to this bit enables the peripheral selection in PMUXn to control the pad. In this configuration, the
physical pin state may still be read from the Data Input Value register (IN) if PINCFGy.INEN is set.
Bit76543210
PULLEN INEN PMUXEN
Access R R/W R R/W R/W R/W R/W R/W
Reset00000000
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22. EVSYS – Event System
22.1 Overview
The Event System (EVSYS) allows autonomous, low-latency and configurable communication between peripherals.
Several peripherals can be configured to emit and/or respond to signals known as events. The exact condition to
generate an event, or the action taken upon receiving an event, is specific to each module. Peripherals that respond to
events are called event users. Peripherals that emit events are called event generators. A peripheral can have one or
more event generators and can have one or more event users.
Communication is made without CPU intervention and without consuming system resources such as bus or RAM
bandwidth. This reduces the load on the CPU and other system resources, compared to a traditional interrupt-based
system.
22.2 Features
zSystem for direct peripheral-to-peripheral communication and signaling
zEight configurable event channels, where each channel can:
zBe connected to any event generator
zProvide a pure asynchronous, resynchronized or synchronous path
z58 event generators
z14 event users
zConfigurable edge detector
zPeripherals can be event generators, event users or both
zSleepWalking and interrupt for operation in low-power modes
zSoftware event generation
zEach event user can choose which channel to listen to
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22.3 Block Diagram
Figure 22-1. Event System Block Dia gram
22.4 Signal Description
Not applicable.
22.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
22.5.1 I/O Lines
Not applicable.
22.5.2 Power Management
The EVSYS can be used to wake up the CPU from all sleep modes, even if the clock used by the EVSYS channel and
the EVSYS bus clock are disabled. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
In all power save modes where the clock for the EVSYS is stopped, the device can wake up the EVSYS clock.
Some event generators can generate an event when the system clock is stopped. The generic clock (GCLK) for this
channel will be restarted if the channel uses a synchronized path or a resynchronized path, without waking the system
from sleep. The clock remains active only as long as necessary to handle the event. After the event has been handled,
the clock will be turned off and the system will remain in the original sleep mode. This is known as SleepWalking. When
an asynchronous path is used, there is no need for the clock to be activated for the event to be propagated to the user.
On a software reset, all registers are set to their reset values and any ongoing events are canceled.
22.5.3 Clocks
The EVSYS bus clock (CLK_EVSYS_APB) can be en abled and disabled in the Power Manager, and the default state of
CLK_EVSYS_APB can be found in the Peripheral Clock Masking section in “PM – Power Manager” on page 100.
PERIPHERALS
EVSYS
CHANNELS
USER
MUX PERIPHERALS
GCLK
GENERATOR
EVENTS
CLOCK REQUESTS
USERS EVENTS
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Each EVSYS channel has a dedicated generic clock (GCLK_EVSYS_x). These are used for detection and propagation
of events for each channel. These clocks must be configured and enabled in the generic clock controller before using the
EVSYS. Please refer to “GCLK – Generic Clock Controller” on page 78 for details.
22.5.4 DMA
Not applicable.
22.5.5 Interrupts
The interrupt request line is connected to the interrupt controller. Using the EVSYS interrupts requires the interrupt
controller to be configured first. Please refer to “Nested Vector Interrupt Controller” on page 24 for details.
22.5.6 Events
Not applicable.
22.5.7 Debug Operation
When the CPU is halted in debug mode, the EVSYS continues normal operation. If the EVSYS is configured in a way
that requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss may
result during debugging.
22.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following register:
zInterrupt Flag Status and Clear register (INTFLAG)
Write-protection is denoted by the Write-Protected property in the register description.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
22.5.9 Analog Connections
Not applicable.
22.6 Functional Description
22.6.1 Principle of Operation
Event users are connected to multiplexers that have all available event channels as input. The multiplexer must be
configured to select one of these channels. The channels can be configured to route signals from any event generator,
but cannot be connected to multiple event generators.
22.6.2 Basic Operation
22.6.2.1 Initialization
The peripheral that is to act as event generator should be configured to be able to generate events. The periphera l to act
as event user should be configured to handle incoming events.
When this has been done, the event system is ready to be configured. The configuration must follow this order:
1. Configure the event user by performing a single 16-bit write to the User Multiplexer register (USER) with:
1.1. The channel that is to be connected to a user written to the Channel bit group (USER.CHANNEL)
1.2. The user to connect the channel to written to the User bit group (USER.USER)
2. Configure the channel by performing a single 32-bit write to the Channel (CHANNEL) register with:
2.1. The channel to be configured written to the Channel Selection bit group (CHANNEL.CHANNEL)
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2.2. The path to be used written to the Path Selection bit group (CHANNEL.PATH)
2.3. The type of edge detection to use on the channel written to the Edge Selection bit group
(CHANNEL.EDGSEL)
2.4. The event generator to be used written to the Event Generator bit group (CHANNEL.EVGEN)
22.6.2.2 Enabling, Disabling and Resetting
The EVSYS is always enabled.
The EVSYS is reset by writing a one to the Software Reset bit in the Contro l register (CTRL.SWRST). All registers in the
EVSYS will be reset to their initial state. Refer to the CTRL register for details.
22.6.2.3 User Multiplexer Setup
Each user multiplexer is dedicated to one event user. A user multiplexer receives all event channel outputs and must be
configured to select one of these channels. The user must always be configured before the channel is configured. A full
list of selectable users can be found in the User Multiplexer register (USER) description. Refer to Table 22-6 for details.
To configure a user multiplexer, the USER register must be written in a single 16-bit write.
It is possible to read out the configuration of a user by first selecting the user by writing to USER.USER using an 8-bit
write and then performing a read of the USER register.
Figure 22-2. User MUX
22.6.2.4 Channel Setup
The channel to be used with an event user must be configured with an event generator. The path of the channel should
be configured, and when using a synchronous path or resynchronized path, the edge selection should be configured. All
these configurations are available in the Channel register (CHANNEL).
To configure a channel, the Channel register must be written in a single, 32-bit write.
It is possible to read out the configuration of a channel by first selecting the channel by writing to CHANNEL.CHANNEL
using a, 8-bit write, and then performing a read of the CHANNEL register.
USER
MUX
PERIPHERAL A PERIPHERAL B
USER.CHANNEL
USER_EVT_x USER_EVT_y USER_EVT_z
CHANNEL_EVT_0
CHANNEL_EVT_1
CHANNEL_EVT_m
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Event Generators
The event generator is selected by writing to the Event Generator bit group in the Channel register (CHANNEL.EVGEN).
A full list of selectable generators can be found in the CHANNEL register description. Refer to Table 22-3 for details.
The channels are not connected to any of the event generators (CHANNEL.EVGEN = 0x00) by default.
22.6.2.5 Channel Path
There are three different ways to propagate the event provided by an event generator:
zAsynchronous path
zSynchronous path
zResynchronized path
Figure 22-3. Channel
The path is selected by writing to the Path Selection bit group in the Channel register (CHANNEL.PATH).
Asynchronous Path
When using the asynchronous path, the events are propagated from the event generator to the event user with no
intervention from the event system. This means that if the GCLK_EVSYS_x for the channel used is inactive, the event
will still be propagated to the user.
Events propagated in the asynchronous path cannot generate any interrupts, and no channel status bits will indicate the
state of the channel. No edge detection is available; this must be handled in the event user.
When the event generator and the event user share the same generic clock, using the asynchronous path will propag ate
the event with the least amount of latency.
CHANNEL.SWEVT
CHANNEL m
CHANNEL.EVGEN
PERIPHERALS
SLEEPWALKING
DETECTOR
CLOCK_REQUEST_m
CHANNEL.PATH
RESYNC
EDGE
DETECTION
CHANNEL.EDGSEL
CHANNEL_EVT_m
GENERATORS EVENTS
SYNC
ASYNC
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Synchronous Path
The synchronous path should be used when the event generator and the event channel share the same generic clock. If
they do not share the same clock, a logic change from the event generator to the event channel might not be detected in
the channel, which means that the event will not be propagated to the event user.
When using the synchronous path, the channel is capable of generating interrupts. The channel status bits in the
Channel Status register (CHSTATUS) are also updated and available for use.
If the Generic Clocks Request bit in the Control register (CTRL.GCLKREQ) is zero, the channel operates in
SleepWalking mode and request the configured generic clock only when an event is to be propagated through the
channel. If CTRL.GCLKREQ is one, the generic clock will always be on for the configured channel.
Resynchronized Path
The resynchronized path should be used when the event generator and the event channel do not share the same clock.
When the resynchronized path is used, resynchronization of the event from the event generator is done in the channel.
When the resynchronized path is used, the channel is capable of generating interrupts. The channel status bits in the
Channel Status register (CHSTATUS) are also updated and available for use.
If the Generic Clocks Request bit in the Control register (CTRL.GCLKREQ) is zero, the channel operates in
SleepWalking mode and request the configured generic clock only when an event is to be propagated through the
channel. If CTRL.GCLKREQ is one, the generic clock will always be on for the configured channel.
22.6.2.6 Edge Detection
When synchronous or resynchronized paths are used, edge detection must be used. The event system can perform
edge detection in three different ways:
zGenerate an event only on the rising edge
zGenerate an event only on the falling edge
zGenerate an event on rising and falling edges.
Edge detection is selected by writing to the Edge Selection bit group in the Channel register (CHANNEL.EDGSEL).
If the generator event is a pulse, the Both Edges method must not be selected. Use the Rising Edge or Falling Edge
detection method, depending on the generator event default level.
22.6.2.7 The Overrun Channel x Interrupt
The Overrun Channel x interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.OVRx) is set and the
optional interrupt is generated in the following two cases:
zAt least one of the event users on channel x is not ready when a new event occurs
zAn event occurs when the previous event on channel x has not yet been handled by all event users
INTFLAG.OVRx will be set when using a synchronous or resynchronized path, but not when using an asynchronous
path.
22.6.2.8 The Event Detected Channel x Interrupt
The Event Detected Channel x interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.EVDx) is set when
an event coming from the event generator configured on channel x is detected.
INTFLAG.EVDx will be set when using a synchronous and resynchronized path, but not when using an asynchronous
path.
22.6.2.9 Channel Status
The Channel Status register (CHSTATUS) updates the status of the channels when a synchronous or resynchronized
path is in use. There are two different status bits in CHSTATUS for each of the available channels: The
CHSTATUS.CHBUSYx bit is set to one if an event on the corresponding channel x has not been handled by all event
users connected to that channel.
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The CHSTATUS.USRRDYx bit is set to one if all event users connected to the corresponding channel x are ready to
handle incoming events on that channel.
22.6.2.10 Software Event
A software event can be initiated on a channel by writing a one to the Software Event bit in the Channel register
(CHANNEL.SWEVT) together with the Channel bits (CHANNEL.CHANNEL). This will generate a software event on the
selected channel.
The software event can be used for application debugging, and functions like any event generator. To use the software
event, the event path must be configured to either a synchronous path or resynchronized path (CHANNEL.PATH = 0x0
or 0x1), edge detection must be configured to rising-edge detection (CHANNEL.EDGSEL= 0x1) and the Generic Clock
Request bit must be set to one (CTRL.GCLKREQ=0x1).
22.6.3 Interrupts
The EVSYS has the following interrupt sources:
zOverrun Channel x interrupt (INTFLAG)
zEvent Detected Channel x interrupt (INTFLAG)
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the EVSYS is reset.
See the INTFLAG register for details on how to clear interrupt flags. The EVSYS has one common interrupt request line
for all the interrupt sources. The user must read the INTFLAG register to determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated.
Please refer to “Nested Vector Interrupt Controller” on page 24 for details.
22.6.4 Sleep Mode Operation
The EVSYS can generate interrupts to wake up the device from any sleep mode.
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22.7 Register Summary
Offset Name Bit Pos.
0x00 CTRL
7:0 GCLKREQ SWRST
0x01 Reserved
0x02 Reserved
0x03 Reserved
0x04
CHANNEL
7:0 CHANNEL[7:0]
0x05 15:8 SWEVT
0x06 23:16 EVGEN[7:0]
0x07 31:24 EDGSEL[1:0] PATH[1:0]
0x08 USER 7:0 USER[7:0]
0x09 15:8 CHANNEL[7:0]
0x0A Reserved
0x0B Reserved
0x0C
CHSTATUS
7:0 USRRDY7 USRRDY6 USRRDY5 USRRDY4 USRRDY3 USRRDY2 USRRDY1 USRRDY0
0x0D 15:8 CHBUSY7 CHBUSY6 CHBUSY5 CHBUSY4 CHBUSY3 CHBUSY2 CHBUSY1 CHBUSY0
0x0E 23:16
0x0F 31:24
0x10
INTENCLR
7:0 OVR7 OVR6 OVR5 OVR4 OVR3 OVR2 OVR1 OVR0
0x11 15:8 EVD7 EVD6 EVD5 EVD4 EVD3 EVD2 EVD1 EVD0
0x12 23:16
0x13 31:24
0x14
INTENSET
7:0 OVR7 OVR6 OVR5 OVR4 OVR3 OVR2 OVR1 OVR0
0x15 15:8 EVD7 EVD6 EVD5 EVD4 EVD3 EVD2 EVD1 EVD0
0x16 23:16
0x17 31:24
0x18
INTFLAG
7:0 OVR7 OVR6 OVR5 OVR4 OVR3 OVR2 OVR1 OVR0
0x19 15:8 EVD7 EVD6 EVD5 EVD4 EVD3 EVD2 EVD1 EVD0
0x1A 23:16
0x1B 31:24
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22.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Please refer to “Register Access Protection” on page
311 and “PAC – Peripheral Access Controller” on page 27 for details.
22.8.1 Control
Name: CTRL
Offset: 0x00
Reset: 0x00
Property: Write-Protected
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – GCLKREQ: Generic Clock Requests
This bit is used to determine whether the generic clocks used for the different channels should be on all the time or
only when an event needs the generic clock. Events propagated trough asynchronous paths will not need a
generic clock.
0: Generic clock is requested and turned on only if an event is detected.
1: Generic clock for a channel is always on.
zBits 3:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – SWRST: Software Reset
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the EVSYS to their initial state.
Writing a one to CTRL.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Bit76543210
GCLKREQ SWRST
Access R R R R/W R R R W
Reset00000000
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22.8.2 Channel
This register allows the user to configure the channel specified in the CHANNEL bit group. To write to this register, do a
single, 32-bit write of all the configuration and channel selection data.
To read from this register, first do an 8-bit write to the CHANNEL.CHANNEL bit group specifying the channel
configuration to be read, and then read the Channel register (CHANNEL).
Name: CHANNEL
Offset: 0x04
Reset: 0x00000000
Property: Write-Protected
zBits 31:28 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 27:26 – EDGSEL: Edge Detection Selection
These bits set the type of edge detection to be used on the channel.
These bits must be written to zero when using the asynchronous path.
Bit3130292827262524
EDGSEL[1:0] PATH[1:0]
Access R R R R R/W R/W R/W R/W
Reset00000000
Bit2322212019181716
EVGEN[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
SWEVT
AccessRRRRRRRR/W
Reset00000000
Bit76543210
CHANNEL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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Table 22-1. Edge Detection Selection
zBits 25:24 – PATH: Path Selection
These bits are used to chose which path will be used by the selected channel.
The path choice can be limited by the channel source, see Table 22-6.
Table 22-2. Path Selection
zBits 23:16 – EVGEN: Event Generator
These bits are used to choose the event generator to connect to the selected channel.
Value Name Description
0x0 NO_EVT_OUTPUT No event output when using the resyn c hronized or synchronous path
0x1 RISING_EDGE Event detection only on the rising edge of the signal from the event generator
0x2 FALLING_EDGE Event detection only on the falling edge of the signal from the event generator
0x3 BOTH_EDGES Event detection on rising and falling e dges of the signal from the event
generator
Value Name Description
0x0 SYNCHRONOUS Synchronous path
0x1 RESYNCHRONIZED Resynchronized path
0x2 ASYNCHRONOUS Asynchronous path
0x3 -Reserved
Table 22-3. Event Generator Selection
Value Event Generator Description
0x00 NONE No event generator selected
0x01 RTC CMP0 Co mpare 0 (mode 0 and 1) or Alarm 0 (mode 2)
0x02 RTC CMP1 Compare 1
0x03 RTC OVF Overflow
0x04 RTC PER0 Period 0
0x05 RTC PER1 Period 1
0x06 RTC PER2 Period 2
0x07 RTC PER3 Period 3
0x08 RTC PER4 Period 4
0x09 RTC PER5 Period 5
0x0A RTC PER6 Period 6
0x0B RTC PER7 Period 7
0x0C EIC EXTINT0 External Interrupt 0
0x0D EIC EXTINT1 External Interrupt 1
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0x0E EIC EXTINT2 External Interrupt 2
0x0F EIC EXTINT3 External Interrupt 3
0x10 EIC EXTINT4 External Interrupt 4
0x11 EIC EXTINT5 External Interrupt 5
0x12 EIC EXTINT6 External Interrupt 6
0x13 EIC EXTINT7 External Interrupt 7
0x14 EIC EXTINT8 External Interrupt 8
0x15 EIC EXTINT9 External Interrupt 9
0x16 EIC EXTINT10 External Interrupt 10
0x17 EIC EXTINT11 External Interrupt 11
0x18 EIC EXTINT12 External Interrupt 12
0x19 EIC EXTINT13 External Interrupt 13
0x1A EIC EXTINT14 External Interrupt 14
0x1B EIC EXTINT15 External Interrupt 15
0x1C TC0 OVF Overflow/Underflow
0x1D TC0 MC0 Match/Capture 0
0x1E TC0 MC1 Match/Capture 1
0x1F TC1 OVF Overflow/Underflow
0x20 TC1 MC0 Match/Capture 0
0x21 TC1 MC1 Match/Capture 1
0x22 TC2 OVF Overflow/Underflow
0x23 TC2 MC0 Match/Capture 0
0x24 TC2 MC1 Match/Capture 1
0x25 TC3 OVF Overflow/Underflow
0x26 TC3 MC0 Match/Capture 0
0x27 TC3 MC1 Match/Capture 1
0x28 TC4 OVF Overflow/Underflow
0x29 TC4 MC0 Match/Capture 0
0x2A TC4 MC1 Match/Capture 1
0x2B TC5 OVF Overflow/Underflow
0x2C TC5 MC0 Match/Capture 0
0x2D TC5 MC1 Match/Capture 1
0x2E TC6 OVF Overflow/Underflow
Table 22-3. Event Generator Selection (Continued)
Value Event Generator Description
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zBits 15:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 8 – SWEVT: Software Event
This bit is used to insert a software event on the channel selected by the CHANNEL.CHANNEL bit group.
This bit must be written together with CHANNEL.CHANNELusing a 16-bit write.
Writing a zero to this bit has no effect.
Writing a one to this bit will trigger a software event for the corresponding channel.
This bit will always return zero when read.
zBits 7:0 – CHANNEL: Channel Selection
These bits are used to select the channel to be set up or read from.
0x2F TC6 MC0 Match/Capture 0
0x30 TC6 MC1 Match/Capture 1
0x31 TC7 OVF Overflow/Underflow
0x32 TC7 MC0 Match/Capture 0
0x33 TC7 MC1 Match/Capture 1
0x34 ADC RESRDY Result Ready
0x35 ADC WINMON Window Monitor
0x36 AC COMP0 Comparator 0
0x37 AC COMP1 Comparator 1
0x38 AC WIN Window 0
0x39 DAC EMPTY Data Buffer Empty
0x3A PTC EOC End of Conversion
0x3B PTC WCOMP Window Comparator
0x3C-0xFF Reserved
Table 22-3. Event Generator Selection (Continued)
Value Event Generator Description
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Table 22-4. Channel Selection
Value Channel Number
0x00 0
0x01 1
0x02 2
0x03 3
0x04 4
0x05 5
0x06 6
0x07 7
0x08-0xFF Reserved
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22.8.3 User Multiplexer
This register is used to configure a specified event user. To write to this register, do a single, 16-bit write of all the
configuration and event user selection data.
To read from this register, first do an 8-bit write to the USER.USER bit group specifying the event user configuration to be
read, and then read USER.
Name: USER
Offset: 0x08
Reset: 0x0000
Property: Write-protected
zBits 15:8 – CHANNEL: Channel Event Selection
These bits are used to select the channel to connect to the event user.
Please note that to select channel n, the value (n+1) must be written to the USER.CHANNEL bit group.
zBits 7:0 – USER: User Multiplexer Selection
These bits select the event user to be configured with a channel, or the event user to read the channel value from.
Bit151413121110 9 8
CHANNEL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
USER[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Table 22-5. Channel Even t Selection
Value Channel Number
0x00 No channel output selected
0x01 0
0x02 1
0x03 2
0x04 3
0x05 4
0x06 5
0x07 6
0x08 7
0x09-0xFF Reserved
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Table 22-6. User Multiple xer Selection
USER[7:0] User Multiplexer Description Path Type
0x00 TC0 Asynchronous, synchronous and resync hronized paths
0x01 TC1 Asynchronous, synchronous and resync hronized paths
0x02 TC2 Asynchronous, synchronous and resync hronized paths
0x03 TC3 Asynchronous, synchronous and resync hronized paths
0x04 TC4 Asynchronous, synchronous and resync hronized paths
0x05 TC5 Asynchronous, synchronous and resync hronized paths
0x06 TC6 Asynchronous, synchronous and resync hronized paths
0x07 TC7 Asynchronous, synchronous and resync hronized paths
0x08 ADC START ADC start conversion Asynchronous path only
0x09 ADC SYNC Flush ADC Asynchronous path only
0x0A AC COMP0 Start comparator 0 Asynchronous path only
0x0B AC COMP1 Start comparator 1 Asynchronous path only
0x0C DAC START DAC start conversion Asynchronous path only
0x0D PTC STCONV PTC start conversion Asynchronous path only
0x0E-0xFF Reserved Reserved
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22.8.4 Channel Status
Name: CHSTATUS
Offset: 0x0C
Reset: 0x000000FF
Property: –
zBits 31:16 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 15:8 – CHBUSYx: Channel Busy x
This bit is cleared when channel x is idle
This bit is set if an event on channel x has not been handled by all event users connected to channel x.
zBits 7:0 – USRRDYx: User Ready for Channel x
This bit is cleared when at least one of the event users connected to the channel is not ready.
This bit is set when all event users connected to channel x are ready to handle incoming events on channel x.
Bit 3130292827262524
AccessRRRRRRRR
Reset00000000
Bit 2322212019181716
AccessRRRRRRRR
Reset00000000
Bit 151413121110 9 8
CHBUSY7 CHBUSY6 CHBUSY5 CHBUSY4 CHBUSY3 CHBUSY2 CHBUSY1 CHBUSY0
AccessRRRRRRRR
Reset00000000
Bit76543210
USRRDY7 USRRDY6 USRRDY5 USRRDY4 USRRDY3 USRRDY2 USRRDY1 USRRDY0
AccessRRRRRRRR
Reset00000000
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22.8.5 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x10
Reset: 0x00000000
Property: Write-Protected
zBits 31:16 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 15:8 – EVDx: Event Detected Channel x Interrupt Enable
0: The Event Detected Channel x interrupt is disabled.
1: The Event Detected Channel x interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Event Detected Channel x Interrupt Enable bit, which disables the Event
Detected Channel x interrupt.
zBits 7:0 – OVRx: Overrun Channel x Interrupt Enable
0: The Overrun Channel x interrupt is disabled.
1: The Overrun Channel x interrupt is enabled.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
AccessRRRRRRRR
Reset00000000
Bit151413121110 9 8
EVD7 EVD6 EVD5 EVD4 EVD3 EVD2 EVD1 EVD0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
OVR7 OVR6 OVR5 OVR4 OVR3 OVR2 OVR1 OVR0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overrun Channel x Interrupt Enable bit, which disables the Overrun Channel
x interrupt.
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22.8.6 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x14
Reset: 0x00000000
Property: Write-Protected
zBits 31:16 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 15:8 – EVDx: Event Detected Channel x Interrupt Enable
0: The Event Detected Channel x interrupt is disabled.
1: The Event Detected Channel x interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Event Detected Channel x Interrupt Enable bit, which enables the Event
Detected Channel x interrupt.
zBits 7:0 – OVRx: Overrun Channel x Interrupt Enable
0: The Overrun Channel x interrupt is disabled.
1: The Overrun Channel x interrupt is enabled.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
AccessRRRRRRRR
Reset00000000
Bit151413121110 9 8
EVD7 EVD6 EVD5 EVD4 EVD3 EVD2 EVD1 EVD0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
OVR7 OVR6 OVR5 OVR4 OVR3 OVR2 OVR1 OVR0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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Writing a zero to this bit has no effect.
Writing a one to this bit will set the Overrun Channel x Interrupt Enable bit, which enables the Overrun Channel x
interrupt.
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22.8.7 Interrupt Flag S tatus and Clear
Name: INTFLAG
Offset: 0x18
Reset: 0x00000000
Property: –
zBits 31:16 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 15:8 – EVDx: Event Detected Channel x
This flag is set on the next CLK_EVSYS_APB cycle when an event is being propagated through the channel, and
an interrupt request will be generated if INTENCLR/SET.EVDx is one.
When the event channel path is asynchronous, the EVDx interrupt flag will not be set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Event Detected Channel n interrupt flag.
zBits 7:0 – OVRx: Overrun Channel x
This flag is set on the next CLK_EVSYS cycle after an overrun channel condition occurs, and an interrupt request
will be generated if INTENCLR/SET.OVRx is one.
There are two possible overrun channel conditions:
zOne or more of the event users on channel x are not ready when a new event occurs
zAn event happens when the previous event on channel x has not yet been handled by all event users
When the event channel path is asynchronous, the OVRx interrupt flag will not be set.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
AccessRRRRRRRR
Reset00000000
Bit151413121110 9 8
EVD7 EVD6 EVD5 EVD4 EVD3 EVD2 EVD1 EVD0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
OVR7 OVR6 OVR5 OVR4 OVR3 OVR2 OVR1 OVR0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overrun Channel x interrupt flag.
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23. SERCOM – Serial Communication Interface
23.1 Overview
The serial communication interface (SERCOM) can be configured to support a number of modes; I2C, SPI and USART.
Once configured and enabled, all SERCOM resources are dedicated to the selected mode.
The SERCOM serial engine consists of a transmitter and receiver, baud-rate generator and address matching
functionality. It can be configured to use the internal generic clock or an external clock, making operation in all sleep
modes possible.
23.2 Features
zCombined interface configurable as one of the following:
zI2C – Two-wire serial interface
zSMBus™ compatible.
zSPI – Serial peripheral interface
zUSART – Universal synchronous and asynchronous serial receiver and transmitter
zSingle transmit buffer and double receive buffer
zBaud-rate generator
zAddress match/mask logic
zOperational in all sleep modes
23.3 Block Diagram
Figure 23-1. SERCOM Block Diagram
23.4 Signal Description
See the respective SERCOM mode chapters for details:
z“SERCOM USART – SERCOM Universal Synchronous and Asynchronous Receiver and Transmitter” on page
340
z“SERCOM SPI – SERCOM Serial Peripheral Interface” on page 364
z“SERCOM I2C – SERCOM Inter-Integrated Circuit” on page 389
TX/RX DATA
CONTROL/STATUS
Mode n
SERCOM
BAUD/ADDR
Transmitter
Register Interface
Serial Engine
Receiver
Mode 0
Mode 1
Baud Rate
Generator
Address
Match
Mode Specific
PAD[3:0]
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23.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
23.5.1 I/O Lines
Using the SERCOM I/O lines requires the I/O pins to be configured using port configuration (PORT). Refer to “PORT” on
page 284 for details.
From Figure 23-1 one can see that the SERCOM has four internal pads, PAD[3:0]. The signals from I2C, SPI and USART
are routed through these SERCOM pads via a multiplexer. The configuration of the multiplexer is available from the
different SERCOM modes. Refer to the mode specific chapters for details:
z“SERCOM USART – SERCOM Universal Synchronous and Asynchronous Receiver and Transmitter” on page
340
z“SERCOM SPI – SERCOM Serial Peripheral Interface” on page 364
z“SERCOM I2C – SERCOM Inter-Integrated Circuit” on page 389
23.5.2 Power Management
The SERCOM can operate in any sleep mode.SERCOM interrupts can be used to wake up the device from sleep
modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
23.5.3 Clocks
The SERCOM bus clock (CLK_SERCOMx_APB) is enabled by default, and can be enabled and disabled in the Power
Manager. Refer to “PM – Power Manager” on page 100 for details.
Two generic clocks are used by the SERCOM: GCLK_SERCOMx_CORE and GCLK_SERCOMx_SLOW. The core clock
(GCLK_SERCOMx_CORE) is required to clock the SERCOM while operating as a master, while the slow clock
(GCLK_SERCOMx_SLOW) is only required for certain functions. See specific mode chapters for details.
These clocks must be configured and enabled in the Generic Clock Controller (GCLK) before using the SERCOM. Refer
to “GCLK – Generic Clock Controller” on page 78 for details.
These generic clocks are asynchronous to the user interface clock (CLK_SERCOMx_APB). Due to this asynchronicity,
writes to certain registers will require synchronization between the clock domains. Refer to “Synchronization” on page
339 for further details.
23.5.4 DMA
Not applicable.
23.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the SERCOM interrupts requires the Interrupt
Controller to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
23.5.6 Events
Not applicable.
23.5.7 Debug Operation
When the CPU is halted in debug mode, the SERCOM continues normal operation. If the SERCOM is configured in a
way that requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss
may result during debugging. The SERCOM can be forced to halt operation during debugging.
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23.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following registers:
zInterrupt Flag Status and Clear register (INTFLAG)
zAddress register (ADDR)
zData register (DATA)
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode, all write-protection is automatically disabled. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
23.5.9 Analog Connections
Not applicable.
23.6 Functional Description
23.6.1 Principle of Operation
The basic structure of the SERCOM serial engine is shown in Figure 23-2. Fields shown in capital letters are
synchronous to the system clock and accessible by the CPU, while fields with lowercase letters can be configured to run
on the GCLK_SERCOMx_CORE clock or an external clock.
Figure 23-2. SERCOM Serial Engine
The transmitter consists of a single write buffer and a shift register. The receiver consists of a two-level receive buffer and
a shift register. The baud-rate generator is capable of running on the GCLK_SERCOMx_CORE clock or an external
clock. Address matching logic is included for SPI and I2C operation.
Transmitter
Baud Rate Generator
= =
Selectable
Internal Clk
(GCLK)
Ext Clk
Receiver
Address Match
baud rate generator
tx shift register
rx shift register
rx bufferstatus
BAUD TX DATA ADDR/ADDRMASK
RX DATASTATUS
1/- /2- /16
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23.6.2 Basic Operation
23.6.2.1 Initialization
The SERCOM must be configured to the desired mode by writing to the Operating Mode bits in the Control A register
(CTRLA.MODE). Refer to Figure 23-1 for details.
Table 23-1. SERCOM Modes
For further initialization information, see the respective SERCOM mode chapters.
23.6.2.2 Enabling, Disabling and Resetting
The SERCOM is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The SERCOM is
disabled by writing a zero to CTRLA.ENABLE.
The SERCOM is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers
in the SERCOM, except DBGCTRL, will be reset to their initial state, and the SERCOM will be disabled. Refer to the
CTRLA register descriptions for details.
23.6.2.3 Clock Generation – Baud-Rate Generator
The baud-rate generator, as shown in Figure 23-3, is used for internal clock generation for asynchronous and
synchronous communication. The generated output frequency (fBAUD) is determined by the Baud register (BAUD) setting
and the baud reference frequency (fREF). The baud reference clock is the serial engine clock, and it can be internal or
external.
For asynchronous operation, the /16 (divide-by-16) output is used when transmitting and the /1 (divide-by-1) output is
used when receiving. For synchronous operation the /2 (divide-by-2) output is used. This functionality is automatically
configured, depending on the selected operating mode.
CTRLA.MODE Description
0x0 USART with external clock
0x1 USART with internal clock
0x2 SPI in slave operation
0x3 SPI in master operation
0x4 I2C slave operation
0x5 I2C master operation
0x6-0x7 Reserved
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Figure 23-3. Baud Rate Generator
Table 23-2 contains equations for calculating the baud rate (in bits per second) and for calculating the BAUD register
value for each mode of operation.
For asynchronous mode, the BAUD register value is 16 bits (0 to 65,535), while for synchronous mode, the BAUD
register value is 8 bits (0 to 255).
Table 23-2. Baud Rate Equations
Asynchronous Mode BAUD Value Selection
The formula given for fBAUD calculates the average frequency over 65,536 fREF cycles. Although the BAUD register can be
set to any value between 0 and 65,536, the values that will change the average frequency of fBAUD over a single frame
are more constrained. The BAUD register values that will affect the average frequency over a single frame lead to an
integer increase in the cycles per frame (CPF)
where
zD represent the data bits per frame
zS represent the sum of start and first stop bits, if present
Base
Period
Selectable
Internal Clk
(GCLK)
Ext Clk
CTRLA.MODE[0]
0
1
0
1
0
1
0
1
f
ref
Clock
Recovery
Tx Clk
Rx Clk
CTRLA.MODE
/2 /8
/1 /2 /16
Baud Rate Generator
Operating Mode Condition Baud Rate (Bits Per Second) BAUD Register V a lue Calculation
Asynchronous
Synchronous
16
f
fREF
BAUD ≤
⎟
⎠
⎞
⎜
⎝
⎛−= 536,65
1
16 BAUD
f
fREF
BAUD
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−= f
f
REF
BAUD
BAUD 161536,65
2
f
fREF
BAUD ≤
)1(2 +
=BAUD
f
fREF
BAUD
1
2−= f
f
BAUD
REF
BAUD
)( SDCPF ff
BAUD
REF +=
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Table 23-3 shows the BAUD register value versus baud frequency at a serial engine frequency of 48MHz. This assumes
a D value of 8 bits and an S value of 2 bits (10 bits, including start and stop bits).
Table 23-3. BAUD Register Value vs. Baud Frequency
BAUD Register Value Serial Engine CPF fBAUD at 48MHz Serial Engine Frequency (fREF)
0 – 406 160 3MHz
407 – 808 161 2.981MHz
809 – 1205 162 2.963MHz
...
65206 31775 15.11kHz
65207 31871 15.06kHz
65208 31969 15.01kHz
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23.6.3 Additional Features
23.6.3.1 Address Match and Mask
The SERCOM address match and mask feature is capable of matching one add ress with a mask, two unique addresses
or a range of addresses, based on the mode selected. The match uses seven or eight bits, depending on the mode.
Address With Ma sk
An address written to the Address bits in the Address register (ADDR.ADDR) with a mask written to the Address Mask
bits in the Address register (ADDR.ADDRMASK) will yield an address match. All bits that are masked are not included in
the match. Note that setting the ADDR.ADDRMASK to all zeros will match a single unique address, while setting
ADDR.ADDRMASK to all ones will result in all addresses being accepted.
Figure 23-4. Address With Mask
Two Unique Addresses
The two addresses written to ADDR and ADDRMASK will cause a match.
Figure 23-5. Two Unique Addresses
Address Rang e
The range of addresses between and including ADDR.ADDR and ADDR.ADDRMASK will cause a match. ADDR.ADDR
and ADDR.ADDRMASK can be set to any two addresses, with ADDR.ADDR acting as the upper limit and
ADDR.ADDRMASK acting as the lower limit.
Figure 23-6. Address Range
23.6.4 DMA Operation
Not applicable.
rx shift register
ADDRMASK
ADDR
== Match
ADDRMASK
rx shift register
ADDR
==
Match
==
ADDRMASK rx shift register ADDR
==
Match
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23.6.5 Interrupts
Interrupt sources are mode-specific. See the respective SERCOM mode chapters for details.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the SERCOM is reset. See the register description for details on how to clear interrupt
flags.
The SERCOM has one common interrupt request line for all the interrupt sources. The user must read the INTFLAG
register to determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to “Nested Vector Interrupt
Controller” on page 24 for details.
23.6.6 Events
Not applicable.
23.6.7 Sleep Mode Operation
The peripheral can operate in any sleep mode where the selected serial clock is running. This clock can be external or
generated by the internal baud-rate generator.
The SERCOM interrupts can be used to wake up the device from sleep modes. Refer to the different SERCOM mode
chapters for details.
23.6.8 Synchronization
Due to the asynchronicity between CLK_SERCOMx_APB and GCLK_SERCOMx_CORE, some registers must be
synchronized when accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete. The Synchronization
Ready interrupt can be used to signal when synchronization is complete.
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
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24. SERCOM USART – SERCOM Universal Synchronous and Asynchronous
Receiver and Transmitter
24.1 Overview
The universal synchronous and asynchronous receiver and transmitter (USART) is one of the available modes in the
Serial Communication Interface (SERCOM).
Refer to “SERCOM – Serial Communication Interface” on page 332 for details.
The USART uses the SERCOM transmitter and receiver configured as shown in Figure 24-1. Fields shown in capital
letters are synchronous to the CLK_SERCOMx_APB and accessible by the CPU, while fields with lowercase letters can
be configured to run on the internal generic clock or an external clock.
The transmitter consists of a single write buffer, a shift register and control logic for handling different frame formats. The
write buffer allows continuous data transmission without any delay between frames.
The receiver consists of a two-level receive buffer and a shift register. Status information for the received data is
available for error checking. Data and clock recovery units ensure robust synchronization and noise filtering during
asynchronous data reception.
24.2 Features
zFull-duplex operation
zAsynchronous (with clock reconstruction) or synchronous operation
zInternal or external clock source for asynchronous and synchronous operation
zBaud-rate generator
zSupports serial frames with 5, 6, 7, 8 or 9 data bits and 1 or 2 stop bits
zOdd or even parity generation and parity check
zSelectable LSB- or MSB-first data transfer
zBuffer overflow and frame error detection
zNoise filtering, including false start-bit detection and digital low-pass filter
zCan operate in all sleep modes
zOperation at speeds up to half the system clock for internall y g enerated clock s
zOperation at speeds up to the system cloc k for e xte rnal ly gene rate d cloc ks
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24.3 Block Diagram
Figure 24-1. USART Block Diagram
24.4 Signal Description
Please refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One
signal can be mapped on several pins.
24.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
24.5.1 I/O Lines
Using the USART’s I/O lines requires the I/O pins to be configured using port configuration (PORT).
Refer to “PORT” on page 284 for details.
When the SERCOM is used in USART mode, the pins should be configured according to Table 24-1. If the receiver or
transmitter is disabled, these pins can be used for other purposes.
Table 24-1. USART Pin Configuration
TxD
RxD
XCK
rx shift register
TX DATA
tx shift register
rx buffer
RX DATA
status
STATUS
BAUD
baud rate generator
Internal Clk
(GCLK)
/1 - /2 - /16
Signal name
Signal Name Type Description
PAD[3:0] Digital I/O General SERCOM pins
Pin Pin Configu r ati on
TxD Output
RxD Input
XCK Output or input
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The combined configuration of PORT and the Transmit Data Pinout and Receive Data Pinout bit groups (refer to the
Control A register description) will define the physical position of the USART signals in Table 24-1.
24.5.2 Power Management
The USART can continue to operate in any sleep mode where the selected source clock is running. The USART
interrupts can be used to wake up the device from sleep modes. The events can trigger other operations in the system
without exiting sleep modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
24.5.3 Clocks
The SERCOM bus clock (CLK_SERCOMx_APB, where x represents the specific SERCOM instance number) can be
enabled and disabled in the Power Manager, and the default state of CLK_SERCOMx_APB can be found in the
Peripheral Clock Masking section in “PM – Power Manager” on page 100.
A generic clock (GCLK_SERCOMx_CORE) is required to clock the SERCOMx_CORE. This clock must be configured
and enabled in the Generic Clock Controller before using the SERCOMx_CORE. Refer to “GCLK – Generic Clock
Controller” on page 78 for details.
This generic clock is asynchronous to the bus clock (CLK_SERCOMx_APB). Due to this asynchronicity, writes to certain
registers will require synchronization between the clock domains. Refer to “Synchronization” on page 348 for further
details.
24.5.4 DMA
Not applicable.
24.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the USART interrupts requires the Interrupt
Controller to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
24.5.6 Events
Not applicable.
24.5.7 Debug Operation
When the CPU is halted in debug mode, the USART continues normal operation. If the USART is configured in a way
that requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss may
result during debugging. The USART can be forced to halt operation during debugging.
Refer to DBGCTRL for details.
24.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following registers:
zInterrupt Flag Status and Clear register (INTFLAG)
zStatus register (STATUS)
zData register (DATA)
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
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24.5.9 Analog Connections
Not applicable.
24.6 Functional Description
24.6.1 Principle of Operation
The USART uses three communication lines for data transfer:
zRxD for receiving
zTxD for transmitting
zXCK for the transmission clock in synchronous operation
USART data transfer is frame based, where a serial frame consists of:
z1 start bit
z5, 6, 7, 8 or 9 data bits
zMSB or LSB first
zNo, even or odd parity bit
z1 or 2 stop bits
A frame starts with the start bit followed by one character of data bits. If enabled, the parity bit is inserted after the data
bits and before the first stop bit. One frame can be directly followed by a new frame, or the communication line can return
to the idle (high) state. Figure 24-2 illustrates the possible frame formats. Bits inside brackets are optional.
Figure 24-2. Frame Formats
St Start bit; always low
(n) Data bits; 0 to 8
P Parity bit; odd or even
Sp Stop bit; always high
IDLE No transfers on the communication line; always high in this state
24.6.2 Basic Operation
24.6.2.1 Initialization
The following registers are enable-protected, meaning they can only be written when the USART is disabled
(CTRL.ENABLE is zero):
zControl A register (CTRLA), except the Enable (ENABLE) and Software Reset (SWRST) bits
zControl B register (CTRLB), except the Receiver Enable (RXEN) and Transmitter Enable (TXEN) bits
zBaud register (BAUD)
Any writes to these registers when the USART is enabled or is being enabled (CTRL.ENABLE is one) will be discarded.
Writes to these registers) while the peripheral is being disabled will be completed after the disabling is complete.
Before the USART is enabled, it must be configured, as outlined in the following steps:
zUSART mode with external or internal clock must be selected first by writing 0x0 or 0x1 to the Operating Mode bit
group in the Control A register (CTRLA.MODE)
1 2 3 4 [5] [6] [7] [8]0St(IDLE) Sp1 [Sp2] (St/IDLE)[P]
Frame
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zCommunication mode (asynchronous or synchronous) must be selected by writing to the Communication Mode bit
in the Control A register (CTRLA.CMODE)
zSERCOM pad to use for the receiver must be selected by writing to the Receive Data Pinout bit group in the
Control A register (CTRLA.RXPO)
zSERCOM pads to use for the transmitter and external clock must be selected by writing to the Transmit Data
Pinout bit in the Control A register (CTRLA.TXPO)
zCharacter size must be selected by writing to the Character Size bit group in the Control B register
(CTRLB.CHSIZE)
zMSB- or LSB-first data transmission must be selected by writing to the Data Order bit in the Control A register
(CTRLA.DORD)
zWhen parity mode is to be used, even or odd p arity must be selected by writing to the Parity Mode bit in the Control
B register (CTRLB.PMODE) and enabled by writing 0x1 to the Frame Format bit group in the Control A register
(CTRLA.FORM)
zNumber of stop bits must be selected by writing to the Stop Bit Mode bit in the Control B register
(CTRLB.SBMODE)
zWhen using an internal clock, the Baud register (BAUD) must be written to generate the desired baud rate
zThe transmitter and receiver can be enabled by writing ones to the Receiver Enable an d T ransmitter Enable bit s in
the Control B register (CTRLB.RXEN and CTRLB.TXEN)
24.6.2.2 Enabling, Disabling and Resetting
The USART is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The USART is
disabled by writing a zero to CTRLA.ENABLE.
The USART is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in
the USART, except DBGCTRL, will be reset to their initial state, and the USART will be disabled. Refer to the CTRLA
register for details.
24.6.2.3 Clock Generation and Selection
For both synchronous and asynchronous modes, the clock used for shifting and sampling data can be generated
internally by the SERCOM baud-rate generator or supplied externally through the XCK line. Synchronous mode is
selected by writing a one to the Communication Mode bit in the Control A register (CTRLA.CMODE) and asynchronous
mode is selected by writing a zero to CTRLA.CMODE. The internal clock source is selected by writing 0x1 to the
Operation Mode bit group in the Control A register (CTRLA.MODE) and the external clock source is selected by writing
0x0 to CTRLA.MODE.
The SERCOM baud-rate generator is configured as shown in Figure 24-3. When CTRLA.CMODE is zero, the baud-rate
generator is automatically set to asynchronous mode and the 16-bit Baud register value is used. When CTRLA.CMODE
is one, the baud-rate generator is automatically set to synchronous mode and the eight LSBs of the Baud register are
used. Refer to “Clock Generation – Baud-Rate Generator” on page 335 for details on configuring the baud rate.
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Figure 24-3. Clock Generation
Synchronous Clock Operation
When synchronous mode is used, the CTRLA.MODE bit group controls whether the transmission clock (XCK line) is an
input or output. The dependency between the clock edges and data sampling or data change is the same for internal and
external clocks. Data input on the RxD pin is sampled at the opposite XCK clock edge as data is driven on the TxD pin.
The Clock Polarity bit in the Control A register (CTRLA.CPOL) selects which XCK clock edge is used for RxD sampling
and which is used for TxD change. As shown in Figure 24-4, when CTRLA.CPOL is zero, the data will be changed on the
rising XCK edge and sampled on the falling XCK edge. If CTRLA.CPOL is one, the data will be changed on the falling
edge of XCK and sampled on the rising edge of XCK.
Figure 24-4. Synchronous Mode XCK Timing
When the clock is provided through XCK (CTRLA.MODE is 0x0), the shift registers operate directly on the XCK clock.
This means that XCK is not synchronized with the system clock and, therefore, can operate at frequencies up to the
system frequency.
24.6.2.4 Data Register
The USART Transmit Data register (TxDATA) and USART Receive Data register(RxDATA) share the same I/O address,
referred to as the Data register (DATA). Writing the DATA register will update the Transmit Data register. Reading the
DATA register will return the contents of the Receive Data register.
XCK
Baud Rate Generator
Base
Period /2
/2 /16/1
CTRLA.CMODE
0
1
1
0
1
0Tx Clk
Rx Clk
Internal Clk
(GCLK)
0
1
CTRLA.MODE[0]
/8
Sample
RxD / TxD
XCK
CTRLA.CPOL=1
Sample
RxD / TxD
XCK
CTRLA.CPOL=0
Change
Change
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24.6.2.5 Data Transmission
A data transmission is initiated by loading the DATA register with the data to be sent. The data in TxDATA is moved to
the shift register when the shift register is empty and ready to send a new frame. When the shift register is loaded with
data, one complete frame will be transmitted.
The Transmit Complete interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.TXC) is set, and the
optional interrupt is generated, when the entire frame in the shift register has been shifted out and there is no new data
written to the DATA register.
The DATA register should only be written when the Data Register Empty flag in the Interrupt Flag Status and Clear
register (INTFLAG.DRE) is set, which indicates that the register is empty and ready for new data.
Disabling the Transmitter
Disabling the transmitter will not become effective until any ongoing and pending transmissions are completed, i.e., when
the transmit shift register and TxDATA do not contain data to be transmitted. The transmitter is disabled by writing a zero
to the Transmitter Enable bit in the Control B register (CTRLB.TXEN).
24.6.2.6 Data Reception
The receiver starts data reception when a valid start bit is detected. Each bit that follows the start bit will be sampled at
the baud rate or XCK clock, and shifted into the receive shift register until the first stop bit of a frame is received. When
the first stop bit is received and a complete serial frame is present in the receive shift register, the contents of the shift
register will be moved into the two-level receive buffer. The Receive Complete interrupt flag in the Interrupt Flag Status
and Clear register (INTFLAG.RXC) is set, and the optional interrupt is generated. A second stop bit will be ignored by the
receiver.
The received data can be read by reading the DATA register. DATA should not be read unless the Receive Complete
interrupt flag is set.
Disabling the Receiver
Disabling the receiver by writing a zero to the Receiver Enable bit in the Control B register (CTRLB.RXEN) will flush the
two-level receive buffer, and data from ongoing receptions will be lost.
Error Bits
The USART receiver has three error bits. The Frame Error (FERR), Buffer Overflow (BUFOVF) and Parity Error (PERR)
bits can be read from the Status (STATUS) register. Upon error detection, the corresponding bit will be set until it is
cleared by writing a one to it. These bits are also automatically cleared when the receiver is disabled.
There are two methods for buffer overflow notification. When the immediate buffer overflow notification bit (CTRLA.IBON)
is set, STATUS.BUFOVF is raised immediately upon buffer overflow. Software can then empty the receive FIFO by
reading RxDATA until the receive complete interrupt flag (INTFLAG.RXC) goes low.
When CTRLA.IBON is zero, the buffer overflow condition travels with data through the receive FIFO. After the received
data is read, STATUS.BUFOVF will be set along with INTFLAG.RXC.
Asynchronous Data Reception
The USART includes a clock recovery and data recovery unit for handling asynchronous data reception. The clock
recovery logic is used to synchronize the incoming asynchronous serial frames at the RxD pin to the internally generated
baud-rate clock. The data recovery logic samples and applies a low-pass filter to each incoming bit, thereby improving
the noise immunity of the receiver. The asynchronous reception operational range depends on the accuracy of the
internal baud-rate clock, the rate of the incoming frames and the frame size (in number of bits).
Asynchronous Operational Range
The operational range of the receiver depends on the difference between the received bit rate and the internally
generated baud rate. If the baud rate of an external transmitter is too high or too low compared to the internally generated
baud rate, the receiver will not be able to synchronize the frames to the start bit.
There are two possible sources for a mismatch in baud rate. The reference clock will always have some minor instability.
In addition, the baud-rate generator can not always do an exact division of the reference clock frequency to get the baud
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rate desired. In this case, the BAUD register value should be selected to give the lowest possible error. Refer to
“Asynchronous Mode BAUD Value Selection” on page 336 for details.
Recommended maximum receiver baud-rate errors for various character sizes are shown in the table below.
Table 24-2. Asynchronous Receiver Error
The recommended maximum receiver baud-rate error assumes that the receiver and transmitter equally divide the
maximum total error.
The following equations can be used to calculate the ratio of the incoming data rate and internal receiver baud rate:
where:
zDis the sum of character size and parity size (D = 5 to 10 bits)
zRSLOW is the ratio of the slowest incoming data rate that can be accepted in relation to the receiver baud rate
zRFAST is the ratio of the fastest incoming data rate that can be accepted in relation to the receiver baud rate
24.6.3 Additional Features
24.6.3.1 Parity
Even or odd parity can be selected for error checking by writing 0x1 to the Frame Format bit group in the Control A
register (CTRLA.FORM). If even parity is selected by writing a zero to the Parity Mode bit in the Control B register
(CTRLB.PMODE), the parity bit of the outgoing frame is set to one if the number of data bits that are one is odd (making
the total number of ones even). If odd parity is selected by wr iting a one to CTRLB.PMODE, the parity bit of the outg oing
frame is set to one if the number of data bits that are one is even (making the total number of ones odd).
When parity checking is enabled, the parity checker calculates the parity of the data bits in incoming frames and
compares the result with the parity bit of the corresponding frame. If a parity error is detected, the Parity Error bit in the
Status register (STATUS.PERR) is set.
24.6.4 Interrupts
The USART has the following interrupt sources:
zReceive Complete
zTransmit Complete
zData Register Empty
D
(Data bits + Parity) RSLOW(%) RFAST(%) Max Total Error (%) Recommended Max
Rx Error (%)
594.12 107.69 +5.88/-7.69 ±2.5
694.92 106.67 +5.08/-6.67 ±2.0
795.52 105.88 +4.48/-5.88 ±2.0
896.00 105.26 +4.00/-5.26 ±2.0
996.39 104.76 +3.61/-4.76 ±1.5
10 96.70 104.35 +3.30/-4.35 ±1.5
6)1(16 )1(16
++
+
=DD
RSLOW
8)1(16 )2(16
++
+
=DD
RFAST
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Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the USART is reset. See the register description for details on how to clear interrupt
flags.
The USART has one common interrupt request line for all the interrupt sources. The user must read INTFLAG to
determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to “Nested Vector Interrupt
Controller” on page 24 for details.
24.6.5 Events
Not applicable.
24.6.6 Sleep Mode Operation
When using internal clocking, writing the Run In Standby bit in the Control A register (CTRLA.RUNSTDBY) to one will
allow GCLK_SERCOMx_CORE to be enabled in all sleep modes. Any interrupt can wake up the device.
When using external clocking, writing a one to CTRLA.RUNSTDBY will allow the Receive Complete interrupt.to wake up
the device.
If CTRLA.RUNSTDBY is zero, the internal clock will be disabled when any ongoing transfer is finished. A Transfer
Complete interrupt can wake up the device. When using external clocking, this will be disconnected when any ongoing
transfer is finished, and all reception will be dropped.
24.6.7 Synchronization
Due to the asynchronicity between CLK_SERCOMx_APB and GCLK_SERCOMx_CORE, some registers must be
synchronized when accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete.
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following bits need synchronization when written:
zSoftware Reset bit in the Control A register (CTRLA.SWRST)
zEnable bit in the Control A register (CTRLA.ENABLE)
zReceiver Enable bit in the Control B register (CTRLB.RXEN)
zTransmitter Enable bit in the Control B register (CTRLB.TXEN)
CTRLB.RXEN and CTRLB.TXEN behave somewhat differently than described above. Refer to CTRLB register
description for details.
Synchronization is denoted by the Write-Synchronized property in the register description.
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24.7 Register Summary
Offset Name Bit Pos.
0x00
CTRLA
7:0 RUNSTDBY MODE[2:0] ENABLE SWRST
0x01 15:8 IBON
0x02 23:16 RXPO[1:0] TXPO
0x03 31:24 DORD CPOL CMODE FORM[3:0]
0x04
CTRLB
DBGCTRL
7:0 SBMODE CHSIZE[2:0]
0x05 15:8 PMODE
0x06 23:16 RXEN TXEN
0x07 31:24
0x08 7:0 DBGSTOP
0x09 Reserved
0x0A BAUD 7:0 BAUD[7:0]
0x0B 15:8 BAUD[15:8]
0x0C INTENCLR 7:0 RXC TXC DRE
0x0D INTENSET 7:0 RXC TXC DRE
0x0E INTFLAG 7:0 RXC TXC DRE
0x0F Reserved
0x10 STATUS 7:0 BUFOVF FERR PERR
0x11 15:8 SYNCBUSY
0x12 Reserved
0x13 Reserved
0x14 Reserved
0x15 Reserved
0x16 Reserved
0x17 Reserved
0x18 DATA 7:0 DATA[7:0]
0x19 15:8 DATA[8]
0x1A Reserved
0x1B Reserved
0x1C Reserved
0x1D Reserved
0x1E Reserved
0x1F Reserved
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24.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Refer to “Register Access Protection” on page 342
for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Synchronized
property in each individual register description. Refer to “Synchronization” on page 348 for details.
Some registers are enable-protected, meaning they can only be written when the USART is disabled. Enable-protection
is denoted by the Enable-Protected property in each individual register description.
24.8.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00000000
Property: Enable-Protected, Write-Protected, Write-Synchronized
zBit 31 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
Bit3130292827262524
DORD CPOL CMODE FORM[3:0]
Access R R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit2322212019181716
RXPO[1:0] TXPO
Access R R R/W R/W R R R R/W
Reset00000000
Bit151413121110 9 8
IBON
AccessRRRRRRRR
Reset00000000
Bit76543210
RUNSTDBY MODE[2:0] ENABLE SWRST
Access R/W R R R/W R/W R/W R/W R/W
Reset00000000
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zBit 30 – DORD: Data Order
This bit indicates the data order when a character is shifted out from the Data register.
0: MSB is transmitted first.
1: LSB is transmitted first.
This bit is not synchronized.
zBit 29 – CPOL: Clock Polarity
This bit indicates the relationship between data output change and data input sampling in synchronous mode.
This bit is not synchronized.
Table 24-3. Clock Polarity
zBit 28 – CMODE: Communication Mode
This bit indicates asynchronous or synchronous communication.
0: Asynchronous communication.
1: Synchronous communication.
This bit is not synchronized.
zBits 27:24 – FORM[3:0]: Frame Format
These bits define the frame format.
These bits are not synchronized.
Table 24-4. Frame Format
zBits 23:22 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 21:20 – RXPO[1:0]: Receive Data Pinout
These bits define the receive data (RxD) pin configuration.
These bits are not synchronized.
CPOL TxD Change RxD Sample
0x0 Rising XCK edge Falling XCK edge
0x1 Falling XCK edge Rising XCK edge
FORM[3:0] Description
0x0 USART frame
0x1 USART frame with parity
0x2-0xF Reserved
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zBits 19:17 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 16 – TXPO: Transmit Data Pinout
This bit defines the transmit data (TxD) and XCK pin configurations.
This bit is not synchronized.
Table 24-6. Transmit Data Pinout
zBits 15:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 8 – IBON: Immediate Buffer Overflow Notification
This bit controls when the buffer overflow status bit (STATUS.BUFOVF) is asserted when a buffer overflow occurs.
0: STATUS.BUFOVF is asserted when it occurs in the data stream.
1: STATUS.BUFOVF is asserted immediately upon buffer overflow.
zBit 7 – RUNSTDBY: Run In Standby
This bit defines the functionality in standby sleep mode.
This bit is not synchronized.
Table 24-7. Run In Standby
zBits 6:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:2 – MODE: Operating Mode
Table 24-5. Receive Data Pinout
RXPO[1:0] Name Description
0x0 PAD[0] SERCOM PAD[0] is used for data reception
0x1 PAD[1] SERCOM PAD[1] is used for data reception
0x2 PAD[2] SERCOM PAD[2] is used for data reception
0x3 PAD[3] SERCOM PAD[3] is used for data reception
TXPO TxD Pin Location XCK Pin Location (When Applicable)
0x0 SERCOM PAD[0] SERCOM PAD[1]
0x1 SERCOM PAD[2] SERCOM PAD[3]
RUNSTDBY External Clock Internal Clock
0x0 External clock is disconnected when
ongoing transfer is finished. All
reception is dropped.
0x1 Generic clock is enabled in all sleep modes. An y
interrupt can wake up the device.
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These bits must be written to 0x0 or 0x1 to select the USART serial communication interface of the SERCOM.
0x0: USART with external clock.
0x1: USART with internal clock.
These bits are not synchronized.
zBit 1 – ENABLE: Enable
0: The peripheral is disabled or being disabled.
1: The peripheral is enabled or being enabled.
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/disabled. The
value written to CTRLA.ENABLE will read back immediately and the Synchronization Busy bit in the Status regis-
ter (STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY is cleared when the operation is complete.
This bit is not enable-protected.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the SERCOM, except DBGCTRL, to their initial state, and the SER-
COM will be disabled.
Writing a one to CTRLA.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST
and STATUS.SYNCBUSY will both be cleared when the reset is complete.
This bit is not enable-protected.
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24.8.2 Control B
Name: CTRLB
Offset: 0x04
Reset: 0x00000000
Property: Enable-Protected, Write-Protected, Write-Synchronized
zBits 31:18 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 17 – RXEN: Receiver Enable
0: The receiver is disabled or being enabled.
1: The receiver is enabled or will be enabled when the USART is enabled.
Writing a zero to this bit will disable the USART receiver. Disabling the receiver will flush the receive buffer and
clear the FERR, PERR and BUFOVF bits in the STATUS register.
Writing a one to CTRLB.RXEN when the USART is disabled will set CTRLB.RXEN immediately. When the USART
is enabled, CTRLB.RXEN will be cleared, and STATUS.SYNCBUSY will b e set and remain set until the receiver is
enabled. When the receiver is enabled, CTRLB.RXEN will read back as one.
Writing a one to CTRLB.RXEN when the USART is enabled will set STATUS.SYNCBUSY, which will remain set
until the receiver is enabled, and CTRLB.RXEN will read back as one.
This bit is not enable-protected.
zBit 16 – TXEN: Transmitter Enable
0: The transmitter is disabled or being enabled.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
RXEN TXEN
AccessRRRRRRR/WR/W
Reset00000000
Bit151413121110 9 8
PMODE
Access R R R/W R R R R/W R
Reset00000000
Bit76543210
SBMODE CHSIZE[2:0]
Access R R/W R R R R/W R/W R/W
Reset00000000
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1: The transmitter is enabled or will be enabled when the USART is enabled.
Writing a zero to this bit will disable the USART transmitter. Disabling the transmitter will not become effective until
ongoing and pending transmissions are completed.
Writing a one to CTRLB.TXEN when the USART is disabled will set CTRLB.TXEN immediately. When the USART
is enabled, CTRLB.TXEN will be cleared, and STATUS.SYNCBUSY will be set and remain set until the transmitter
is enabled. When the transmitter is enabled, CTRLB.TXEN will read back as one.
Writing a one to CTRLB.TXEN when the USART is enabled will set STATUS.SYNCBUSY, which will remain set
until the receiver is enabled, and CTRLB.TXEN will read back as one.
This bit is not enable-protected.
zBits 15:14 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 13 – PMODE: Parity Mode
This bit selects the type of parity used when parity is enabled (CTRLA.FORM is one). The transmitter will automat-
ically generate and send the parity of the transmitted data bits within each frame. The receiver will generate a
parity value for the incoming data and parity bit, compare it to the parity mode and, if a mismatch is de tected, STA-
TUS.PERR will be set.
0: Even parity.
1: Odd parity.
This bit is not synchronized.
zBits 12:7 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 6 – SBMODE: Stop Bit Mode
This bit selects the number of stop bits transmitted.
0: One stop bit.
1: Two stop bits.
This bit is not synchronized.
zBits 5:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 2:0 – CHSIZE[2:0]: Character Size
These bits select the number of bits in a character.
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These bits are not synchronized.
Table 24-8. Character Size
CHSIZE[2:0] Description
0x0 8 bits
0x1 9 bits
0x2-0x4 Reserved
0x5 5 bits
0x6 6 bits
0x7 7 bits
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24.8.3 Debug Control
Name: DBGCTRL
Offset: 0x08
Reset: 0x00
Property: Write-Protected
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – DBGSTOP: Debug Stop Mode
This bit controls the baud-rate generator functionality when the CPU is halted by an external debugger.
0: The baud-rate generator continues normal operation when the CPU is halted by an external debugger.
1: The baud-rate generator is halted when the CPU is halted by an external debugger.
Bit76543210
DBGSTOP
AccessRRRRRRRR/W
Reset00000000
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24.8.4 Baud
Name: BAUD
Offset: 0x0A
Reset: 0x0000
Property: Enable-Protected, Write-Protected
zBits 15:0 – BAUD: Baud Value
These bits control the clock generation, as described in the SERCOM Baud Rate section.
Bit151413121110 9 8
BAUD[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
BAUD[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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24.8.5 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x0C
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – RXC: Receive Complete Interrupt Enable
0: Receive Complete interrupt is disabled.
1: Receive Complete interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Receive Complete Interrupt Enable bit, which disables the Receive Complete
interrupt.
zBit 1 – TXC: Transmit Complete Interrupt Enable
0: Transmit Complete interrupt is disabled.
1: Transmit Complete interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Transmit Complete Interrupt Enable bit, which disables the Receive Complete
interrupt.
zBit 0 – DRE: Data Register Empty Interrupt Enable
0: Data Register Empty interrupt is disabled.
1: Data Register Empty interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Data Register Empty Interrupt Enable bit, which disables the Data Register
Empty interrupt.
Bit76543210
RXC TXC DRE
Access R R R R R R/W R/W R/W
Reset00000000
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24.8.6 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR) .
Name: INTENSET
Offset: 0x0D
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – RXC: Receive Complete Interrupt Enable
0: Receive Complete interrupt is disabled.
1: Receive Complete interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Receive Complete Interrupt Enable bit, which enables the Receive Complete
interrupt.
zBit 1– TXC: Transmit Complete Interrupt Enable
0: Transmit Complete interrupt is disabled.
1: Transmit Complete interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Transmit Complete Interrupt Enable bit, which enables the Transmit Complete
interrupt.
zBit 0 – DRE: Data Register Empty Interrupt Enable
0: Data Register Empty interrupt is disabled.
1: Data Register Empty interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Data Register Empty Interrupt Enable bit, which enables the Data Register
Empty interrupt.
Bit76543210
RXC TXC DRE
AccessRRRRRR/WR/WR/W
Reset00000000
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24.8.7 Interrupt Flag S tatus and Clear
Name: INTFLAG
Offset: 0x0E
Reset: 0x00
Property:
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
z--Bit 2 – RXC: Receive Complete
This flag is cleared by reading the Data register (DATA) or by disabling the receiver.
This flag is set when there are unread data in DATA.
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
zBit 1 – TXC: Transmit Complete
This flag is cleared by writing a one to it or by writing new data to DATA.
This flag is set when the entire frame in the transmit shift register has been shifted out and there are no new data
in DATA.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the flag.
zBit 0 – DRE: Data Register Empty
This flag is cleared by writing new data to DATA.
This flag is set when DATA is empty and ready to be written.
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
Bit76543210
RXC TXC DRE
AccessRRRRRRR/WR
Reset00000000
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24.8.8 Status
Name: STATUS
Offset: 0x10
Reset: 0x0000
Property:
zBit 15 – SYNCBUSY: Synchronization Busy
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 14:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – BUFOVF: Buffer Overflow
Reading this bit before reading the Data register will indicate the error status of the next character to be read.
This bit is cleared by writing a one to the bit or by disabling the receiver.
This bit is set when a buffer overflow condition is detected. A buffer overflow occurs when the receive buffer is full,
there is a new character waiting in the receive shift register and a new start bit is detected.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear it.
zBit 1 – FERR: Frame Error
Reading this bit before reading the Data register will indicate the error status of the next character to be read.
This bit is cleared by writing a one to the bit or by disabling the receiver.
This bit is set if the received character had a frame error, i.e., when the first stop bit is zero.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear it.
zBit 0 – PERR: Parity Error
Reading this bit before reading the Data register will indicate the error status of the next character to be read.
This bit is cleared by writing a one to the bit or by disabling the receiver.
This bit is set if parity checking is enabled (CTRLA.FORM is one) and a parity error is detected.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear it.
Bit151413121110 9 8
SYNCBUSY
Access R/W R R R R R R R
Reset00000000
Bit76543210
BUFOVF FERR PERR
Access R R R R R R/W R/W R/W
Reset00000000
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24.8.9 Data
Name: DATA
Offset: 0x18
Reset: 0x0000
Property: -
zBits 15:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 8:0 – DATA[8:0]: Data
Reading these bits will return the contents of the Receive Data register. The register should be read only when the
Receive Complete Interrupt Flag bit in the Interrupt Flag Status and Clear register (INTFLAG.RXCIF) is set. The
status bits in STATUS should be read before reading the DATA value in order to get any corresponding error.
Writing these bits will write the Transmit Data register. This register should be written only when the Data Register
Empty Interrupt Flag bit in the Interrupt Flag Status and Clear register (INTFLAG.DREIF) is set.
Bit151413121110 9 8
DATA[8]
AccessRRRRRRRR/W
Reset00000000
Bit76543210
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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25. SERCOM SPI – SERCOM Serial Peripheral Interface
25.1 Overview
The serial peripheral interface (SPI) is one of the available modes in the Serial Communication Interface (SERCOM).
Refer to “SERCOM – Serial Communication Interface” on page 332 for details.
The SPI uses the SERCOM transmitter and receiver configured as shown in “Full-Duplex SPI Master Slave
Interconnection” on page 364. Each side, master and slave, depicts a separate SPI containing a shift register, a transmit
buffer and two receive buffers. In addition, the SPI master uses the SERCOM baud-rate generator, while the SPI slave
can use the SERCOM address match logic. Fields shown in capital letters are synchronous to CLK_SERCOMx_APB
and accessible by the CPU, while fields with lowercase letters are synchronous to the SCK clock.
25.2 Features
zFull-duplex, four-wire interface (MISO, MOSI, SCK, _SS)
zSingle-buffered transmitter, double-buffered receiver
zSupports all four SPI modes of operation
zSingle data direction operation allows alternate function on MISO or MOSI pin
zSelectable LSB- or MSB-first data transfer
zMaster operation:
zSerial clock speed up to half the system clock
z8-bit clock generator
zSlave operation:
zSerial clock speed up to the system clock
zOptional 8-bit address match operation
zOperation in all sleep modes
25.3 Block Diagram
Figure 25-1. Full-Duplex SPI Master Slave Interconnection
25.4 Signal Description
Refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One signal
can be mapped to one of several pins.
shift register shift register
Master Slave
MISO
MOSI
SCK
_SS
Tx DATA
rx buffer
Rx DATA
Tx DATA
rx buffer
Rx DATA
==
ADDR/ADDRMASKBAUD
baud rate generator
Address Match
Signal Name Type Description
PAD[3:0] Digital I/O General SERCOM pins
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25.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
25.5.1 I/O Lines
Using the SERCOM’s I/O lines requires the I/O pins to be configured using port configuration (PORT). Refer to “PORT”
on page 284 for details.
When the SERCOM is configured for SPI operation, the pins should be configured according to Table 25-1. If the
receiver is disabled, the data input pin can be used for other purposes. In master mode the slave select line (_SS) is
controlled by software.
Table 25-1. SPI Pin Configuration
The combined configuration of PORT and the Data In/Data Out and Data Out Pinout bit groups in Control A register will
define the physical position of the SPI signals in Table 25-1.
25.5.2 Power Management
The SPI can continue to operate in any sleep mode. The SPI interrupts can be used to wake up the device from sleep
modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
25.5.3 Clocks
The SERCOM bus clock (CLK_SERCOMx_APB) can be enabled and disabled in the Power Manager, and the default
state of CLK_SERCOMx_APB can be found in the Peripheral Clock Masking section in the “PM – Power Manager” on
page 100.
A generic clock (GCLK_SERCOMx_CORE) is required to clock the SPI. This clock must be configured and enabled in
the Generic Clock Controller before using the SPI. Refer to “GCLK – Generic Clock Controller” on page 78 for details.
This generic clock is asynchronous to the bus clock (CLK_SERCOMx_APB). Due to this asynchronicity, writes to certain
registers will require synchronization between the clock domains. Refer to “Synchronization” on page 372 for further
details.
25.5.4 DMA
Not applicable.
25.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the SPI, interrupts requires the Interrupt
Controller to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
25.5.6 Events
Not applicable.
Pin Master SPI Slave SPI
MOSI Output Input
MISO Input Output
SCK Output Input
_SS User defined outp ut enable Input
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25.5.7 Debug Operation
When the CPU is halted in debug mode, the SPI continues normal operation. If the SPI is configured in a way that
requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss may result
during debugging. The SPI can be forced to halt operation during debugging. Refer to the Debug Control (DBGCTRL)
register for details.
25.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following registers:
zInterrupt Flag Clear and Status register (INTFLAG)
zStatus register (STATUS)
zData register (DATA)
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
25.5.9 Analog Connections
Not applicable.
25.6 Functional Description
25.6.1 Principle of Operation
The SPI is a high-speed synchronous data transfer interface. It allows fast communication between the device and
peripheral devices.
The SPI can operate as master or slave. As master, the SPI initiates and controls all data transactions. The SPI is sin gle
buffered for transmitting and double buffered for receiving. When transmitting data, the Data register can be loaded with
the next character to be transmitted while the current transmissio n is in progress. For receiving, this means that the data
is transferred to the two-level receive buffer upon reception, and the receiver is ready for a new character.
The SPI transaction format is shown in Figure 25-2, where each transaction can contain one or more characters. The
character size is configurable, and can be either 8 or 9 bits.
Figure 25-2. SPI Transaction Format
The SPI master must initiate a transaction by pulling low the slave select line (_SS) of the desired slave. The master and
slave prepare data to be sent in their respective shift registers, and the master generates the serial clock on the SCK line.
Data are always shifted from master to slave on the master output, slave input line (MOSI), and from slave to master on
the master input, slave output line (MISO). The master signals the end of the transaction by pulling the _SS line high.
As each character is shifted out from the master, another character is shifted in from the slave.
Character
Transaction
MOSI/MISO
_SS
Character 0 Character 1 Character 2
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25.6.2 Basic Operation
25.6.2.1 Initialization
The following registers are enable-protected, meaning that they can only be written when the SPI is disabled
(CTRL.ENABLE is zero):
zControl A register (CTRLA), except Enable (CTRLA.ENABLE) and Software Reset (CTRLA.SWRST)
zControl B register (CTRLB), except Receiver Enable (RXEN)
zBaud register (BAUD)
zAddress register (ADDR)
Any writes to these registers when the SPI is enabled or is being enabled (CTRL.ENABLE is one) will be discarded.
Writes to these registers while the SPI is being disabled will be completed after the disabling is complete.
Enable-protection is denoted by the Enable-Protection property in the register description.
Before the SPI is enabled, it must be configured, as outlined by the following steps:
zSPI mode in master or slave operation must be selected by writing 0x2 or 0x3 to the Operating Mode bit group in
the Control A register (CTRLA.MODE)
zTransfer mode must be selected by writing the Clock Polarity bit and the Clock Phase bit in the Control A register
(CTRLA.CPOL and CTRLA.CPHA)
zTransaction format must be selected by writing the Frame Format bit group in the Control A register
(CTRLA.FORM)
zSERCOM pad to use for the receiver must be selected by writing the Data In Pinout bit in the Control A register
(CTRLA.DIPO)
zSERCOM pads to use for the transmitter, slave select and serial clock must be selected by writing the Data Out
Pinout bit group in the Control A register (CTRLA.DOPO)
zCharacter size must be selected by writing the Character Size bit in the Control B register (CTRLB.CHSIZE)
zData direction must be selected by writing the Data Order bit in the Control A register (CTRLA.DORD)
zIf the SPI is used in master mode, the Baud register (BAUD) must be written to generate the desired baud rate
zThe receiver can be enabled by writing a one to the Receiver Enable bit in the Control B register (CTRLB.RXEN)
25.6.2.2 Enabling, Disabling and Resetting
The SPI is enabled b y writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The SPI is disabled by
writing a zero to CTRLA.ENABLE.
The SPI is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in the
SPI, except DBGCTRL, will be reset to their initial state, and the SPI will be disabled. Refer to CTRLA for details.
25.6.2.3 Clock Generation
In SPI master operation (CTRLA.MODE is 0x3), the serial clock (SCK) is generated internally using the SERCOM baud-
rate generator. When used in SPI mode, the baud-rate generator is set to synchro nous mode, and the 8-bit Baud register
(BAUD) value is used to generate SCK, clocking the shift register. Refer to “Clock Generation – Baud-Rate Generator”
on page 335 for more details.
In SPI slave operation (CTRLA.MODE is 0x2), the clock is provided by an external master on the SCK pin. This clock is
used to directly clock the SPI shift register.
25.6.2.4 Data Register
The SPI Transmit Data register (TxDATA) and SPI Receive Data register (RxDATA) share the same I/O address,
referred to as the SPI Data register (DATA). Writing the DATA register will update the Transmit Data register. Reading
the DATA register will return the contents of the Receive Data register.
25.6.2.5 SPI Transfer Modes
There are four combinations of SCK phase and polarity with respect to the serial data. The SPI data transfer modes are
shown in Table 25-2 and Figure 25-3. SCK phase is selected by the Clock Phase bit in the Control A register
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(CTRLA.CPHA). SCK polarity is selected by the Clock Polarity bit in the Control A register (CTRLA.CPOL). Data bits are
shifted out and latched in on opposite edges of the SCK signal, ensuring sufficient time for the data signals to stabilize.
Table 25-2. SPI Transfer Modes
Leading edge is the first clock edge in a clock cycle, while trailing edge is the second clock edge in a clock cycle.
Figure 25-3. SPI Transfer Modes
Mode CPOL CPHA Leading Edge Trailing Edge
0 00Rising, sample Falling, setup
1 01Rising, setup Falling, sample
2 10Falling, sample Rising, setup
3 11Falling, setup Rising, sample
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25.6.2.6 Transferring Data
Master
When configured as a master (CTRLA.MODE is 0x3), the _SS line can be located at any general purpose I/O pin, and
must be configured as an output. When the SPI is ready for a data transaction, software must pull the _SS line low.
When writing a character to the Data register (DATA), the character will be transferred to the shift register when the shift
register is empty. Once the contents of TxDATA have been transferred to the shift register, the Data Register Empty flag
in the Interrupt Flag Status and Clear register (INTFLAG.DRE) is set, and a new character can be written to DATA.
As each character is shifted out from the master, another character is shifted in from the slave. If the receiver is enabled
(CTRLA.RXEN is one), the contents of the shift register will be transferred to the two-level receive buffer. The transfer
takes place in the same clock cycle as the last data bit is shifted in, and the Receive Complete Interrupt flag in the
Interrupt Flag Status and Clear register (INTFLAG.RXC) will be set. The received data can be retrieved by reading
DATA.
When the last character has been transmitted and there is no valid data in DATA, the Transmit Complete Interrupt flag in
the Interrupt Flag Status and Clear register (INTFLAG.TXC) is set. When the transaction is finished, the master must
indicate this to the slave by pulling the _SS line high.
Slave
When configured as a slave (CTRLA.MODE is 0x2), the SPI in terface will remain inactive, with the MISO line tri-stated as
long as the _SS pin is pulled high. Software may update the contents of DATA at any time, as long as the Data Register
Empty flag in the Interrupt Status and Clear register (INTFLAG.DRE) is set.
When _SS is pulled low and SCK is running, the slave will sample and shift out data according to the transaction mode
set. When the contents of TxDATA have been loaded into the shift register, INTFLAG.DRE is set, and new data can be
written to DATA. Similar to the master, the slave will receive one character for each character transmitted. On the same
clock cycle as the last data bit of a character is received, the character will be transferred into the two-level receive buffer.
The received character can be retrieved from DATA when INTFLAG.RCX is set.
When the master pulls the _SS line high, the transaction is done and the Transmit Complete Interrupt flag in the Interrupt
Flag Status and Clear register (TXC) is set.
Once DATA is written, it takes three SCK clocks to load the shift register. After the DATA register is empty, it takes three
CLK_SERCOM_APB cycles for INTFLAG.DRE to be set.
25.6.2.7 Receiver Error Bit
The SPI receiver has one error bit: the Buffer Overflow bit (BUFOVF), which can be read from the Status register
(STATUS). Upon error detection, the bit will be set until it is cleared by writing a one to it. The bit is also automatically
cleared when the receiver is disabled.
There are two methods for buffer overflow notification. When the immediate buffer overflow notification bit (CTRLA.IBON)
is set, STATUS.BUFOVF is raised immediately upon buffer overflow. Software can then empty the receive FIFO by
reading RxDATA until the receive complete interrupt flag (INTFLAG.RXC) goes low.
When CTRLA.IBON is zero, the buffer overflow condition travels with data through the receive FIFO. After the received
data is read, STATUS.BUFOVF will be set along with INTFLAG.RXC, and RxDATA will be zero.
25.6.3 Additional Features
25.6.3.1 Address Recognition
When the SPI is configured for slave operation (CTRLA.MODE is 0x2) with address recognition (CTRLA.FORM is 0x2),
the SERCOM address recognition logic is enabled. When address recognition is enabled, the first character in a
transaction is checked for an address match. If there is a match, then the Receive Complete Interrupt flag in the Interrupt
Flag Status and Clear register (INTFLAG.RXC) is set, the MISO output is enabled and the transaction is processed. If
there is no match, the transaction is ignored.
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If the device is in sleep mode, an address match can wake up the device in order to process the transaction. If the
address does not match, then the complete transaction is ignored. If a 9-bit frame format is selected, only the lower 8 bits
of the shift register are checked against the Address register (ADDR).
Refer to “Address Match and Mask” on page 338 for further details.
25.6.3.2 Preloading of the Slave Shift Register
When starting a transaction, the slave will first transmit the contents of the shift register before loading new data from
DATA. The first character sent can be either the reset value of the shift register (if this is the first transmission since the
last reset) or the last character in the previous transmission. Preloading can be used to preload data to the shift register
while _SS is high and eliminate sending a dummy character when starting a transaction.
In order to guarantee enough set-up time before the first SCK edge, enough time must be given between _SS going low
and the first SCK sampling edge, as shown in Figure 25-4.
Preloading is enabled by setting the Slave Data Preload Enable bit in the Control B register (CTRLB.PLOADEN).
Figure 25-4. Timing Using Preloading
Only one data character written to DATA will be preloaded into the shift register while the synchronized _SS signal (see
Figure 25-4) is high. The next character written to DATA before _SS is pulled low will be stored in DATA until transfer
begins. If the shift register is not preloaded, the current contents of the shift register will be shifted out.
25.6.3.3 Master with Several Slaves
If the bus consists of several SPI slaves, an SPI master can use general purpose I/O pins to control the _SS line to each
of the slaves on the bus, as shown in Figure 25-5. In this configuration, the single selected SPI slave will drive the tri-
state MISO line.
Figure 25-5. Multiple Slaves in Parallel
_SS
Synchronization to
system domain
MISO to SCK
setup time
Required _SS to SCK time using
PRELOADEN
_SS synchronized to
system domain
SCK
shift register shift register
MOSI
MISO
SCK
_SS [0]
MOSI
MISO
_SS
SCK
shift register
MOSI
MISO
_SS
SCK
SPI Master
SPI Slave 0
_SS[n-1]
SPI Slave n-1
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An alternate configuration is shown in Figure 25-6. In this configuration, all n attached slaves are connected in series. A
common _SS line is provided to all slaves, enabling them simultaneously. The master must shift n characters for a
complete transaction.
Figure 25-6. Multiple Slaves in Series
25.6.4 Interrupts
The SPI has the following interrupt sources:
zReceive Complete
zTransmit Complete
zData Register Empty
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the SPI is reset. See the register description for details on how to clear interrupt flags.
The SPI has one common interrupt request line for all the interrupt sources. The user must read INTFLAG to determine
which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to “Nested Vector Interrupt
Controller” on page 24 for details.
For details on clearing interrupt flags, refer to INTFLAG.
25.6.5 Events
Not applicable.
25.6.6 Sleep Mode Operation
During master operation, the generic clock will continue to run in idle sleep mode. If the Run In Standby bit in the Control
A register (CTRLA.RUNSTDBY) is one, the GCLK_SERCOM_CORE will also be enabled in standby sleep mode. Any
interrupt can wake up the device.
If CTRLA.RUNSTDBY is zero during master operation, GLK_SERCOMx_CORE will be disabled when the ongoing
transaction is finished. Any interrupt can wake up the device.
During slave operation, writing a one to CTRLA.RUNSTDBY will allow the Receive Complete interrupt to wake up the
device.
shift register shift register
MOSI
MISO
SCK
_SS
MOSI
MISO
_SS
SCK
shift register
MOSI
MISO
_SS
SCK
SPI Master SPI Slave 0
SPI Slave n-1
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If CTRLA.RUNSTDBY is zero during slave operation, all reception will be dropped, including the ongoing transaction.
25.6.7 Synchronization
Due to the asynchronicity between CLK_SERCOMx_APB and GCLK_SERCOMx_CORE, some registers must be
synchronized when accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete.
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following bits need synchronization when written:
zSoftware Reset bit in the Control A register (CTRLA.SWRST)
zEnable bit in the Control A register (CTRLA.ENABLE)
zReceiver Enable bit in the Control B register (CTRLB.RXEN)
CTRLB.RXEN behaves somewhat differently than described above. Refer to CTRLB for details.
Write-synchronization is denoted by the Write-Synchronized property in the register description.
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25.7 Register Summary
Offset Name Bit Pos.
0x00
CTRLA
7:0 RUNSTDBY MODE[2:0] ENABLE SWRST
0x01 15:8 IBON
0x02 23:16 DIPO[1:0] DOPO[1:0]
0x03 31:24 DORD CPOL CPHA FORM[3:0]
0x04
CTRLB
7:0 PLOADEN CHSIZE[2:0]
0x05 15:8 AMODE[1:0]
0x06 23:16 RXEN
0x07 31:24
0x08 DBGCTRL 7:0 DBGSTOP
0x09 Reserved
0x0A BAUD 7:0 BAUD[7:0]
0x0B Reserved
0x0C INTENCLR 7:0 RXC TXC DRE
0x0D INTENSET 7:0 RXC TXC DRE
0x0E INTFLAG 7:0 RXC TXC DRE
0x0F Reserved
0x10 STATUS 7:0 BUFOVF
0x11 15:8 SYNCBUSY
0x12 Reserved
0x13 Reserved
0x14
ADDR
7:0 ADDR[7:0]
0x15 15:8
0x16 23:16 ADDRMASK[7:0]
0x17 31:24
0x18 DATA 7:0 DATA[7:0]
0x19 15:8 DATA[8]
0x1A Reserved
0x1B Reserved
0x1C Reserved
0x1D Reserved
0x1E Reserved
0x1F Reserved
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25.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Refer to “Register Access Protection” on page 366
for details.
Some registers require synchronization when read and/or written. Write-synchronization is denoted by the Write-
Synchronized property in each individual register description. Refer to “Synchronization” on page 372 for details.
Some registers are enable-protected, meaning they can only be written when the USART is disabled. Enable-protection
is denoted by the Enable-Protected property in each individual register description.
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25.8.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00000000
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBit 31 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 30 – DORD: Data Order
This bit indicates the data order when a character is shifted out from the Data register.
0: MSB is transferred first.
1: LSB is transferred first.
This bit is not synchronized.
zBit 29 – CPOL: Clock Polarity
In combination with the Clock Phase bit (CPHA), this bit determines the SPI transfer mode.
0: SCK is low when idle. The leading edge of a clock cycle is a rising edge, while the trailing edge is a falling edge.
1: SCK is high when idle. The leading edge of a clock cycle is a falling edge, while the trailing edge is a rising edge.
This bit is not synchronized.
zBit 28 – CPHA: Clock Phase
In combination with the Clock Polarity bit (CPOL), this bit determines the SPI transfer mode.
Bit3130292827262524
DORD CPOL CPHA FORM[3:0]
Access R R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit2322212019181716
DIPO[1:0] DOPO[1:0]
Access R R R/W R/W R R R R/W
Reset00000000
Bit151413121110 9 8
IBON
AccessRRRRRRRR
Reset00000000
Bit76543210
RUNSTDBY MODE[2:0] ENABLE SWRST
Access R/W R R R/W R/W R/W R/W R/W
Reset00000000
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0: The data is sampled on a leading SCK edge and changed on a trailing SCK edge.
1: The data is sampled on a trailing SCK edge and changed on a leading SCK edge.
This bit is not synchronized.
Table 25-3. SPI Transfer Modes
zBits 27:24 – FORM[3:0]: Frame Format
Table 25-4 shows the various frame formats supported by the SPI. When a frame format with address is selected ,
the first byte received is checked against the ADDR register.
Table 25-4. Frame Format
zBits 23:22 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 21:20 – DIPO[1:0]: Data In Pinout
These bits define the data in (DI) pad configurations.
In master operation, DI is MISO.
In slave operation, DI is MOSI.
These bits are not synchronized.
Table 25-5. Data In Pino ut
zBits 19:18 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Mode CPOL CPHA Leading Edge Trailing Edge
0x0 0 0 Rising, sample Falling, change
0x1 0 1 Rising, change Falling, sample
0x2 1 0 Falling, sample Rising, chang e
0x3 1 1 Falling, change Rising, sample
FORM[3:0] Name Description
0x0 SPI SPI frame
0x1 -Reserved
0x2 SPI_ADDR SPI frame with address
0x3-0xF -Reserved
DIPO[1:0] Name Description
0x0 PAD[0] SERCOM PAD[0] is used as data input
0x1 PAD[1] SERCOM PAD[1] is used as data input
0x2 PAD[2] SERCOM PAD[2] is used as data input
0x3 PAD[3] SERCOM PAD[3] is used as data input
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zBit 17:16 – DOPO: Data Out Pinout
This bit defines the available pad configurations for data out (DO) and the serial clock (SCK). In slave operation,
the slave select line (_SS) is controlled by DOPO, while in master operation the _SS line is controlled by the port
configuration.
In master operation, DO is MOSI.
In slave operation, DO is MISO.
This bit is not synchronized.
Table 25-6. Data Out Pinout
zBits 15:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 8 – IBON: Immediate Buffer Overflow Notification
This bit controls when the buffer overflow status bit (STATUS.BUFOVF) is asserted when a buffer overflow occurs.
0: STATUS.BUFOVF is asserted when it occurs in the data stream.
1: STATUS.BUFOVF is asserted immediately upon buffer overflow.
zBit 7 – RUNSTDBY: Run In Standby
This bit defines the functionality in standby sleep mode.
These bits are not synchronized.
Table 25-7. Run In Standby Configuration
zBits 6:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:2 – MODE: Operating Mode
These bits must be written to 0x2 or 0x3 to select the SPI serial communication interface of the SERCOM.
0x2: SPI slave operation
0x3: SPI master operation
These bits are not synchronized.
zBit 1 – ENABLE: Enable
0: The peripheral is disabled or being disabled.
1: The peripheral is enabled or being enabled.
DOPO DO SCK Slave _SS Master _SS
0x0 SERCOM_PAD0 SERCOM_PAD1 SERCOM_PAD2 System configuration
0x1 SERCOM_PAD2 SERCOM_PAD3 SERCOM_PAD1 System configuration
0x2 SERCOM_PAD3 SERCOM_PAD1 SERCOM_PAD2 System configuration
0x3 SERCOM_PAD0 SERCOM_PAD3 SERCOM_PAD1 System configuration
RUNSTDBY Slave Master
0x0 Disabled. All reception is dropped,
including the ongoing transaction. Generic clock is disabled when ongoing transaction is
finished. All interrupts can wake up the device.
0x1 Wake on Receive Complete interrupt. Generic clock is enabled while in sleep modes. All
interrupts can wake up the device.
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Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY is cleared when the operation is complete.
This bit is not enable-protected.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the SERCOM, except DBGCTRL, to their initial state, and the SER-
COM will be disabled.
Writing a one to CTRL.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST
and STATUS.SYNCBUSY will both be cleared when the reset is complete.
This bit is not enable-protected.
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25.8.2 Control B
Name: CTRLB
Offset: 0x04
Reset: 0x00000000
Property: Write-Protected, Enable-Protected
zBits 31:18 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 17 – RXEN: Receiver Enable
0: The receiver is disabled or being enabled.
1: The receiver is enabled or it will be enabled when SPI is enabled.
Writing a zero to this bit will disable the SPI receiver immediately. The receive buffer will be flushed, data from
ongoing receptions will be lost and STATUS.BUFOVF will be cleared.
Writing a one to CTRLB.RXEN when the SPI is disabled will set CTRLB.RXEN immediately. When the SPI is
enabled, CTRLB.RXEN will be cleared, STATUS.SYNCBUSY will be set and remain set until the receiver is
enabled. When the receiver is enabled CTRLB.RXEN will read back as one.
Writing a one to CTRLB.RXEN when the SPI is enabled will set STATUS.SYNCBUSY, which will remain set until
the receiver is enabled, and CTRLB.RXEN will read back as one.
This bit is not enable-protected.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
RXEN
AccessR/WR/WR/WRRRRR
Reset00000000
Bit151413121110 9 8
AMODE[1:0]
AccessR/WR/WRRRRRR
Reset00000000
Bit76543210
PLOADEN CHSIZE[2:0]
Access R R/W R R R R/W R/W R/W
Reset00000000
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zBit 16 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 15:14 – AMODE: Address Mode
These bits set the slave addressing mode when the frame format (CTRLA.FORM) with address is used. They are
unused in master mode.
Table 25-8. Address Mode
zBits 13:7 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 6 – PLOADEN: Slave Data Preload Enable
Setting this bit will enable preloading of the slave shift register when there is no transfer in progress. If the _SS line
is high when DATA is written, it will be transferred immediately to the shift register.
zBits 5:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 2:0 – CHSIZE[2:0]: Character Size
Table 25-9. Character Size
AMODE[1:0] Name Description
0x0 MASK ADDRMASK is used as a mask to the ADDR register
0x1 2_ADDRS The slave responds to the two unique addresses in ADDR and ADDRMASK
0x2 RANGE The slave responds to the range of addresses between and including ADDR
and ADDRMASK. ADDR is the upper limit
0x3 Reserved
CHSIZE[2:0] Name Description
0x0 8BIT 8 bits
0x1 9BIT 9 bits
0x2-0x7 Reserved
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25.8.3 Debug Control
Name: DBGCTRL
Offset: 0x08
Reset: 0x00
Property: Write-Protected
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – DBGSTOP: Debug Stop Mode
This bit controls the functionality when the CPU is halted by an external debugger.
0: The baud-rate generator continues normal operation when the CPU is halted by an external debugger.
1: The baud-rate generator is halted when the CPU is halted by an external debugger.
Bit76543210
DBGSTOP
AccessRRRRRRRR/W
Reset00000000
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25.8.4 Baud Rate
Name: BAUD
Offset: 0x0A
Reset: 0x00
Property: Write-Protected, Enable-Protected
zBits 7:0 – BAUD: Baud Register
These bits control the clock generation, as described in the SERCOM “Clock Generation – Baud-Rate Generator”
on page 335.
Bit76543210
BAUD[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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25.8.5 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x0C
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – RXC: Receive Complete Interrupt Enable
0: Receive Complete interrupt is disabled.
1: Receive Complete interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Receive Complete Interrupt Enable bit, which disables the Receive Complete
interrupt.
zBit 1 – TXC: Transmit Complete Interrupt Enable
0: Transmit Complete interrupt is disabled.
1: Transmit Complete interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Transmit Complete Interrupt Enable bit, which disable the Transmit Complete
interrupt.
zBit 0 – DRE: Data Register Empty Interrupt Enable
0: Data Register Empty interrupt is disabled.
1: Data Register Empty interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Data Register Empty Interrupt Enable bit, which disables the Data Register
Empty interrupt.
Bit76543210
RXC TXC DRE
AccessRRRRRR/WR/WR/W
Reset00000000
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25.8.6 Interrupt Enable Set
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x0D
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – RXC: Receive Complete Interrupt Enable
0: Receive Complete interrupt is disabled.
1: Receive Complete interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Receive Complete Interrupt Enable bit, which enables the Receive Complete
interrupt.
zBit 1 – TXC: Transmit Complete Interrupt Enable
0: Transmit Complete interrupt is disabled.
1: Transmit Complete interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Transmit Complete Interrupt Enable bit, which enables the Transmit Complete
interrupt.
zBit 0 – DRE: Data Register Empty Interrupt Enable
0: Data Register Empty interrupt is disabled.
1: Data Register Empty interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Data Register Empty Interrupt Enable bit, which enables the Data Register
Empty interrupt.
Bit76543210
RXC TXC DRE
AccessRRRRRR/WR/WR/W
Reset00000000
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25.8.7 Interrupt Flag S tatus and Clear
Name: INTFLAG
Offset: 0x0E
Reset: 0x00
Property: -
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – RXC: Receive Complete
This flag is cleared by reading the Data (DATA) register or by disabling the receiver.
This flag is set when there are unread data in the receive buffer. If address matching is enabled, the first data
received in a transaction will be an address.
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
zBit 1 – TXC: Transmit Complete
This flag is cleared by writing a one to it or by writing new data to DATA.
In master mode, this flag is set when the data have been shifted out and there are no new data in DATA.
In slave mode, this flag is set when the _SS pin is pulled high. If address matching is enabled, this flag is only set
if the transaction was initiated with an address match.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the flag.
zBit 0 – DRE: Data Register Empty
This flag is cleared by writing new data to DATA.
This flag is set when DATA is empty and ready for new data to transmit.
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
Bit76543210
RXC TXC DRE
AccessRRRRRRR/WR
Reset00000000
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25.8.8 Status
Name: STATUS
Offset: 0x10
Reset: 0x0000
Property: –
zBit 15 – SYNCBUSY: Synchronization Busy
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is in progress.
zBits 14:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – BUFOVF: Buffer Overflow
Reading this bit before reading DATA will indicate the error status of the next character to be read.
This bit is cleared by writing a one to the bit or by disabling the receiver.
This bit is set when a buffer overflow condition is detected. An overflow condition occurs if the two-level receive
buffer is full when the last bit of the incoming character is shifted into the shift register. All characters shifted into
the shift registers before the overflow condition is eliminated by reading DATA will be lost.
When set, the corresponding RxDATA will be 0.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear it.
zBits 1:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit151413121110 9 8
SYNCBUSY
AccessRRRRRRRR
Reset00000000
Bit76543210
BUFOVF
AccessRRRRRR/WRR
Reset00000000
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25.8.9 Address
Name: ADDR
Offset: 0x14
Reset: 0x00000000
Property: Write-Protected, Enable-Protected
zBits 31:24 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 23:16 – ADDRMASK[7:0]: Address Mask
These bits hold the address mask when the transaction format (CTRLA.FORM) with address is used.
zBits 15:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:0 – ADDR[7:0]: Address
These bits hold the address when the transaction format (CTRLA.FORM) with address is used.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
ADDRMASK[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
ADDR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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25.8.10 Data
Name: DATA
Offset: 0x18
Reset: 0x0000
Property: –
zBits 15:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 8:0 – DATA[8:0]: Data
Reading these bits will return the contents of the receive data buffer. The register should be read only when the
Receive Complete Interrupt Flag bit in the Interrupt Flag Status and Clear register (INTFLAG.RXCIF) is set.
Writing these bits will write the transmit data buffer. This register should be written only when the Data Register
Empty Interrupt Flag bit in the Interrupt Flag Status and Clear register (INTFLAG.DREIF) is set.
Bit151413121110 9 8
DATA[8]
AccessRRRRRRRR/W
Reset00000000
Bit76543210
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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26. SERCOM I2C – SERCOM Inter-Integrated Circuit
26.1 Overview
The inter-integrated circuit (I2C) interface is one of the available modes in the serial communication interface (SERCOM).
Refer to “SERCOM – Serial Communication Interface” on page 332 for details.
The I2C interface uses the SERCOM transmitter and receiver configured as shown in Figure 26-1. Fields shown in capital
letters are registers accessible by the CPU, while lowercase fields are internal to the SERCOM. Each side, master and
slave, depicts a separate I2C interface containing a shift register, a transmit buffer and a receive buffer. In addition, the
I2C master uses the SERCOM baud-rate generator, while the I2C slave uses the SERCOM address match logic.
26.2 Features
zMaster or slave operation
zPhilips I2C compatible
zSMBus™ compatible
z100kHz and 400kHz support at low system clock frequencies
zPhysical interface includes:
zSlew-rate limited outputs
zFiltered inputs
zSlave operation:
zOperation in all sleep modes
zWake-up on address match
zAddress match in hardware for:
z7-bit unique address and/or 7-bit general call addres s
z7-bit address range
zTwo unique 7-bit addresses
26.3 Block Diagram
Figure 26-1. I2C Single-Master Single-Slave Interconnection
shift register shift register
Master Slave
SDA
SCL
Tx DATA
Rx DATA
Tx DATA
Rx DATA ==
ADDR/ADDRMASKBAUD
baud rate generator SCL low hold
0
0
0
0
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26.4 Signal Description
Refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One signal
can be mapped on several pins. Note that not all the pins are I2C pins. Refer to Table 5-1 for details on the pin type for
each pin.
26.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
26.5.1 I/O Lines
Using the SERCOM’s I/O lines requires the I/O pins to be configured. Refer to “PORT” on page 284 for details.
26.5.2 Power Management
The I2C will continue to operate in any sleep mode whe re the selected source clock is running. I2C interrupts can be used
to wake up the device from sleep modes. The events can trigger other operations in the system without exiting sleep
modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
26.5.3 Clocks
The SERCOM bus clock (CLK_SERCOMx_APB, where i represents the specific SERCOM instance number) is enabled
by default, and can be enabled and disabled in the Power Manager. Refer to “PM – Power Manager” on page 100 for
details.
The SERCOM bus clock (CLK_SERCOMx_APB) is enabled by default, and can be enabled and disabled in the Power
Manager. Refer to “PM – Power Manager” on page 100 for details.
Two generic clocks are used by the SERCOM (GCLK_SERCOMx_CORE and GCLK_SERCOM_SLOW). The core clock
(GCLK_SERCOMx_CORE) is required to clock the SERCOM while operating as a master, while the slow clock
(GCLK_SERCOM_SLOW) is required only for certain functions. These clocks must be configured and enabled in the
Generic Clock Controller (GCLK) before using the SERCOM. Refer to “GCLK – Generic Clock Controller” on page 78 for
details.
These generic clocks are asynchronous to the SERCOM bus clock (CLK_SERCOMx_APB). Due to this asynchronicity,
writes to certain registers will require synchronization between the clock domains. Refer to the “Synchronization” on page
402 section for further details.
26.5.4 DMA
Not applicable.
26.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the I2C interrupts requires the Interrupt Controller
to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
26.5.6 Events
Not applicable.
Signal Name Type Description
PAD[0] Digital I/O SDA
PAD[1] Digital I/O SCL
PAD[2] Digital I/O SDA_OUT (4-wire)
PAD[3] Digital I/O SDC_OUT (4-wire)
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26.5.7 Debug Operation
When the CPU is halted in debug mode, the I2C interface continues normal operation. If the I2C interface is configured in
a way that requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss
may result during debugging. The I2C interface can be forced to halt operation during debugging.
Refer to the DBGCTRL register for details.
26.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following registers:
zInterrupt Flag Status and Clear register (INTFLAG)
zStatus register (STATUS)
zAddress register (ADDR)
zData register (DATA)
Write-protection is denoted by the Write-Protected property in the register description.
Write-protection does not apply to accesses through en external debugger. Refer to“PAC – Peripheral Access Controller”
on page 27 for details.
26.5.9 Analog Connections
Not applicable.
26.6 Functional Description
26.6.1 Principle of Operation
The I2C interface uses two physical lines for communication:
zSerial Data Line (SDA) for packet transfer
zSerial Clock Line (SCL) for the bus clock
A transaction starts with the start condition, followed by a 7-bit address and a direction bit (read or write) sent from the I2C
master. The addressed I2C slave will then acknowledge (ACK) the address, and data packet transactions can
commence. Every 9-bit data packet consists of 8 data bits followed by a one-bit reply indicating whether the data was
acknowledged or not. In the event that a data packet is not acknowledged (NACK), whether sent from the I2C slave or
master, it will be up to the I2C master to either terminate the co nnection by issuing the stop condition, or send a repeated
start if more data is to be transceived.
Figure 26-2 illustrates the possible transaction formats and Figure 26-3 explains the legend used.
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Figure 26-2. Basic I2C Transaction Diagram
Figure 26-3. Transa ction Diagram Syntax
26.6.2 Basic Operation
26.6.2.1 Initialization
The following registers are enable-protected, meaning they can be written only when the I2C interface is disabled
(CTRLA.ENABLE is zero):
zControl A register (CTRLA), except Enable (CTRLA.ENABLE) and Software Reset (CTRLA.SWRST)
zControl B register (CTRLB), except Acknowledge Action (CTRLB.ACKACT) and Command (CTRLB.CMD)
zBaud Rate register (BAUD)
zAddress register (ADDR) while in slave operation
PS ADDRESS
6 ... 0
R/W ACK ACK
7 ... 0
DATA ACK/NACK
7 ... 0
DATA
SDA
SCL
S A A/AR/WADDRESS DATA PA DATA
Address Packet Data Packet #0
Transaction
Data Packet #1
Direction
"0"
"1"
Master Drives Bus
Slave Drives Bus
Either Master or Slave
Drives Bus
S
Sr
P
START Condition
Repeated START Condition
STOP Condition
A
A
Acknowledge (ACK)
Not Acknowledge (NACK)
R
W
Master Read
Master Write
Data Packet Direction:
"0"
"1"
Acknowledge:
Bus Driver: Special Bus Conditions
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Any writes to these bits or registers when the I2C interface is enabled or is being enabled (CTRLA.ENABLE is one) will
be discarded. Writes to these registers while the I2C interface is being disabled will be completed after the disabling is
complete.
Enable-protection is denoted by the Enable-Protection property in the register description.
Before the I2C interface is enabled, it must be configured as outlined by the following steps:
I2C mode in master or slave operation must be selected by writing 0x4 or 0x5 to the Operating Mode bit group in the
Control A register (CTRLA.MODE)
zSCL low time-out can be enabled by writing to the SCL Low Time-Out bit in the Control A register
(CTRLA.LOWTOUT)
zIn master operation, the inactive bus time-out can be set in the Inactive Time-Out bit group in the Control A
register (CTRLA.INACTOUT)
zHold time for SDA can be set in the SDA Hold Time bit group in the Control A register (CTRLA.SDAHOLD)
zSmart operation can be enabled by writing to the Smart Mode Enable bit in the Control B register
(CTRLB.SMEN)
zIn slave operation, the address match configuration must be set in the Address Mode bit group in the
Control B register (CTRLB.AMODE)
zIn slave operation, the addresses must be set, according to the selected address configuration, in the
Address and Address Mask bit groups in the Address register (ADDR.ADDR and ADDR.ADDRMASK)
zIn master operation, the Baud Rate register (BAUD) must be written to generate the desired baud rate
26.6.2.2 Enabling, Disabling and Resetting
The I2C interface is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The I2C
interface is disabled by writing a zero to CTRLA.ENABLE. The I2C interface is reset by writing a one to the Software
Reset bit in the Control A register (CTRLA.SWRST). All registers in the I2C interface, except DBGCTRL, will be reset to
their initial state, and the I2C interface will be disabled. Refer to CTRLA for details.
26.6.2.3 I2C Bus State Logic
The bus state logic includes several logic blocks that continuously monitor the activity on the I2C bus lines in all sleep
modes. The start and stop detectors and the bit counter are all essential in the process of determining the current bus
state. The bus state is determined according to the state diagram shown in Figure 26-4. Software can get the current bus
state by reading the Master Bus State bits in the Status register (STATUS.BUSSTATE). The value of
STATUS.BUSSTATE in the figure is shown in binary.
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Figure 26-4 . Bus State Diagram
The bus state machine is active when the I2C master is enabled. After the I2C master has been enabled, the bus state is
unknown. From the unknown state, the bus state machine can be forced to enter the idle state by writing to
STATUS.BUSSTATE accordingly. However, if no action is taken by software, the bus state will become idle if a stop
condition is detected on the bus. If the inactive bus time-out is enabled, the bus state will change from unknown to idle on
the occurrence of a time-out. Note that after a known bus state is established, the bus state logic will not re-enter the
unknown state from either of the other states.
When the bus is idle it is ready for a new transaction. If a start condition is issued on the bus by another I2C master in a
multimaster setup, the bus becomes busy until a stop condition is detected. The stop condition will cause the bus to re-
enter the IDLE state. If the inactive bus time-out (SMBus) is enabled, the bus state will change from busy to idle on the
occurrence of a time-out. If a start condition is generated internally by writing the Address bit group in the Address
register (ADDR.ADDR) while in idle state, the owner state is entered. If the complete transaction was performed without
interference, i.e., arbitration not lost, the I2C master is allowed to issue a stop condition, which in turn will cause a change
of the bus state back to idle. However, if a packet collision is detected, the arbitration is assumed lost and the bus state
becomes busy until a stop condition is detected.
A repeated start condition will change the bus state only if arbitration is lost while issuing a repeated start.
26.6.2.4 Clock Generation
The Master I2C clock (SCL) frequency is determined by a number of factors. The low (TLOW) and high (T_HIGH) times are
determined by the Baud Rate register (BAUD), while the rise (TRISE) and fall (TFALL) times are determined by the bus
topology. Because of the wired-AND logic of the bus, TFALL will be considered as part of TLOW. Likewise, TRISE will be in a
state between TLOW and THIGH until a high state has been detected.
P + Timeout
RESET
Wri te ADDR
(S)
IDLE
(0b01)
SBUSY
(0b11)
P + Ti meout
UNKNOWN
(0b00)
OWNER
(0b10)
Arbitration
Lost
Command P
Wri te ADDR (Sr)
Sr
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Figure 26-5. SCL Timing
The following parameters are timed using the SCL low time period. This comes from the Master Baud Rate Low bit group
in the Baud Rate register (BAUD.BAUDLOW) when non-zero, or the Master Baud Rate bit group in the Baud Rate
register (BAUD.BAUD) when BAUD.BAUDLOW is zero.
zTLOW – Low period of SCL clock
zTSU;STO – Set-up time for stop condition
zTBUF – Bus free time between stop and start conditions
zTHD;STA – Hold time (repeated) start condition
zTSU;STA – Set-up time for repeated start condition
zTHIGH is timed using the SCL high time count from BAUD.BAUD
zTRISE is determined by the bus impedance; for internal pull-ups. Refer to “Electrical Characteristics” on page
562 for details.
zTFALL is determined by the open-drain current limit and bus impedance; can typically be regarded as zero.
Refer to “Electrical Characteristics” on page 562 for details.
The SCL frequency is given by:
When BAUD.BAUDLOW is zero, the BAUD.BAUD value is used to time both SCL high and SCL low. In this case the
following formula will give the SCL frequency:
When BAUD.BAUDLOW is non-zero, the following formula is used to determine the SCL frequency:
T
HD;STA
T
LOW
T
HIGH
T
BUF
T
RISE
SCL
SDA
T
SU;STO
T
SU;STA
PS Sr
T
FALL
RISEHIGHLOW
SCL TTT
f++
=1
RISE
GCLK
GCLK
SCL TBAUD f
f
f++
=)5(2
RISE
GCLK
GCLK
SCL TBAUDLOWBAUD f
f
f+++
=10
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When BAUDLOW is non-zero, the following formula can be used to determine the SCL frequency:
The following formulas can be used to determine the SCL TLOW and THIGH times:
26.6.2.5 I2C Master Operation
The I2C master is byte-oriented and interrupt based. The number of interrupts generated is kept at a minimum by
automatic handling of most events. Auto-triggering of operations and a special smart mode, which can be enabled by
writing a one to the Smart Mode Enable bit in the Control A register (CTRLA.SMEN), are included to reduce software
driver complexity and code size.
The I2C master operates according to the behavior diagram shown in Figure 26-6. The circles with a capital letter M
followed by a number (M1, M2... etc.) indicate which node in the figure the bus logic can jump to based on software or
hardware interaction.
This diagram is used as reference for the description of the I2C master operation throughout the document.
RISE
GCLK
GCLK
SCL TBAUDLOWBAUD f
f
f+++
=10
GCLK
low f
BAUDLOWBAUD
T5. +
=
GCLK
HIGH fBAUDBAUD
T5. +
=
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Figure 26-6. I2C Ma ster Behavioral Diagram
Transmitting Address Packets
The I2C master starts a bus transaction by writing ADDR.ADDR with the I2C slave address and the direction bit. If the bus
is busy, the I2C master will wait until the bus becomes idle before continuing the operation. When the bus is idle, the I2C
master will issue a start condition on the bus. The I2C master will then transmit an address packet using the address
written to ADDR.ADDR.
After the address packet has been transmitted by the I2C master, one of four cases will arise, based on arbitration and
transfer direction.
Case 1: Arbitration lost or bus error during address packet transmission
If arbitration was lost during transmission of the address packet, the Master on Bus bit in the Interrupt Flag register
(INTFLAG.MB) and the Arbitration Lost bit in the Status register (STATUS.ARBLOST) are both set. Serial d ata output to
SDA is disabled, and the SCL is released, which disables clock stretching. In effect the I2C master is no longer allowed to
perform any operation on the bus until the bus is idle again. A bus error will behave similarly to the arbitration lost
condition. In this case, the MB interrupt flag and Master Bus Error bit in the Status register (STATUS.BUSERR) are both
set in addition to STATUS.ARBLOST.
The Master Received Not Acknowledge bit in the Status register (STATUS.RXNACK) will always contain the last
successfully received acknowledge or not acknowledge indication.
In this case, software will typically inform the application code of the condition and then clear the interrupt flag before
exiting the interrupt routine. No other flags have to be cleared at this poin t, because all flags will be cleared automatically
the next time the ADDR.ADDR register is written.
Case 2: Address packet transmit complete – No ACK received
If no I2C slave device responds to the address packet, then the INTFLAG.MB interrupt flag is set and STATUS.RXNACK
is set. The clock hold is active at this point, preventing further activity on the bus.
IDLE SBUSYBUSY P
Sr
P
M3
M3
M2
M2
M1
M1
RDATA
ADDRESS
W
A/ADATA
Wait for
IDLE
APPLICATION
S
W
S
W
Sr
P
M3
M2
BUSY
M4
A
S
W
A/A
A/A
A/A
M4
A
IDLE
IDLE
MASTER READ INTERRUPT + HOLD
MASTER WRITE INTERRUPT + HOLD
S
W
S
W
S
W
BUSYR/W
S
WSoftware interaction
The master provides data
on the bus
Addressed slave provides
data on the bus
A
A
R/W
BUSY
M4
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The missing ACK response can indicate that the I2C slave is busy with other tasks or sleeping and, therefore, not able to
respond. In this event, the next step can be either issuing a stop condition (recommended) or resending the address
packet by using a repeated start condition. However, the reason for the missing acknowledge can be that an invalid I2C
slave address has been used or that the I2C slave is for some reason disconnected or faulty. If using SMBus logic, the
slave must ACK the address, and hence no action means the slave is not available on the bus.
Case 3: Address packet transmit complete – Write packet, Master on Bus set
If the I2C master receives an acknowledge response from the I2C slave, INTFLAG.MB is set and STATUS.RXNACK is
cleared. The clock hold is active at this point, preventing further activity on the bus.
In this case, the software implementation becomes highly protocol dependent. Three possible actions can enable the I2C
operation to continue. The three options are:
zThe data transmit operation is initiated by writing the data byte to be transmitted into DATA.DATA.
zTransmit a new address packet by writing ADDR.ADDR. A repeated start condition will automatically be
inserted before the address packet.
zIssue a stop condition, consequently terminating the transaction.
Case 4: Address packet transmit complete – Read packet, Slave on Bus set
If the I2C master receives an ACK from the I2C slave, the I2C master proceeds to receive the next byte of data from the
I2C slave. When the first data byte is received, the Slave on Bus bit in the Interrupt Flag register (INTFLAG.SB) is set and
STATUS.RXNACK is cleared. The clock hold is active at this point, preventing further activity on the bus.
In this case, the software implementation becomes highly protocol dependent. Three possible actions can enable the I2C
operation to continue. The three options are:
zLet the I2C master continue to read data by first acknowledging the dat a received. This is automatically done
when reading DATA.DATA if the smart mode is enabled.
zTransmit a new address packet.
zTerminate the transaction by issuing a stop condition.
An ACK or NACK will be automatically transmitted for the last two alternatives if smart mode is enabled. The
Acknowledge Action bit in the Control B register (CTRLB.ACKACT) determines whether ACK or NACK should be sent.
Transmitting Data Packets
When an address packet with direction set to write (STATUS.DIR is zero) has been successfully transmitted,
INTFLAG.MB will be set and the I2C master can start transmitting data by writing to DATA.DATA. The I2C master
transmits data via the I2C bus while continuously monitoring for packet collisions. If a collision is detected, the I2C master
looses arbitration and STATUS.ARBLOST is set. If the transmit was successful, the I2C master automatically receives an
ACK bit from the I2C slave and STATUS.RXNACK will be cleared. INTFLAG.MB will be set in both cases, regardless of
arbitration outcome.
Testing STATUS.ARBLOST and handling the arbitration lost condition in the beginning of the I2C Master on Bus interrupt
is recommended. This can be done, as there is no difference between handling address and data packet arbitration.
STATUS.RXNACK must be checked for each data packet transmitted before the next data packet transmission can
commence. The I2C master is not allowed to continue transmitting data packets if a NACK is given from the I2C slave.
Receiving Data Packets
When INTFLAG.SB is set, the I2C master will already have received one data packet. The I2C master must respond by
sending either an ACK or NACK. Sending a NACK might not be successfully executed as arbitration can be lost during
the transmission. In this case, a loss of arbitration will cause INTFLAG.SB to not be set on completion. Instead,
INTFLAG.MB will be used to indicate a change in arbitration. Handling of lost arbitration is the same as for data bit
transmission.
26.6.2.6 I2C Slave Operation
The I2C slave is byte-oriented and interrupt-based. The number of interrupts generated is kept at a minimum by
automatic handling of most events. Auto triggering of operations and a special smart mode, which can be enabled by
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writing a 1 to the Smart Mode Enable bit in the Control A register (CTRLA.SMEN), are included to reduce software’s
complexity and code size.
The I2C slave operates according to the behavior diagram shown in Figure 26-7. The circles with a capital S followed by
a number (S1, S2... etc.) indicate which node in the figure the bus logic can jump to based on software or hardware
interaction.
This diagram is used as reference for the description of the I2C slave operation throughout the document.
Figure 26-7. I2C Slav e Behavioral Diagram
Receiving Address Packets
When the I2C slave is properly configured, it will wait for a start condition to be detected. When a start condition is
detected, the successive address packet will be received and checked by the address match logic. If the received
address is not a match, the packet is rejected and the I2C slave waits for a new start condition. The I2C slave Address
Match bit in the Interrupt Flag register (INTFLAG.AMATCH) is set when a start condition followed by a valid address
packet is detected. SCL will be stretched until the I2C slave clears INTFLAG.AMATCH. Because the I2C slave holds the
clock by forcing SCL low, the software is given unlimited time to respond to the address.
The direction of a transaction is determined by reading the Read / Write Direction bit in the Status register
(STATUS.DIR), and the bit will be updated only when a valid address packet is received.
If the Transmit Collision bit in the Status register (STATUS.COLL) is set, this indicates that the last packet addressed to
the I2C slave had a packet collision. A collision causes the SDA and SCL lines to be released without any notification to
software. The next AMATCH interrupt is, therefore, the first indication of the previous packet’s collision. Collisions are
intended to follow the SMBus Address Resolution Protocol (ARP).
After the address packet has been received from the I2C master, one of two cases will arise based on transfer direction.
Case 1: Address packet accepted – Read flag set
The STATUS.DIR bit is one, indicating an I2C master read operation. The SCL line is forced low, stretching the bus clock.
If an ACK is sent, I2C slave hardware will set the Data Ready bit in the Interrupt Flag register (INTFLAG.DRDY),
S
S3
ADDRESS
S2
A
S1
R
W
DATA A/A
DATA
P
S2
Sr
S3
P
S2
Sr
S3
SLAVE ADDRESS INTERRUPT SLAVE DATA INTERRUPT
A
S
W
S
W
S
W
S
W
A/A A/A
A
S1
S
W
Interrupt on STOP
Condition Enabled
S1
SLAVE STOP INTERRUPT
S
WSoftware interaction
The master provides data
on the bus
Addressed slave provides
data on the bus
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indicating data are needed for transmit. If not acknowledge is sent, the I2C slave will wait for a new start condition and
address match.
Typically, software will immediately acknowledge the address packet by sending an ACK/NACK bit. The I2C slave
command CTRLB.CMD = 3 can be used for both read and write operation as the command execution is dependent on
the STATUS.DIR bit.
Writing a one to INTFLAG.AMATCH will also cause an ACK/NACK to be sent corresponding to the CTRLB.ACKACT bit.
Case 2: Address packet accepted – Write flag set
The STATUS.DIR bit is cleared, indicating an I2C master write operation. The SCL line is forced low, stretching the bus
clock. If an ACK is sent, the I2C slave will wait for data to be received. Data, repeated start or stop can be received.
If not acknowledge is sent, the I2C slave will wait for a new start condition and address match.
Typically, software will immediately acknowledge the address packet by sending an ACK/NACK bit. The I2C slave
command CTRLB.CMD = 3 can be used for both read and write operation as the command execution is dependent on
STATUS.DIR.
Writing a one to INTFLAG.AMATCH will also cause an ACK/NACK to be sent corresponding to the CTRLB.ACKACT bit.
Receiving and Transmitting Data Packets
After the I2C slave has received an address packet, it will respond according to the direction either by waiting for the data
packet to be received or by starting to send a data packet by writing to DATA.DATA. When a data packet is received or
sent, INTFLAG.DRDY will be set. Then, if the I2C slave was receiving data, it will send an acknowledge according to
CTRLB.ACKACT.
Case 1: Data received
INTFLAG.DRDY is set, and SCL is held low pending SW interaction.
Case 2: Data sent
When a byte transmission is successfully completed, the INTFLAG.DRDY interrupt flag is set. If NACK is received, the
I2C slave must expect a stop or a repeated start to be received. The I2C slave must release the data line to allow the I2C
master to generate a stop or repeated start.
Upon stop detection, the Stop Received bit in the Interrupt Flag register (INTFLAG.PREC) will be set and the I2C slave
will return to the idle state.
26.6.3 Additional Features
26.6.3.1 SMBus
The I2C hardware incorporates hardware SCL low time-out, which allows a time-out to occur if the clock line is held low
too long. This time-out is driven by the GCLK_SERCOM_SLOW clock. The I2C interface also allows for a SMBus
compatible SDA hold time.
26.6.3.2 Smart Mode
The I2C interface incorporates a special smart mode that simplifies application code and minimizes the user interaction
needed to keep hold of the I2C protocol. The smart mode accomplishes this by letting the reading of DATA.DATA
automatically issue an ACK or NACK based on the state of CTRLB.ACKACT.
26.6.3.3 4-Wire Mode
Setting the Pin Usage bit in the Control A register (CTRLA.PINOUT) for master or slave to 4-wire mode enables
operation as shown in Figure 26-8. In this mode, the internal I2C tri-state drivers are bypassed, and an external, I2C-
compliant tri-state driver is needed when connecting to an I2C bus.
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Figure 26-8. I2C Pad Interface
26.6.3.4 Quick Command
Setting the Quick Command Enable bit in the Control B register (CTRLB.QCEN) enables quick command. When quick
command is enabled, the corresponding interrupt flag is set immediately after the slave acknowledges the address. At
this point, the software can either issue a stop command or a repeated start by writing CTRLB.CMD or ADDR.ADDR.
26.6.4 Interrupts
The I2C slave has the following interrupt sources:
zData Ready
zAddress Match
zStop Received
The I2C master has the following interrupt sources:
zSlave on Bus
zMaster on Bus
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the I2C is reset. See INTFLAG for details on how to clear interrupt flags.
The I2C has one common interrupt request line for all the interrupt sources. The user must read INTFLAG to determine
which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to “Nested Vector Interrupt
Controller” on page 24 for details.
26.6.5 Sleep Mode Operation
During I2C master operation, the generic clock (GCLK_SERCOMx_CORE) will continue to run in idle sleep mode. If the
Run In Standby bit in the Control A register (CTRLA.RUNSTDBY) is one, the GLK_SERCOMx_CORE will also run in
standby sleep mode. Any interrupt can wake up the device.
If CTRLA.RUNSTDBY is zero during I2C master operation, the GLK_SERCOMx_CORE will be disabled when an
ongoing transaction is finished. Any interrupt can wake up the device.
During I2C slave operation, writing a one to CTRLA.RUNSTDBY will allow the Address Match interrupt to wake up the
device.
In I2C slave operation, all receptions will be dropped when CTRLA.RUNSTDBY is zero.
SCL/SDA
pad
I2C
Driver
SCL_OUT/
SDA_OUT
pad
PINOUT
PINOUT
SCL_IN/
SDA_IN
SCL_OUT/
SDA_OUT
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26.6.6 Synchronization
Due to the asynchronicity between CLK_SERCOMx_APB and GCLK_SERCOMx_CORE, some registers must be
synchronized when accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete.
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following register needs synchronization when written:
zData (DATA) when in smart mode
The following bits need synchronization when written:
zSoftware Reset bit in the Control A register (CTRLA.SWRST)
zEnable bit in the Control A register (CTRLA.ENABLE)
zWrite to Bus State bits in the Status register (STATUS.BUSSTATE)
zAddress bits in the Address register (ADDR.ADDR) when in master operation
Write-synchronization is denoted by the Write-Synchronized property in the register description.
The following register needs synchronization when read:
zData (DATA) when in smart mode
Read-synchronization is denoted by the Read-Synchronized property in the register description.
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26.7 Register Summary
Table 26-1. Register Summary – Slave Mode
Offset Name Bit
Pos.
0x00
CTRLA
7:0 RUNSTDBY MODE[2:0]=100 ENABLE SWRST
0x01 15:8
0x02 23:16 SDAHOLD[1:0] PINOUT
0x03 31:24 LOWTOUT
0x04
CTRLB
7:0
0x05 15:8 AMODE[1:0] SMEN
0x06 23:16 ACKACT CMD[1:0]
0x07 31:24
0x08 Reserved
... Reserved
0x0B Reserved
0x0C INTENCLR 7:0 DRDY AMATCH PREC
0x0D INTENSET 7:0 DRDY AMATCH PREC
0x0E INTFLAG 7:0 DRDY AMATCH PREC
0x0F Reserved
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0x10
STATUS
7:0 CLKHOLD LOWTOUT SR DIR RXNACK COLL BUSERR
0x11 15:8 SYNCBUSY
0x12 Reserved
0x13 Reserved
0x14
ADDR
7:0 ADDR[6:0] GENCEN
0x15 15:8
0x16 23:16 ADDRMASK[6:0]
0x17 31:24
0x18
DATA
7:0 DATA[7:0]
0x19 15:8
Table 26-1. Register Summary – Slave Mode (Continu ed)
Offset Name Bit
Pos.
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Table 26-2. Register Summary – Master Mode
Offset Name Bit
Pos
0x00
CTRLA
7:0 RUNSTDBY MODE[2:0]=101 ENABLE SWRST
0x01 15:8
0x02 23:16 SDAHOLD[1:0] PINOUT
0x03 31:24 LOWTOUT INACTOUT[1:0]
0x04
CTRLB
7:0
0x05 15:8 QCEN SMEN
0x06 23:16 ACKACT CMD[1:0]
0x07 31:24
0x08 DBGCTRL 7:0 DBGSTOP
0x09 Reserved
0x0A
BAUD
7:0 BAUD[7:0]
0x0B 15:8 BAUDLOW[7:0]
0x0C INTENCLR 7:0 SB MB
0x0D INTENSET 7:0 SB MB
0x0E INTFLAG 7:0 SB MB
0x0F Reserved
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0x10
STATUS
7:0 CLKHOLD LOWTOUT BUSSTATE[1:0] RXNACK ARBLOST BUSERR
0x11 15:8 SYNCBUSY
0x12 Reserved
0x13 Reserved
0x14
ADDR
7:0 ADDR[7:0]
0x15 15:8
0x16 Reserved
0x17 Reserved
0x18
DATA
7:0 DATA[7:0]
0x19 15:8
Table 26-2. Register Summary – Master Mode (Continued)
Offset Name Bit
Pos
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26.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Please refer to“Register Access Protection” on page
391 for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Write-Synchronized
or the Read-Synchronized property in each individual register description. Please refer to “Synchronization” on page 402
for details.
Some registers are enable-protected, meaning they can only be written when the I2C is disabled. Enable-protection is
denoted by the Enable-Protected property in each individual register description.
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26.8.1 I2C Slave Register Description
26.8.1.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00000000
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBit 31 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 30 – LOWTOUT: SCL Low Time-Out
This bit enables the SCL low time-out. If SCL is held low for 25ms-35ms, the slave will release its clock hold, if
enabled, and reset the internal state machine. Any interrupts set at the time of time-out will remain set.
0: Time-out disabled.
1: Time-out enabled.
This bit is not synchronized.
zBits 29:22 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 21:20 – SDAHOLD[1:0]: SDA Hold Time
These bits define the SDA hold time with respect to the negative edge of SCL.
Bit3130292827262524
LOWTOUT
AccessRR/WRRRRRR
Reset00000000
Bit2322212019181716
SDAHOLD[1:0] PINOUT
Access R R R/W R/W R R R R/W
Reset00000000
Bit 15 14 13 12 11 10 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
RUNSTDBY MODE[2:0]=100 ENABLE SWRST
Access R/W R R R/W R/W R/W R/W R/W
Reset00000000
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Table 26-3. SDA Hold Time
These bits are not synchronized.
zBits 19:17 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 16 – PINOUT: Pin Usage
This bit sets the pin usage to either two- or four-wire operation:
0: 4-wire operation disabled
1: 4-wire operation enabled
This bit is not synchronized.
zBits 15:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 7 – RUNSTDBY: Run in Standby
This bit defines the functionality in standby sleep mode.
0: Disabled – All reception is dropped.
1: Wake on address match, if enabled.
This bit is not synchronized.
zBits 6:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:2 – MODE[2:0]: Operating Mode
These bits must be written to 0x04 to select the I2C slave serial communication interface of the SERCOM.
These bits are not synchronized.
zBit 1 – ENABLE: Enable
0: The peripheral is disabled.
1: The peripheral is enabled.
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY will be cleared when the operation is complete.
This bit is not enable-protected.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Value Name Description
0x0 DIS Disabled
0x1 75 50-100ns hold time
0x2 450 300-600ns hold time
0x3 600 400-800ns hold time
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Writing a one to this bit resets all registers in the SERCOM, except DBGCTRL, to their initial state, and the SER-
COM will be disabled.
Writing a one to CTRLA.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST
and STATUS.SYNCBUSY will both be cleared when the reset is complete.
This bit is not enable-protected.
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26.8.1.2 Control B
Name: CTRLB
Offset: 0x04
Reset: 0x00000000
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBits 31:19 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 18 – ACKACT: Acknowledge Action
0: Send ACK
1: Send NACK
The Acknowledge Action (ACKACT) bit defines the slave's acknowledge behavior after an address or data byte is
received from the master. The acknowledge action is executed when a command is written to the CMD bits. If
smart mode is enabled (CTRLB.SMEN is one), the acknowledge action is performed when the DATA register is
read.
This bit is not enable-protected.
This bit is not write-synchronized.
zBits 17:16 – CMD[1:0]: Command
Writing the Command bits (CMD) triggers the slave operation as defined in Table 26-4. The CMD bits are strobe
bits, and always read as zero. The operation is dependent on the slave interrupt flags, INTFLAG.DRDY and INT-
FLAG.AMATCH, in addition to STATUS.DIR (See Table 26-4).
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
ACKACT CMD[1:0]
AccessRRRRRR/WR/WR/W
Reset00000000
Bit151413121110 9 8
AMODE[1:0] SMEN
AccessR/WR/WRRRRRR/W
Reset00000000
Bit76543210
AccessRRRRRRRR
Reset00000000
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All interrupt flags (INTFLAG.DRDY, INTFLAG.AMATCH and INTFLAG.PREC) are automatically cleared when a
command is given.
This bit is not enable-protected.
Table 26-4. Command Description
zBits 15:14 – AMODE[1:0]: Address Mode
These bits set the addressing mode according to Table 26-5.
Table 26-5. Address Mode Desc ription
Note: 1. See “SERCOM – Serial Communication Interface” on page 332 for additional information.
These bits are not write-synchronized.
zBits 13:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 8 – SMEN: Smart Mode Enable
This bit enables smart mode. When smart mode is enabled, acknowledge action is sent when DATA.DATA is
read.
0: Smart mode is disabled.
1: Smart mode is enabled.
This bit is not write-synchronized.
CMD[1:0] DIR Action
0x0 X(No action)
0x1 X(Reserved)
0x2
Used to complete a transaction in response to a data interrupt (DRDY)
0 (Master write) Execute acknowledge action succeeded by waiting for any start (S/Sr) condition
1 (Master read) Wait for any start (S/Sr) condition
0x3
Used in response to an address interrupt (AMATCH)
0 (Master write) Execute acknowledge action succeeded by reception of next byte
1 (Master read) Execute acknowledge action su cceeded by slave data interrupt
Used in response to a data interrupt (DRDY)
0 (Master write) Execute acknowledge action succeeded by reception of next byte
1 (Master read) Execute a byte read operatio n followed by ACK/NACK reception
Value Name Description
0x0 MASK The slave responds to the address written in ADDR.ADDR masked by the value in
ADDR.ADDRMASK(1).
0x1 2_ADDRS The slave responds to the two unique add resses in ADDR.ADDR and ADDR.ADDRMASK.
0x2 RANGE The slave responds to the range of add resses between and including ADDR.ADDR and
ADDR.ADDRMASK. ADDR.ADDR is the upper limit.
0x3 -Reserved.
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zBits 7:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
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26.8.1.3 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x0C
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – DRDY: Data Ready Interrupt Enable
0: The Data Ready interrupt is disabled.
1: The Data Ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Data Ready bit, which disables the Data Ready interrupt.
zBit 1 – AMATCH: Address Match Interrupt Enable
0: The Address Match interrupt is disabled.
1: The Address Match interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Address Match Interrupt Enable bit, which disables the Address Match
interrupt.
zBit 0 – PREC: Stop Received Interrupt Enable
0: The Stop Received interrupt is disabled.
1: The Stop Received interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Stop Received bit, which disables the Stop Received interrupt.
Bit76543210
DRDY AMATCH PREC
AccessRRRRRR/WR/WR/W
Reset00000000
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26.8.1.4 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x0D
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – DRDY: Data Ready Interrupt Enable
0: The Data Ready interrupt is disabled.
1: The Data Ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Data Ready bit, which enables the Data Ready interrupt.
zBit 1 – AMATCH: Address Match Interrupt Enable
0: The Address Match interrupt is disabled.
1: The Address Match interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Address Match Interrupt Enable bit, which enables the Address Match interrupt.
zBit 0 – PREC: Stop Received Interrupt Enable
0: The Stop Received interrupt is disabled.
1: The Stop Received interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Stop Received bit, which enables the Stop Received interrupt.
Bit76543210
DRDY AMATCH PREC
AccessRRRRRR/WR/WR/W
Reset00000000
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26.8.1.5 Interrupt Flag Status and Clear
Name: INTFLAG
Offset: 0x0E
Reset: 0x00
Property: -
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – DRDY: Data Ready
This flag is set when a I2C slave byte transmission is successfully completed.
The flag is cleared by hardware when either:
zWriting to the DATA register.
zReading the DATA register with smart mode enabled.
zWriting a valid command to the CMD register.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Data Ready interrupt flag. Optionally, the flag can be cleared manually by writ-
ing a one to INTFLAG.DRDY.
zBit 1 – AMATCH: Address Match
This flag is set when the I2C slave address match logic detects that a valid address has been received.
The flag is cleared by hardware when CTRL.CMD is written.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Address Match interrupt flag. Optionally the flag can be cleared manually by
writing a one to INTFLAG.AMATCH. When cleared, an ACK/NACK will be sent according to CTRLB.ACKACT.
zBit 0 – PREC: Stop Received
This flag is set when a stop condition is detected for a transaction being processed. A stop condition detected
between a bus master and another slave will not set this flag.
This flag is cleared by hardware after a command is issued on the next address match.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Stop Received interrupt flag. Optionally, the flag can be cleared manually by
writing a one to INTFLAG.PREC.
Bit 76543210
DRDY AMATCH PREC
Access RRRRRR/WR/WR/W
Reset 00000000
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26.8.1.6 Status
Name: STATUS
Offset: 0x10
Reset: 0x0000
Property: -
zBit 15 – SYNCBUSY: Synchronization Busy
This bit is set when the synchronization of registers between clock domains is started.
This bit is cleared when the synchronization of registers between the clock domains is complete.
zBits 14:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 7 – CLKHOLD: Clock Hold
The slave Clock Hold bit (STATUS.CLKHOLD) is set when the slave is holding the SCL line low, stretching the I2C
clock. Software should consider this bit a read-only status flag that is set when INTFLAG.DRDY or INT-
FLAG.AMATCH is set.
This bit is automatically cleared when the corresponding interrupt is also cleared.
zBit 6 – LOWTOUT: SCL Low Time-out
This bit is set if an SCL low time-out occurs.
This bit is cleared automatically if responding to a new start condition with ACK or NACK (write 3 to CTRLB.CMD)
or when INTFLAG.AMATCH is cleared.
0: No SCL low time-out has occurred.
1: SCL low time-out has occurred.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the status.
zBit 5 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 4 – SR: Repeated Start
When INTFLAG.AMATCH is raised due to an address match, SR indicates a repeated start or start condition.
0: Start condition on last address match
1: Repeated start condition on last address match
This flag is only valid while the INTFLAG.AMATCH flag is one.
Bit 151413121110 9 8
SYNCBUSY
AccessRRRRRRRR
Reset00000000
Bit76543210
CLKHOLD LOWTOUT SR DIR RXNACK COLL BUSERR
Access R R/W R R R R R/W R/W
Reset00000000
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zBit 3 – DIR: Read / Write Direction
The Read/Write Direction (STATUS.DIR) bit stores the direction of the last address packet received from a master.
0: Master write operation is in progress.
1: Master read operation is in progress.
zBit 2 – RXNACK: Received Not Acknowledge
This bit indicates whether the last data packet sent was acknowledged or not.
0: Master responded with ACK.
1: Master responded with NACK.
zBit 1 – COLL: Transmit Collision
If set, the I2C slave was not able to transmit a high data or NACK bit, the I2C slave will immediately release the
SDA and SCL lines and wait for the next packet addressed to it.
This flag is intended for the SMBus address resolution protocol (ARP). A detected collision in non-ARP situations
indicates that there has been a protocol violation, and should be treated as a bus error.
Note that this status will not trigger any interrupt, and should be checked by software to verify that the data were
sent correctly. This bit is cleared automatically if responding to an address match with an ACK or a NACK (writing
0x3 to CTRLB.CMD), or INTFLAG.AMATCH is cleared.
0: No collision detected on last data byte sent.
1: Collision detected on last data byte sent.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the status.
zBit 0 – BUSERR: Bus Error
The Bus Error bit (STATUS.BUSERR) indicates that an illegal bus condition has occurred on the bus, regardless
of bus ownership. An illegal bus condition is detected if a protocol violating start, repeated start or stop is de tected
on the I2C bus lines. A start condition directly followed by a stop condition is one example of a protocol violation. If
a time-out occurs during a frame, this is also considered a protocol violation, and will set STATUS.BUSERR.
This bit is cleared automatically if responding to an address match with an ACK or a NACK (writing 0x3 to
CTRLB.CMD) or INTFLAG.AMATCH is cleared.
0: No bus error detected.
1: Bus error detected.
Writing a one to this bit will clear the status.
Writing a zero to this bit has no effect.
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26.8.1.7 Address
Name: ADDR
Offset: 0x14
Reset: 0x00000000
Property: Write-Protected, Enable-Protected
zBits 31:24 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 23:17 – ADDRMASK[6:0]: Address Mask
The ADDRMASK bits acts as a second address match register, an address mask register or the lower limit of an
address range, depending on the CTRLB.AMODE setting.
zBits 16:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:1 – ADDR[6:0]: Address
The slave address (ADDR) bits contain the I2C slave address used by the slave address match logic to determine
if a master has addressed the slave. When using 7-bit addressing, the address register (ADDR.ADDR) represents
the slave address.
If using 10-bit addressing, the address match logic only supports hardware address recognition of the first 2 bits of
a 10-bit address. If writing ADDR.ADDR = "0b1111 0xx," 'xx' represents bits 9 and 8 or the slave address. The next
byte received is bits 7 to 0 in the 10-bit address, and this must be handled by software.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
ADDRMASK[6:0]
AccessR/WR/WR/WR/WR/WR/WR/W R
Reset00000000
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
ADDR[6:0] GENCEN
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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When the address match logic detects a match, INTFLAG. AMATCH is set and STATUS.DIR is updated to indicate
whether it is a read or a write transaction.
zBit 0 – GENCEN: General Call Address Enable
Writing a one to GENCEN enables general call address recognition. A general call address is an address of all
zeroes with the direction bit written to zero (master write).
0: General call address recognition disabled.
1: General call address recognition enabled.
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26.8.1.8 Data
Name: DATA
Offset: 0x18
Reset: 0x0000
Property: Write-Synchronized, Read-Synchronized
zBits 15:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:0 – DATA[7:0]: Data
The slave data register I/O location (DATA.DATA) provides access to the master transmit and receive data buf-
fers. Reading valid data or writing data to be transmitted can be successfully done only when SCL is held low by
the slave (STATUS.CLKHOLD is set). An exception occurs when reading the last data byte after the stop condition
has been received.
Accessing DATA.DATA auto-triggers I2C bus operations. The operation performed depends on the state of
CTRLB.ACKACT, CTRLB.SMEN and the type of access (read/write).
Writing or reading DATA.DATA when not in smart mode does not require synchronization.
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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26.8.2 I2C Master Register Description
26.8.2.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00000000
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBit 31 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 30 – LOWTOUT: SCL Low Time-Out
This bit enables the SCL low time-out. If SCL is held low for 25ms-35ms, the master will release its clock hold, if
enabled, and complete the current transaction. A stop condition will automatically be transmitted.
INTFLAG.SB or INTFLAG.MB will be set as normal, but the clock hold will be released. The STATUS.LOWTOUT
and STATUS.BUSERR status bits will be set.
0: Time-out disabled.
1: Time-out enabled.
This bit is not synchronized.
zBits 29:28 – INACTOUT[1:0]: Inactive Time-Out
If the inactive bus time-out is enabled and the bus is inactive for longer than the time-out setting, the bus state logic
will be set to idle. An inactive bus arise when either an I2C master or slave is holding the SCL low. The available
time-outs are given in Table 26-6.
Bit 3130292827262524
LOWTOUT INACTOUT[1:0]
Access R R/W R/W R/W R R R R
Reset00000000
Bit 2322212019181716
SDAHOLD[1:0] PINOUT
Access R R R/W R/W R R R R/W
Reset00000000
Bit 151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
RUNSTDBY MODE[2:0]=101 ENABLE SWRST
Access R/W R R R/W R/W R/W R/W R/W
Reset00000000
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Enabling this option is necessary for SMBus compatibility, but can also be used in a non-SMBus set-up.
Table 26-6. Inactive Timout
Calculated time-out periods are based on a 100kHz baud rate.
These bits are not synchronized.
zBits 27:22 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 21:20 – SDAHOLD[1:0]: SDA Hold Time
These bits define the SDA hold time with respect to the negative edge of SCL.
Table 26-7. SDA Hold Time
These bits are not synchronized.
zBits 19:17 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 16 – PINOUT: Pin Usage
This bit set the pin usage to either two- or four-wire operation:
0: 4-wire operation disabled.
1: 4-wire operation enabled.
This bit is not synchronized.
zBits 15:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 7 – RUNSTDBY: Run in Standby
This bit defines the functionality in standby sleep mode.
0: GCLK_SERCOMx_CORE is disabled and the I2C master will not operate in standby sleep mode.
1: GCLK_SERCOMx_CORE is enabled in all sleep modes allowing the master to operate in standby sleep mode.
This bit is not synchronized.
Value Name Description
0x0 DIS Disabled
0x1 55US 5-6 SCL cycle time-out (50-60µs)
0x2 105US 10-11 SCL cycle time-out (100-110µs)
0x3 205US 20-21 SCL cycle time-out (200-210µs)
Value Name Description
0x0 DIS Disabled
0x1 75NS 50-100ns hold time
0x2 450NS 300-600ns hold time
0x3 600NS 400-800ns hold time
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zBits 6:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:2 – MODE[2:0]: Operating Mode
These bits must be written to 0x5 to select the I2C master serial communication interface of the SERCOM.
These bits are not synchronized.
zBit 1 – ENABLE: Enable
0: The peripheral is disabled.
1: The peripheral is enabled.
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY will be cleared when the operation is complete.
This bit is not enable-protected.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the SERCOM, except DBGCTRL, to their initial state, and the SER-
COM will be disabled.
Writing a one to CTRLA.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST
and STATUS.SYNCBUSY will both be cleared when the reset is complete.
This bit is not enable-protected.
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26.8.2.2 Control B
Name: CTRLB
Offset: 0x04
Reset: 0x00000000
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBits 31:19 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 18 – ACKACT: Acknowledge Action
The Acknowledge Action (ACKACT) bit defines the I2C master's acknowledge behavior after a data byte is
received from the I2C slave. The acknowledge action is executed when a command is written to CTRLB.CMD, or if
smart mode is enabled (CTRLB.SMEN is written to one), when DATA.DATA is read.
0: Send ACK.
1: Send NACK.
This bit is not enable-protected.
This bit is not write-synchronized.
zBits 17:16 – CMD[1:0]: Command
Writing the Command bits (CMD) triggers the master operation as defined in Table 26-8. The CMD bits are strobe
bits, and always read as zero. The acknowledge action is only valid in master read mode. In master write mode, a
command will only result in a repeated start or stop condition. The CTRLB.ACKACT bit and the CMD bits can be
written at the same time, and then the acknowledge action will be updated before the command is triggered.
Bit3130292827262524
AccessRRRRRRRR
Reset00000000
Bit2322212019181716
ACKACT CMD[1:0]
Access R R R R R R/W R/W R/W
Reset00000000
Bit151413121110 9 8
QCEN SMEN
AccessRRRRRRRR/W
Reset00000000
Bit76543210
AccessRRRRRRRR
Reset00000000
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Commands can only be issued when the Slave on Bus interrupt flag (INTFLAG.SB) or Master on Bus interrupt flag
(INTFLAG.MB) is one.
If CMD 0x1 is issued, a repeated start will be issued followed by the transmission of the current address in
ADDR.ADDR. If another address is desired, ADDR.ADDR must be written instead of the CMD bits. This will trigger
a repeated start followed by transmission of the new address.
Issuing a command will set STATUS.SYNCBUSY.
Table 26-8. Command Description
These bits are not enable-protected.
zBits 15:10 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 9 – QCEN: Quick Command Enable
Setting the Quick Command Enable bit (QCEN) enables quick command.
0: Quick Command is disabled.
1: Quick Command is enabled.
This bit is not write-synchronized.
zBit 8 – SMEN: Smart Mode Enable
This bit enables smart mode. When smart mode is enabled, acknowledge action is sent when DATA.DATA is
read.
0: Smart mode is disabled.
1: Smart mode is enabled.
This bit is not write-synchronized.
zBits 7:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
CMD[1:0] DIR Action
0x0 X(No action)
0x1 XExecute acknowledge action succeeded by repe ated Start
0x2 0 (Write) No operation
1 (Read) Execute acknowledge action succeeded by a byte read operation
0x3 XExecute acknowledge action succeeded by issuing a stop condition
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26.8.2.3 Debug Control
Name: DBGCTRL
Offset: 0x08
Reset: 0x00
Property: Write-Protected
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – DBGSTOP: Debug Stop Mode
This bit controls functionality when the CPU is halted by an external debugger.
0: The baud-rate generator continues normal operation when the CPU is halted by an external debugger.
1: The baud-rate generator is halted when the CPU is halted by an external debugger.
Bit76543210
DBGSTOP
AccessRRRRRRRR/W
Reset00000000
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26.8.2.4 Baud Rate
Name: BAUD
Offset: 0x0A
Reset: 0x0000
Property: Write-Protected, Enable-Protected
zBits 15:8 – BAUDLOW[7:0]: Master Baud Rate Low
If the Master Baud Rate Low bit group (BAUDLOW) has a non-zero value, the SCL low time will be described by
the value written.
For more information on how to calculate the frequency, see “SERCOM I2C – SERCOM Inter-Integrated Circuit”
on page 389.
zBits 7:0 – BAUD[7:0]: Master Baud Rate
The Master Baud Rate bit group (BAUD) is used to derive the SCL high time if BAUD.BAUDLOW is non-zero. If
BAUD.BAUDLOW is zero, BAUD will be used to generate both high and low periods of the SCL.
For more information on how to calculate the frequency, see “SERCOM I2C – SERCOM Inter-Integrated Circuit”
on page 389.
Bit151413121110 9 8
BAUDLOW[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
BAUD[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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26.8.2.5 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x0C
Reset: 0x00
Property: Write-Protected
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – SB: Slave on Bus Interrupt Enable
0: The Slave on Bus interrupt is disabled.
1: The Slave on Bus interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Slave on Bus Interrupt Enable bit, which disables the Slave on Bus interrupt.
zBit 0 – MB: Master on Bus Interrupt Enable
0: The Master on Bus interrupt is disabled.
1: The Master on Bus interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Master on Bus Interrupt Enable bit, which disables the Master on Bus
interrupt.
Bit76543210
SB MB
AccessRRRRRRR/WR/W
Reset00000000
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26.8.2.6 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x0D
Reset: 0x00
Property: Write-Protected
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – SB: Slave on Bus Interrupt Enable
0: The Slave on Bus interrupt is disabled.
1: The Slave on Bus interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Slave on Bus Interrupt Enable bit, which enables the Slave on Bus interrupt.
zBit 0 – MB: Master on Bus Interrupt Enable
0: The Master on Bus interrupt is disabled.
1: The Master on Bus interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Master on Bus Interrupt Enable bit, which enables the Master on Bus interrupt.
Bit76543210
SB MB
AccessRRRRRRR/WR/W
Reset00000000
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26.8.2.7 Interrupt Flag Status and Clear
Name: INTFLAG
Offset: 0x0E
Reset: 0x00
Property: -
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – SB: Slave on Bus
The Slave on Bus flag (SB) is set when a byte is successfully received in master read mode, i.e., no arbitration lost
or bus error occurred during the operation. When this flag is set, the master forces the SCL line low, stretching the
I2C clock period. The SCL line will be released and SB will be cleared on one of the following actions:
zWriting to ADDR.ADDR
zWriting to DATA.DATA
zReading DATA.DATA when smart mode is enabled (CTRLB.SMEN)
zWriting a valid command to CTRLB.CMD
Writing a one to this bit location will clear the SB flag. The transaction will not continue or be terminated until one of
the above actions is performed.
Writing a zero to this bit has no effect.
zBit 0 – MB: Master on Bus
The Master on Bus flag (MB) is set when a byte is transmitted in master write mode. The flag is set regardless of
the occurrence of a bus error or an arbitration lost condition. MB is also set when arbitration is lost during sending
of NACK in master read mode, and when issuing a start condition if the bus state is unknown. When this flag is set
and arbitration is not lost, the master forces the SCL line low, stretching the I2C clock period. The SCL line will be
released and MB will be cleared on one of the following actions:
zWriting to ADDR.ADDR
zWriting to DATA.DATA
zReading DATA.DATA when smart mode is enabled (CTRLB.SMEN)
zWriting a valid command to CTRLB.CMD
If arbitration is lost, writing a one to this bit location will clear the MB flag.
If arbitration is not lost, writing a one to this bit location will clear the MB flag. The transaction will not continue or be
terminated until one of the above actions is performed.
Writing a zero to this bit has no effect.
Bit76543210
SB MB
AccessRRRRRRR/WR/W
Reset00000000
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26.8.2.8 Status
Name: STATUS
Offset: 0x10
Reset: 0x0000
Property: Write-Synchronized
zBit 15 – SYNCBUSY: Synchronization Busy
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 14:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 7 – CLKHOLD: Clock Hold
The Master Clock Hold flag (STATUS.CLKHOLD) is set when the master is holding the SCL line low, stretching
the I2C clock. Software should consider this bit a read-only status flag that is set when INTFLAG.SB or INT-
FLAG.MB is set. When the corresponding interrupt flag is cleared and the next operation is given, this bit is
automatically cleared.
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
This bit is not write-synchronized.
zBit 6 – LOWTOUT: SCL Low Time-Out
This bit is set if an SCL low time-out occurs.
Writing a one to this bit location will clear STATUS.LOWTOUT. Normal use of the I2C interface does not require
the LOWTOUT flag to be cleared by this method. This flag is automatically cleared when either:
zWriting to ADDR.ADDR
zWriting to DATA.DATA
zReading DATA.DATA when smart mode is enabled (CTRLB.SMEN)
zWriting a valid command to CTRLB.CMD
Writing a zero to this bit has no effect.
This bit is not write-synchronized.
zBits 5:4 – BUSSTATE[1:0]: Bus State
These bits indicate the current I2C bus state as defined in Table 26-9. After enabling the SERCOM as an I2C mas-
ter, the bus state will be unknown.
Bit151413121110 9 8
SYNCBUSY
AccessRRRRRRRR
Reset00000000
Bit76543210
CLKHOLD LOWTOUT BUSSTATE[1:0] RXNACK ARBLOST BUSERR
Access R R/W R R/W R R R/W R/W
Reset00000000
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Table 26-9. Bus State
When the master is disabled, the bus-state is unknown. When in the unknown state, writing 0x1 to BUSSTATE forces the
bus state into the idle state. The bus state cannot be forced into any other state.
Writing STATUS.BUSSTATE to idle will set STATUS.SYNCBUSY.
zBit 3 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 2 – RXNACK: Received Not Acknowledge
This bit indicates whether the last address or data packet sent was acknowledged or not.
0: Slave responded with ACK.
1: Slave responded with NACK.
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
This bit is not write-synchronized.
zBit 1 – ARBLOST: Arbitration Lost
The Arbitration Lost flag (STATUS.ARBLOST) is set if arbitration is lost while transmitting a high data bit or a
NACK bit, or while issuing a start or repeated start condition on the bus. The Master on Bus interrupt flag (INT-
FLAG.MB) will be set when STATUS.ARBLOST is set.
Writing the ADDR.ADDR register will automatically clear STATUS.ARBLOST.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear it.
This bit is not write-synchronized.
zBit 0 – BUSERR: Bus Error
The Bus Error bit (STATUS.BUSERR) indicates that an illegal bus condition has occurred on the bus, regardless
of bus ownership. An illegal bus condition is detected if a protocol violating start, repeated start or stop is de tected
on the I2C bus lines. A start condition directly followed by a stop condition is one example of a protocol violation. If
a time-out occurs during a frame, this is also considered a protocol violation, and will set BUSERR.
If the I2C master is the bus owner at th e time a bus error occurs, STATUS.ARBLOST and INTFLAG.MB will be set
in addition to BUSERR.
Writing the ADDR.ADDR register will automatically clear the BUSERR flag.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear it.
This bit is not write-synchronized.
Value Name Description
0x0 Unknown The bus state is unknown to the I2C master and will wait for a stop condition to be
detected or wait to be forced into an idle state by software
0x1 Idle The bus state is waiting for a transaction to be initialized
0x2 Owner The I2C master is the current owner of the bus
0x3 Busy Some other I2C master owns the bus
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26.8.2.9 Address
Name: ADDR
Offset: 0x14
Reset: 0x0000
Property: Write-Synchronized
zBits 15:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:0 – ADDR[7:0]: Address
When ADDR is written, the consecutive operation will depend on the bus state:
Unknown: INTFLAG.MB and STATUS.BUSERR are set, and the operation is terminated.
Busy: The I2C master will await further operation until the bus becomes idle.
Idle: The I2C master will issue a start condition followed by th e address written in ADDR. If the address is acknowl-
edged, SCL is forced and held low, and STATUS.CLKHOLD and INTFLAG.MB are set.
Owner: A repeated start sequence will be performed. If the previous transaction was a read, the acknowledge
action is sent before the repeated start bus condition is issued on the bus. Writing ADDR to issue a repeated start
is performed while INTFLAG.MB or INTFLAG.SB is set.
Regardless of winning or loosing arbitration, the entire address will be sent. If arbitration is lost, only ones are
transmitted from the point of loosing arbitration and the rest of the address length.
STATUS.BUSERR, STATUS.ARBLOST, INTFLAG.MB and INTFLAG.SB will be cleared when ADDR is written.
The ADDR register can be read at any time without interfering with ongoing bus activity, as a read access does not
trigger the master logic to perform any bus protocol related operations.
The I2C master control logic uses bit 0 of ADDR as the bus protocol’s read/write flag (R/W); 0 for write and 1 for
read.
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
ADDR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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26.8.2.10 Data
Name: DATA
Offset: 0x18
Reset: 0x0000
Property: Write-Synchronized, Read-Synchronized
zBits 15:8 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 7:0 – DATA[7:0]: Data
The master data register I/O location (DATA) provides access to the master transmit and receive data buffers.
Reading valid data or writing data to be transmitted can be successfully done only when SCL is held low by the
master (STATUS.CLKHOLD is set). An exception occurs when reading the last data byte after the stop condition
has been sent.
Accessing DATA.DATA auto-triggers I2C bus operations. The operation performed depends on the state of
CTRLB.ACKACT, CTRLB.SMEN and the type of access (read/write).
Writing or reading DATA.DATA when not in smart mode does not require synchronization.
Bit151413121110 9 8
AccessRRRRRRRR
Reset00000000
Bit76543210
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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27. TC – Timer/Counter
27.1 Overview
The TC consists of a counter, a prescaler, compare/capture channels and control logic. The counter can be set to count
events, or it can be configured to count clock pulses. The counter, together with the compare/capture channels, can be
configured to timestamp input events, allowing capture of frequency and pulse width. It can also perform waveform
generation, such as frequency generation and pulse-width modulation (PWM).
27.2 Features
zSelectable configuration
z8-, 16- or 32-bit TC, with compare/capture channels
zWaveform generation
zFrequency generation
zSingle-slope pulse-width modulation
zInput capture
zEvent capture
zFrequency capture
zPulse-width capture
zOne input event
zInterrupts/output events on:
zCounter overflow/underflow
zCompare match or capture
zInternal prescaler
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27.3 Block Diagram
Figure 27-1. Timer/Counter Block Diagram
PERPER
PrescalerPrescaler
Control logicControl logic
Control logicControl logic
Waveform Waveform
generationgeneration
COUNTCOUNT
CC0CC0
Base CounterBase Counter
CounterCounter
Compare / CaptureCompare / Capture
TOPTOP
ZEROZERO
= 0= 0
=
match
match
UPDATEUPDATE
eventevent
=
OVF/UNF
OVF/UNF
(INT Req.)(INT Req.)
ERRERR
(INT Req.)(INT Req.)
WOx OutWOx Out
CCxCCx
(INT Req.)(INT Req.)
countcount
clearclear
loadload
directiondirection
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27.4 Signal Description
Refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
27.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
27.5.1 I/O Lines
Using the TC’s I/O lines requires the I/O pins to be configured. Refer to “PORT” on page 284 for details.
27.5.2 Power Management
The TC can continue to operate in any sleep mode where the selected source clock is running. The TC interrupts can be
used to wake up the device from sleep modes. The events can trigger other operations in the system without exiting
sleep modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
27.5.3 Clocks
The TC bus clock (CLK_TCx_APB, where x repre sents the specific TC instance number) can be enabled and disabled in
the Power Manager, and the default state of CLK_TCx_APB can be found in the Peripheral Clock Masking section in
“PM – Power Manager” on page 100.
The different TC instances are paired, even and odd, starting from TC0, and use the same generic clock, GCLK_TCx.
This means that the TC instances in a TC pair cannot be set up to use different GCLK_TCx clocks.
This generic clock is asynchronous to the user interface clock (CLK_TCx_APB). Due to this asynchronicity, accessing
certain registers will require synchronization between the clock domains. Refer to “Synchronization” on page 447 for
further details.
27.5.4 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the TC interrupts requires the interrupt controller
to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
27.5.5 Events
To use the TC event functionality, the corresponding events need to be configured in the event system. Refer to “EVSYS
– Event System” on page 309 for details.
27.5.6 Debug Operation
When the CPU is halted in debug mode the TC will halt normal operation. The TC can be forced to continue operation
during debugging. Refer to the DBGCTRL register for details.
27.5.7 Register Access Protection
All registers with write-access are optionally write-protected by the peripheral access controller (PAC), except the
following registers:
zInterrupt Flag register (INTFLAG)
zStatus register (STATUS)
Signal Name Type Description
WO[1:0] Digital output Waveform output
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zRead Request register (READREQ)
zCount register (COUNT)
zPeriod register (PER)
zCompare/Capture Value registers (CCx)
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
27.5.8 Analog Connections
Not applicable.
27.6 Functional Description
27.6.1 Principle of Operation
The counter in the TC can be set to count on events from the Event System, or on the GCLK_TCx frequency. The pulses
from GCLK_TCx will go through the prescaler, where it is possible to divide the frequency down.
The value in the counter is passed to the compare/capture channels, where it can either be compared with user defined
values or captured on a predefined event.
The TC can be configured as an 8-, 16- or 32-bit counter. Which mode is chosen will determine the maximum range of
the counter. The counter range combined with the operating frequency will determine the maximum time resolution
achievable with the TC peripheral.
The TC can be set to count up or down. By default, the counter will operate in a continuous mode, where the counter will
wrap to the zero respectively top value it counts from when reaching the top respectively zero.
When one of the compare/capture channels is used in compare mode, the TC can be used for waveform generation.
Upon a match between the counter and the value in one or more of the Compare/Capture Value registers (CCx), one or
more output pins on the device can be set to toggle. The CCx registers and the counter can thereby be used in frequency
generation and PWM generation.
Capture mode can be used to automatically capture the period and pulse width of signals.
27.6.2 Basic Operation
27.6.2.1 Initialization
The following register is enable-protected, meaning that it can only be written when the TC is disabled (CTRLA.ENABLE
is zero):
zControl A register (CTRLA), except the Run Standby (RUNSTDBY), Enable (ENABLE) and Software Reset
(SWRST) bits
The following bits are enable-protected:
zEvent Action bits in the Event Control register (EVCTRL.EVACT)
Enable-protected bits in the CTRLA register can be written at the same time as CTRLA.ENABLE is written to one, but not
at the same time as CTRLA.ENABLE is written to zero.
Before the TC is enabled, it must be configured, as outlined by the following steps:
zThe TC bus clock (CLK_TCx_APB) must be enabled
zThe mode (8, 16 or 32 bits) of the TC must be selected in the TC Mode bit group in the Control A register
(CTRLA.MODE). The default mode is 16 bits
zOne of the wavegen modes must be selected in the Waveform Generation Operation bit group in the Control A
register (CTRLA.WAVEGEN)
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zIf the GCLK_TCx frequency used should be prescaled, this can be selected in the Prescaler bit group in the
Control A register (CTRLA.PRESCALER)
zIf the prescaler is used, one of the presync modes must be chosen in the Prescaler and Counter Synchronization
bit group in the Control A register (CTRLA.PRESYNC)
zOne-shot mode can be selected by writing a one to the One-Shot bit in the Control B Set register
(CTRLBSET.ONESHOT)
zIf the counter should count down from the top value, write a one to the Counter Direction bit in the Control B Set
register (CTRLBSET.DIR)
zIf capture operations are to be used, the individual channels must be enabled for capture in the Capture Channel x
Enable bit group in the Control C register (CTRLC.CPTEN)
zThe waveform output for individual channels can be inverted using the Output Waveform Invert Enable bit group in
the Control C register (CTRLC.INVEN)
27.6.2.2 Enabling, Disabling and Resetting
The TC is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The TC is disabled by
writing a zero to CTRLA.ENABLE.
The TC is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in the
TC, except DBGCTRL, will be reset to their initial state, and the TC will be disabled. Refer to the CTRLA register for
details.
The TC should be disabled before the TC is reset to avoid undefined behavior.
27.6.2.3 Prescaler Selection
As seen in Figure 27-2, the GCLK_TC clock is fed into the internal prescaler. Prescaler output intervals from 1 to 1/1024
are available. For a complete list of available prescaler outputs, see the register description for the Prescaler bit group in
the Control A register (CTRLA.PRESCALER).
The prescaler consists of a counter that counts to the selected prescaler value, whereupon the output of the prescaler
toggles.
When the prescaler is set to a value greater than one, it is necessary to choose whether the prescaler should reset its
value to zero or continue counting from its current value on the occurrence of an overflow or underflow. It is also
necessary to choose whether the TC counter should wrap around on the next GCLK_TC clock pulse or the next
prescaled clock pulse (CLK_TC_CNT of Figure 27-2). To do this, use the Prescaler and Counter Synchronization bit
group in the Control A register (CTRLA.PRESYNC).
If the counter is set to count events from the event system, these will not pass through the prescaler, as seen in Figure
27-2.
Figure 27-2. Prescaler
27.6.2.4 TC Mode
The counter mode is selected with the TC Mode bit group in the Control A register (CTRLA.MODE). By default, the
counter is enabled in the 16-bit counter mode.
Three counter modes are available:
PRESCALER
GCLK_TC /
{1,2,4,8,64,256,1024}
GCLK_TC
Prescaler CNT
CLK_TC_CNT
EVACT
EVENT
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zCOUNT8: The 8-bit TC has its own Period register (PER). This register is used to store the period value that can
be used as the top value for waveform generation.
zCOUNT16: This is the default counter mode. There is no dedicated period register in this mode.
zCOUNT32: This mode is achieved by pairing two 16-bit TC peripherals. This pairing is explained in “Clocks” on
page 438. The even-numbered TC instance will act as master to the odd-numbered TC peripheral, which will act
as a slave. The slave status of the slave is indicated by reading the Slave bit in the Status register
(STATUS.SLAVE). The registers of the slave will not reflect the registers of the 32-bit counter. Writing to any of the
slave registers will not affect the 32-bit counter. Normal access to the slave COUNT and CCx registers is not
allowed.
27.6.2.5 Counter Operations
The counter can be set to count up or down. When the counter is counting up and the top value is reached, the counter
will wrap around to zero on the next clock cycle. When counting down, the counter will wrap around to the top value when
zero is reached. For one-shot mode, the counter will continue to count after a wraparound occurs.
To set the counter to count down, write a one to the Direction bit in the Control B Set register (CTRLBSET.DIR). To count
up, write a one to the Direction bit in the Control B Clear register (CTRLBCLR.DIR).
Each time the counter reaches the top value or zero, it will set the Overflow Interrupt flag in the Interrupt Flag Status and
Clear register (INTFLAG.OVF). It is also possible to generate an event on overflow or underflow when the
Overflow/Underflow Event Output Enable bit in the Event Control register (EVCTRL.OVFEO) is one.
The counter value can be read from the Counter Value register (COUNT) or a new value can be written to the COUNT
register. Figure 27-3 gives an example of writing a new counter value. The COUNT value will always be zero when
starting the TC, unless some other value has been written to it or the TC has been stopped at some value other than
zero.
Figure 27-3. Counter Operati on
Stop Command
On the stop command, which can be evoked in the Command bit group in the Con trol B Set register (CTRLBSET.CMD),
the counter will retain its current value. All waveforms are cleared. The counter stops counting, and the Stop bit in the
Status register is set (STATUS.STOP).
Retrigger Command and Event Action
Retriggering can be evoked either as a software command, using the Retrigger command in the Control B Set register
(CTRLBSET.CMD), or as a retrigger event action, using the Event Action bit group in the Event Control register
(EVCTRL.EVACT).
When a retrigger is evoked while the counter is running, the counter will wrap to the top value or zero, depending on the
counter direction..
DIR
COUNT
TOP
COUNTwrittenD i recti on Change
Period (T)
BOT
"update "
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When a retrigger is evoked with the counter stopped, the counter will continue counting from the value in the COUNT
register.
Note: When retrigger event action is configured and enabled as an event action, enabling the counter will not start the
counter. The counter will start at the next incoming event and restart on any following event.
Count Event Action
When the count event action is configured, every new incoming event will make the counter increment or decrement,
depending on the state of the direction bit (CTRLBSET.DIR).
Start Event Action
When the TC is configured with a start event action in the EVCTRL.EVACT bit group, enabling the TC does not make the
counter start; the start is postponed until the next input event or software retrigger action. When the counter is running,
an input event has not effect on the counter.
27.6.2.6 Compare Operations
When using the TC with the Compare/Capture Value registers (CCx) configured for compare operation, the counter
value is continuously compared to the values in the CCx registers. This can be used for timer or waveform operation.
Waveform Output Operations
The compare channels can be used for waveform generation on the corresponding I/O pins. To make the waveform
visible on the connected pin, the following requirements must be fulfilled:
zChoose a waveform generation operation
zOptionally, invert the waveform output by writing the corresponding Output Waveform Invert Enable bit in the
Control C register (CTRLC.INVx)
zEnable the corresponding multiplexor in the PORT
The counter value is continuously compared with each CCx available. When a compare match occurs, the Match or
Capture Channel x interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.MCx) is set on the next zero-to-
one transition of CLK_TC_CNT (see Figure 27-4). An interrupt and/or event can be generated on such a condition when
INTENSET.MCx and/or EVCTRL.MCEOx is one.
One of four configurations in the Waveform Generation Operation bit group in the Control A register (CTRLA.WAVEGEN)
must be chosen to perform waveform generation. This will influence how the waveform is generated and impose
restrictions on the top value. The four configurations are:
zNormal frequency (NFRQ)
zMatch frequency (MFRQ)
zNormal PWM (NPWM)
zMatch PWM (MPWM)
When using NPWM or NFRQ, the top value is determined by the counter mode. In 8-bit mode, the Period register (PER)
is used as the top value and the top value can be changed by writing to the PER register. In 16- and 32-bit mode, the top
value is fixed to the maximum value of the counter.
Frequency Operation
When NFRQ is used, the output waveform (WO[x]) toggles every time CCx and the counter are equal, and the interrupt
flag corresponding to that channel will be set.
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Figure 27-4. Normal Frequency Operation
When MFRQ is used, the value in CC0 will be used as the top value and WO[0] will toggle on every overflow/underflow.
Figure 27-5. Match Frequency Operation
PWM Operation
In PWM operation, the CCx registers control the duty cycle of the waveform generator output. Figure 27-6 shows how the
WO[x] output is set at a start or a compare match between the COUNT value and the top value, and cleared on the
compare match between the COUNT value and CCx register value.
COUNT
Zero
"wraparound "
TOP
CNT w r itten
CCx
WO[x]
COUNT
" wraparound "
TOP
COUNT writtenDirecti o n Chan g e
Period (T)
Zero
WO[0]
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Figure 27-6. Normal PWM Operation
In match operation, Compare/Capture register CC0 is used as the top value, and in this case WO[0] will toggle on every
overflow/underflow.
The following equation is used to calculate the exact period for a single-slope PWM (RPWM_SS) waveform:
where N represent the prescaler divider used (1, 2, 4, 8, 16, 64, 256, 1024).
Changing the Top Value
Changing the top value while the counter is running is possible. If a new top value is written when the counter value is
close to zero and counting down, the counter can be reloaded with the previous top value, due to synchronization delays.
If this happens, the counter will count one extra cycle before the new top value is used.
Figure 27-7. Changing the Top Value when Counting Down
COUNT
TOP
Period (T)
"match "
Zero
WO[x]
CCn= BOT
CCn
CCn= TOP "wraparound "
RPWM_SS TOP 1+()log 2()log
-----------------------------------=
fPWM_SS fCLK_TC
NTOP 1+()
------------------------------
=
COUNT
MAX
"reload"
"write"
ZERO
N ew TO P valu e
Th at is h ig h er th an
Current COUNT
New TOP value
That i s Lower th an
Current COUNT
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When counting up a change from a top value that is lower relative to the old top value can make the counter miss this
change if the counter value is larger than the new top value when the change occurred. This will make the counter count
to the max value. An example of this can be seen in Figure 27-8.
Figure 27-8. Changing the Top Value when Counting Up
27.6.2.7 Capture Operations
To enable and use capture operations, the event line into the TC must be enabled using the TC Event Input bit in the
Event Control register (EVCTRL.TCEI). The capture channels to be used must also be enabled in the Capture Channel x
Enable bit group in the Control C register (CTRLC.CPTENx) before capture can be performed.
Event Capture Action
The compare/capture channels can be used as input capture channels to capture any event from the Event System and
give them a timestamp. Because all capture channels use the same event line, only one capture channel should be
enabled at a time when performing event capture.
Figure 27-9 shows four capture events for one capture channel.
Figure 27-9. Input Capture Timing
When the Capture Interrupt flag is set and a new capture event is detected, there is nowhere to store the new timestamp.
As a result, the Error Interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.ERR) is set.
COUNT
MAX
Co u n ter Wr apar o u n d
"wraparound "
"write"
ZERO
New TOP value
That i s Lower than
Current COUNT
New TOP value
That i s higher than
Current COUNT
events
COUNT
TOP
ZERO
Capt ure 0 Capture 1 C apture 2 Capt ure 3
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Period and Pulse-Width Capture Action
The TC can perform two input captures and restart the counter on one of the edges. This enables the TC to measure the
pulse width and period. This can be used to characterize the frequency and duty cycle of an input signal:
When using PPW event action, the period (T) will be captured into CC0 and the pulse width (tp) in CC1. In PWP event
action, the pulse width (tp) will be captured in CC0 and the period (T) in CC1.
Selecting PWP (pulse-width, period) or PPW (period, pulse-width) in the Event Action bit group in the Event Control
register (EVCTRL.EVACT) enables the TC to performs two capture actions, one on the rising edge and one on the falling
edge.
The TC Inverted Event Input in the Event Control register (EVCTRL.TCINV) is used to select whether the wraparound
should occur on the rising edge or the falling edge. If EVCTRL.TCINV is written to one, the wraparound will happen on
the falling edge. The event source to be captured must be an asynchronous event.
To fully characterize the frequency and duty cycle of the input signal, activate capture on CC0 and CC1 by writing 0x3 to
the Capture Channel x Enable bit group in the Control C register (CTRLC.CPTEN). When only one of these
measurements is required, the second channel can be used for other purposes.
The TC can detect capture overflow of the input capture channels. When the Capture Interrupt flag is set and a new
capture event is detected, there is nowhere to store the new timestamp. Asa result, INTFLAG.ERR is set.
27.6.3 Additional Features
27.6.3.1 One-Shot Operation
When one-shot operation is enabled, the counter automatically stops on the next counter overflow or underflow
condition. When the counter is stopped, STATUS.STOP is automatically set by hardware and the waveform outputs are
set to zero.
One-shot operation can be enabled by writing a one into the One-Shot bit in the Control B Set register
(CTRLBSET.ONESHOT) and disabled by writing a one to the One-Shot bit in the Control B Clear register
(CTRLBCLR.ONESHOT). When enabled, it will count until an overflow or underflow occurs. The one-shot operation can
be restarted with a retrigger command, a retrigger event or a start event.
When the counter restarts its operation, the Stop bit in the Status register (STATUS.STOP) is automatically cleared by
hardware.
27.6.4 Interrupts
The TC has the following interrupt sources:
zOverflow/Underflow: OVF
zCompare or Capture Channels
zCapture Overflow Error: ERR
zSynchronization Ready: SYNCRDY
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
f1
T
---=
dutyCycle tp
T
----=
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to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the TC is reset. See the INTFLAG register for details on how to clear interrupt flags.
The TC has one common interrupt request line for all the interrupt sources. The user must read the INTFLAG register to
determine which interrupt condition is present. Note that interrupts must be globally enabled for interrupt requests to be
generated. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
27.6.5 Events
The TC can generate the following output events:
zOverflow/Underflow (OVF)
zMatch or Capture (MC)
Writing a one to an Event Output bit in the Event Control register (EVCTRL.MCEO) enables the corresponding output
event. Writing a zero to this bit disables the corresponding output event.
To enable one of the following event actions, write to the Event Action bit group (EVCTRL.EVACT).
zStart the counter
zRetrigger counter
zIncrement or decrement counter (depends on counter direction)
zCapture event
zCapture period
zCapture pulse width
Writing a one to the TC Event Input bit in the Event Control register (EVCTRL.TCEI) enables input events to the TC.
Writing a zero to this bit disables input events to the TC. Refer to “EVSYS – Event System” on page 309 for details on
configuring the Event System.
27.6.6 Sleep Mode Operation
The TC can be configured to operate in any sleep mode. To be able to run in standby, the RUNSTDBY bit in the Control
A register (CTRLA.RUNSTDBY) must be written to one. The TC can wake up the device using interrupts from any sleep
mode or perform actions through the Event System.
27.6.7 Synchronization
Due to the asynchronicity between CLK_TCx_APB and GCLK_TCx some registers must be synchronized when
accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status
register(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronizati on is complete. The
synchronization Ready interrupt can be used to signal when sync is complete. This can be accessed via the
Synchronization Ready Interrupt Flag in the Interrupt Flag Status and Clear register (INTFLAG.SYNCRDY).
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following bits need synchronization when written:
zSoftware Reset bit in the Control A register (CTRLA.SWRST)
zEnable bit in the Control A register (CTRLA.ENABLE)
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Write-synchronization is denoted by the Write-Synchronized property in the register description.
The following registers need synchronization when written:
zControl B Clear register (CTRLBCLR)
zControl B Set register (CTRLBSET)
zControl C register (CTRLC)
zCount Value register (COUNT)
zPeriod Value register (PERIOD)
zCompare/Capture Value registers (CCx)
Write-synchronization is denoted by the Write-Synchronized property in the register description.
The following registers need synchronization when read:
zControl B Clear register (CTRLBCLR)
zControl B Set register (CTRLBSET)
zControl C register (CTRLC)
zCount Value register (COUNT)
zPeriod Value register (PERIOD)
zCompare/Capture Value registers (CCx)
Read-synchronization is denoted by the Read-Synchronized property in the register description.
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27.7 Register Summary
Table 27-1. Register Summary – 8-Bit Mode Registers
Offset Name Bit Pos.
0x00 CTRLA 7:0 WAVEGEN[1:0] MODE[1:0] ENABLE SWRST
0x01 15:8 PRESCSYNC[1:0] RUNSTDBY PRESCALER[2:0]
0x02 READREQ 7:0 ADDR[4:0]
0x03 15:8 RREQ RCONT
0x04 CTRLBCLR 7:0 CMD[1:0] ONESHOT DIR
0x05 CTRLBSET 7:0 CMD[1:0] ONESHOT DIR
0x06 CTRLC 7:0 CPTEN1 CPTEN0 INVEN1 INVEN0
0x07 Reserved
0x08 DBGCTRL 7:0 DBGRUN
0x09 Reserved
0x0A EVCTRL 7:0 TCEI TCINV EVACT[2:0]
0x0B 15:8 MCEO1 MCEO0 OVFEO
0x0C INTENCLR 7:0 MC1 MC0 SYNCRDY ERR OVF
0x0D INTENSET 7:0 MC1 MC0 SYNCRDY ERR OVF
0x0E INTFLAG 7:0 MC1 MC0 SYNCRDY ERR OVF
0x0F STATUS 7:0 SYNCBUSY SLAVE STOP
0x10 COUNT 7:0 COUNT[7:0]
0x11 Reserved
0x12 Reserved
0x13 Reserved
0x14 PER 7:0 PER[7:0]
0x15 Reserved
0x16 Reserved
0x17 Reserved
0x18 CC0 7:0 CC[7:0]
0x19 CC1 7:0 CC[7:0]
0x1A Reserved
0x1B Reserved
0x1C Reserved
0x1D Reserved
0x1E Reserved
0x1F Reserved
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Table 27-2. Register Summary – 16-Bit Mod e Registers
Offset Name Bit Pos.
0x00 CTRLA 7:0 WAVEGEN[1:0] MODE[1:0] ENABLE SWRST
0x01 15:8 PRESCSYNC[1:0] RUNSTDBY PRESCALER[2:0]
0x02 READREQ 7:0 ADDR[4:0]
0x03 15:8 RREQ RCONT
0x04 CTRLBCLR 7:0 CMD[1:0] ONESHOT DIR
0x05 CTRLBSET 7:0 CMD[1:0] ONESHOT DIR
0x06 CTRLC 7:0 CPTEN1 CPTEN0 INVEN1 INVEN0
0x07 Reserved
0x08 DBGCTRL 7:0 DBGRUN
0x09 Reserved
0x0A EVCTRL 7:0 TCEI TCINV EVACT[2:0]
0x0B 15:8 MCEO1 MCEO0 OVFEO
0x0C INTENCLR 7:0 MC1 MC0 SYNCRDY ERR OVF
0x0D INTENSET 7:0 MC1 MC0 SYNCRDY ERR OVF
0x0E INTFLAG 7:0 MC1 MC0 SYNCRDY ERR OVF
0x0F STATUS 7:0 SYNCBUSY SLAVE STOP
0x10 COUNT 7:0 COUNT[7:0]
0x11 15:8 COUNT[15:8]
0x12 Reserved
0x13 Reserved
0x14 Reserved
0x15 Reserved
0x16 Reserved
0x17 Reserved
0x18 CC0 7:0 CC[7:0]
0x19 15:8 CC[15:8]
0x1A CC1 7:0 CC[7:0]
0x1B 15:8 CC[15:8]
0x1C Reserved
0x1D Reserved
0x1E Reserved
0x1F Reserved
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Table 27-3. Register Summary – 32-Bit Mod e Registers
Offset Name Bit Pos.
0x00 CTRLA 7:0 WAVEGEN[1:0] MODE[1:0] ENABLE SWRST
0x01 15:8 PRESCSYNC[1:0] RUNSTDBY PRESCALER[2:0]
0x02 READREQ 7:0 ADDR[4:0]
0x03 15:8 RREQ RCONT
0x04 CTRLBCLR 7:0 CMD[1:0] ONESHOT DIR
0x05 CTRLBSET 7:0 CMD[1:0] ONESHOT DIR
0x06 CTRLC 7:0 CPTEN1 CPTEN0 INVEN1 INVEN0
0x07 Reserved
0x08 DBGCTRL 7:0 DBGRUN
0x09 Reserved
0x0A EVCTRL 7:0 TCEI TCINV EVACT[2:0]
0x0B 15:8 MCEO1 MCEO0 OVFEO
0x0C INTENCLR 7:0 MC1 MC0 SYNCRDY ERR OVF
0x0D INTENSET 7:0 MC1 MC0 SYNCRDY ERR OVF
0x0E INTFLAG 7:0 MC1 MC0 SYNCRDY ERR OVF
0x0F STATUS 7:0 SYNCBUSY SLAVE STOP
0x10
COUNT
7:0 COUNT[7:0]
0x11 15:8 COUNT[15:8]
0x12 23:16 COUNT[23:16]
0x13 31:24 COUNT[31:24]
0x14 Reserved
0x15 Reserved
0x16 Reserved
0x17 Reserved
0x18
CC0
7:0 CC[7:0]
0x19 15:8 CC[15:8]
0x1A 23:16 CC[23:16]
0x1B 31:24 CC[31:24]
0x1C
CC1
7:0 CC[7:0]
0x1D 15:8 CC[15:8]
0x1E 23:16 CC[23:16]
0x1F 31:24 CC[31:24]
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27.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Please refer to the Register Access Protection
section and the PAC chapter for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Write-Synchronized
or Read-Synchronized property in each individual register description. Refer to the Synchronization section for details.
Some registers are enable-protected, meaning they can only be written when the TC is disabled. Enable-protection is
denoted by the Enable-Protected property in each individual register description.
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27.8.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x0000
Property: Write-Protected, Enable-Protected, Write-Synchronized
zBits 15:14 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 13:12 – PRESCSYNC[1:0]: Prescaler and Counter Synchronization
These bits select whether the counter should wrap around on the next GCLK_TCx clock or the next prescaled
GCLK_TCx clock. It also makes it possible to reset the prescaler.
The options are as shown in Table 27-4.
These bits are not synchronized.
Table 27-4. Prescaler and Co unter Synchronization
zBit 11 – RUNSTDBY: Run in Standby
This bit is used to keep the TC running in standby mode:
0: The TC is halted in standby.
1: The TC continues to run in standby.
This bit is not synchronized.
zBits 10:8 – PRESCALER[2:0]: Prescaler
These bits select the counter prescaler factor, as shown in Table 27-5.
These bits are not synchronized.
Bit151413121110 9 8
PRESCSYNC[1:0] RUNSTDBY PRESCALER[2:0]
Access R R R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
WAVEGEN[1:0] MODE[1:0] ENABLE SWRST
Access R R/W R/W R R/W R/W R/W R/W
Reset00000000
Value Name Description
0x0 GCLK Reload or reset the counter on next generic clock
0x1 PRESC Reload or reset the counter on next prescaler clock
0x2 RESYNC Reload or reset the counter on next generic clock. Re set the prescaler counter
0x3 -Reserved
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Table 27-5. Prescaler
zBit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 6:5 – WAVEGEN[1:0]: Waveform Generation Operation
These bits select the waveform generation operation. They affect the top value, as shown in “Waveform Output
Operations” on page 442. It also controls whether frequency or PWM waveform generation should be used. How
these modes differ can also be seen from “Waveform Output Operations” on page 442.
These bits are not synchronized.
Table 27-6. Waveform Generation Operation
Note: 1. This depends on the TC mode. In 8-bit mode, the top value is the Period Value register (PER). In 16- and
32-bit mode it is the maximum value.
zBit 4 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 3:2 – MODE[1:0]: TC Mode
These bits select the TC mode, as shown in Table 27-7.
These bits are not synchronized.
Value Name Description
0x0 DIV1 Prescaler: GCLK_TC
0x1 DIV2 Prescaler: GCLK_TC/2
0x2 DIV4 Prescaler: GCLK_TC/4
0x3 DIV8 Prescaler: GCLK_TC/8
0x4 DIV16 Prescaler: GCLK_TC/1 6
0x5 DIV64 Prescaler: GCLK_TC/6 4
0x6 DIV256 Prescaler: GCLK_TC/2 56
0x7 DIV1024 Prescaler: GCLK_TC/1 024
Value Name Operation Top Value Output Waveform
on Match Output Waveform
on Wraparound
0x0 NFRQ Normal frequency PER(1)/Max Toggle No action
0x1 MFRQ Match frequency CC0 Toggle No action
0x2 NPWM Normal PWM PER(1)/Max Set Clear
0x3 MPWM Match PWM CC0 Set Clear
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Table 27-7. TC Mode
zBit 1 – ENABLE: Enable
0: The peripheral is disabled.
1: The peripheral is enabled.
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/disabled. The
value written to CTRLA.ENABLE will read back immediately, and the Synchronization Busy bit in the Status regis-
ter (STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY will be cleared when the operation is complete.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the TC, except DBGCTRL, to their initial state, and the TC will be
disabled.
Writing a one to CTRLA.SWRST will always take precedence; all other writes in the same write-operation will be
discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST
and STATUS.SYNCBUSY will both be cleared when the reset is complete.
Value Name Description
0x0 COUNT16 Counter in 16-bit mode
0x1 COUNT8 Counter in 8-bit mode
0x2 COUNT32 Counter in 32-bit mode
0x3 -Reserved
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27.8.2 Read Request
For a detailed description of this register and its use, refer to the“Synchronization” on page 447.
Name: READREQ
Offset: 0x02
Reset: 0x0000
Property: -
zBit 15 – RREQ: Read Request
Writing a zero to this bit has no effect.
This bit will always read as zero.
Writing a one to this bit requests synchronization of the register pointed to by the Address bit group (READ-
REQ.ADDR) and sets the Synchronization Busy bit in the Status register (STATUS.SYNCBUSY).
zBit 14 – RCONT: Read Continuously
0: Continuous synchronization is disabled.
1: Continuous synchronization is enabled.
When continuous synchronization is enabled, the register pointed to by the Address bit group (READREQ.ADDR)
will be synchronized automatically every time the register is updated.
zBits 13:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:0 – ADDR[4:0]: Address
These bits select the offset of the register that needs read synchronization. In the TC, only COUNT and CCx are
available for read synchronization.
Bit151413121110 9 8
RREQ RCONT
AccessWR/WRRRRRR
Reset00000000
Bit76543210
ADDR[4:0]
Access R R R R/W R/W R/W R/W R/W
Reset00000000
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27.8.3 Control B Clear
This register allows the user to change this register without doing a read-modify-write operation. Changes in this register
will also be reflected in the Control B Set (CTRLBSET) register.
Name: CTRLBCLR
Offset: 0x04
Reset: 0x00
Property: Write-Protected, Write-Synchronized, Read-Synchronized
zBits 7:6 – CMD[1:0]: Command
These bits are used for software control of retriggering and stopping the TC. When a command has been exe-
cuted, the CMD bit group will read back as zero. The commands are executed on the next prescaled GCLK_TC
clock cycle.
Writing a zero to one of these bits has no effect.
Writing a one to one of these bits will clear the pending command.
Table 27-8. Command
zBits 5:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – ONESHOT: One-Shot
This bit controls one-shot operation of the TC. When in one-shot mode, the TC will stop counting on th e next over-
flow/underflow condition or a stop command.
0: The TC will wrap around and continue counting on an overflow/underflow condition.
1: The TC will wrap around and stop on the next underflow/overflow condition.
Writing a zero to this bit has no effect
Writing a one to this bit will disable one-shot operation.
zBit 1 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 0 – DIR: Counter Direction
This bit is used to change the direction of the counter.
0: The timer/counter is counting up (incrementing).
Bit76543210
CMD[1:0] ONESHOT DIR
Access R/W R/W R R R R/W R R/W
Reset00000000
Value Name Description
0x0 NONE No action
0x1 RETRIGGER Force a start, restart or retrigger
0x2 STOP Force a stop
0x3 -Reserved
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1: The timer/counter is counting down (decrementing).
Writing a zero to this bit has no effect.
Writing a one to this bit will make the counter count up.
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27.8.4 Control B Set
This register allows the user to change this register without doing a read-modify-write operation. Changes in this register
will also be reflected in the Control B Set (CTRLBCLR) register.
Name: CTRLBSET
Offset: 0x05
Reset: 0x00
Property: Write-Protected, Write-Synchronized, Read-Synchronized
zBits 7:6 – CMD[1:0]: Command
These bits is used for software control of retri ggering and stopping the TC. When a command has been executed,
the CMD bit group will be read back as zero. The commands are executed on the next prescaled GCLK_TC clock
cycle.
Writing a zero to one of these bits has no effect.
Writing a one to one of these bits will set a command.
Table 27-9. Command
zBits 5:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – ONESHOT: One-Shot
This bit controls one-shot operation of the TC. When active, the TC will stop counting on the next overflow/under-
flow condition or a stop command.
0: The TC will wrap around and continue counting on an overflow/underflow condition.
1: The timer/counter will wrap around and stop on the next underflow/overflow condition.
Writing a zero to this bit has no effect.
Writing a one to this bit will enable one-shot operation.
zBit 1 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 0 – DIR: Counter Direction
This bit is used to change the direction of the counter.
0: The timer/counter is counting up (incrementing).
Bit76543210
CMD[1:0] ONESHOT DIR
Access R/W R/W R R R R/W R R/W
Reset00000000
Value Name Description
0x0 NONE No action
0x1 RETRIGGER Force a start, restart or retrigger
0x2 STOP Force a stop
0x3 -Reserved
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1: The timer/counter is counting down (decrementing).
Writing a zero to this bit has no effect
Writing a one to this bit will make the counter count down.
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27.8.5 Control C
Name: CTRLC
Offset: 0x06
Reset: 0x00
Property: Write-Protected, Write-Synchronized, Read-Synchronized
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:4 – CPTENx: Capture Channel x Enable
These bits are used to select whether channel x is a capture or a compare channel.
Writing a one to CPTENx enables capture on channel x.
Writing a zero to CPTENx disables capture on channel x.
zBits 3:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – INVENx: Output Waveform x Invert Enable
These bits are used to select inversion on the output of channel x.
Writing a one to INVENx inverts the output from WO[x].
Writing a zero to INVENx disables inversion of the output from WO[x].
Bit76543210
CPTEN1 CPTEN0 INVEN1 INVEN0
Access R R R/W R/W R R R/W R/W
Reset00000000
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27.8.6 Debug Control
Name: DBGCTRL
Offset: 0x08
Reset: 0x00
Property: Write-Protected
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – DBGRUN: Debug Run Mode
This bit is not affected by a software reset, and should not be changed by software while the TC is enabled.
0: The TC is halted when the device is halted in debug mode.
1: The TC continues normal operation when the device is halted in debug mode.
Bit76543210
DBGRUN
AccessRRRRRRRR/W
Reset00000000
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27.8.7 Event Control
Name: EVCTRL
Offset: 0x0A
Reset: 0x0000
Property: Write-Protected, Enable-Protected
zBits 15:14 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 13:12 – MCEOx: Match or Capture Channel x Event Output Enable
These bits control whether event match or capture on channel x is enabled or not and generated for every match
or capture.
0: Match/Capture event on channel x is disabled and will not be generated.
1: Match/Capture event on channel x is enabled and will be generated for every compare/capture.
These bits are not enable-protected.
zBits 11:9 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 8 – OVFEO: Overflow/Underflow Event Output Enable
This bit is used to enable the Overflow/Underflow event. When enabled an event will be generated when the coun-
ter overflows/underflows.
0: Overflow/Underflow event is disabled and will not be generated.
1: Overflow/Underflow event is enabled and will be generated for every counter overflow/underflow.
This bit is not enable-protected.
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 5 – TCEI: TC Event Input
This bit is used to enable input events to the TC.
0: Incoming events are disabled.
1: Incoming events are enabled.
This bit is not enable-protected.
Bit151413121110 9 8
MCEO1 MCEO0 OVFEO
Access R R R/W R/W R R R R/W
Reset00000000
Bit76543210
TCEI TCINV EVACT[2:0]
Access R R R/W R/W R R/W R/W R/W
Reset00000000
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zBit 4 – TCINV: TC Inverted Event Input
This bit inverts the input event source when used in PWP or PPW measurement.
0: Input event source is not inverted.
1: Input event source is inverted.
This bit is not enable-protected.
zBit 3 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 2:0 – EVACT[2:0]: Event Action
These bits define the event action the TC will perform on an event,as shown in Table 27-10.
Table 27-10. Event Action
Value Name Description
0x0 OFF Event action disabled
0x1 RETRIGGER Start, restart or retrigger TC on event
0x2 COUNT Count on event
0x3 START Start TC on event
0x4 -Reserved
0x5 PPW Period captured in CC0, pulse width in CC1
0x6 PWP Period captured in CC1, pulse width in CC0
0x7 -Reserved
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27.8.8 Interrupt Enable Clear
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x0C
Reset: 0x00
Property: Write-Protected
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:4 – MCx: Match or Capture Channel x Interrupt Enable
0: The Match or Capture Channel x interrupt is disabled.
1: The Match or Capture Channel x interrupt is enabled.
Writing a zero to MCx has no effect.
Writing a one to MCx will clear the corresponding Match or Capture Channel x Interrupt Disable/Enable bit, which
disables the Match or Capture Channel x interrupt.
zBit 3 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The Synchronization Ready interrupt is disabled.
1: The synchronization ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Synchronization Ready Interrupt Disable/Enable bit, which disables the Syn-
chronization Ready interrupt.
zBit 2 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 1 – ERR: Error Interrupt Enable
0: The Error interrupt is disabled.
1: The Error interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Error Interrupt Disable/Enable bit, which disables the Compare interrupt.
zBit 0 – OVF: Overflow Interrupt Enable
0: The Overflow interrupt is disabled.
1: The Overflow interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overflow Interrupt Disable/Enable bit, which disables the Overflow interrupt.
Bit76543210
MC1 MC0 SYNCRDY ERR OVF
Access R R/W R/W R/W R/W R R/W R/W
Reset00000000
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27.8.9 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x0D
Reset: 0x00
Property: Write-Protected
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:4 – MCx: Match or Capture Channel x Interrupt Enable
0: The Match or Capture Channel x interrupt is disabled.
1: The Match or Capture Channel x interrupt is enabled.
Writing a zero to MCx has no effect.
Writing a one to MCx will set the corresponding Match or Capture Channel x Interrupt Enable bit, which enables
the Match or Capture Channel x interrupt.
zBit 3 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The Synchronization Ready interrupt is disabled.
1: The Synchronization Ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Synchronization Ready Interrupt Disable/Enable bit, which enables the Syn-
chronization Ready interrupt.
zBit 2 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 1 – ERR: Error Interrupt Enable
0: The Error interrupt is disabled.
1: The Error interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Error Interrupt bit, which enables the Error interrupt.
zBit 0 – OVF: Overflow Interrupt Enable
0: The Overflow interrupt is disabled.
1: The Overflow interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Overflow Interrupt Enable bit, which enables the Overflow interrupt.
Bit76543210
MC1 MC0 SYNCRDY ERR OVF
Access R R R/W R/W R/W R R/W R/W
Reset00000000
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27.8.10 Interrupt Flag Status and Clear
Name: INTFLAG
Offset: 0x0E
Reset: 0x00
Property: -
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:4 – MCx: Match or Capture Channel x
This flag is set on the next CLK_TC_CNT cycle after a match with the compare condition or once CCx register
contain a valid capture value, and will generate an interrupt request if the corresponding Match or Capture Chan-
nel x Interrupt Enable bit in the Interrupt Enable Set register (INTENSET.MCx) is one.
Writing a zero to one of these bits has no effect.
Writing a one to one of these bits will clear the corresponding Match or Capture Channel x interrupt flag
In capture mode, this flag is automatically cleared when CCx register is read.
zBit 3 – SYNCRDY: Synchronization Ready
This flag is set on a 1-to-0 transition of the Synchronization Busy bit in the Status register (STATUS.SYNCBUSY),
except when the transition is caused by an enable or software reset, and will generate an interrupt request if the
Synchronization Ready Interrupt Enable bit in the Interrupt Enable Set register (INTENSET.SYNCRDY) is one.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Synchronization Ready interrupt flag
zBit 2 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBit 1 – ERR: Error
This flag is set if a new capture occurs on a channel when the corresponding Match or Capture Channel x interrupt
flag is one, in which case there is nowhere to store the new capture.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Error interrupt flag.
zBit 0 – OVF: Overflow
This flag is set on the next CLK_TC_CNT cycle after an overflow condition occurs, and will generate an interrupt if
INTENCLR/SET.OVF is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Overflow interrupt flag.
Bit76543210
MC1 MC0 SYNCRDY ERR OVF
Access R R R/W R/W R/W R R/W R/W
Reset00000000
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27.8.11 Status
Name: STATUS
Offset: 0x0F
Reset: 0x08
Property: -
zBit 7 – SYNCBUSY: Synchronization Busy
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 6:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – SLAVE: Slave
This bit is set when the even-numbered master TC is set to run in 32-bit mode. The odd-numbered TC will be the
slave.
zBit 3 – STOP: Stop
This bit is set when the TC is disabled, on a Stop command or on an overflow or underflow condition when the
One-Shot bit in the Control B Set register (CTRLBSET.ONESHOT) is one.
0: Counter is running.
1: Counter is stopped.
zBits 2:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit76543210
SYNCBUSY SLAVE STOP
AccessRRRRRRRR
Reset00001000
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27.8.12 Counter Value
27.8.12.1 8-Bit Mode
Name: COUNT
Offset: 0x10
Reset: 0x00
Property: Write-Synchronized, Read-Synchronized
zBits 7:0 – COUNT[7:0]: Counter Value
These bits contain the current counter value.
Bit76543210
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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27.8.12.2 16-Bit Mode
Name: COUNT
Offset: 0x10
Reset: 0x0000
Property: Write-Synchronized, Read-Synchronized
zBits 15:0 – COUNT[15:0]: Counter Value
These bits contain the current counter value.
Bit151413121110 9 8
COUNT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
COUNT[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
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27.8.12.3 32-Bit Mode
Name: COUNT
Offset: 0x10
Reset: 0x00000000
Property: Write-Synchronized, Read-Synchronized
zBits 31:0 – COUNT[31:0]: Counter Value
These bits contain the current counter value.
Bit3130292827262524
COUNT[31:24]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit151413121110 9 8
COUNT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit2322212019181716
COUNT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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27.8.13 Period Value
The Period Value register is available only in 8-bit TC mode. It is not available in 16-bit and 32-bit TC modes.
27.8.13.1 8-Bit Mode
Name: PER
Offset: 0x14
Reset: 0xFF
Property: Write-Synchronized, Read-Synchronized
zBits 7:0 – PER[7:0]: Period Value
These bits contain the counter period value in 8-bitTC mode.
Bit76543210
PER[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset11111111
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27.8.14 Compare/Capture
27.8.14.1 8-Bit Mode
Name: CCx
Offset: 0x18+i*0x1 [i=0..3]
Reset: 0x00
Property: Write-Synchronized, Read-Synchronized
zBits 7:0 – CC[7:0]: Compare/Capture Value
These bits contain the compare/capture value in 8-bit TC mode. In frequency or PWM waveform match operation
(CTRLA.WAVEGEN), the CC0 register is used as a period register.
Bit76543210
CC[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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27.8.14.2 16-Bit Mode
Name: CCx
Offset: 0x18+i*0x2 [i=0..3]
Reset: 0x0000
Property: Write-Synchronized, Read-Synchronized
zBits 15:0 – CC[15:0]: Compare/Capture Value
These bits contain the compare/capture value in 16-bit TC mode. In frequency or PWM waveform match operation
(CTRLA.WAVEGEN), the CC0 register is used as a period register.
Bit151413121110 9 8
CC[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
CC[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
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27.8.14.3 32-Bit Mode
Name: CCx
Offset: 0x18+i*0x4 [i=0..3]
Reset: 0x00000000
Property: Write-Synchronized, Read-Synchronized
zBits 31:0 – CC[31:0]: Compare/Capture Value
These bits contain the compare/capture value in 32-bit TC mode. In frequency or PWM waveform match opera-
tion (CTRLA.WAVEGEN), the CC0 register is used as a period register.
Bit3130292827262524
CC[31:24]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit2322212019181716
CC[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit151413121110 9 8
CC[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
CC[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
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28. ADC – Analog-to-Digital Converter
28.1 Overview
The Analog-to-Digital Converter (ADC) converts analog signals to digital values. The ADC has 12-bit resolution, and is
capable of converting up to 350ksps. The input selection is flexible, and both differential and single-ended measurements
can be performed. An optional gain stage is available to increase the dynamic range. In addition, several internal signal
inputs are available. The ADC can provide both signed and unsigned results.
ADC measurements can be started by either application software or an incoming event from another peripheral in the
device. ADC measurements can be started with predictable timing, and without software intervention.
Both internal and external reference voltages can be used.
An integrated temperature sensor is available for use with the ADC. The bandgap voltage as well as the scaled I/O and
core voltages can also be measured by the ADC.
The ADC has a compare function for accurate monitoring of user-defined thresholds, with minimum software intervention
required.
The ADC may be configured for 8-, 10- or 12-bit results, reducing the conversion time. ADC conversion results are
provided left- or right-adjusted, which eases calculation when the result is represented as a signed value.
28.2 Features
z8-, 10- or 12-bit resolution
zUp to 350,000 samples per second (ksps)
zDifferential and single-ended inputs
zUp to 32 analog inputs
z25 positive and 10 negative, incl uding internal and external
zFive internal inputs
zBandgap
zTemperature sensor
zDAC
zScaled core supply
zScaled I/O supply
z1/2x to 16x gain
zSingle, continuous and pin-scan conversion options
zWindowing monitor with selectable channel
zConversion range:
zVref [1v to VDDANA -0.6V]
zADCx * GAIN [0V to -Vref ]
zBuilt-in internal reference and external reference options
zFour bits for reference selection
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zEvent-triggered conversion for accurate timing (one event input)
zHardware gain and offset compensation
zAveraging and oversampling with decimation to support, up to 16-bit result
zSelectable sampling time
28.3 Block Diagram
Figure 28-1. ADC Block Diagram
28.4 Signal Description
Note: 1. Refer to “Configuration Summary” on page 3 for details on exact number of analog input channels.
Refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
ADC
ADC0
ADCn
...
INT.SIG
ADC0
ADCn
INT.SIG
...
REFCTRL
INT1V
INTVCC
AREFB
OFFSETCORR
GAINCORRSWTRIG
EVCTRL
AVGCTRL
WINCTRL
SAMPCTRL WINUT
POST
PROCESSING
PRESCALER
CTRLA
WINLT
AREFA
CTRLB
RESULT
INPUTCTRL
Signal Name Type Description
AREFA Analog input External reference voltage A
AREFB Analog input External reference voltage B
ADC[19..0](1) Analog input Analog input channels
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28.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
28.5.1 I/O Lines
Using the ADC's I/O lines requires the I/O pins to be configured using the port configuration (PORT).
Refer to “PORT” on page 284 for details.
28.5.2 Power Management
The ADC will continue to operate in any sleep mode where the selected source clock is running. The ADC’s interrupts
can be used to wake up the device from sleep modes. The events can trigger other operations in the system without
exiting the sleep modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
28.5.3 Clocks
The ADC bus clock (CLK_ADC_APB) can be enabled and disabled in the Power Manager, and the default state of
CLK_ADC_APB can be found in the Table 15-1.
A generic clock (GCLK_ADC) is required to clock the ADC. This clock must be configured and enabled in the Generic
Clock Controller (GCLK) before using the ADC. Refer “GCLK – Generic Clock Controller” on page 78 for details.
This generic clock is asynchronous to the bus clock (CLK_ADC_APB). Due to this asynchronicity, writes to certain
registers will require synchronization between the clock domains. Refer to “Synchronization” on page 486 for further
details.
28.5.4 Interrupts
The interrupt request line is con nected to the int errupt controller. Using ADC inte rrupts requires the interrupt controller to
be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
28.5.5 Events
Events are connected to the Event System. Refer to “EVSYS – Event System” on page 309 for details.
28.5.6 Debug Operation
When the CPU is halted in debug mode, the ADC will halt normal operation. The ADC can be forced to continue
operation during debugging. Refer to the Debug Control register (DBGCTRL) for details.
28.5.7 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following register:
zInterrupt Flag Status and Clear register (INTFLAG)
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode or the CPU reset is extended, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
28.5.8 Analog Connections
I/O-pins AIN0 to AIN19 as well as the AREFA/AREFB reference voltage pin are analog inputs to the ADC.
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28.5.9 Calibration
The values BIAS_CAL and LINEARITY_CAL from the production test must be loaded from the NVM Software Calibration
Row into the ADC Calibration register (CALIB) by software to achieve specified accuracy.
The gain and offset correction values from the production test can be loaded from the Software Calibration Row into the
GAINCORR and OFFSETCORR registers by software to achieve specified accuracy.
Refer to “NVM Software Calibration Row Mapping” on page 22 for more details.
28.6 Functional Description
28.6.1 Principle of Operation
By default, the ADC provides results with 12-bit resolution. 8-bit or 10-bit results can be selected in order to reduce the
conversion time. The ADC has an oversampling with decimation option that can extend the resolution to 16 bits. The
input values can be either internal (e.g., internal temperature sensor) or external (connected I/O pins). The user can also
configure whether the conversion should be single-ended or differential.
28.6.2 Basic Operation
28.6.2.1 Initialization
Before enabling the ADC, the asynchronous clock source must be selected and enabled, and the ADC referen ce must be
configured. The first conversion after the reference is changed must not be used. All other configuration registers must
be stable during the conversion. The source for GCLK_ADC is selected and enabled in the System Controller
(SYSCTRL). Refer to “SYSCTRL – System Controller” on page 127 for more details.
When GCLK_ADC is enabled, the ADC can be enabled by writing a one to the Enable bit in the Control Register A
(CTRLA.ENABLE).
28.6.2.2 Enabling, Disabling and Reset
The ADC is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The ADC is disabled
by writing a zero to CTRLA.ENABLE.
The ADC is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in the
ADC, except DBGCTRL, will be reset to their initial state, and the ADC will be disabled. Refer to the CTRLA register for
details.
The ADC must be disabled before it is reset.
28.6.2.3 Basic Operation
In the most basic configuration, the ADC sample values from the configured internal or external sources (INPUTCTRL
register). The rate of the conversion is dependent on the combination of the GCLK_ADC frequency and the clock
prescaler.
To convert analog values to digital values, the ADC needs first to be initialized, as described in “Initialization” on page
479. Data conversion can started either manually, by writing a one to the Start bit in the Software Trigger register
(SWTRIG.START), or automatically, by configuring an automatic trigger to initiate the conversions. A free-running mode
could be used to continuously convert an input channel. There is no need for a trigger to start the conversion. It will start
automatically at the end of previous conversion.
The automatic trigger can be configured to trigger on many different conditions.
The result of the conversion is stored in the Result register (RESULT) as it becomes available, overwriting the result from
the previous conversion.
To avoid data loss if more than one channel is enabled, the conversion result must be read as it becomes available
(INTFLAG.RESRDY). Failing to do so will result in an overrun error condition, indicated by the OVERRUN bit in the
Interrupt Flag Status and Clear register (INTFLAG.OVERRUN).
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To use an interrupt handler, the corresponding bit in the Interrupt Enable Set register (INTENSET) must be written to
one.
28.6.3 Prescaler
The ADC is clocked by GCLK_ADC. There is also a prescaler in the ADC to enable conversion at lower clock rates. .
Refer to CTRLB for details on prescaler settings.
Figure 28-2. ADC Prescaler
The propagation delay of an ADC measurement is given by:
28.6.4 ADC Resolution
The ADC supports 8-bit, 10-bit and 12-bit resolutions. Resolution can be changed by writing the Resolution bit group in
the Control B register (CTRLB.RESSEL). After a reset, the resolution is set to 12 bits by default.
Ta ble 28-1. Delay Gain
INTPUTCTRL.GAIN[3:0]
Delay Gain (in CLK_ADC Period)
Differential Mode Single-Ended Mode
0x0 0 0
0x1 0 1
0x2 1 1
0x3 1 2
0x4 2 2
0x5 ... 0xE Reserved Reserved
0xF 0 1
GCLK_ADC 9-BIT PRESCALER
CTRLB.PRESCALER[2:0]
DIV512
DIV256
DIV128
DIV64
DIV32
DIV16
DIV8
DIV4
CLK_ADC
PropagationDelay 1Resolution
2
---------------------------- DelayGain++
fADC
--------------------------------------------------------------------------=
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28.6.5 Differential and Single-Ended Conversions
The ADC has two conversion options: differential and single-ended. When measuring signals where the positive input is
always at a higher voltage than the negative input, the single-ended conversion should be used in order to have full 12-
bit resolution in the conversion, which has only positive values. The negative input must be connected to ground. This
ground could be the internal GND, IOGND or an external ground connected to a pin. Refer to INPUTCTRL for selection
details. If the positive input may go below the negative input, creating some negative results, the differential mode should
be used in order to get correct results. The configuration of the conversion is done in the Differential Mode bit in the
Control B register (CTRLB.DIFFMODE). These two types of conversion could be run in single mode or in free-running
mode. When set up in free-running mode, an ADC input will continuously sample and do new conversions. The
INTFLAG.RESRDY bit will be set at the end of each conversion.
28.6.5.1 Conversion Timing
Figure 28-3 shows the ADC timing for a single conversion without gain. The writing of the ADC Start Conversion bit
(SWTRIG.START) or Start Conversion Event In bit (EVCTRL.STARTEI) must occur at least one CLK_ADC_APB cycle
before the CLK_ADC cycle on which the conversion starts. The input channel is sampled in the first half CLK_ADC
period. The sampling time can be increased by using the Sampling Time Length bit group in the Sampling Time Control
register (SAMPCTRL.SAMPLEN). Refer to Figure 28-4 for example on increased sampling time.
Figure 28-3. ADC Timing for One Conversion in Differential Mode without Gain
Figure 28-4. ADC Timing for One Conversion in Differential Mode without Gain, but with Increased Sampling Time
12345678
CLK_ADC
START
SAMPLE
INT
Converting Bit
MSB10987654321LSB
12345678
CLK_ADC
START
SAMPLE
INT
Converting Bit
MSB10987654321LSB
91011
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Figure 28-5. ADC Timing for Free Running in Differential Mode without Gain
Figure 28-6. ADC Timing for One Conversion in Single-Ended Mode without Gain
Figure 28-7. ADC Timing for Free Running in Single-Ended Mode without Gain
12345678
CLK_ADC
START
SAMPLE
INT
Converting Bit
9101112 13 14 15 16
1110987654321011 109876543210111098765
12345678
CLK_ADC
START
SAMPLE
INT
Converting Bit
91011
AMPLIFY
MSB10987654321LSB
12345678
CLK_ADC
START
SAMPLE
INT
Converting Bit
9101112 13 14 15 16
11109876543210 11 109876543210 1110
AMPLIFY
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28.6.6 Accumulation
The result from multiple consecutive conversions can be accumulated. The number of samples to be accumulated is
specified by writing to the Number of Samples to be Collected field in the Average Control register
(AVGCTRL.SAMPLENUM) as described in Table 28-2. When accumulating more than 16 samples, the result will be too
large for the 16-bit RESULT register. To avoid overflow, the result is shifted right automatically to fit within the 16
available bits. The number of automatic right shifts are specified in Table 28-2. Note that to be able to perform the
accumulation of two or more samples, the Conversion Result Re solution field in the Control B register (CTRLB.RESSEL)
must be written to one.
Table 28-2. Accumulation
28.6.7 Averaging
Averaging is a feature that increases the sample accuracy, though at the cost of reduced sample rate. This feature is
suitable when operating in noisy conditions. Averaging is done by accumulating m samples, as described in
“Accumulation” on page 483, and divide the result by m. The averaged result is available in the RESULT register. The
number of samples to be accumulated is specified by writing to AVGCTRL.SAMPLENUM as described in Table 28-3.
The division is obtained by a combination of the automatic right shift described above, and an additional right shift that
must be specified by writing to the Adjusting Result/Division Coefficient field in AVGCTRL (AVGCTRL.ADJRES) as
described in Table 28-3. Note that to be able to perform the averaging of two or more samples, the Conversion Result
Resolution field in the Control B register (CTRLB.RESSEL) must be written to one.
Averaging AVGCTRL.SAMPLENUM samples will reduce the effective sample rate by .
When the required average is reached, the INTFLAG.RESRDY bit is set.
Number of
Accumulated Samples AVGCTRL.
SAMPLENUM Intermediate
Result Precision Number of Automatic
Right Shifts Final Result
Precision Automatic
Division Factor
10x0 12 bits 012 bits 0
20x1 13 bits 013 bits 0
40x2 14 bits 014 bits 0
80x3 15 bits 015 bits 0
16 0x4 16 bits 016 bits 0
32 0x5 17 bits 116 bits 2
64 0x6 18 bits 216 bits 4
128 0x7 19 bits 316 bits 8
256 0x8 20 bits 416 bits 16
512 0x9 21 bits 516 bits 32
1024 0xA 22 bits 616 bits 64
Reserved 0xB –0xF 12 bits 12 bits 0
1
AVGCTRL.SAMPLENUM
-------------------------------------------------------------------
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Table 28-3. Averagin g
28.6.8 Oversampling and Decimation
By using oversampling and decimation, the ADC resolution can be increased from 12 bits to up to 16 bits. To increase
the resolution by n bits, 4n samples must be accumulated. The result must then be shifted right by n bits. This right shift is
a combination of the automatic right shift and the value written to AVGCTRL.ADJRES. To obtain the correct resolution,
the ADJRES must be configured as described in the table below. This method will result in n bit extra LSB resolution.
Table 28-4. Configuration Required for Oversampling and Decimation
28.6.9 Window Monitor
The window monitor allows the conversion result to be compared to some predefined threshold values. Supported
modes are selected by writing the Window Monitor Mode bit group in the Window Monitor Control register
(WINCTRL.WINMODE[2:0]). Thresholds are given by writing the Window Monitor Lower Threshold register (WINLT) and
Window Monitor Upper Threshold register (WINUT).
If differential input is selected, the WINLT and WINUT are evaluated as signed values. Otherwise they are evaluated as
unsigned values.
Number of
Accumulated
Samples AVGCTRL.
SAMPLENUM
Intermediate
Result
Precision
Number of
Automatic
Right Shifts Division
Factor AVGCTRL.
ADJRES
Total
Number
of Right
Shifts
Final
Result
Precision
Automatic
Division
Factor
10x0 12 bits 0 1 0x0 12 bits 0
20x1 13 0 2 0x1 112 bits 0
40x2 14 0 4 0x2 212 bits 0
80x3 15 0 8 0x3 312 bits 0
16 0x4 16 016 0x4 412 bits 0
32 0x5 17 116 0x4 512 bits 2
64 0x6 18 216 0x4 612 bits 4
128 0x7 19 316 0x4 712 bits 8
256 0x8 20 416 0x4 812 bits 16
512 0x9 21 516 0x4 912 bits 32
1024 0xA 22 616 0x4 10 12 bits 64
Reserved 0xB –0xF 0x0 12 bits 0
Result
Resolution Number of Samples
to Average AVGCTRL.SAMPLENUM[3:0]
Number of
Automatic Right
Shifts AVGCTRL.ADJRES[2:0]
13 bits 41 = 4 0x2 00x1
14 bits 42 = 16 0x4 00x2
15 bits 43 = 64 0x6 20x1
16 bits 44 = 256 0x8 40x0
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Another important point is that the significant WINLT and WINUT bits are given by the precision selected in the
Conversion Result Resolution bit group in the Control B register (CTRLB.RESSEL). This means that if 8-bit mode is
selected, only the eight lower bits will be considered. In addition, in differential mode, the eighth bit will be considered as
the sign bit even if the ninth bit is zero.
The INTFLAG.WINMON interrupt flag will be set if the conversion result matches the window monitor condition.
28.6.10 Offset and Gain Correction
Inherent gain and offset errors affect the absolute accuracy of the ADC. The offset error is defined as the deviation of the
actual ADC’s transfer function from an ideal straight line at zero input voltage. The offset error cancellation is handled by
the Offset Correction register (OFFSETCORR). The offset correction value is subtracted from the converted data before
writing the Result register (RESULT). The gain error is defined as the deviation of the last output step’s midpoint from the
ideal straight line, after compensating for offset error. The gain error cancellation is handled by the Gain Correction
register (GAINCORR). To correct these two errors, the Digital Correction Logic Enabled bit in the Control B register
(CTRLB.CORREN) must be written to one.
Offset and gain error compensation results are both calculated according to:
In single conversion, a latency of 13 GCLK_ADC is added to the availability of the final result. Since the correction time is
always less than the propagation delay, this latency appears in free-running mode only during the first conversion. After
that, a new conversion will be initialized when a conversion completes. All other conversion results are available at the
defined sampling rate.
Figure 28-8. ADC Timing Correction Enabled
28.6.11 Additional Features
z
28.6.12 Interrupts
The ADC has the following interrupt sources:
zResult Conversion Ready: RESRDY
zOverrun: OVERRUN
zWindow Monitor: WINMON
zSynchronization Ready: SYNCRDY
Result Conversion value OFFSETCORR–()GAINCORR⋅=
START
CONV0 CONV1 CONV2 CONV3
CORR0 CORR1 CORR2 CORR3
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Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR) register. An interru pt request is generate d when the
interrupt flag is set and the corresponding interrup t is enabled. The interrupt reque st remains active until the interrupt flag
is cleared, the interrupt is disabled or the peripheral is reset. An interrupt flag is cleared by writing a one to the
corresponding bit in the INTFLAG register. Each peripheral can have one interrupt request line per interrupt source or
one common interrupt request line for all the interrupt sources. This is device dependent.
Refer to “Nested Vector Interrupt Controller” on page 24 for details. If the peripheral has one common interrupt request
line for all the interrupt sources, the user must read the INTFLAG register to determine which interrupt condition is
present.
28.6.13 Events
The peripheral can generate the following output events:
zResult Ready (RESRDY)
zWindow Monitor (WINMON)
Output events must be enabled to be generated. Writing a one to an Event Output bit in the Event Control register
(EVCTRL.xxEO) enables the corresponding output event. Writing a zero to this bit disables the corresponding output
event. The events must be correctly routed in the Event System. Refer to “EVSYS – Event System” on page 309 for
details.
The peripheral can take the following actions on an input event:
zADC start conversion (START)
zADC conversion flush (FLUSH)
Input events must be enabled for the corresponding action to be taken on any input event. Writing a one to an Event
Input bit in the Event Control register (EVCTRL.xxEI) enables the corresponding action on the input event. Writing a zero
to this bit disables the corresponding action on the input event. Note that if several events are connected to the
peripheral, the enabled action will be taken on any of the incoming events. The events must be correctly routed in the
Event System. Refer to “EVSYS – Event System” on page 309 for details.
28.6.14 Sleep Mode Operation
The Run in Standby bit in the Control A register (CTRLA.RUNSTDBY) controls the behavior of the ADC during standby
sleep mode. When the bit is zero, the ADC is disabled during sleep, but maintains its current configuration. When
the bit is one, the ADC continues to operate during sleep. Note that when RUNSTDBY is zero, the analog
blocks are powered off for the lowest power consumption. This necessitates a start-up time delay when the system
returns from sleep.
When RUNSTDBY is one, any enabled ADC interrupt source can wake up the CPU. However, ADC conversion
will be triggerable by events only while the CPU is idle.
28.6.15 Synchronization
Due to the asynchronicity between CLK_ADC_APB and GCLK_ADC, some registers must be synchronized when
accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete. The Synchronization
Ready interrupt can be used to signal when synchronization is complete.
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If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following bits need synchronization when written:
zSoftware Reset bit in the Control A register (CTRLA.SWRST)
zEnable bit in the Control A register (CTRLA.ENABLE)
The following registers need synchronization when written:
zControl B (CTRLB)
zSoftware Trigger (SWTRIG)
zWindow Monitor Control (WINCTRL)
zInput Control (INPUTCTRL)
zWindow Upper/Lower Threshold (WINUT/WINLT)
Write-synchronization is denoted by the Write-Synchronized property in the register description.
The following registers need synchronization when read:
zSoftware Trigger (SWTRIG)
zInput Control (INPUTCTRL)
zResult (RESULT)
Read-synchronization is denoted by the Read-Synchronized property in the register description.
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28.7 Register Summary
Offset Name Bit pos.
0x00 CTRLA 7:0 RUNSTDBY ENABLE SWRST
0x01 REFCTRL 7:0 REFCOMP REFSEL[3:0]
0x02 AVGCTRL 7:0 ADJRES[2:0] SAMPLENUM[3:0]
0x03 SAMPCTRL 7:0 SAMPLEN[5:0]
0x04 CTRLB 7:0 RESSEL[1:0] CORREN FREERUN LEFTADJ DIFFMODE
0x05 15:8 PRESCALER[2:0]
0x06 Reserved
0x07 Reserved
0x08 WINCTRL 7:0 WINMODE[2:0]
0x09 Reserved
0x0A Reserved
0x0B Reserved
0x0C SWTRIG 7:0 START FLUSH
0x0D Reserved
0x0E Reserved
0x0F Reserved
0x10
INPUTCTRL
7:0 MUXPOS[4:0]
0x11 15:8 MUXNEG[4:0]
0x12 23:16 INPUTOFFSET[3:0] INPUTSCAN[3:0]
0x13 31:24 GAIN[3:0]
0x14 EVCTRL 7:0 WINMONEO RESRDYEO SYNCEI STARTEI
0x15 Reserved
0x16 INTENCLR 7:0 SYNCRDY WINMON OVERRUN RESRDY
0x17 INTENSET 7:0 SYNCRDY WINMON OVERRUN RESRDY
0x18 INTFLAG 7:0 SYNCRDY WINMON OVERRUN RESRDY
0x19 STATUS 7:0 SYNCBUSY
0x1A RESULT 7:0 RESULT[7:0]
0x1B 15:8 RESULT[15:8]
0x1C WINLT 7:0 WINLT[7:0]
0x1D 15:8 WINLT[15:8]
0x1E Reserved
0x1F Reserved
0x20 WINUT 7:0 WINUT[7:0]
0x21 15:8 WINUT[15:8]
0x22 Reserved
0x23 Reserved
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28.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Refer to “Register Access Protection” on page 478
for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Write-Synchronized
or the Read-Synchronized property in each individual register description. Refer to “Synchronization” on page 486 for
details.
Some registers are enable-protected, meaning they can be written only when the ADC is disabled. Enable-protection is
denoted by the Enable-Protected property in each individual register description.
28.8.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – RUNSTDBY: Run in Standby
This bit indicates whether the ADC will continue running in standby sleep mode or not:
0: The ADC is halted during standby sleep mode.
1: The ADC continues normal operation during standby sleep mode.
zBit 1 – ENABLE: Enable
0: The ADC is disabled.
1: The ADC is enabled.
Due to synchronization, there is a delay from writing CTRLA.ENABLE unt il the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY will be cleared when the operation is complete.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the ADC, except DBGCTRL, to their initial state, and the ADC will be
disabled.
Bit 76543210
RUNSTDBY ENABLE SWRST
AccessRRRRRR/WR/WR/W
Reset00000000
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Writing a one to CTRL.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST
and STATUS.SYNCBUSY will both be cleared when the reset is complete.
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28.8.2 Reference Control
Name: REFCTRL
Offset: 0x01
Reset: 0x00
Property: Write-Protected
zBit 7 – REFCOMP: Reference Buffer Offset Compensation Enable
The accuracy of the gain stage can be increased by enabling the reference buffer offset compensation. This will
decrease the input impedance and thus increase the start-up time of the reference.
0: Reference buffer offset compensation is disabled.
1: Reference buffer offset compensation is enabled.
zBits 6:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 3:0 – REFSEL[3:0]: Reference Selection
These bits select the reference for the ADC according to Table 28-5.
Table 28-5. Reference Selection
Bit 76543210
REFCOMP REFSEL[3:0]
Access R/W R R R R/W R/W R/W R/W
Reset00000000
Value Name Description
0x0 INT1V 1.0V voltage reference
0x1 INTVCC0 1/1.48 VDDANA
0x2 INTVCC1 1/2 VDDANA (only for VDDANA >
2.0V)
0x3 AREFA External reference
0x4 AREFB External reference
0x5-0xF Reserved Reserved
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28.8.3 Average Control
Name: AVGCTRL
Offset: 0x02
Reset: 0x00
Property: Write-Protected
zBit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 6:4 – ADJRES[2:0]: Adjusting Result / Division Coefficient
These bits define the division coefficient in 2n steps.
zBits 3:0 – SAMPLENUM[3:0]: Number of Samples to be Collected
These bits define how many samples should be added together.The result will be available in the Result register
(RESULT). Note: if the result width increases, CTRLB.RESSEL must be changed.
Table 28-6. Number of Samples to be Collected
Bit 76543210
ADJRES[2:0] SAMPLENUM[3:0]
Access R R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Value Name Description
0x0 1 sample
0x1 2 samples
0x2 4 samples
0x3 8 samples
0x4 16 samples
0x5 32 samples
0x6 64 samples
0x7 128 samples
0x8 256 samples
0x9 512 samples
0xA 1024 samples
0xB-0xF Reserved
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28.8.4 Sampling Time Control
Name: SAMPCTRL
Offset: 0x03
Reset: 0x00
Property: Write-Protected
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:0 – SAMPLEN[5:0]: Sampling Time Length
These bits control the ADC sampling time in number of half CLK_ADC cycles, depending of the prescaler value,
thus controlling the ADC input impedance. Sampling time is set according to the equation:
Bit 76543210
SAMPLEN[5:0]
AccessR R R/WR/WR/WR/WR/WR/W
Reset00000000
Sampling time SAMPLEN 1+()
CLKADC
2
----------------------
⎝⎠
⎛⎞
⋅=
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28.8.5 Control B
Name: CTRLB
Offset: 0x04
Reset: 0x0000
Property: Write-Synchronized, Write-Protected
zBits 15:11 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 10:8 – PRESCALER[2:0]: Prescaler Configuration
These bits define the ADC clock relative to the peripheral clock according to Table 28-7. These bits can only be
written while the ADC is disabled.
Table 28-7. Prescaler Configuration
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:4 – RESSEL[1:0]: Conversion Result Resolution
These bits define whether the ADC completes the conversion at 12-, 10- or 8-bit result resolution. These bits can
be written only while the ADC is disabled.
Bit 151413121110 9 8
PRESCALER[2:0]
AccessRRRRRR/WR/WR/W
Reset00000000
Bit76543210
RESSEL[1:0] CORREN FREERUN LEFTADJ DIFFMODE
Access R R R/W R/W R/W R/W R/W R/W
Reset00000000
Value Name Description
0x0 DIV4 Peripheral clock divided by 4
0x1 DIV8 Peripheral clock divided by 8
0x2 DIV16 Peripheral clock divided by 16
0x3 DIV32 Peripheral clock divided by 32
0x4 DIV64 Peripheral clock divided by 64
0x5 DIV128 Peripheral clock divided by 128
0x6 DIV256 Peripheral clock divided by 256
0x7 DIV512 Peripheral clock divided by 512
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Table 28-8. Conversion Result Resolution
zBit 3 – CORREN: Digital Correction Logic Enabled
0: Disable the digital result correction.
1: Enable the digital result correction. The ADC conversion result in the RESULT register is then corrected for gain
and offset based on the values in the GAINCAL and OFFSETCAL registers. Conversion time will be increased by
X cycles according to the value in the Offset Correction Value bit group in the Offset Correction register.
This bit can be changed only while the ADC is disabled.
zBit 2 – FREERUN: Free Running Mode
0: The ADC run is single conversion mode.
1: The ADC is in free running mode and a new conversion will be initiated when a previous conversion completes.
This bit can be changed only while the ADC is disabled.
zBit 1 – LEFTADJ: Left-Adjusted Result
0: The ADC conversion result is right-adjusted in the RESULT register.
1: The ADC conversion result is left-adjusted in the RESULT register. The high byte of the 12-bit result will be
present in the upper part of the result register. Writing this bit to zero (default) will right-adjust the value in the
RESULT register.
This bit can be changed only while the ADC is disabled.
zBit 0 – DIFFMODE: Differential Mode
0: The ADC is running in singled-ended mode.
1: The ADC is running in differential mode. In this mode, the voltage difference between the MUXPOS and MUX-
NEG inputs will be converted by the ADC.
This bit can be changed only while the ADC is disabled.
Value Name Description
0x0 12BIT 12-bit result
0x1 16BIT For averaging mode output
0x2 10BIT 10-bit result
0x3 8BIT 8-bit result
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28.8.6 Window Monitor Control
Name: WINCTRL
Offset: 0x08
Reset: 0x00
Property: Write-Synchronized, Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 2:0 – WINMODE[2:0]: Window Monitor Mode
These bits enable and define the window monitor mode. Table 28-9 shows the mode selections.
Table 28-9. Window Monitor Mode
Bit76543210
WINMODE[2:0]
AccessRRRRRR/WR/WR/W
Reset00000000
Value Name Description
0x0 No window mode (default)
0x1 Mode 1: RESULT > WINLT
0x2 Mode 2: RESULT < WINUT
0x3 Mode 3: WINLT < RESULT < WINUT
0x4 Mode 4:!(WINLT < RESULT < WINUT)
0x5-0x7 Reserved
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28.8.7 Software Trigger
Name: SWTRIG
Offset: 0x0C
Reset: 0x00
Property: Write-Synchronized, Write-Protected
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – START: ADC Start Conversion
0: The ADC will not start a conversion.
1: The ADC will start a conversion. The bit is cleared by hardware when the conversion has started. Setting this bit
when it is already set has no effect.
Writing this bit to zero will have no effect.
zBit 0 – FLUSH: ADC Conversion Flush
0: No flush action.
1: The ADC pipeline will be flushed. A flush will restart the ADC clock on the next peripheral clock edge, and all
conversions in progress will be aborted and lost. This bit is cleared until the ADC has been flushed.
After the flush, the ADC will resume where it left off; i.e., if a conversion was pending, the ADC will start a new
conversion.
Writing this bit to zero will have no effect.
Bit76543210
START FLUSH
AccessRRRRRRR/WR/W
Reset00000000
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28.8.8 Input Control
Name: INPUTCTRL
Offset: 0x10
Reset: 0x00000000
Property: Write-Synchronized, Write-Protected
zBits 31:28 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 27:24 – GAIN[3:0]: Gain Factor Selection
These bits set the gain factor of the ADC gain stage according to the values shown in Table 28-10.
Bit3130292827262524
GAIN[3:0]
AccessRRRRR/WR/WR/WR/W
Reset00000000
Bit2322212019181716
INPUTOFFSET[3:0] INPUTSCAN[3:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit151413121110 9 8
MUXNEG[4:0]
Access R R R R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
MUXPOS[4:0]
Access R R R R/W R/W R/W R/W R/W
Reset00000000
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zBits 23:20 – INPUTOFFSET[3:0]: Positive Mux Setting Offset
The pin scan is enabled when INPUTSCAN != 0. Writing these bits to a value other than zero causes the first con-
version triggered to be converted using a positive input equal to MUXPOS + INPUTOFFSET. Setting this register
to zero causes the first conversion to use a positive input equal to MUXPOS.
After a conversion, the INPUTOFFSET register will be incremented by one, causing the next conversion to be
done with the positive input equal to MUXPOS + INPUTOFFSET. The sum of MUXPOS and INPUTOFFSET gives
the input that is actually converted.
zBits 19:16 – INPUTSCAN[3:0]: Number of Input Channels Included in Scan
This register gives the number of input sources included in the pin scan. The number of input sources included is
INPUTSCAN + 1. The input channels included are in the range from MUXPOS + INPUTOFFSET to MUXPOS +
INPUTOFFSET + INPUTSCAN.
The range of the scan mode must not exceed the number of input channels available on the device.
zBits 15:13 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 12:8 – MUXNEG[4:0]: Negative Mux Input Selection
These bits define the Mux selection for the negative ADC input. Table 28-11 shows the possible input selections.
Table 28-10. Gain Factor Selection
Value Name Description
0x0 1X 1x
0x1 2X 2x
0x2 4X 4x
0x3 8X 8x
0x4 16X 16x
0x5-0xE –Reserved
0xF DIV2 1/2x
Table 28-11. Negative Mux Input Selection
Value Name Description
0x00 PIN0 ADC AIN0 pin
0x01 PIN1 ADC AIN1 pin
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zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 4:0 – MUXPOS[4:0]: Positive Mux Input Selection
These bits define the Mux selection for the positive ADC input. Table 28-12 shows the possible input selections. If
the internal bandgap voltage or temperature sensor input channel is selected, then the Sampling Time Length bit
group in the Sampling Control register must be written with a corresponding value.
0x02 PIN2 ADC AIN2 pin
0x03 PIN3 ADC AIN3 pin
0x04 PIN4 ADC AIN4 pin
0x05 PIN5 ADC AIN5 pin
0x06 PIN6 ADC AIN6 pin
0x07 PIN7 ADC AIN7 pin
0x08-0x17 –Reserved
0x18 GND Internal ground
0x19 IOGND I/O ground
0x1A-0x1F –Reserved
Table 28-12. Positive Mux Input Selection
MUXPOS[4:0] Group configu ration Description
0x00 PIN0 ADC AIN0 pin
0x01 PIN1 ADC AIN1 pin
0x02 PIN2 ADC AIN2 pin
0x03 PIN3 ADC AIN3 pin
0x04 PIN4 ADC AIN4 pin
0x05 PIN5 ADC AIN5 pin
0x06 PIN6 ADC AIN6 pin
0x07 PIN7 ADC AIN7 pin
0x08 PIN8 ADC AIN8 pin
0x09 PIN9 ADC AIN9 pin
0x0A PIN10 ADC AIN10 pin
0x0B PIN11 ADC AIN11 pin
0x0C PIN12 ADC AIN12 pin
0x0D PIN13 ADC AIN13 pin
Table 28-11. Neg ative Mux Input Selection (Continued)
Value Name Description
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0x0E PIN14 ADC AIN14 pin
0x0F PIN15 ADC AIN15 pin
0x10 PIN16 ADC AIN16 pin
0x11 PIN17 ADC AIN17 pin
0x12 PIN18 ADC AIN18 pin
0x13 PIN19 ADC AIN19 pin
0x14-0x17 Reserved
0x18 TEMP Temperature reference
0x19 BANDGAP Bandgap voltage
0x1A SCALEDCOREVCC 1/4 scaled core supply
0x1B SCALEDIOVCC 1/4 scaled I/O supply
0x1C DAC DAC output
0x1D-0x1F Reserved
Table 28-12. Positive Mux Input Selection (Continued)
MUXPOS[4:0] Group configu ration Description
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28.8.9 Event Control
Name: EVCTRL
Offset: 0x14
Reset: 0x00
Property: Write-Protected
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 5 – WINMONEO: Window Monitor Event Out
This bit indicates whether the Window Monitor event output is enabled or not and an output event will be gener-
ated when the window monitor detects something.
0: Window Monitor event output is disabled and an event will not be generated.
1: Window Monitor event output is enabled and an event will be generated.
zBit 4 – RESRDYEO: Result Ready Event Out
This bit indicates whether the Result Ready event output is enabled or not and an output event will be generated
when the conversion result is available.
0: Result Ready event output is disabled and an event will not be generated.
1: Result Ready event output is enabled and an event will be generated.
zBits 3:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – SYNCEI: Synchronization Event In
0: A flush and new conversion will not be triggered on any incoming event.
1: A flush and new conversion will be triggered on any incoming event.
zBit 0 – STARTEI: Start Conversion Event In
0: A new conversion will not be triggered on any incoming event.
1: A new conversion will be triggered on any incoming event.
Bit765 43210
WINMONEO RESRDYEO SYNCEI STARTEI
Access R R R/W R/W R R R/W R/W
Reset000 00000
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28.8.10 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x16
Reset: 0x00
Property: Write-Protected
zBits 7:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 3 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The Synchronization Ready interrupt is disabled.
1: The Synchronization Ready interrupt is enabled, and an interrupt request will be generated when the Synchroni-
zation Ready interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Synchronization Ready Interrupt Enable bit and the corresponding interrupt
request.
zBit 2 – WINMON: Window Monitor Interrupt Enable
0: The window monitor interrupt is disabled.
1: The window monitor interrupt is enabled, and an interrupt request will be generated when the Window Monitor
interrupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Window Monitor Interrupt Enable bit and the corresponding interrupt request.
zBit 1 – OVERRUN: Overrun Interrupt Enable
0: The Overrun interrupt is disabled.
1: The Overrun interrupt is enabled, and an interrupt request will be generated when the Overrun interrupt flag is
set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overrun Interrupt Enable bit and the corresponding interrupt request.
zBit 0 – RESRDY: Result Ready Interrupt Enable
0: The Result Ready interrupt is disabled.
1: The Result Ready interrupt is enabled, and an interrupt request will be generated when the Result Ready inter-
rupt flag is set.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Result Ready Interrupt Enable bit and the corresponding interrupt request.
Bit76543210
SYNCRDY WINMON OVERRUN RESRDY
Access R R R R R/W R/W R/W R/W
Reset00000000
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28.8.11 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x17
Reset: 0x00
Property: Write-Protected
zBits 7:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 3 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The Synchronization Ready interrupt is disabled.
1: The Synchronization Ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Synchronization Ready Interrupt Enable bit, which enables the Synchronization
Ready interrupt.
zBit 2 – WINMON: Window Monitor Interrupt Enable
0: The Window Monitor interrupt is disabled.
1: The Window Monitor interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Window Monitor Interrupt bit and enable the Window Monitor interrupt.
zBit 1 – OVERRUN: Overrun Interrupt Enable
0: The Overrun interrupt is disabled.
1: The Overrun interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Overrun Interrupt bit and enable the Overrun interrupt.
zBit 0 – RESRDY: Result Ready Interrupt Enable
0: The Result Ready interrupt is disabled.
1: The Result Ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Result Ready Interrupt bit and enable the Result Ready interrupt.
Bit76543210
SYNCRDY WINMON OVERRUN RESRDY
Access R R R R R/W R/W R/W R/W
Reset00000000
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28.8.12 Interrupt Flag Status and Clear
Name: INTFLAG
Offset: 0x18
Reset: 0x00
Property: –
zBits 7:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 3 – SYNCRDY: Synchronization Ready
This flag is cleared by writing a one to the flag.
This flag is set on a one-to-zero transition of the Synchronization Busy bit in the Status register (STATUS.SYNC-
BUSY), except when caused by an enable or software reset, and will generate an interrupt request if
INTENCLR/SET.SYNCRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Synchronization Ready interrupt flag.
zBit 2 – WINMON: Window Monitor
This flag is cleared by writing a one to the flag or by reading the RESULT register.
This flag is set on the next GCLK_ADC cycle after a match with the window monitor condition, and an interrupt
request will be generated if INTENCLR/SET.WINMON is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Window Monitor interrupt flag.
zBit 1 – OVERRUN: Overrun
This flag is cleared by writing a one to the flag.
This flag is set if RESULT is written before the previous value has been read by CPU, and an interrupt request will
be generated if INTENCLR/SET.OVERRUN is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Overrun interrupt flag.
zBit 0 – RESRDY: Result Ready
This flag is cleared by writing a one to the flag or by reading the RESULT register.
This flag is set when the conversion result is available, and an interrupt will be generated if INTEN-
CLR/SET.RESRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Result Ready interrupt flag.
Bit76543210
SYNCRDY WINMON OVERRUN RESRDY
Access R R R R R/W R/W R/W R/W
Reset00000000
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28.8.13 Status
Name: STATUS
Offset: 0x19
Reset: 0x00
Property: –
zBit 7 – SYNCBUSY: Synchronization Busy
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 6:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit76543210
SYNCBUSY
AccessRRRRRRRR
Reset00000000
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28.8.14 Result
Name: RESULT
Offset: 0x1A
Reset: 0x0000
Property: Read-Synchronized
zBits 15:0 – RESULT[15:0]: Result Conversion Value
These bits will hold up to a 16-bit ADC result, depending on the configuration.
In single-ended without averaging mode, the ADC conversion will produce a 12-bit result, which can be left- or
right-shifted, depending on the setting of CTRLB.LEFTADJ.
If the result is left-adjusted (CTRLB.LEFTADJ), the high byte of the result will be in bit position [15:8], while the
remaining 4 bits of the result will be placed in bit locations [7:4]. This can be used only if an 8-bit result is required;
i.e., one can read only the high byte of the entire 16-bit register.
If the result is not left-adjusted (CTRLB.LEFTADJ) and no oversampling is used, the result will be available in bit
locations [11:0], and the result is then 12 bits long.
If oversampling is used, the result will be located in bit locations [15:0], depending on the settings of the Average
Control register (AVGCTRL).
Bit151413121110 9 8
RESULT[15:8]
AccessRRRRRRRR
Reset00000000
Bit76543210
RESULT[7:0]
AccessRRRRRRRR
Reset00000000
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28.8.15 Window Monitor Lower Threshold
Name: WINLT
Offset: 0x1C
Reset: 0x0000
Property: Write-Synchronized, Write-Protected
zBits 15:0 – WINLT[15:0]: Window Lower Threshold
If the window monitor is enabled, these bits define the lower threshold value.
Bit151413121110 9 8
WINLT[15:8]
Acces
sR/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
WINLT[7:0]
Acces
sR/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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28.8.16 Window Monitor Upper Threshold
Name: WINUT
Offset: 0x20
Reset: 0x0000
Property: Write-Synchronized, Write-Protected
zBits 15:0 – WINUT[15:0]: Window Upper Threshold
If the window monitor is enabled, these bits define the upper threshold value.
Bit151413121110 9 8
WINUT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
Bit76543210
WINUT[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
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28.8.17 Gain Correction
Name: GAINCORR
Offset: 0x24
Reset: 0x0000
Property: Write-Protected
zBits 15:12 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 11:0 – GAINCORR[11:0]: Gain Correction Value
If the CTRLB.CORREN bit is one, these bits define how the ADC conversion result is compensated for gain error
before being written to the result register. The gain correction is a fractional value, a 1-bit integer plus an 11-bit
fraction, and therefore ½ <= GAINCORR < 2. GAINCORR values range from 0.10000000000 to 1.11111111111.
Bit151413121110 9 8
GAINCORR[11:8]
AccessRRRRR/WR/WR/WR/W
Reset00000000
Bit76543210
GAINCORR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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28.8.18 Offset Correc tion
Name: OFFSETCORR
Offset: 0x26
Reset: 0x0000
Property: Write-Protected
zBits 15:12 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 11:0 – OFFSETCORR[11:0]: Offset Correction Value
If the CTRLB.CORREN bit is one, these bits define how the ADC conversion result is compensated for offset error
before being written to the Result register. This OFFSETCORR value is in two’s complement format.
Bit151413121110 9 8
OFFSETCORR[11:8]
Access R R R R R/W R/W R/W R/W
Reset00000000
Bit76543210
OFFSETCORR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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28.8.19 Calibration
Name: CALIB
Offset: 0x28
Reset: 0x0000
Property: Write-Protected
zBits 15:11 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 10:8 – BIAS_CAL[2:0]: Bias Calibration Value
This value from production test must be loaded from the NVM software calibration row into the CALIB register by
software to achieve the specified accuracy.
The value must be copied only, and must not be changed.
zBits 7:0 – LINEARITY_CAL[7:0]: Linearity Calibration Value
This value from production test must be loaded from the NVM software calibration row into the CALIB register by
software to achieve the specified accuracy.
The value must be copied only, and must not be changed.
Bit151413121110 9 8
BIAS_CAL[2:0]
AccessRRRRRR/WR/WR/W
Reset00000000
Bit76543210
LINEARITY_CAL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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28.8.20 Debug Control
Name: DBGCTRL
Offset: 0x2A
Reset: 0x00
Property: Write-Protected
zBits 7:1 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 0 – DBGRUN: Debug Run
0: The ADC is halted during debug mode.
1: The ADC continues normal operation during debug mode.
This bit can be changed only while the ADC is disabled.
This bit should be written only while a conversion is not ongoing.
Bit76543210
DBGRUN
AccessRRRRRRRR/W
Reset00000000
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29. AC – Analog Comparators
29.1 Overview
The Analog Comparator (AC) supports two individual comparators. Each comparator (COMP) compares the voltage
levels on two inputs, and provides a digital output based on this comparison. Each comparator may be configured to
generate interrupt requests and/or peripheral events upon several different combinations of input change.
Hysteresis and propagation delay are two important properties of the comparators; dynamic behavior. Both parameters
may be adjusted to achieve the optimal operation for each application.
The input selection includes four shared analog port pins and several internal signals. Each comparator output state can
also be output on a pin for use by external devices.
The comparators are always grouped in pairs on each port. The AC module may implement one pair. These are called
Comparator 0 (COMP0) and Comparator 1 (COMP1). They have identical behaviors, but separate control registers. The
pair can be set in window mode to compare a signal to a voltage range instead of a single voltage level.
29.2 Features
zTwo individual comparators
zSelectable propagation delay versus current consumption
zSelectable hysteresis
zOn/Off
zAnalog comparator outputs available on pins
zAsynchronous or synchronous
zFlexible input selection
zFour pins selectable for positive or negative inputs
zGround (for zero crossing)
zBandgap reference voltage
z64-level programmable VDD scaler per comparator
zDAC
zInterrupt generation on:
zRising or falling edge
zToggle
zEnd of comparison
zWindow function interrupt generation on:
zSignal above window
zSignal inside window
zSignal below window
zSignal outside window
zEvent generation on:
zComparator output
zWindow function inside/outside window
zOptional digital filter on comparator output
zLow-power option
zSingle-shot support
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29.3 Block Diagram
Figure 29-1. Analog Comparator Block Di a gram
29.4 Signal Description
Refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
29.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
29.5.1 I/O Lines
Using the AC’s I/O lines requires the I/O pins to be configured. Refer to the PORT chapter for details.
Refer to “PORT” on page 284 for details.
29.5.2 Power Management
The AC will continue to operate in any sleep mode where the selected source clock is running. The AC’s interrupts can
be used to wake up the device from sleep modes. The events can trigger other operations in the system without exiting
sleep modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
INTERRUPT MODE
ENABLE
ENABLE
HYSTERESIS
HYSTERESIS
DAC
VDD
SCALER
BANDGAP
+
-
+
-
CMP0
CMP1
INTERRUPTS
EVENTS
GCLK_AC
AIN3
AIN2
AIN1
AIN0
COMP0
COMP1
COMPCTRLn WINCTRL
INTERRUPT
SENSITIVITY
CONTROL
&
WINDOW
FUNCTION
Signal Name Type Description
AIN[3..0] Analog input Comp arator inputs
CMP[1..0] Digital output Comparator outputs
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29.5.3 Clocks
The AC bus clock (CLK_AC_APB) can be enabled and disabled in the Power Manager, and the default state of the
CLK_AC_APB can be found in the Peripheral Clock Masking section of “PM – Power Manager” on page 100.
Two generic clocks (GCLK_AC_DIG and GCLK_AC_ANA) are used by the AC. The digital clock (GCLK_AC_DIG) is
required to provide the sampling rate for the comparators, while the analog clock (GCLK_AC_ANA) is required for low-
voltage operation (VDD < 2.5V) to ensure that the resistance of the analog input multiplexors remains low. These clocks
must be configured and enabled in the Generic Clock Controller before using the peripheral.
Refer to “GCLK – Generic Clock Controller” on page 78 for details.
These generic clocks are asynchronous to the CLK_AC_APB clock. Due to this asynchronicity, writes to certain registers
will require synchronization between the clock domains. Refer to “Synchronization” on page 525 for further details.
29.5.4 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the AC interrupts requires the Interrupt Controller
to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
29.5.5 Events
The events are connected to the Event System. Using the events requires the Event System to be configured first. Refer
to “EVSYS – Event System” on page 309 for details.
29.5.6 Debug Operation
When the CPU is halted in debug mode, the peripheral continues normal operation. If the peripheral is configured in a
way that requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss
may result during debugging.
29.5.7 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following registers:
zControl B register (CTRLB)
zInterrupt Flag register (INTFLAG)
Write-protection is denoted by the Write-Protected property in the register description.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
29.5.8 Analog Connections
Each comparator has up to four I/O pins that can be used as analog inputs. Each pair of comparators shares the same
four pins. These pins must be configured for analog operation before using them as comparator inputs.
Any internal reference source, such as a bandgap reference voltage or the DAC, must be configured and enabled prior to
its use as a comparator input.
29.5.9 Other Dependencies
Not applicable.
29.6 Functional Description
29.6.1 Principle of Operation
Each comparator has one positive input and one negative input. Each positive input may be chosen from a selection of
analog input pins. Each negative input may be chosen from a selection of analog input pins or internal inputs, such as a
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bandgap reference voltage. The digital output from the comparator is one when the difference between the positive and
the negative input voltage is positive, and zero otherwise.
The individual comparators can be used independently (normal mode) or grouped in pairs to generate a window
comparison (window mode).
29.6.2 Basic Operation
29.6.2.1 Initialization
Before enabling the AC, the input and output events must be configured in the Event Control register (EVCTRL). These
settings cannot be changed while the AC is enabled.
Each individual comparator must also be configured by its respective Comparator Control register (COMPCTRLx) before
that comparator is enabled. These settings cannot be changed while the comparator is enabled.
zSelect the desired measurement mode with COMPCTRLx.SINGLE. See “Starting a Comparison” on page
518 for more details
zSelect the desired hysteresis with COMPCTRLx.HYST. See “Input Hysteresis” on page 522 for more details
zSelect the comparator speed versus power with COMPCTRLx.SPEED. See “Propagation Delay vs. Power
Consumption” on page 522 for more details
zSelect the interrupt source with COMPCTRLx.INTSEL
zSelect the positive and negative input sources with the COMPCTRLx.MUXPOS and
COMPCTRLx.MUXNEG bits. See section “Selecting Comparator Inputs” on page 520 for more details
zSelect the filtering option with COMPCTRLx.FLEN
29.6.2.2 Enabling, Disabling and Resetting
The AC is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The individual
comparators must be also enabled by writing a one to the Enable bit in the Comparator x Control registers
(COMPCTRLx.ENABLE). The AC is disabled by writing a zero to CTRLA.ENABLE. This will also disable the individual
comparators, but will not clear their COMPCTRLx.ENABLE bits.
The AC is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in the
AC, except DEBUG, will be reset to their initial state, and the AC will be disabled. Refer to the CTRLA register for details.
29.6.2.3 Starting a Comparison
Each comparator channel can be in one of two different measurement modes, determined by the Single bit in the
Comparator x Control register (COMPCTRLx.SINGLE):
zContinuous measurement
zSingle-shot
After being enabled, a start-up delay is required before the result of the comparison is ready. This start-up time is
measured automatically to account for environmental changes, such as temperature or voltage supply level, and is
specified in “Electrical Characteristics” on page 562.
During the start-up time, the COMP output is not available. If the supply voltage is below 2.5V, the start-up time is also
dependent on the voltage doubler. If the supply voltage is guaranteed to be above 2.5V, the voltage doubler can be
disabled by writing the Low-Power Mux bit in the Control A register (CTRLA.LPMUX) to one.
The comparator can be configured to generate interrupts when the output toggles, when the output changes from zero to
one (rising edge), when the output changes from one to zero (falling edge) or at the end of the comparison. An end-of-
comparison interrupt can be used with the single-shot mode to chain further events in the system, regardless of the state
of the comparator outputs. The interrupt mode is set by the Interrupt Selection bit group in the Comparator Control
register (COMPCTRLx.INTSEL). Events are generated using the comparator output state, regardless of whether the
interrupt is enabled or not.
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Continuous Measurement
Continuous measurement is selected by writing COMPCTRLx.SINGLE to zero. In continuous mode, the comparator is
continuously enabled and performing comparisons. This ensures that the result of the latest comparison is always
available in the Current State bit in the Status A register (STATUSA.STATEx). After the start-up time has passed, a
comparison is done and STATUSA is updated. The Comparator x Ready bit in the Status B register
(STATUSB.READYx) is set, and the appropriate peripheral events and interrupts are also generated. New comparisons
are performed continuously until the COMPCTRLx.ENABLE bit is written to zero. The start-up time applies only to the
first comparison.
In continuous operation, edge detection of the comparator output for interrupts is done by comparing the current and
previous sample. The sampling rate is the GCLK_AC_ DIG frequency. An example of continuous measurement is shown
in Figure 29-2.
Figure 29-2. Continuous Measurement Exam ple
For low-power operation, comparisons can be performed d uring sleep modes without a clock. The comparator is enabled
continuously, and changes in the state of the comparator are detected asynchronously. When a toggle occurs, the Power
Manager will start GCLK_AC_DIG to register the appropriate peripheral events and interrupts. The GCLK_AC_DIG clock
is then disabled again automatically, unless configured to wake up the system from sleep.
Single-Shot
Single-shot operation is selected by writing COMPCTRLx.SINGLE to one. During single-shot operation, the comparator
is normally idle. The user starts a single comparison by writing a one to the respective Start Comparison bit in the write-
only Control B register (CTRLB.STARTx). The comparator is enabled, and after the start-up time has passed, a single
comparison is done and STATUSA is updated. Appropriate peripheral events and interrupts are also generated. No new
comparisons will be performed.
Writing a one to CTRLB.STARTx also clears the Comparator x Ready bit in the Status B register (STATUSB.READYx).
STATUSB.READYx is set automatically by hardware when the single comparison has completed. To remove the need
for polling, an additional means of starting the comparison is also available. A read of the Status C register (STATUSC)
will start a comparison on all comparators currently configured for single-shot operation. The read will stall the bus until
all enabled comparators are ready. If a comparator is already busy with a comparison, the read will stall until the current
comparison is compete, and a new comparison will not be started.
A single-shot measurement can also be triggered by the Event System. Writing a one to the Comparator x Event Input bit
in the Event Control Register (EVCTRL.COMPEIx) enables triggering on incoming peripheral events. Each comparator
can be triggered independently by separate events. Event-triggered operation is similar to user-triggered operation; the
difference is that a peripheral event from another hardware module causes the hardware to automatically start the
comparison and clear STATUSB.READYx.
To detect an edge of the comparator output in single-shot operation fo r the purpose of interrupts, the result of th e current
measurement is compared with the result of the previous measurement (one sampling period earlier). An example of
single-shot operation is shown in Figure 29-3.
GCLK_AC
STATUSB.READYx
Sampled
Comparator Output
COMPCTRLx.ENABLE
tSTARTUP
Write ‘1’
2-3 cycles
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Figure 29-3. Single-Shot Example
For low-power operation, event-triggered measurements can be performed during sleep modes. When the event occurs,
the Power Manager will start GCLK_AC_DIG. The comparator is enabled, and after the startup time has passed, a
comparison is done and appropriate peripheral events and interrupts are also generated. The comparator and
GCLK_AC_DIG are then disabled again automatically, unless configured to wake up the system from sleep.
29.6.3 Selecting Comparator Inputs
Each comparator has one positive and one negative input. The positive input is fed from an external input pin (AINx). The
negative input can be fed either from an external input pin (AINx) or from one of the several internal reference voltage
sources common to all comparators. The user selects the input source as follows:
zThe positive input is selected by the Positive Input MUX Select bit group in the Comparator Control register
(COMPCTRLx.MUXPOS)
zThe negative input is selected by the Negative Input MUX Select bit group in the Comparator Control
register (COMPCTRLx.MUXNEG)
In the case of using an external I/O pin, the selected pin must be configured for analog usage in the PORT Controller by
disabling the digital input and output. The switching of the analog input multiplexors is controlled to minimize crosstalk
between the channels. The input selection must be changed only while the individual comparator is disabled.
29.6.4 Window Operation
Each comparator pair can be configured to work together in window mode. In this mode, a voltage range is defined, and
the comparators give information about whether an input signal is within this range or not. Window mode is enabled by
the Window Enable x bit in the Window Control register (WINCTRL.WENx). Both comparators in a pair must have the
same measurement mode setting in their respective Comparator Control Registers (COMPCTRLx.SINGLE).
To physically configure the pair of comparators for window mode, the same I/O pin should be chosen for each
comparator’s positive input to create the shared input signal. The negative inputs define the range for the window. In
Figure 29-4, COMP0 defines the upper limit and COMP1 defines the lower limit of the window, as shown but the window
will also work in the opposite configuration with COMP0 lower and COMP1 higher. The current state of the window
function is available in the Window x State bit group of the Status register (STATUS.WSTATEx).
Window mode can be configured to generate interrupts when the input voltage changes to below the window, when the
input voltage changes to above the window, when the input voltage changes into the window or when the input voltage
changes outside the window. The interrupt selections are set by the Window Interrupt Selection bit group in the Window
Control register (WINCTRL.WINTSELx[1:0]). Events are generated using the inside/outside state of the window,
regardless of whether the interrupt is enabled or not. Note that the individual comparator outputs, interrupts and events
continue to function normally during window mode.
When the comparators are configured for window mode and single-shot mode, measurements are performed
simultaneously on both comparators. Writing a one to either Start Comparison bit in the Control B register
(CTRLB.STARTx) starts a measurement. Likewise either peripheral event can start a measurement.
GCLK_AC
STATUSB.READYx
Sampled
Comparator Output
CTRLB.STARTx
tSTARTUP
Write ‘1’
tSTARTUP
Write ‘1’
2-3 cycles 2-3 cycles
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Figure 29-4. Comparators in Window Mode
29.6.5 Voltage Doubler
The AC contains a voltage doubler that can reduce the resistance of the analog multiplexors when the supply voltage is
below 2.5V. The voltage doubler is normally switched on/off automatically based on the supply level. When enabling the
comparators, additional start-up time is required for the voltage doubler to settle. If the supply voltage is guaranteed to be
above 2.5V, the voltage doubler can be disabled by writing the Low-Power Mux bit in the Control A register
(CTRLA.LPMUX) to one. Disabling the voltage doubler saves power and reduces the start-up time.
29.6.6 VDD Scaler
The VDD scaler generates a reference voltage that is a fraction of the device’s supply voltage, with 64 levels. One
independent voltage channel is dedicated for each comparator. The scaler is enabled when a comparator’s Negative
Input Mux bit group in its Comparator Control register (COMPCTRLx.MUXNEG) is set to five and the comparator is
enabled. The voltage of each channel is selected by the Value bit group in the Scaler x registers
(SCALERx.VALUE[5:0]).
+
-
+
-
STATE0
STATE1
WSTATE[1:0]
INTERRUPTS
EVENTS
INPUT SIGNAL
UPPER LIMIT OF WINDOW
COMP0
COMP1
INTERRUPT
SENSITIVITY
CONTROL
&
WINDOW
FUNCTION
LOWER LIMIT OF WINDOW
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Figure 29-5. VDD Scaler
29.6.7 Input Hysteresis
Application software can selectively enable/disable hysteresis for the comparison. Applying hysteresis will help prevent
constant toggling of the output, which can be caused by noise when the input signals are close to each other. Hysteresis
is enabled for each comparator individually by the Hysteresis Mode bit in the Comparator x Control register
(COMPCTRLx.HYST). Hysteresis is available only in continuous mode (COMPCTRLx.SINGLE=0).
29.6.8 Propagation Delay vs. Power Consumption
It is possible to trade off comparison speed for power efficiency to get the shortest possible propagation delay or the
lowest power consumption. The speed setting is configured for each comparator individually by the Speed bit group in
the Comparator x Control register (COMPCTRLx.SPEED). The Speed bits select the amount of bias current provided to
the comparator, and as such will also affect the start-up time.
29.6.9 Filtering
The output of the comparators can be digitally filtered to reduce noise using a simple digital filter. The filtering is
determined by the Filter Length bits in the Comparator Control x register (COMPCTRLx.FLEN), and is independent for
each comparator. Filtering is selectable from none, 3-bit majority (N=3) or 5-bit majority (N=5) functions. Any change in
the comparator output is considered valid only if N/2+1 out of the last N samples agree. The filter sampling rate is the
CLK_AC frequency scaled by the prescaler setting in the Control A register (CTRLA.PRESCALER).
Note that filtering creates an additional delay of N-1 sampling cycles from when a comparison is started until the
comparator output is validated. For continuous mode, the first valid output will occur when the required number of filter
samples is taken. Subsequent outputs will be generated every cycle based on the current sample plus the previous N-1
samples, as shown in Figure 29-6. For single-shot mode, the comparison completes after the Nth filter sample, as shown
in Figure 29-7.
COMPCTRLx.MUXNEG
== 5 SCALERx.
VALUE
to
COMPx
6
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Figure 29-6. Continuous Mode Fil te ri ng
Figure 29-7. Single-Shot Filtering
During sleep modes, filtering is supported only for single-shot measurements. Filtering must be disabled if continuous
measurements will be done during sleep modes, or the resulting interrupt/event may be generated incorrectly.
29.6.10 Comparator Output
The output of each comparator can be routed to an I/O pin by setting the Output bit group in the Comparator Control x
register (COMPCTRLx.OUT). This allows the comparator to be used by external circuitry. Either the raw, non-
synchronized output of the comparator or the CLK_AC-synchronized version, including filtering, can be used as the I/O
signal source. The output appears on the corresponding CMP[x] pin.
29.6.11 Offset Compensation
The Swap bit in the Comparator Control registers (COMPCTRLx.SWAP) controls switching of the input signals to a
comparator's positive and negative terminals. When the comparator terminals are swapped, the output signal from the
comparator is also inverted, as shown in Figure 29-8. This allows the user to measure or compensate for the comparator
input offset voltage. As part of the input selection, COMPCTRLx.SWAP can be changed only while the comparator is
disabled.
Figure 29-8. Input Swapping for Offset Compensation
Sampling Clock
Sampled
Comparat or O ut put
3-bit M ajorit y
Filt er O u tput
5-bit M ajorit y
Filt er O u tput
Sampling Clock
3-bit Sampled
Compar at or Output
3-bit M ajor ity
Filter O utput
Start
5-bit Sampled
Compar at or Output
5-bit M ajor ity
Filter O utput
t
SUT
M
U
XP
OS
M
U
XNE
G
+
-
COMPx
S
WAP
ENABLE
HY
S
TERE
S
I
S
S
WA
P
C
MPx
COMPCTRLx
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29.7 Additional Features
29.7.1 Interrupts
The peripheral has the following interrupt sources:
zComparator: COMP0, COMP1(INTENCLR, INTSET, INTFLAG)
zWindow: WIN0(INTENCLR, INTSET, INTFLAG)
Comparator interrupts are generated based on the conditions selected by the Interrupt Selection bit group in the
Comparator Control registers (COMPCTRLx.INTSEL). Window interrupts are generated based on the conditions
selected by the Window Interrupt Selection bit group in the Window Control register (WINCTRL.WINTSEL[1:0]).
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the peripheral is reset. An interrupt flag is cleared by writing a one to the
corresponding bit in the INTFLAG register.
Each peripheral can have one interrupt request line per interrupt source or one common interrupt request line for all the
interrupt sources. If the peripheral has one common interrupt request line for all the interrupt sources, the user must read
the INTFLAG register to determine which interrupt condition is present.
For details on clearing interrupt flags, refer to the INTFLAG register description.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to “Nested Vector Interrupt
Controller” on page 24 for details.
29.7.2 Events
The peripheral can generate the following output events:
zComparator: COMPEO0, COMPEO1(EVCTRL)
zWindow: WINEO0(EVCTRL)
Output events must be enabled to be generated. Writing a one to an Event Output bit in the Event Control register
(EVCTRL.COMPEOx) enables the corresponding output event. Writing a zero to this bit disables the corresponding
output event. The events must be correctly routed in the Event System. Refer to “EVSYS – Event System” on page 309
for details.
The peripheral can take the following actions on an input event:
zSingle-shot measurement
zSingle-shot measurement in window mode
Input events must be enabled for the corresponding action to be taken on any input event. Writing a one to an Event
Input bit in the Event Control register (EVCTRL.COMPEIx) enables the corresponding action on input event. Writing a
zero to a bit disables the corresponding action on input event. Note that if several events are connected to the peripheral,
the enabled action will be taken on any of the incoming events. The events must be correctly routed in the Event System.
Refer to “EVSYS – Event System” on page 309 for details.
When EVCTRL.COMPEIx is one, the event will start a comparison on COMPx after the start-up time delay. In normal
mode, each comparator responds to its corresponding input event independently. For a pair of comparators in window
mode, either comparator event will trigger a comparison on both comparators simultaneously.
29.7.3 Sleep Mode Operation
The Run in Standby bit in the Control A register (CTRLA.RUNSTDBY) controls the behavior of the AC during standby
sleep mode. When the bit is zero, the comparator pair is disabled during sleep, but maintains its current configuration.
When the bit is one, the comparator pair continues to operate during sleep. Note that when RUNSTDBY is zero, the
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analog blocks are powered off for the lowest power consumption. This necessitates a start-up time delay when the
system returns from sleep.
When RUNSTDBY is one, any enabled AC interrupt source can wake up the CPU. However, single-shot comparisons
will be triggerable by events only while the CPU is idle. The AC can also be used during sleep modes where the clock
used by the AC is disabled, provided that the AC is still powered (not in shutdown). In this case, the behavior is slightly
different and depends on the measurement mode, as listed in Table 29-1.
Table 29-1. Sleep Mode Operation
29.7.3.1 Continuous Measurement during Sleep
When a comparator is enabled in continuous measurement mode and GCLK_AC_DIG is disabled during sleep, the
comparator will remain continuously enabled and will function asynchronously. The current state of the comparator is
asynchronously monitored for changes. If an edge matching the interrupt condition is found, GCLK_AC_DIG is started to
register the interrupt condition and generate events. If the interrupt is enabled in the Interrupt Enable registers
(INTENCLR/SET), the AC can wake up the device; otherwise GCLK_AC_DIG is disabled until the next edge detection.
Filtering is not possible with this configuration.
Figure 29-9. Continuous Mode SleepWalking
29.7.3.2 Single-Shot Measurement during Sleep
For low-power operation, event-triggered measurements can be performed during sleep modes. When the event occurs,
the Power Manager will start GCLK_AC_DIG. The comparator is enabled, and after the start-up time has passed, a
comparison is done, with filtering if desired, and the appropriate peripheral events and interrupts are also generated, as
shown in Figure 29-10 The comparator and GCLK_AC_DIG are then disabled again automatically, unless configured to
wake the system from sleep. Filtering is allowed with this configuration.
Figure 29-10.Single-Shot SleepWalking
29.7.4 Synchronization
Due to the asynchronicity between CLK_MODULE_APB and GCLK_MODULE, some registers must be synchronized
when accessed. A register can require:
COMPCTRLx.MODE RUNSTDBY=0 RUNSTDBY=1
0 (Continuous) COMPx disabled GCLK_AC_DIG stopped, COMPx enabled
1 (Single-shot) COMPx disabled GCLK_AC_DIG stopped, COMPx enabled only
when triggered by an input event
GCLK_AC
Comparator
Ou t p ut or Event
Compar ator St at e
GCLK_AC
Comparator
Ou t put or Event
In put Eve nt t
STARTUP
t
STARTUP
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zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete.
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following bits need synchronization when written:
zSoftware Reset bit in Control A register (CTRLA.SWRST)
zEnable bit in Control A register (CTRLA.ENABLE)
zEnable bit in Comparator Control register (COMPCTRLn.ENABLE)
The following register need synchronization when written:
zWindow Control register (WINCTRL)
Refer to the Synchronization chapter for further details.
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29.8 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 RUNSTDBY ENABLE SWRST
0x01 CTRLB 7:0 START1 START0
0x02 EVCTRL 7:0 WINEO0 COMPEO1 COMPEO0
0x03 15:8 COMPEI1 COMPEI0
0x04 INTENCLR 7:0 WIN0 COMP1 COMP0
0x05 INTENSET 7:0 WIN0 COMP1 COMP0
0x06 INTFLAG 7:0 WIN0 COMP1 COMP0
0x07 Reserved
0x08 STATUSA 7:0 WSTATE0[1:0] STATE1 STATE0
0x09 STATUSB 7:0 SYNCBUSY READY1 READY0
0x0A STATUSC 7:0 WSTATE0[1:0] STATE1 STATE0
0x0B Reserved
0x0C WINCTRL 7:0 WINTSEL0[1:0] WEN0
0x0D Reserved
0x0E Reserved
0x0F Reserved
0x10
COMPCTRL0
7:0 INTSEL[1:0] SPEED[1:0] SINGLE ENABLE
0x11 15:8 SWAP MUXPOS[1:0] MUXNEG[2:0]
0x12 23:16 HYST OUT[1:0]
0x13 31:24 FLEN[2:0]
0x14
COMPCTRL1
7:0 INTSEL[1:0] SPEED[1:0] SINGLE ENABLE
0x15 15:8 SWAP MUXPOS[1:0] MUXNEG[2:0]
0x16 23:16 HYST OUT[1:0]
0x17 31:24 FLEN[2:0]
0x18 Reserved
... Reserved
0x1F Reserved
0x20 SCALER0 7:0 VALUE[5:0]
0x21 SCALER1 7:0 VALUE[5:0]
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29.9 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Refer to “Register Access Protection” on page 517
for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Write-Synchronized
or the Read-Synchronized property in each individual register description. Refer to “Synchronization” on page 525 for
details.
Some registers are enable-protected, meaning they can be written only when the AC is disabled. Enable-protection is
denoted by the Enable-Protected property in each individual register description.
29.9.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property: Write-Protected, Write-Synchronized
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – RUNSTDBY: Run in Standby
This bit controls the behavior of the comparators during standby sleep mode.
0: The comparator pair is disabled during sleep.
1: The comparator pair continues to operate during sleep.
This bit is not synchronized
zBit 1 – ENABLE: Enable
0: The AC is disabled.
1: The AC is enabled. Each comparator must also be enabled individually by the Enable bit in the Comparator
Control register (COMPCTRLn.ENABLE).
Due to synchronization, there is delay from updating the register until the peripheral is enabled/disabled. The value
written to CTRL.ENABLE will read back immediately after being written. STATUS.SYNCBUSY is set. STA-
TUS.SYNCBUSY is cleared when the peripheral is enabled/disabled.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the AC to their initial state, and the AC will be disabled.
Bit76543210
RUNSTDBY ENABLE SWRST
AccessRRRRRR/WR/WR/W
Reset00000000
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Writing a one to CTRL.SWRST will always take precedence, meaning that all other writes in the same write-oper-
ation will be discarded.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST
and STATUS.SYNCBUSY will both be cleared when the reset is complete.
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29.9.2 Control B
Name: CTRLB
Offset: 0x01
Reset: 0x00
Property: –
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – STARTx: Comparator x Start Comparison
Writing a zero to this field has no effect.
Writing a one to STARTx starts a single-shot comparison on COMPx if both the Single-Shot and Enable bits in the
Comparator x Control Register are one (COMPCTRLx.SINGLE and COMPCTRLx.ENABLE). If comparator x is
not implemented, or if it is not enabled in single-shot mode, writing a one has no effect.
This bit always reads as zero.
Bit 76543210
START1 START0
AccessRRRRRRWW
Reset00000000
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29.9.3 Event Control
Name: EVCTRL
Offset: 0x02
Reset: 0x0000
Property: Write-Protected, Enable-Protected
zBits 15:10 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 9:8 – COMPEIx: Comparator x Event Input
Note that several actions can be enabled for incoming events. If several events are connected to the peripheral,
the enabled action will be taken for any of the incoming events. There is no way to tell which of the incoming
events caused the action.
These bits indicate whether a comparison will start or not on any incoming event.
0: Comparison will not start on any incoming event.
1: Comparison will start on any incoming event.
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – WINEO0: Window 0 Event Output Enable
This bit indicates whether the window 0 function can generate a peripheral event or not.
0: Window 0 event is disabled.
1: Window 0 event is enabled.
zBits 3:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – COMPEOx: Comparator x Event Output Enable
These bits indicate whether the comparator x output can generate a peripheral event or not.
0: COMPx event generation is disabled.
1: COMPx event generation is enabled.
Bit 151413121110 9 8
COMPEI1 COMPEI0
AccessRRRRRRR/WR/W
Reset00000000
Bit76543210
WINEO0 COMPEO1 COMPEO0
Access R R R R/W R R R/W R/W
Reset00000000
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29.9.4 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x04
Reset: 0x00
Property: Write-Protected
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – WIN0: Window 0 Interrupt Enable
Reading this bit returns the state of the Window 0 interrupt enable.
0: The Window 0 interrupt is disabled.
1: The Window 0 interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit disables the Window 0 interrupt.
zBits 3:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – COMPx: Comparator x Interrupt Enable
Reading this bit returns the state of the Comparator x interrupt enable.
0: The Comparator x interrupt is disabled.
1: The Comparator x interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit disables the Comparator x interrupt.
Bit76543210
WIN0 COMP1 COMP0
Access R R R R/W R R R/W R/W
Reset00000000
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29.9.5 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x05
Reset: 0x00
Property: Write-Protected
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – WIN0: Window 0 Interrupt Enable
Reading this bit returns the state of the Window 0 interrupt enable.
0: The Window 0 interrupt is disabled.
1: The Window 0 interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit enables the Window 0 interrupt.
zBits 3:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – COMPx: Comparator x Interrupt Enable
Reading this bit returns the state of the Comparator x interrupt enable.
0: The Comparator x interrupt is disabled.
1: The Comparator x interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Ready interrupt bit and enable the Ready interrupt.
Bit 76543210
WIN0 COMP1 COMP0
Access R R R R/W R R R/W R/W
Reset00000000
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29.9.6 Interrupt Flag S tatus and Clear
Name: INTFLAG
Offset: 0x06
Reset: 0x00
Property: –
zBits 7:5 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 4 – WIN0: Window 0
This flag is set according to the Window 0 Interrupt Selection bit group in the WINCTRL register (WINC-
TRL.WINTSEL0) and will generate an interrupt if INTENCLR/SET.WIN0 is also one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Window 0 interrupt flag.
zBits 3:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – COMPx: Comparator x
Reading this bit returns the status of the Comparator x interrupt flag. If comparator x is not implemented, COMPx
always reads as zero.
This flag is set according to the Interrupt Selection bit group in the Comparator x Control register (COMPC-
TRLx.INTSEL) and will generate an interrupt if INTENCLR/SET.COMPx is also one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Comparator x interrupt flag.
Bit76543210
WIN0 COMP1 COMP0
Access R R R R/W R R R/W R/W
Reset00000000
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29.9.7 Status A
Name: STATUSA
Offset: 0x08
Reset: 0x00
Property: –
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:4 – WSTATE0[1:0]: Window 0 Current State
These bits show the current state of the signal if the window 0 mode is enabled, according to Table 29-2. If the win-
dow 0 function is not implemented, WSTATE0 always reads as zero.
Table 29-2. Window Mode Current State
zBits 3:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – STATEx: Comparator x Current State
This bit shows the current state of the output signal fr om COMPx. STATEx is valid only when STATUSB.READYx
is one.
Bit76543210
WSTATE0[1:0] STATE1 STATE0
AccessRRRRRRRR
Reset00000000
Value Name Description
0x0 ABOVE Signal is above window
0x1 INSIDE Signal is inside window
0x2 BELOW Signal is below window
0x3 –Reserved
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29.9.8 Status B
Name: STATUSB
Offset: 0x09
Reset: 0x00
Property: –
zBit 7 – SYNCBUSY: Synchronization Busy
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 6:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – READYx: Comparator x Ready
This bit is cleared when the comparator x output is not ready.
This bit is set when the comparator x output is ready.
Bit 76543210
SYNCBUSY READY1 READY0
AccessRRRRRRRR
Reset00000000
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29.9.9 Status C
STATUSC is a copy of STATUSA (see STATUSA register), with the additional feature of automatically starting single-
shot comparisons. A read of STATUSC will start a comparison on all comparators currently configured for single-shot
operation. The read will stall the bus until all enabled comparators are ready. If a comparator is already busy with a
comparison, the read will stall until the current comparison is compete, and a new comparison will not be started.
Name: STATUSC
Offset: 0x0A
Reset: 0x00
Property: –
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:4 – WSTATE0[1:0]: Window 0 Current State
These bits show the current state of the signal if the window 0 mode is enabled. If the window 0 function is not
implemented, WSTATE0 always reads as zero.
Table 29-3. Window Mode Current State
zBits 3:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 1:0 – STATEx: Comparator x Current State
This bit shows the current state of the output signal from COMPx. If comparator x is not implemented, STATEx
always reads as zero. STATEx is only valid when STATUSB.READYx is one.
Bit76543210
WSTATE0[1:0] STATE1 STATE0
AccessRRRRRRRR
Reset00000000
Value Name Description
0x0 ABOVE Signal is above window
0x1 INSIDE Signal is inside window
0x2 BELOW Signal is below window
0x3 –Reserved
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29.9.10 Window Control
Name: WINCTRL
Offset: 0x0C
Reset: 0x00
Property: Write-Synchronized, Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 2:1 – WINTSEL0: Window 0 Interrupt Selection
These bits configure the interrupt mode for the comparator window 0 mode.
Table 29-4. Window 0 Interrupt Selection
zBit 0 – WEN0: Window 0 Mode Enable
0: Window mode is disabled for comparators 0 and 1.
1: Window mode is enabled for comparators 0 and 1.
Bit76543210
WINTSEL0[1:0] WEN0
AccessRRRRRR/WR/WR/W
Reset00000000
Value Name Description
0x0 ABOVE Interrupt on signal above window
0x1 INSIDE Interrupt on signal inside window
0x2 BELOW Interrupt on signal below window
0x3 OUTSIDE Interrupt on signal outside window
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29.9.11 Scaler n
Name: SCALERn
Offset: 0x20+n*0x1 [n=0..1]
Reset: 0x00
Property: Write-Protected
zBits 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 5:0 – VALUE[5:0]: Scaler Value
These bits define the scaling factor for channel n of the VDD voltage scaler. The output voltage, VSCALE, is:
Bit 76543210
VALUE[5:0]
Access R R R/W R/W R/W R/W R/W R/W
Reset00000000
VSCALE VDD VALUE 1+()⋅
64
--------------------------------------------------=
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29.9.12 Comparator Control n
The configuration of comparator n is protected while comparator n is enabled (COMPCTRLn.ENABLE = 1). Changes to
the other bits in COMPCTRLn can only occur when COMPCTRLn.ENABLE is zero.
Name: COMPCTRLn
Offset: 0x10+n*0x4 [n=0..1]
Reset: 0x00000000
Property: Write-Protected, Write-Synchronized
zBits 31:27 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBits 26:24 – FLEN[2:0]: Filter Length
These bits configure the filtering for comparator n. COMPCTRLn.FLEN can only be written while COMPC-
TRLn.ENABLE is zero.
These bits are not synchronized.
Bit 3130292827262524
FLEN[2:0]
AccessRRRRRR/WR/WR/W
Reset00000000
Bit 2322212019181716
HYST OUT[1:0]
Access R R R R R/W R R/W R/W
Reset00000000
Bit 151413121110 9 8
SWAP MUXPOS[1:0] MUXNEG[2:0]
Access R/W R R/W R/W R R/W R/W R/W
Reset00000000
Bit76543210
INTSEL[1:0] SPEED[1:0] SINGLE ENABLE
Access R R/W R/W R R/W R/W R/W R/W
Reset00000000
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Table 29-5. Filter Length
zBits 23:20 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 19 – HYST: Hysteresis Enable
This bit indicates the hysteresis mode of comparator n. Hysteresis is available only for continuous mode (COMPC-
TRLn.SINGLE=0). COMPCTRLn.HYST can be written only while COMPCTRLn.ENABLE is zero.
0: Hysteresis is disabled.
1: Hysteresis is enabled.
These bits are not synchronized.
zBit 18 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 17:16 – OUT[1:0]: Output
These bits configure the output selection for comparator n. COMPCTRLn.OUT can be written only while COMPC-
TRLn.ENABLE is zero.
These bits are not synchronized.
Table 29-6. Output Selection
zBit 15 – SWAP: Swap Inputs and Invert
This bit swaps the positive and negative inputs to COMPn and inverts the outpu t. Th is function can be used for off-
set cancellation. COMPCTRLn.SWAP can be written only while COMPCTRLn.ENABLE is zero.
0: The output of MUXPOS connects to the positive input, and the output of MUXNEG connects to the negative
input.
1: The output of MUXNEG connects to the positive input, and the output of MUXPOS connects to the negative
input.
These bits are not synchronized.
Value Name Description
0x0 OFF No filtering
0x1 MAJ3 3-bit majori ty fu n c ti on (2 of 3)
0x2 MAJ5 5-bit majori ty fu n c ti on (3 of 5)
0x3-0x7 N/A Reserved
Value Name Description
0x0 OFF The output of COMPn is not routed to the COMPn I/O
port
0x1 ASYNC The asynchronous output of COMPn is routed to the
COMPn I/O port
0x2 SYNC The synchronous output (including filtering) of COMPn
is routed to the COMPn I/O port
0x3 N/A Reserved
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zBit 14 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 13:12 – MUXPOS[1:0]: Positive Input Mux Selection
These bits select which input will be connected to the positive input of comparator n. COMPCTRLn.MUXPOS can
be written only while COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Table 29-7. Positive Input Mux Selection
zBit 11 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 10:8 – MUXNEG[2:0]: Negative Input Mux Selection
These bits select which input will be connected to the negative input of comparator n. COMPCTRLn.MUXNEG can
only be written while COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Table 29-8. Negative Input Mux Selection
zBit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 6:5 – INTSEL[1:0]: Interrupt Selection
These bits select the condition for comparator n to generate an interrupt or event. COMPCTRLn.INTSEL can be
written only while COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Value Name Description
0x0 PIN0 I/O pin 0
0x1 PIN1 I/O pin 1
0x2 PIN2 I/O pin 2
0x3 PIN3 I/O pin 3
Value Name Description
0x0 PIN0 I/O pin 0
0x1 PIN1 I/O pin 1
0x2 PIN2 I/O pin 2
0x3 PIN3 I/O pin 3
0x4 GND Ground
0x5 VSCALE VDD scaler
0x6 BANDGAP Internal bandgap voltage
0x7 DAC DAC output
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Table 29-9. Interrupt Selectio n
zBit 4 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
zBits 3:2 – SPEED[1:0]: Speed Selection
This bit indicates the speed/propagation delay mode of comparator n. COMPCTRLn.SPEED can be written only
while COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Table 29-10. Speed Selection
zBit 1 – SINGLE: Single-Shot Mode
This bit determines the operation of comparator n. COMPCTRLn.SINGLE can be written only while COMPC-
TRLn.ENABLE is zero.
0: Comparator n operates in continuous measurement mode.
1: Comparator n operates in single-shot mode.
These bits are not synchronized.
zBit 0 – ENABLE: Enable
Writing a zero to this bit disables comparator n.
Writing a one to this bit enables comparator n.
After writing to this bit, the value read back will not change until the action initiated by the writing is complete. Due
to synchronization, there is a latency of at least two GCLK_AC_DIG clock cycles from updating the register until
the comparator is enabled/disabled. The bit will continue to read the previous state while the change is in prog ress.
Writing a one to COMPCTRLn.ENABLE will prevent further changes to the other bits in COMPCTRLn. These bits
remain protected until COMPCTRLn.ENABLE is written to zero and the write is synchronized.
Value Name Description
0x0 TOGGLE Interrupt on comparator output toggle
0x1 RISING Interrupt on comparator output rising
0x2 FALLING Interrupt on comp ara t or ou tp u t fa ll i n g
0x3 EOC Interrupt on end of comparison (single-shot mode only)
Value Name Description
0x0 LOW Low speed
0x1 HIGH High speed
0x2-0x3 Reserved
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30. DAC – Digital-to-Analog Converter
30.1 Overview
The Digital-to-Analog Converter (DAC) converts a digital value to a voltage. The DAC has one channel with 10-bit
resolution, and it is capable of converting up to 350,000 samples per second (350ksps).
30.2 Features
zDAC with 10-bit resolution
zUp to 350ksps conversion rate
zMultiple trigger sources
zHigh-drive capabilities
zOutput can be used as input to the Analog Comparator (AC)
30.3 Block Diagram
Figure 30-1. DAC Block Diagram
30.4 Signal Description
Refer to “I/O Multiplexing and Considerations” on page 11 for the pin mapping of this peripheral. One signal can be
mapped on several pins.
DAC10 output
driver
AC
AVCC
START
VOUT
EVENT
CONTROL
EVCTRL
DATA
CTRLA
EMPTY
INT1V VREFP
DATABUF
CTRLB
STATUS
ADC
Signal Name Type Description
VOUT Analog output DAC output
VREFP Analog input External reference
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30.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
30.5.1 I/O Lines
Using the DAC’s I/O lines requires the I/O pins to be configured using the port configuration (PORT).
Refer to “PORT” on page 284 for details.
30.5.2 Power Management
The DAC will continue to operate in any sleep mode where the selected source clock is running. The DAC interrupts can
be used to wake up the device from sleep modes. The events can trigger other operations in the system without exiting
sleep modes. Refer to “PM – Power Manager” on page 100 for details on the different sleep modes.
30.5.3 Clocks
The DAC bus clock (CLK_DAC_APB) can be enabled and disabled in the Power Manager, and the default state of
CLK_DAC_APB can be found in the Peripheral Clock Masking section in “PM – Power Manager” on page 100.
A generic clock (GCLK_DAC) is required to clock the DAC. This clock must be configured and enabled in the Generic
Clock Controller before using the DAC. Refer to “GCLK – Generic Clock Controller” on page 78 for details.
This generic clock is asynchronous to the bus clock (CLK_DAC). Due to this asynchronicity, writes t o certain registers will
require synchronization between the clock domains. Refer to “Synchronization” on page 548 for further details.
30.5.4 DMA
Not applicable.
30.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the DAC interrupts requires the Interrupt
Controller to be configured first. Refer to “Nested Vector Interrupt Controller” on page 24 for details.
30.5.6 Events
The events are connected to the Event System. Refer to “EVSYS – Event System” on page 309 for details on how to
configure the Event System.
30.5.7 Debug Operation
When the CPU is halted in debug mode the DAC continues normal operation. If the DAC is configured in a way that
requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss may result
during debugging.
30.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following register:
zInterrupt Flag Status and Clear register (INTFLAG)
Write-protection is denoted by the Write-Protection property in the register description.
When the CPU is halted in debug mode, all write-protection is automatically disabled.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 27 for details.
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30.5.9 Analog Connections
Not applicable.
30.6 Functional Description
30.6.1 Principle of Operation
The Digital-to-Analog Converter (DAC) converts the digital value written to the Data register (DATA) into an analog
voltage on the DAC output. By default, a conversion is started when new data is written to DATA, and the corresponding
voltage is available on the DAC output after the conversion time. It is also possible to enable events from the Event
System to trigger the conversion.
30.6.2 Basic Operation
30.6.2.1 Initialization
Before enabling the DAC, it must be configured by selecting the voltage reference using the Reference Selection bits in
the Control B register (CTRLB.REFSEL).
30.6.2.2 Enabling, Disabling and Resetting
The DAC is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The DAC is disabled
by writing a zero to CTRLA.ENABLE.
The DAC is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in the
DAC will be reset to their initial state, and the DAC will be disabled. Refer to the CTRLA register for details.
30.6.2.3 Enabling the Output Buffer
To enable the DAC output on the VOUT pin, the output driver must be enabled by writing a one to the External Output
Enable bit in the Control B register (CTRLB.EOEN).
The DAC output buffer provides a high-drive-strength output, and is capable of driving both resistive and capacitive
loads. To minimize power consumption, the output buffer should be enabled only when external output is needed.
30.6.3 Additional Features
30.6.3.1 Conversion Range
The conversion range is between GND and the selected DAC voltage reference. The default voltage reference is the
internal 1V (INT1V) reference voltage. The other voltage reference options are the 3.3V analog supply voltage (AVCC =
VDDANA) and the external voltage reference (VREFP). The voltage reference is selected by writing to the Reference
Selection bits in the Control B register (CTRLB.REFSEL). The output voltage from the DAC can be calculated using the
following formula:
30.6.3.2 DAC as an Internal Reference
The DAC output can be internally enabled as input to the analog comparator. This is enabled by writing a one to the
Internal Output Enable bit in the Control B register (CTRLB.IOEN). It is possible to have the internal and external output
enabled simultaneously.
The DAC output can also be enabled as input to the Analog-to-Digital Converter. In this case, the output buffer must be
enabled.
VDAC DATA
0x3FF
-----------------VREF⋅=
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30.6.3.3 Data Buffer
The Data Buffer register (DATABUF) and the Data register (DATA) are linked together to form a two-stage FIFO. The
DAC uses the Start Conversion event to load data from DATABUF into DATA and start a new conversion. The Start
Conversion event is enabled by writing a one to the Start Event Input bit in the Event Control register
(EVCTRL.STARTEI). If a Start Conversion event occurs when DATABUF is empty, an Underrun interrupt request is
generated if the Underrun interrupt is enabled.
The DAC can generate a Data Buffer Empty event when DATABUF becomes empty and new data can be loaded to the
buffer. The Data Buffer Empty event is enabled by writing a one to the Empty Event Output bit in the Event Control
register (EVCTRL.EMPTYEO). A Data Buffer Empty interrupt request is generated if the Data Buffer Empty interrupt is
enabled.
30.6.3.4 Voltage Pump
When the DAC is used at operating voltages lower than 2.5V, the voltage pump must be enabled. This enabling is done
automatically, depending on operating voltage.
The voltage pump can be disabled by writing a one to the Voltage Pump Disable bit in the Control B register
(CTRLB.VPD). This can be used to reduce power consumption when the operating voltage is above 2.5V.
The voltage pump uses the asynchronous GCLK_DAC clock, and requires that the clock frequency be at least four times
higher than the sampling period.
30.6.3.5 Sampling Period
As there is no automatic indication that a conversion is done, the sampling period must be greater than or equal to the
specified conversion time.
30.6.4 DMA Operation
Not applicable.
30.6.5 Interrupts
The DAC has the following interrupt sources:
zData Buffer Empty
zUnderrun
zSynchronization Ready
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be individually enabled by writing a one
to the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled by writing a one to the
corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is generated when the interrupt
flag is set and the corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is
cleared, the interrupt is disabled or the DAC is reset. See the register description for details on how to clear interrupt
flags.
The DAC has one common interrupt request line for all the interrupt sources. The user must read the INTFLAG register
to determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to “Nested Vector Interrupt
Controller” on page 24 for details.
30.6.6 Events
The DAC can generate the following output events:
zData Buffer Empty (EMPTY)
Writing a one to an Event Output bit in the Event Control register (EVCTRL.xxEO) enables the corresponding output
event. Writing a zero to this bit disables the corresponding output event. Refer to “EVSYS – Event System” on page 3 09
for details on configuring the event system.
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The DAC can take the following actions on an input event:
zStart Conversion (START)
Writing a one to an Event Input bit in the Event Control register (EVCTRL.xxEI) enables the corresponding action on an
input event. Writing a zero to this bit disables the corresponding action on input event. Note that if several events are
connected to the DAC, the enabled action will be taken on any of the incoming events. Refer to “EVSYS – Event System”
on page 309 for details on configuring the event system.
30.6.7 Sleep Mode Operation
The generic clock for the DAC is running in idle sleep mode. If the Run In Standby bit in the Control A register
(CTRLA.RUNSTDBY) is one, the DAC output buffer will keep its value in standby sleep mode. If CTRLA.RUNSTDBY is
zero, the DAC output buffer will be disabled in standby sleep mode.
30.6.8 Synchronization
Due to the asynchronicity between CLK_DAC_APB and GCLK_DAC, some registers must be synchronized when
accessed. A register can require:
zSynchronization when written
zSynchronization when read
zSynchronization when written and read
zNo synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete. The Synchronization
Ready interrupt can be used to signal when synchronization is complete.
If an operation that requires synchronization is executed while STATUS.SYNCBUSY is one, the bus will be stalled. All
operations will complete successfully, but the CPU will be stalled and interrupts will be pending as long as the bus is
stalled.
The following bits need synchronization when written:
zSoftware Reset bit in the Control A register (CTRLA.SWRST)
zEnable bit in the Control A register (CTRLA.ENABLE)
zAll bits in the Data register (DATA)
zAll bits in the Data Buffer register (DATABUF)
Synchronization is denoted by the Write-Synchronized property in the register description.
The following bits need synchronization when read:
zAll bits in the Data register (DATA)
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30.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 RUNSTDBY ENABLE SWRST
0x01 CTRLB 7:0 REFSEL[1:0] VPD LEFTADJ IOEN EOEN
0x02 EVCTRL 7:0 EMPTYEO STARTEI
0x03 Reserved
0x04 INTENCLR 7:0 SYNCRDY EMPTY UNDERRUN
0x05 INTENSET 7:0 SYNCRDY EMPTY UNDERRUN
0x06 INTFLAG 7:0 SYNCRDY EMPTY UNDERRUN
0x07 STATUS 7:0 SYNCBUSY
0x08 DATA 7:0 DATA[7:0]
0x09 15:8 DATA[15:8]
0x0A Reserved
0x0B Reserved
0x0C DATABUF 7:0 DATABUF[7:0]
0x0D 15:8 DATABUF[15:8]
0x0E Reserved
0x0F Reserved
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30.8 Register Description
Registers can be 8, 16 or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
the Write-Protected property in each individual register description. Refer to “Register Access Protection” on page 545
for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Synchronized
property in each individual register description. Refer to “Synchronization” on page 548 for details.
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30.8.1 Control A
Name: CTRLA
Offset: 0x0
Reset: 0x00
Property: Write-Protected, Write-Synchronized
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – RUNSTDBY: Run in Standby
0: The DAC output buffer is disabled in standby sleep mode.
1: The DAC output buffer can be enabled in standby sleep mode.
This bit is not synchronized.
zBit 1 – ENABLE: Enable
0: The peripheral is disabled or being disabled.
1: The peripheral is enabled or being enabled.
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/disabled. The
value written to CTRL.ENABLE will read back immediately and the Synchronization Busy bit in the Status register
(STATUS.SYNCBUSY) will be set. STATUS.SYNCBUSY is cleared when the operation is complete.
zBit 0 – SWRST: Software Reset
0: There is no reset operation ongoing.
1: The reset operation is ongoing.
Writing a zero to this bit has no effect.
Writing a one to this bit resets the all registers in the DAC to their initial state, and the DAC will be disabled.
Writing a one to CTRLA.SWRST will always take precedence, meaning that all other writes in the same write oper-
ation will be discarded.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST
and STATUS.SYNCBUSY will both be cleared when the reset is complete.
Bit76543210
RUNSTDBY ENABLE SWRST
AccessRRRRRR/WR/WR/W
Reset00000000
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30.8.2 Control B
Name: CTRLB
Offset: 0x1
Reset: 0x00
Property: Write-Protected
zBits 7:6 – REFSEL[1:0]: Reference Selection
These bits select the reference voltage for the DAC according to Table 30-1.
Table 30-1. Reference Selection
zBits 5:4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 3 – VPD: Voltage Pump Disable
This bit controls the behavior of the voltage pump.
0: Voltage pump is turned on/off automatically.
1: Voltage pump is disabled.
zBit 2 – LEFTADJ: Left-Adjusted Data
This bit controls how the 10-bit conversion data is adjusted in the Data and Data Buffer registers.
0: DATA and DATABUF registers are right-adjusted.
1: DATA and DATABUF registers are left-adjusted.
zBit 1 – IOEN: Internal Output Enable
0: Internal DAC output not enabled.
1: Internal DAC output enabled to be used by the AC.
zBit 0 – EOEN: External Output Enable
0: The DAC output is turned off.
1: The high-drive output buffer drives the DAC output to the VOUT pin.
Bit76543210
REFSEL[1:0] - VPD LEFTADJ IOEN EOEN
AccessR/WR/W R R R/WR/WR/WR/W
Reset00000000
REFSEL[1:0] Reference Selection Description
0x0 INT1V Internal 1.0V reference
0x1 AVCC AVCC
0x2 VREFP External reference
0x3 Reserved
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30.8.3 Event Control
Name: EVCTRL
Offset: 0x2
Reset: 0x00
Property: Write-Protected
zBits 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 1 – EMPTYEO: Data Buffer Empty Event Output
This bit indicates whether or not the Data Buffer Empty event is enabled and will be generated when the Data Buf-
fer register is empty.
0: Data Buffer Empty event is disabled and will not be generated.
1: Data Buffer Empty event is enabled and will be generated.
zBit 0 – STARTEI: Start Conversion Event Input
This bit indicates whether or not the Start Conversion event is enabled and data are loaded from the Data Buffer
register to the Data register upon event reception.
0: A new conversion will not be triggered on an incoming event.
1: A new conversion will be triggered on an incoming event.
Bit76543210
EMPTYEO STARTEI
AccessRRRRRRR/WR/W
Reset00000000
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30.8.4 Interrupt Enable Clear
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Set register (INTENSET).
Name: INTENCLR
Offset: 0x4
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The Synchronization Ready interrupt is disabled.
1: The Synchronization Ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Synchronization Ready Interrupt Enable bit, which disables the Synchroniza-
tion Ready interrupt.
zBit 1 – EMPTY: Data Buffer Empty Interrupt Enable
0: The Data Buffer Empty interrupt is disabled.
1: The Data Buffer Empty interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Data Buffe r Empty Interrupt Enable bit, which disables the Data Buffer Empty
interrupt.
zBit 0 – UNDERRUN: Underrun Interrupt Enable
0: The Underrun interrupt is disabled.
1: The Underrun interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Underrun Interrupt Enable bit, which disables the Underrun interrupt.
Bit76543210
SYNCRDY EMPTY UNDERRUN
AccessRRRRRR/WR/WR/W
Reset00000000
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30.8.5 Interrupt Enable Set
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes in this register
will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Name: INTENSET
Offset: 0x5
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – SYNCRDY: Synchronization Ready Interrupt Enable
0: The Synchronization Ready interrupt is disabled.
1: The Synchronization Ready interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Synchronization Ready Interrupt Enable bit, which enables the Synchronization
Ready interrupt.
zBit 1 – EMPTY: Data Buffer Empty Interrupt Enable
0: The Data Buffer Empty interrupt is disabled.
1: The Data Buffer Empty interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Data Buffer Empty Interrupt Enable bit, which enables the Data Buffer Empty
interrupt.
zBit 0 – UNDERRUN: Underrun Interrupt Enable
0: The Underrun interrupt is disabled.
1: The Underrun interrupt is enabled.
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Underrun Interrupt Enable bit, which enables the Underrun interrupt.
Bit76543210
SYNCRDY EMPTY UNDERRUN
AccessRRRRRR/WR/WR/W
Reset00000000
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30.8.6 Interrupt Flag S tatus and Clear
Name: INTFLAG
Offset: 0x6
Reset: 0x00
Property: Write-Protected
zBits 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
zBit 2 – SYNCRDY: Synchronization Ready
This flag is cleared by writing a one to the flag.
This flag is set on a 1-to-0 transition of the Synchronization Busy bit in the Status register (STATUS.SYNCBUSY),
except when the transition is caused by an enable or a software reset, and will generate an interrupt request if
INTENCLR/SET.READY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Synchronization Ready interrupt flag.
zBit 1 – EMPTY: Data Buffer Empty
This flag is cleared by writing a one to the flag or by writing new data to DATABUF.
This flag is set when data is transferred from DATABUF to DATA, and the DAC is ready to receive new data in
DATABUF, and will generate an interrupt request if INTENCLR/SET.EMPTY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Data Buffer Empty interrupt flag.
zBit 0 – UNDERRUN: Underrun
This flag is cleared by writing a one to the flag.
This flag is set when a start conversion event occurs when DATABUF is empty, and will generate an interrupt
request if INTENCLR/SET.UNDERRUN is one.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Underrun interrupt flag.
Bit76543210
SYNCRDY EMPTY UNDERRUN
AccessRRRRRR/WR/WR/W
Reset00000000
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30.8.7 Status
Name: STATUS
Offset: 0x7
Reset: 0x00
Property: Read-Synchronized
zBit 7 – SYNCBUSY: Synchronization Busy Status
This bit is cleared when the synchronization of registers between the clock domains is complete.
This bit is set when the synchronization of registers between clock domains is started.
zBits 6:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to
zero when this register is written. These bits will always return zero when read.
Bit76543210
SYNCBUSY
AccessRRRRRRRR
Reset00000000
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30.8.8 Data
Name: DATA
Offset: 0x8
Reset: 0x0000
Property: Write-Synchronized, Read-Synchronized, Write-Protected
zBits 15:0 – DATA: Data value to be converted
DATA register contains the 10-bit value that is converted to a voltage by the DAC. The adjustment of these 10 bits
within the 16-bit register is controlled by CTRLB.LEFTADJ:
- DATA[9:0] when CTRLB.LEFTADJ is zero.
- DATA[15:6] when CTRLB.LEFTADJ is one.
Bit151413121110 9 8
DATA[15:8]
AccessRRRRRRR/WR/W
Reset00000000
Bit76543210
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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30.8.9 Data Buffer
Name: DATABUF
Offset: 0xC
Reset: 0x0000
Property: Write-Synchronized, Write-Protected
zBits 15:0 – DATABUF: Data Buffer
DATABUF contains the value to be transferred into DATA register.
Bit151413121110 9 8
DATABUF[15:8]
AccessRRRRRRR/WR/W
Reset00000000
Bit76543210
DATABUF[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset00000000
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31. PTC - Peripheral Touch Controller
31.1 Overview
The PTC is intended for acquiring capacitive touch sensor and capacitive proximity sensor signals. The external
capacitive touch sensor is typically formed on a PCB, and the sensor electrodes are connected to the analog charge
integrator of the PTC via device I/O pins. The PTC supports mutual capacitance sensors organized as capacitive touch
matrices in different X-Y configurations, including indium tin oxide (ITO) sensor grids. The PTC requires one pin per X
line and one pin per Y line. No external components are needed.
In self-capacitance mode, the PTC requires just one pin with an X-line driver for each self-capacitance sensor.
31.2 Features
zImplements low-power, high-sensitivity, environmentally robust cap acitive touch buttons, sliders, wheels and proximity
sensing
zSupports mutual capacitance and self-capacitance sensing
z16 buttons in self-capacitance mode
z256 buttons in mutual-capacitance mode
zOne pin per electrode – no external components
zLoad compensating charge sensing
zParasitic capacitance compensation and adjustable gain for superior sensitivity
zZero drift over the temperature and VDD range
zNo need for temperature or VDD compensation
zSingle-shot and free-running charge measurement
zHardware noise filtering and noise signal desynchronization for high conducted immunity
zSelectable channel change delay
zAllows choosing the settling time on a new channel, as required
zAcquisition-start triggered by command or interrupt event
zInterrupt on acquisition-complete
zTo be used in combination with the Atmel® provided QTouch® Library firmware and QTouch Composer tool
31.3 Signal Description
Note: 1. The number of X and Y lines are device dependent. Refer to “Configuration Summa ry” on page 3 for details.
Refer to “I/O Multiplexing and Considerations” on page 11 for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
31.4 Product Dependencies
In order to access the PTC, the user must use the QTouch Composer tool to configure and link the QTouch Library
firmware with the application code.
Name Type Description
X[n:0] Analog input DAC output
Y[m:0] Analog input External reference
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32. Electrical Characteristics
32.1 Disclaimer
All values in this chapter are preliminary and subject to change without further notice.
All typical values are measured at T = 25°C unless otherwise specified. All minimum and maximum values are valid
across operating temperature and voltage unless otherwise specified.
32.2 Absolute Maximum Ratings
Stresses beyond those listed in Table 32-1 may cause permanent damage to the device. This is a stress rating only and
functional operation of the device at these or other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device
reliability.
Table 32-1. Absolute maximum ratings
32.3 General Operating Ratings
The device must operate within the ratings listed in Table 32-2 in order for all other electrical characteristics and typical
characteristics of the device to be valid.
Ta ble 32-2. General operating conditions(1)
(1) These values are based on characteriza tion. These values are not covered by test limits in production.
Symbol Parameter Min. Max. Units
VDD Power supply voltage 3.63 V
IVDD Current into a VDD pin 50 mA
IGND Current out of a GND pin 50 mA
VPIN Pin voltage with respect to GND and VDD GND-0.3V VDD+0.3V V
IPIN I/O pin sink/source current mA
Symbol Parameter Condition Min. Typ. Max. Units
VDD Power supply voltage
I
1.62 3.3 3.63 V
VDDANA Analog supply voltage
I
1.62 3.3 3.63 V
TATemperature range
I
-40 25 85 °C
TJJunction temperature
I
100 °C
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32.4 Supply Characteristics
The following characteristics are applicable to the operating temperature range: TA = -40°C to 85°C, unless otherwise
specified and are valid for a junction temperature up to TJ = 100°C. Please refer to “Power Supply and Start-Up
Considerations” on page 16.
Table 32-3. Supply Characteristics
Table 32-4. Supply Rise Rates
Symbol Conditions
Voltage
Min. Max. Units
VDDIO
VDDIN
VDDANA
Full Voltage Range 1.62 3.63 V
Symbol Parameter Min.
Rise Rate
Units CommentsMax.
VDDIO
VDDIN
VDDANA
DC supply peripheral I/Os,
internal regulator and analog
supply voltage (1)
1. These values are based on simulation. These values are not covered by test limits in production or characterization.
0.34 V/µs
I
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32.5 Maxim um Clock Frequencies
Table 32-5. Maximum Clock Frequen cies
Symbol Parameter Description Max. Units
fCPU CPU clock frequency
I
48 MHz
fAHB AHB clock frequency
I
fAPBA APBA clock frequency
I
fAPBB APBB clock frequency
I
fAPBC APBC clock frequency
I
fGCLK0 GCLK0 clock frequency DFLL48M Reference
fGCLK1 GCLK1 clock frequency WDT
I
fGCLK2 GCLK2 clock frequency RTC
I
fGCLK3 GCLK3 clock frequency EIC
II
fGCLK4 GCLK4 clock frequency EVSYS_CHANNEL_0
I
fGCLK5 GCLK5 clock frequency
I
EVSYS_CHANNEL_1
fGCLK6 GCLK6 clock frequency EVSYS_CHANNEL_2
I
fGCLK7 GCLK7 clock frequency
I
EVSYS_CHANNEL_3
fGCLK8 GCLK8 clock frequency EVSYS_CHANNEL_4
I
fGCLK9 GCLK9 clock frequency EVSYS_CHANNEL_5
I
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fGCLK10 GCLK10 clock frequency EVSYS_CHANNEL_6
I
48 MHz
fGCLK11 GCLK11 clock frequency EVSYS_CHANNEL_7
I
fGCLK12 GCLK12 clock frequency SERCOMx_SLOW
I
fGCLK13 GCLK13 clock frequency SERCOM0_CORE
fGCLK14 GCLK14 clock frequency
I
SERCOM1_CORE
fGCLK15 GCLK15 clock frequency SERCOM2_CORE
I
fGCLK16 GCLK16 clock frequency SERCOM3_CORE
I
fGCLK17 GCLK17 clock frequency SERCOM4_CORE
I
fGCLK18 GCLK18 clock frequency SERCOM5_CORE
I
fGCLK19 GCLK19 clock frequency TC0,TC1
fGCLK20 GCLK20 clock frequency TC2,TC3
fGCLK21 GCLK21 clock frequency TC4,TC5
I
fGCLK22 GCLK22 clock frequency TC6,TC7
I
fGCLK23 GCLK23 clock frequency
I
ADC
fGCLK24 GCLK24 clock frequency AC_DIG
I
fGCLK25 GCLK25 clock frequency AC_ANA
I
fGCLK26 GCLK26 clock frequency DAC
I
fGCLK27 GCLK27 clock frequency PTC
I
Symbol Parameter Description Max. Units
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32.6 Power Consumption
The values in Table 32-6 are measured values of power consumption under the following conditions, except where
noted:
zOperating conditions
zVVDDIN = 3.3V
zWake up time from sleep mode is measured from the edge of the wakeup signal to the execution of the first
instruction fetched in flash.
zOscillators
zXOSC (crystal oscillator) stopped
zXOSC32K (32kHz crystal oscillator) running with external 32kHz crystal
zDFLL48M using XOSC32K as reference and running at 48MHz
zClocks
zDFLL48M used as main clock source
zCPU, AHB clocks undivided
zAPBA clock divided by 4
zAPBB and APBC bridges off
zThe following AHB module clocks are running: NVMCTRL, APBA bridge
zAll other AHB clocks stopped
zThe following peripheral clocks running: PM, SYSCTRL, RTC
zAll other peripheral clocks stopped
zI/Os are inactive with internal pull-up
zCPU is running on flash with 1 wait states
zLow power cache enabled
zBOD12 and BOD33 disabled
Table 32-6. Current Consumption
Mode Conditions TAMin. Typ. Max. Units
ACTIVE
CPU running a Fibonacci algorithm 25°C 109
µA/MHz
85°C 110
CPU running a Fibonacci algorithm
VDDIN=1.8V, CPU is running on
flash with 3 wait states
25°C 109
85°C 110
CPU running a CoreMark algorithm 25°C 140
µA/MHz
85°C 145
CPU running a CoreMark algorithm
VDDIN=1.8V, CPU is running on
flash with 3 wait states
25°C 125
85°C 130
IDLE0
I
25°C 2.35 mA
85°C 2.4 mA
IDLE1
I
25°C 1.9 mA
85°C 2mA
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Table 32-7. Wake-up Time
Figure 32-1. Measurement Schematic
IDLE2
I
25°C 1.7 mA
85°C 1.8 mA
STANDBY
XOSC32K running
RTC running at 1 kHz 25°C 3.2 µA
85°C 30 µA
XOSC32K and RTC stopped 25°C 2µA
85°C 28 µA
Mode Conditions TAMin. Typ. Max. Units
IDLE0 OSC8M used as main clock
source, low power cache disabled 25°C 3.5 µs
85°C µs
IDLE1
I
OSC8M used as main clock
source, low power cache disabled 25°C 12 µs
85°C µs
IDLE2
I
OSC8M used as main clock
source, low power cache disabled 25°C 12.5 µs
85°C µs
STANDBY
I
OSC8M used as main clock
source, low power cache disabled 25°C 20 µs
85°C µs
Mode Conditions TAMin. Typ. Max. Units
VDDIN
VDDCORE
VDDIO
VDDANA
Amp 0
568
Atmel SAM D20 [Preliminary DATASHEET]
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32.7 I/O Pin Characteristics
32.7.1 Normal I/O Pins
Table 32-8. Normal I/O Pins Characteristics
32.7.2 I2C Pins
Refer to “I/O Multiplexing and Considerations” on page 11 to get the list of I2C pins.
Table 32-9. I2C Pins Characteristics in I2C configuration
Symbol Parameter Conditions Min. Typ. Max. Units
RPULL Pull-up - Pull-down resistance (1)
1. These values are based on simulation. These values are not covered by test limits in production or characterization.
I
20 38 (2)
2. These values are based on charac terization. These values are not covered by test limits in production.
60 kΩ
VIL Input low-level voltage VDD=1.6V-2.0V 0.25
V
VDD=2.7V-3.6V 0.3
VIH Input high-level voltage VDD=1.6V-2.0V 0.7
VDD=2.7V-3.6V 0.55
VOL Output low-level voltage VDD>3V, IOL=20mA
I
0.1*VDD 0.2*VDD
VOH Output high-level voltage VDD>3V, IOH=10mA
II
0.8*VDD 0.9*VDD
IOL Output low-level current VDD=1.6V-2.0V 8
mA
VDD=2.7V-3.6V 10
IOH Output high-level current VDD=1.6V-2.0V 4.5
VDD=2.7V-3.6V 10
ILEAK Input leakage current Pull-up resistors
disabled -1 0.015(2) 1µA
Symbol Parameter Condition Min. Typ. Max. Units
RPULL Pull-up - Pull-down resistance (1)
I
20 38 (2) 60 kΩ
569
Atmel SAM D20 [Preliminary DATASHEET]
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I2C pins timing characteristics can be found in “SERCOM in I2C Mode Timing” on page 590.
Table 32-10. I2C Pins Characteristics in PORT Configuration
VIL Input low-level voltage VDD=1.6V-2.0V
I
0.25
V
VDD=2.7V-3.6V 0.3
VIH Input high-level voltage VDD=1.6V-2.0V 0.7
VDD=2.7V-3.6V
I
0.55
VHYS Hysteresis of Schmitt trigger inputs 0.1*VDD
VOL Output low-level voltage
VDD> 2.0V
I,
IOL=3mA 0.4
VDD≤2.0V
IOL=2mA 0.2*VDD
IOL Output low-level current VOL =0.4V 3mA
VOL =0.6V 6
fSCL SCL clock frequency
I
400 kHz
1. These values are based on simulation. These values are not covered by test limits in production or characterization.
2. These values are based on charac terization. These values are not covered by test limits in production.
Symbol Parameter Conditions Min. Typ. Max. Units
RPULL Pull-up - Pull-down resistance (1)
1. These values are based on simulation. These values are not covered by test limits in production or characterization.
I
20 38 (2)
2. These values are based on charac terization. These values are not covered by test limits in production.
60 kΩ
VIL Input low-level voltage VDD=1.6V-2.0V
I
0.25 V
VDD=2.7V-3.6V 0.3
VIH Input high-level voltage VDD=1.6V-2.0V 0.7 V
VDD=2.7V-3.6V
I
0.55
VOL Output low-level voltage VDD>3V, IOL=20mA
A
0.1*VDD 0.2*VDD V
VOH Output high-level voltage VDD>3V, IOH=10
II
mA 0.8*VDD 0.9*VDD V
IOL Output low-level current VDD=1.6V-2.0V 8
mA
VDD=2.7V-3.6V 10
IOH Output high-level current VDD=1.6V-2.0V 4.5
VDD=2.7V-3.6V 10
ILEAK Input leakage current Pull-up resistors
disabled -1 0.015(2) 1µA
Symbol Parameter Condition Min. Typ. Max. Units
570
Atmel SAM D20 [Preliminary DATASHEET]
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(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
32.7.3 XOSC Pin
XOSC pins behave as normal pins when used as normal I/Os. Refer to Table 32-8.
32.7.4 XOSC32 Pin
XOSC32 pins behave as normal pins when used as normal I/Os. Refer to Table 32-8.
32.7.5 External Reset Pin
Reset pin has the same electrical characteristics as normal I/O pins. Refer to Table 32-8.
571
Atmel SAM D20 [Preliminary DATASHEET]
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32.8 Analog Characteristics
32.8.1 Voltage Regulator Characteristics
Table 32-11. VREG Electrical Characteristics
Notice that supplying any external components using VDDCORE pin is not allowed to assure the integrity of the core supply
voltage.
Table 32-12. Decoupling requirements
(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
32.8.2 Power-On Reset (POR) Characteristics
Table 32-13. POR Characteristics
(1) These values are based on simulation. These values are not covered by characterization or test limits in production.
Symbol Parameter Conditions Min. Typ. Max. Units
VDDIN Input voltage range
I
1.62 3.3 3.63 V
VDDCORE DC calibrated output voltage
I
1.23 V
Symbol Parameter Technology Min. Typ. Max. Units
CIN Input regulator capacitor
I
nF
COUT Output regulator capacitor
I
100 (1) 200 (1) nF
Symbol Parameter Conditions Min. Typ. Max. Units
VPOT+ Voltage threshold on VDDIN
rising
I
VDD falls at 1V/ms or slower 1.45 V
VPOT- Voltage threshold on VDDIN
falling 0.99 V
572
Atmel SAM D20 [Preliminary DATASHEET]
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Figure 32-2. POR Operating Principle
32.8.3 Brown-Out Detectors Characteristics
32.8.3.1 BOD33
Table 32-14. BOD33 LEVEL Value
Table 32-15. BOD33 Characteristics(1)
(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
Reset VDD
V
POT+
V
Time
POT-
BOD33.LEVEL Min. Typ. Max. Units
61.71 V
16 2.04 V
31 2.58 V
49 3.24 V
Symbol Parameter Conditions Min. Typ. Max. Units
I
Step size,
between adjacent
values in
BOD33.LEVEL
I
4mV
VHYST Hysteresis
I
46 160 mV
tDET Detection time Time with VDDIN < VTH
necessary to generate
a reset signal 0.9 (1) µs
IBOD33 Current
consumption Continuous mode 33 (1) µA
Sampling mode µA
tSTARTUP Startup time
I
2.2 (1) µs
573
Atmel SAM D20 [Preliminary DATASHEET]
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32.8.3.2 BOD12
The BOD12 threshold level can be configured with the BOD12.LEVEL bits in the SYSCTRL peripheral.
Table 32-16. BOD12 Characteristics(2)
(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
(2) These values are based on characterization except otherwise noted. These values are not covered by test limits in production.
32.8.4 Analog-to-Digital (ADC) characteristics
Symbol Parameter Conditions Min. Typ. Max. Units
I
BOD12 median
threshold value
BOD12LEVEL =
10000b
VDD = 1.23V 1.06(1) V
I
Step size,
between adjacent
values in
BOD12LEVEL
I
0.5 % of
VDD
VHYST Hysteresis
I
22.3 mV
tDET Detection time Time with VDDIN < VTH
necessary to generate a reset
signal 0.1(1) µs
IBOD12 Current
consumption
Continuous mode 20(1) µA
Sampling mode µA
Standby mode 0.01(1) µA
tSTARTUP Startup time
I
0.76 µs
Table 32-17. Operating Conditions
Symbol Parameter Conditions Min. Typ. Max. Units
RES Resolution
I
812 bits
fCLK_ADC ADC Clock frequency
I
30 2100 kHz
Sample rate(1) Single shot 5323 ksps
Free running 5350 ksps
Sampling time(1) 0.5 cycles
Conversion time(1) 1x Ga in 6cycles
VREF Voltage reference range 1.0 VDDANA-0.6 V
VREFINT1V Internal 1V reference (2) 1.0 V
VREFINTVCC0 Internal ratiometric
reference 0(2) VDDANA/1.48 V
VREFINTVCC1 Internal ratiometric
reference 1(2) VDDANA>2.0V VDDANA/2 V
574
Atmel SAM D20 [Preliminary DATASHEET]
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Notes: 1. These values are based on characterization. These values are not covered by test limits in production.
2. These values are based on simulation. These values are not covered by test limits in production or characterization.
3. In this condition and for a sample rate of 350ksps, 1 Conversion at gain 1x takes 6 clock cycles of the ADC clock.
Table 32-18. Differential Mode
Notes: 1. Maximum numbers are based on characterization and not tested in production, and valid for 5% to 95% of the input voltage range.
2. Dynamic parameter numbers are based on characterizatio n and not tested in production.
3. Respect the input common mode voltage through the equation: 0. 2*VDDANA – 0.1V < VCM_IN < 0.95*VDDANA + VREF/ 4 – 0.75V (where VCM_IN is the In put channel
common mode voltage)
Conversion range(1) Differential mode -VREF/GAIN +VREF/GAIN V
Single-ended mode 0.0 +VREF/GAIN V
CSAMPLE Sampling capacitance(2) 3.5 mA
RSAMPLE Input channel source
resistance(2) 2.8 kΩ
IDD DC supply current(1) fCLK_ADC = 2.1MHz
I
(3) 1.15 mA
Symbol Parameter Conditions Min. Typ. Max. Units
ENOB Effective Number Of Bits With gain compensation 10.5 bits
TUE Total Unadjusted Error
I
1x Gain
n
4.3 LSB
INL
I
Integral Non Linearity 1x Gain
n
1.3 LSB
DNL Differential Non Linearity 1x Gain
n
+/-0.5 LSB
I
Gain Error
Ext. Ref 1x 2.5 mV
I
VREF=VDDANA/1.48 -1.5 mV
I
Bandgap -5.0 mV
Gain Accuracy Ext. Ref. 0.5x +/-0.36 %
Ext. Ref. 2x to 16x +/-0.1 %
Offset Error
Ext. Ref. 1x -1.5 mV
VREF=VDDANA/1.48 0.5 mV
Bandgap 3.0 mV
SFDR Spurious Free Dynamic Range 1x Gain
FADC = 2.1MHz
FIN = 40kHz
AIN = 95%FSR
75 dB
SINAD Signal-to-Noise and Distortion 65 dB
SNR Signal-to-Noise Ratio 66 dB
THD Total Harmonic Distortion -77 dB
Noise RMS T=25°C 1.0 mV
Table 32-17. Operating Conditions (Continued)
Symbol Parameter Conditions Min. Typ. Max. Units
575
Atmel SAM D20 [Preliminary DATASHEET]
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Table 32-19. Single-Ende d Mode
Notes: 1. Maximum numbers are based on characterization and not tested in production, and for 5% to 95% of the input voltage
range.
2. Respect the input common mode voltage through the equation: VREF/4 - 0.3*VDDANA – 0.1V < VCM_IN < 0.7*VDDANA +
VREF/4 – 0.75V (where VCM_IN is the Input channel common mode voltage)
32.8.4.1 Performance with the Averaging Digital Feature
Averaging is a feature which increases the sample accuracy. ADC automatically computes an average value of multiple
consecutive conversions. The numbers of samples to be averaged is specified by the Number-of-Samples-to-be-
collected bit group in the Average Control register (AVGCTRL.SAMPLENUM[3:0]) and the averaged output is available
in the Result register (RESULT).
Table 32-20. Averaging feature
32.8.4.2 Performance with the hardware offset and gain correction
Inherent gain and offset errors affect the absolute accuracy of the ADC. The offset error cancellation is handled by the
Offset Correction register (OFFSETCORR) and the gain error cancellation, by the Gain Correction register
(GAINCORR). The offset and gain correction value is subtracted from the converted data before writing the Result
register (RESULT).
Symbol Parameter Conditions Min. Typ. Max. Units
TUE Total Unadjusted Error 1x gain 10.5 LSB
INL Integral Non- Linearity 1x gain 1.6 LSB
DNL Differential Non-Linearity 1x gain +/-0.6 LSB
Gain Error Ext. Ref. 1x 0.7 mV
Gain Accuracy
Ext. Ref.
0.5x +/-0.43 %
Ext. Ref. 2x
to 16X +/-0.3 %
Offset Error Ext. Ref. 1x 1.5 mV
Noise RMS T = 25°C 1.0 mV
Average
Number Conditions SNR (dB) SINAD (dB) SFDR
(dB) ENOB
(bits)
1
In differential mode, 1x gain,
VDDANA=3.0V, VREF=1.0V, 350kSps
66.0 65.0 72.8 9.75
867.6 65.8 75.1 10.62
32 69.7 67.1 75.3 10.85
128 70.4 67.5 75.5 10.91
576
Atmel SAM D20 [Preliminary DATASHEET]
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Table 32-21. Offset and Gain correction feature
32.8.4.3 Inputs and Sample and Hold Acquisition Times
The analog voltage source must be able to charge the sample and hold (S/H) capacitor in the ADC in order to achieve
maximum accuracy. Seen externally the ADC input consists of a resistor ( ) and a capacitor ( ). In
addition, the source resistance ( ) must be taken into account when calculating the required sample and hold
time. Figure 32-3 shows the ADC input channel equivalent circuit.
Figure 32-3. ADC Input
To achieve n bits of accuracy, the capacitor must be charged at least to a voltage of
The minimum sampling time for a given can be found using this formula:
for a 12 bits accuracy:
where
Gain Factor Conditions Offs et Er ror
(mV) Gain
Error(mV) Total Unadjusted
Error(LSB)
0.5x
In differential mode, 1x gain,
VDDANA=3.0V, VREF=1.0V, 350kSps
0.25 1.0 2.4
1x 0.20 0.10 1.5
2x 0.15 -0.15 2.7
8x -0.05 0.05 3.2
16x 0.10 -0.05 6.1
RSAMPLE
CSAMPLE
RSOURCE
R
SOURCE
R
SAMPLE
Analog Input
AINx C
SAMPLE
V
IN
VDDANA/2
CSAMPLE
VCSAMPLE V≥IN 2n1+
–
tSAMPLEHOLD
RSOURCE
tSAMPLEHOLD RSAMPLE R+SOURCE
()CSAMPLE
()×n1+() 2()ln××≥
tSAMPLEHOLD RSAMPLE R+SOURCE
()CSAMPLE
()×9.02×≥
tSAMPLEHOLD 1
2fADC
×
---------------------=
577
Atmel SAM D20 [Preliminary DATASHEET]
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32.8.5 Digital to Analog Converter (DAC) Characteristics
Table 32-22. Operating Conditions(1)
(1) These values are based on specifications otherwise noted.
(2) These values are based on characteriza tion. These values are not covered by test limits in production.
Table 32-23. Clock and Timing (1)
(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
Table 32-24. Accuracy Characteristics
Symbol Parameter Conditions Min. Typ. Max. Units
VDDANA Analog supply voltage
I
1.62 3.63 V
AVREF External reference voltage
I
1.0 VDDANA-0.6 V
Internal reference voltage 1 1 V
Internal reference voltage 2 VDDANA V
I
Linear output voltage range
I
0.05 VDDANA-0.05 V
I
Minimum resistive load
I
5 kΩ
I
Maximum capacitance load
I
100 pF
iDD DC supply current(2) VDDANA=1.6V 100 µA
VDDANA=3.6V 410 µA
Symbol Parameter Conditions Min. Typ. Max. Units
fGCLK_DAC Conversion rate Cload=100pF Normal mode 350 ksps
I
Startup ti me VDD > 2.6V 2.85 µs
VDD < 2.6V 10 µs
Symbol Parameter Conditions Min. Typ. Max. Units
RES Input resolution(1)
I
10 Bits
INL Integral non-linearity
VREF= Ext 1.0V VDD = 1.6V 1.1
LSB
VDD = 3.6V 1.2
VREF = VDDANA VDD = 1.6V 2.2
VDD = 3.6V 1.4
VREF= INT1V VDD = 1.6V 1.3
VDD = 3.6V 1.2
578
Atmel SAM D20 [Preliminary DATASHEET]
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(1) These values are according to specification. These values are not covered by test limits in production or characterization.
32.8.6 Analog Comparator Characteristics
Table 32-25. Electrical and Timi ng(2)
(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
(2) All values based on characterization except where otherwise noted.
DNL Differential non-linearity
VREF= Ext 1.0V VDD = 1.6V +/-1.2
LSB
VDD = 3.6V +/-1.1
VREF= VDDANA VDD = 1.6V +/-1.7
VDD = 3.6V +/-1.1
VREF= INT1V VDD = 1.6V +/-1.4
VDD = 3.6V +/-1.5
I
Gain error
I
+/-5 mV
I
Offset error
I
+/-3 mV
Symbol Parameter Conditions Min. Typ. Max. Units
Symbol Parameter Conditions Min. Typ. Max. Units
I
Positive input voltage
range
I
0 VDDANA V
I
Negative input voltage
range
I
0 VDDANA
I
Offset Hysteresis = 0, Fast mode 0.0 mV
Hysteresis = 0, Low power mode 0.0 mV
IHysteresis Hysteresis = 1, Fast mode 50 mV
Hysteresis = 1, Low power mode 40 mV
IPropagation delay
Changes for VACM=VDDIO/2
100mV overdrive, Fast mode 60 ns
Changes for VACM=VDDIO/2
100mV overdrive, Low power
mode 225 ns
tSTARTUP Startup time
Enable to ready delay
Fast mode 1µs
Enable to ready delay
Low power mode 12 µs
I
64-level voltage scaler Integral non-linearity (INL)
579
Atmel SAM D20 [Preliminary DATASHEET]
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32.8.7 Internal 1.1V Bandgap Reference Characteristics
Table 32-26. Bandgap and Internal 1.1V referen ce characteristics
(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
32.8.8 Temperature Sensor Characteristics
Table 32-27. Temperature Sensor char acteristics(1)
(1) These values are based on characteriza tion. These values are not covered by test limits in production.
Symbol Parameter Conditions Min. Typ. Max. Units
INT1V Internal 1.1V Bandgap reference(1) T= 25°C, after calibration 1.1 V
I
Variation over voltage and
temperature Relative to calibration conditions 1 %
Symbol Parameter Conditions Min. Typ. Max. Units
I
Temperature sensor output
voltage T= 25°C 0.667 V
I
Temperature sensor slope 2.36 mV/°C
I
Variation over VDDANA voltage VDDANA=1.62V to 3.6V 1.05 mV/V
580
Atmel SAM D20 [Preliminary DATASHEET]
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32.9 NVM Characteristics
Table 32-28. Maximum Operating Frequency(1)
(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
Table 32-29. Flash Endurance and Data Retention(1)
(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
Table 32-30. Eeprom Configuration Endurance and Data Retention(1)
(1) These values are based on simulation. These values are not covered by test limits in producti on or characterization.
Table 32-31. NVM Characteristics
VDD range NVM Wait States Maximum Operating Frequency Units
1.62V to 3.63V
014
MHz
128
242
348
2.7V to 3.63V 024
148
Symbol Parameter Conditions Min. Typ. Max. Units
RetNVM10k Retention after up to 10k Average ambient 55°C 10 50 Years
RetNVM1k Retention after up to 1k Average ambient 55°C 20 100 Years
RetNVM100 Retention after up to 100 Average ambient 55°C 25 100 Years
CycNVM Cycling Endurance -40°C < Ta < 85°C 10k 150k Cycles
Symbol Parameter Conditions Min. Typ. Max. Units
RetEEPROM10k Retention a fter up to 10k Average ambient 55°C 20 50 Years
RetEEPROM100 Retention a fter up to 100 Average ambient 55°C 25 100 Years
CycEEPROM Cycling Endurance using
wear leveling algorithm -40°C < Ta < 85°C 100k 150k Cycles
Symbol Parameter Conditions Min. Typ. Max. Units
tFPP Page programmi ng time 2.5 ms
tFRE Row erase time
I
6ms
581
Atmel SAM D20 [Preliminary DATASHEET]
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tFFP Fuse programming time
I
tFEA Erase all page time (EA)
I
tFCE DSU chip erase time
(CHIP_ERASE) 240 ms
Symbol Parameter Conditions Min. Typ. Max. Units
582
Atmel SAM D20 [Preliminary DATASHEET]
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32.10 Oscillators Characteristics
32.10.1 Crystal Oscillator (XOSC) Characteristics
32.10.1.1 Digital Clock Characteristics
The following table describes the characteristics for the oscillator when a digital clock is applied on XIN.
Table 32-32. Digital Clock Characteristics
32.10.1.2 Crystal Oscillator Characteristics
The following table describes the characteristics for the oscilla tor when a crystal is connected between XIN and XOUT as
shown in Figure 32-4. The user must choose a crystal oscillator where the crystal load capacitance CL is within the range
given in the table. The exact value of CL can be found in the crystal datasheet. The capacitance of the external capacitors
(CLEXT) can then be computed as follows:
where CSTRAY is the capacitance of the pins and PCB, CSHUNT is the shunt capacitance of the crystal.
Table 32-33. Crystal Oscillator Characteristics(1)
Symbol Parameter Conditions Min. Typ. Max. Units
fCPXIN XIN clock frequency
I
MHz
tCPXIN XIN clock duty cycle
I
%
Symbol Parameter Conditions Min. Typ. Max. Units
fOUT Crystal oscillator frequency
I
0.4 30 MHz
ESR Crystal Equivalent Series
Resistance
Safety Factor = 3
f = 0.455MHz, CLEXT = 100pF
XOSC.GAIN = 0 9.6K
Ω
f = 2MHz, CLEXT = 20pF
XOSC.GAIN = 0 4.3K
f = 4MHz, CLEXT = 20pF
XOSC.GAIN = 1 2.4K
f = 8MHz, CLEXT = 20pF
XOSC.GAIN = 2 760
f = 16MHz, CLEXT = 20pF
XOSC.GAIN = 3 306
f = 30MHz, CLEXT = 18pF
XOSC.GAIN = 4 295
CXIN Parasitic capacitor load
I
5.85 pF
CXOUT Parasitic capacitor load 3.11 pF
CLEXT 2C
LCSTRAY CSHUNT
––()=
583
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
(1) These values are based on characteriza tion. These values are not covered by test limits in production.
Figure 32-4. Oscillator Connection
32.10.2 External 32kHz Crystal Oscillator (XOSC32K) Characteristics
32.10.2.1 Digital Clock Characteristics
The following table describes the characteristics for the oscillator when a digital clock is applied on XIN32 pin.
Table 32-34. Digital Clock Characteristics
32.10.2.2 Crystal Oscillator Characteristics
Figure 32-4 and the equation in “Crystal Oscillator Characteristics” on page 582 also applies to the 32kHz oscillator
connection. The user must choose a crystal oscillator where the crystal load capacitance CL is within the range given in
the table. The exact value of CL can be found in the crystal datasheet.
tSTARTUP Startup ti me
f = 2MHz,XOSC.GAIN = 0 12000
cycles
f = 4MHz,XOSC.GAIN = 1 5600
f = 8MHz, XOSC.GAIN = 2 7300
f = 16MHz, XOSC.GAIN = 3 7500
f = 30MHz, XOSC.GAIN = 4 9200
Symbol Parameter Conditions Min. Typ. Max. Units
C
SHUNT
L
M
R
M
C
M
C
STRAY
C
LEXT
C
LEXT
Xin
Xout
Crystal
Symbol Parameter Conditions Min. Typ. Max. Units
fCPXIN32 XIN32 clock frequency
I
32.768 kHz
I
XIN32 clock duty cycle
I
50 %
584
Atmel SAM D20 [Preliminary DATASHEET]
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Table 32-35. 32 kHz Crystal Oscillator Characteristics
32.10.3 Digital Frequency Locked Loop (DFLL) Characteristics
Table 32-36. Digital Frequency Locked Loop Characteristics
Symbol Parameter Conditions Min. Typ. Max. Units
fOUT Crystal oscillator frequency
I
32768 Hz
tSTARTUP Startup time (1)
1. These values are based on characterization. These values are not covered by test limits in production.
Rm = 100kΩ, CL = 12.5pF 10000 cycles
CLCrystal load capacitance (2)
2. These values are based on simulation. These values are not cove red by test limits in production or characterization.
I
9
pF
CSHUNT Crystal shunt capacitance (2)
I
0.1
CXIN32 Parasitic capacitor load TQFP64/48/32 packages 3.05
CXOUT32 Parasitic capacitor load 3.29
IXOSC32K Current consumption (2)
I
1200 nA
ESRXTAL
Crystal equivalent series
resistance f=32.768kHz
Safety Factor = 3
CL=12.5pF (Amplitude
control of gain = 63) 313(1) kΩ
Symbol Parameter Conditions Min. Typ. Max. Units
fOUT Output frequency
I
Open loop after calibration
(fine lock) 48 MHz
fREF Reference frequency
I
32.768 kHz
Maximum fine step size (1) Open loop +/-0.5 %
Maximum coarse step size(1) Open loop +/-6
IDFLL Power consumption on VDDANA (2) Open loop,Coarse calibrated
against 48MHz, FINE=128 220 µA
tSTARTUP Startup ti me(1) Open loop after calibration
against 48MHz
fOUT within 90% of final value 2.2
µs
tLCOARSE Coarse lock time(2) Quick lock enabled, Chill
cycle disabled,CSTEP=3,
fREF = 32.768kHz 260
tLFINE Fine lock time(2)
Quick lock disabled, Chill
cycle disabled,
CSTEP=3,FSTEP=1,
fREF = 32.768kHz
700
585
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
32.10.4 32.768kHz Internal oscillator (OSC32K) Characteristics
Table 32-37. 32 kHz RC Oscillator Characteristics
(1) These values are based on characteriza tion. These values are not covered by test limits in production.
32.10.5 Ultra Low Power Internal 32kHz RC Oscillator (OSCULP32K) Characteristics
Ta ble 32-38. Ultra Low Power Internal 32 kHz RC Oscillator Characteristics
32.10.6 8MHz RC Oscillator (OSC8M) Characteristics
Table 32-39. Internal 8MHz RC Oscillator Characteristics
1. These values are based on simulation. These values are not cove red by test limits in production or characterization.
2. These values are based on characterization. These values are not covered by test limits in production.
Symbol Parameter Conditions Min. Typ. Max. Units
fOUT Output frequency Calibrated against a 32.768kHz
reference at 25°C 32.768 kHz
IOSC32K Current consumption
I
µA
tSTARTUP Startup time
I
12 (1) cycle
Duty Duty Cycle
I
50 %
Symbol Parameter Conditions Min. Typ. Max. Units
fOUT Output frequency Calibrated against a 32.768kHz
reference at 25°C 32.768 kHz
iDD
tSTARTUP Startup time
I
10 cycles
Duty Duty Cycle
I
50 %
Symbol Parameter Conditions Min. Typ. Max. Units
fOUT Output frequency (1)
1. These values are based on simulation. These values are not cove red by test limits in production or characterization.
I
8MHz
IOSC8M Current consumption(1)
I
37 µA
tSTARTUP Startup time
I
2.71 µs
Duty Duty cycle(1)
I
50 %
586
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
587
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
32.11 Timing Characteristics
32.11.1 External Reset
Table 32-40. External reset characteristics
32.11.2 SERCOM in SPI Mode Timing
Figure 32-5. SPI timing requirements in master mode
Symbol Parameter Condition Min. Typ. Max. Units
tEXT Minimum reset pulse width
I
10 ns
MSB LSB
BSLBSM
t
MOS
t
MIS
t
MIH
t
SCKW
t
SCK
t
MOH
t
MOH
t
SCKF
t
SCKR
t
SCKW
MOSI
(Data Output)
MISO
(Data Input)
SCK
(CPOL = 1)
SCK
(CPOL = 0)
SS
588
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
Figure 32-6. SPI timing requirements in slave mode
MSB LSB
BSLBSM
t
SIS
t
SIH
t
SSCKW
t
SSCKW
t
SSCK
t
SSH
t
SOSH
tSSCKR tSSCKF
t
SOS
t
SSS
t
SOSS
MISO
(Da
ta Output)
MOSI
(
Data Input)
SCK
(
CPOL = 1)
SCK
(
CPOL = 0)
SS
589
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
Table 32-41. SPI timing characteristics and requirements
Symbol Parameter Conditions Min. Typ. Max. Units
tSCK SCK period Master
ns
tSCKW SCK high/low width Master
tSCKR SCK rise time Master
tSCKF SCK fall time Master
tMIS MISO setup to SCK Master
tMIH MISO hold after SCK Master
tMOS MOSI setup SCK Master
tMOH MOSI hold after SCK Master
tSSCK Slave SCK Period Slave
tSSCKW SCK high/low width Slave
tSSCKR SCK rise time Slave
tSSCKF SCK fall time Slave
tSIS MOSI setup to SCK Slave
tSIH MOSI hold after SCK Slave
tSSS SS setup to SCK Slave
tSSH SS hold after SCK Slave
tSOS MISO setup SCK Slave
tSOH MISO hold after SCK Slave
tSOSS MISO setup after S S low Slave
tSOSH MISO hold after SS high Slave
590
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
32.11.3 SERCOM in I2C Mode Timing
Table 32-42 describes the requirements for devices connected to the I2C Interface Bus. Timing symbols refer to Figure
32-7.
Figure 32-7. I2C In terface Bus Timing
Table 32-42. I2C Interface Timing(1)
(1) These values are based on characteriza tion. These values are not covered by test limits in production.
Symbol Parameter Conditions Min. Typ. Max. Units
tRRise time for both SDA and SCL
I
300 ns
tOF Output fall time from VIHmin to VILmax 10pF < Cb < 400pF 7.0 10.0 50.0 ns
tHD;STA Hold time (repeated) START condition fSCL ≤ 100kHz µs
fSCL > 100kHz
tLOW Low period of SCL Clock fSCL ≤ 100kHz µs
fSCL > 100kHz
tHIGH High period of SCL Clock fSCL ≤ 100kHz µs
fSCL > 100kHz
tSU;STA Setup time for a repeated START
condition fSCL ≤ 100kHz µs
fSCL > 100kHz
tHD;DAT Data hold time fSCL ≤ 100kHz µs
fSCL > 100kHz
tSU;DAT Data setup time fSCL ≤ 100kHz µs
fSCL > 100kHz
tSU;STO Setup time for STOP condition fSCL ≤ 100kHz µs
fSCL > 100kHz
tBUF Bus free time between a STOP and a
START condition fSCL ≤ 100kHz µs
fSCL > 100kHz
T
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T
,/7
T
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T
,/7
T
/&
T
($34!
T
($$!4
T
35$!4
T
3534/
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T
2
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591
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
32.11.4 SWD Timing
Figure 32-8. SWD Interface Signals
Table 32-43. SWD Timings
Symbol Parameter Conditions Min. Typ. Max. Units
Thigh SWDCLK High period
VVDDIO from 3.0V to 3.6V,
maximum external capacitor
= 40pF ns
Tlow SWDCLK Low period
Tos SWDI O output skew to falling
edge SWDCLK
Tis Input Setup time required
between SWDIO
Tih Input Hold time required between
SWDIO and rising edg e
SWDCLK
Stop Park Tri State
AcknowledgeTri State Tri State
Parity Sta
rt
Data Data
Stop Park Tri State
AcknowledgeTri State
Sta
rt
Read Cycle
W
rite Cycle
Tos Thigh Tlow
Tis
Data Data Parity Tri State
Tih
Fro
m debugger to
SWDIO pin
Fro
m debugger to
S
WDCLK pin
S
WDIO pin to
debugger
Fro
m debugger to
SWDIO pin
Fro
m debugger to
S
WDCLK pin
S
WDIO pin to
debugger
592
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
33. Packaging Information
33.1 Thermal Considerations
33.1.1 Thermal Resistance Data
Table 33-1 summarizes the thermal resistance data depending on the package.
Table 33-1. Thermal Resistance Data
33.1.2 Junction Temperature
The average chip-junction temperature, TJ, in °C can be obtained from the following equations:
Equation 1
Equation 2
where:
zθJA = package thermal resistance, Junction-to-ambient (°C/W), provided in Table 33-1
zθJC = package thermal resistance, Junction-to-case thermal resistance (°C/W), provided in Table 33-1
zθHEATSINK = cooling device thermal resistance (°C/W), provided in the manufacturer datasheet
zPD = device power consumption (W)
zTA = ambient temperature (°C)
From “Equation 1” , the user can derive the estimated lifetime of the chip and decide if a cooling device is necessary or
not. If a cooling device is to be fitted on the chip, “Equation 2” should be used to compute the resulting average chip-
junction temperature TJ in °C.
Package Type θJA θJC
32-pin TQFP 68°C/W 25.8°C/W
48-pin TQFP 78.8°C/W 12.3°C/W
64-pin TQFP 66.7°C/W 11.9°C/W
32-pin QFN 37.2°C/W 3.1°C/W
48-pin QFN 33°C/W 11.4°C/W
64-pin QFN 33.5°C/W 11.2°C/W
TJTAPDθJA
×()+=
TJTAPDθHEATSINK θJC
+()×()+=
593
Atmel SAM D20 [Preliminary DATASHEET]
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33.2 Package Drawings
33.2.1 64-pin TQFP
Table 33-2. Device and Pa ckage Maximum Weight
Table 33-3. Package Characteristics
Table 33-4. Package Reference
300 mg
Moisture Sensitivity Level MSL3
JEDEC Drawing Reference MS-026
JESD97 Classification E3
594
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
33.2.2 64-pin QFN
Table 33-5. Device and Pa ckage Maximum Weight
Table 33-6. Package Characteristics
Table 33-7. Package Reference
200 mg
Moisture Sensitivity Level MSL3
JEDEC Drawing Reference MO-220
JESD97 Classification E3
595
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
33.2.3 48-pin TQFP
Table 33-8. Device and Pa ckage Maximum Weight
Table 33-9. Package Characteristics
Table 33-10. Package Reference
140 mg
Moisture Sensitivity Level MSL3
JEDEC Drawing Reference MS-026
JESD97 Classification E3
596
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
33.2.4 48-pin QFN
Table 33-11. Device and Package Maximum Weight
Table 33-12. Package Characteristics
Table 33-13. Package Reference
140 mg
Moisture Sensitivity Level MSL3
JEDEC Drawing Reference MO-220
JESD97 Classification E3
597
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
33.2.5 32-pin TQFP
Table 33-14. Device and Package Maximum Weight
Table 33-15. Package Characteristics
Table 33-16. Package Reference
TBD mg
Moisture Sensitivity Level MSL3
JEDEC Drawing Reference MS-026
JESD97 Classification E3
598
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
33.2.6 32-pin QFN
Table 33-17. Device and Package Maximum Weight
Table 33-18. Package Characteristics
Table 33-19. Package Reference
TBD mg
Moisture Sensitivity Level MSL3
JEDEC Drawing Reference MO-220
JESD97 Classification E3
599
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
33.3 Soldering Profile
Table Table 33-20 gives the recommended soldering profile from J-STD-20.
Table 33-20. Soldering Profile
A maximum of three reflow passes is allowed per component.
188748
Profile Feature Green Package
Average Ramp-up Rate (217°C to peak) 3°C/s max.
Preheat Temperature 175°C ±25°C 150-200°C
Time Maintained Abo ve 217°C 60-150s
Time within 5°C of Actual Peak Temperature 30s
Peak Temperature Range 260°C
Ramp-down Rate 6°C/s max
Time 25°C to Peak Temperature 8 minutes max.
600
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
34. Schematic Checklist
34.1 Introduction
This chapter describes a common checklist which should be used when starting and reviewing the schematics for a
SAM D20 design. This chapter illustrates a recommended power supply connection, how to connect external analog
references, programmer, debugger, oscillator and crystal.
34.2 Power Supply
The SAM D20 supports a single power supply from 1.62 to 3.63V.
34.2.1 Power Supply Connections
Figure 34-1. Power Supply Schematic
Table 34-1. Power Supply Connections, VDDCORE From Internal Regulator
Signal Name Recommended Pin Connection Description
VDDIO
1.6V to 3.6V
Decoupling/filtering capacitors 100nF(1)(2) and 10µF(1)
Decoupling/filtering inductor 10µH(1)(3) Digital supply voltage
VDDANA
1.6V to 3.6V
Decoupling/filtering capacitors 100nF(1)(2) and 10µF(1)
Ferrite bead(4) prevents the VDD noise interfering the
VDDANA
Analog supply voltage
VDDANA
GNDANA
VDDIN
VDDIO
VDDCORE
GND
100nF
100nF
100nF
1.62V-3.63V
10µF
100nF10µF
Close to device
(for every pin)
601
Atmel SAM D20 [Preliminary DATASHEET]
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Notes: 1. These values are only given as typical examples.
2. Decoupling capacitor should be placed close to the device for each supply pin pair in the signal group, low
ESR caps should be used for better decoupling.
3. An inductor should be added between the external power and the VDD for power filtering.
4. Ferrite bead has better filtering performance than the common inductor at high frequencies. It can be added
between VDD and VDDANA for preventing digital noise from entering the analog power domain. The bead
should provide enough impedance (e.g. 50Ω at 20MHz and 220Ω at 100MHz) for separating the digital
power from the analog power domain. Make sure to select a ferrite bead designed for filtering applications
with a low DC resistance to avoid a large voltage drop across the ferrite bead.
34.3 External Analog Reference Connections
The following schematic checklist is only necessary if the application is using one or more of the external analog
references. If the internal references are used instead, the following circuits in Figure 34-2 and Figure 34-3 are not
necessary.
Figure 34-2. External Analog Reference Schematic With Two Referen ces
VDDCORE 1.6V to 1.8V
Decoupling/filtering capacitor 100nF(1)(2) Core supply voltage / external decoupling pin
GND Ground
GNDANA Ground for the analog power domai n
Table 34-1. Power Supply Connections, VDDCORE From Internal Regulator (Continued)
Signal Name Recommended Pin Connection Description
GND
AREFA
EXTERNAL
REFERENCE 1 4.7µF 100nF
GND
AREFB
EXTERNAL
REFERENCE 2 4.7µF 100nF
Close to device
(for every pin)
602
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
Figure 34-3. External Analog Reference Schematic With On e Reference
Notes: 1. These values are given as a typical example.
2. Decoupling capacitor should be placed close to the device for each supply pin pair in the signal group.
Table 34-2. External Analog Reference Co nnections
Signal Name Recommended Pin Connection Description
AREFx
1.0V to VDDANA - 0.6V for ADC
1.0V to VDDANA - 0.6V for DAC
Decoupling/filtering capacitors
100nF(1)(2) and 4.7µF(1)
External reference from AREFx pin on
the analog port
GND Ground
GND
AREFA
EXTERNAL
REFERENCE 4.7µF 100nF
GND
AREFB
100nF
Close to device
(for every pin)
603
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
34.4 External Reset Circuit
The external reset circuit is connected to the RESET pin when the external reset function is used. If the external reset
function has been disabled, the circuit is not necessary. The reset switch can also be removed, if the manual reset is not
necessary. The RESET pin itself has an internal pull-up resistor, hence it is optional to also add an external pull-up
resistor.
Figure 34-4. External Reset Circuit Example Schematic
A pull-up resistor makes sure that the reset does not go low unintended causing a device reset. An additional resistor has
been added in series with the switch to safely discharge the filtering capacitor, i.e. preventing a current surge when
shorting the filtering capacitor which again causes a noise spike that can have a negative effect on the system.
Notes: 1. These values are given as a typical example.
2. The SAM D20 features an internal pull-up resistor on the RESET pin, hence an external pull-up is optional.
34.5 Unused or Unconnected Pins
Unused or unconnected pins (unless marked as NC where applicable) should not be left unconnected and floating.
Floating pins will add to the overall power consumption of the device. To prevent this one should always draw the pin
voltage towards a given level, either VDD or GND, through a pull up/down resistor. External or internal pull up/down
resistors can be used, e.g. the pins can be configured in pull-up or pull-down mode eliminating the need for external
components, for more information see “PORT” on page 284 for details. There are no obvious benefit in choosing external
vs. internal pull resistors.
Table 34-3. Reset Circuit Connections
Signal Name Recommended Pin Connection Description
RESET
Reset low level threshold voltage
VDDIO = 1.6V - 2.0V: Below 0.3 3 * VDDIO
VDDIO = 2.7V - 3.6V: Below 0.3 6 * VDDIO
Decoupling/filter capacitor 100nF(1)
Pull-up resistor 10kΩ(1)(2)
Resistor in series with the switch 330Ω(1)
Reset pin
GND
RESET
100nF
10kΩ
VDD
330Ω
604
Atmel SAM D20 [Preliminary DATASHEET]
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34.6 Clocks and Crystal Oscillators
The SAM D20 can be run from internal or external clock sources, or a mix of internal and external sources. An example
of usage will be to use the internal 8MHz oscillator as source for the system clock, and an external 32.768kHz watch
crystal as clock source for the Real-Time counter (RTC).
34.6.1 External Clock Source
Figure 34-5. External Clock Source Example Schematic
34.6.2 Crystal Oscillator
Figure 34-6. Crystal Oscillator Example Schem a tic
The crystal should be located as close to the device as possible. Long signal lines may cause too high load to operate
the crystal, and cause crosstalk to other parts of the system.
Table 34-5. Crystal Oscillator Checklist
Notes: 1. These values are given only as typical example.
2. Decoupling capacitor should be placed close to the device for each supply pin pair in the signal group.
Table 34-4. External Clock Source Connections
Signal Name Recommended Pin Connection Description
XIN XIN is used as input for an external clock signal Input for inverting oscillator pin
XOUT/GPIO Can be left unconnected or used as normal GPIO
XOUT/GPIO
XIN
NC/GPIO
External
Clock
Signal Name Recommended Pin Connection Description
XIN Load capacitor 15pF(1)(2) External crystal between 0.4 to 30MHz
XOUT Load capacitor 15pF(1)(2)
XOUT
XIN
15pF
15pF
605
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
34.6.3 External Real Time Oscillator
The low frequency crystal oscillator is optimized for use with a 32.768kHz watch crystal. When selecting crystals, load
capacitance and crystal’s Equivalent Series Resistance (ESR) must be taken into consideration. Both values are
specified by the crystal vendor.
SAM D20 oscillator is optimized for very low power consumption, hence close attention should be made when selecting
crystals, see Table 34-6 for maximum ESR recommendations on 9pF and 12.5pF crystals.
The Low-frequency Crystal Oscillator provides an internal load capacitance of typical 3.05pF and 3.29pF. Crystals with
recommended 12.5pF load capacitance can be without external capacitors as shown in Figure 34-7.
Note: Maximum ESR is typical value based on characterization. These values are not covered by test limits in
production.
Figure 34-7. External Real Time Oscillator without Load Capacitor
Crystals specifying load capacitance (CL) higher than 12.5pF, require external capacitors applied as described in Figure
34-8.
To find suitable load capacitance for a 32.768kHz crystal, consult the crystal datasheet.
Figure 34-8. External Real Time Oscillator with Load Capacitor
Notes: 1. These values are given only as typical examples.
2. Decoupling capacitor should be placed close to the device for each supply pin pair in the signal group.
Table 34-6. Maximum ESR Recommendation fo r 32.768kHz Crystal
Crystal C L (pF) Max ESR [kΩ]
12.5 313
Table 34-7. External Real Time Oscillator Checklist
Signal Name Recommended Pin Connection Description
XIN32 Load capacitor 22pF(1)(2) Timer oscillator input
XOUT32 Load capacitor 22pF(1)(2) Timer oscillator output
XOUT32
XIN32
32.768kHz
XOUT32
XIN32
32.768kHz
22pF
22pF
606
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
34.6.4 Calculating the Correct Crystal Decoupling Capacitor
In order to calculate correct load capacitor for a given crystal one can use the model shown in Figure 34-9 which includes
internal capacitors CLn, external parasitic capacitance CELn and external load capacitance CPn.
Figure 34-9. Crystal Circuit With Internal, External and Parasitic Capacitance
Using this model the total capacitive load for the crystal can be calculated as shown in the equation below:
where Ctot is the total load capacitance seen by the crystal, this value should be equal to the load capacitance value
found in the crystal manufacturer datasheet.
The parasitic capacitance CELn can in most applications be disregarded as these are usually very small. If accounted for
the value is dependent on the PCB material and PCB layout.
For some crystal the internal capacitive load provided by the device itself can be enough. To calculate the total load
capacitance in this case. CELn and CPn are both zero, CL1 = CL2 = CL, and the equation reduces to the following:
Table 34-8 shows the device equivalent internal pin capacitance.
XOUT
Internal
CEL1
CL1 CL2
CP1 CP2 CEL2
External
XIN
Ctot
∑CL1CP1CEL1
++ )CL2CP2CEL2
++ )((
CL1CP1CEL1CL2CP2CEL2
++ +++
--------------------------------------------------------------------------------------------------------
=
Ctot
∑CL
2
-------=
607
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
34.7 Programming and Debug Ports
For programming and/or debugging the SAM-ICE can be connected to the device using the Serial Wire Debug, SWD,
interface. The SAM-ICE uses a 20 pin connector to connect to the target, note that only four of the 20 pins and ground
are used. Figure 34-11 shows how the SAM-ICE should be connected to the target. For details please consult with the
SAM-ICE user manual. For connecting to any other programming or debugging tool please refer to that specific
programmer or debugger’s user guide.
The Xplained Pro evaluation board for the SAM D20 supports programming and debugging through the onboard
embedded debugger so no external programmer or debugger is needed.
34.7.1 10-way Serial Wire Debug and Trace Connector
Figure 34-10.10-way Serial Wire Debu g Connections
For debuggers/programmers that support the 10-way ARM debug interface should be connected as shown in Figure 34-
10 with details described in Table 34-9.
Table 34-9. 10-way Serial Wire De bug Connections
Table 34-8. Equivalent Inter nal Pin Capacitance
Symbol Value Description
CXIN32 3.05pF Equivalent internal pin capacitance
CXOUT32 3.29pF Equivalent internal pin capacitance
Signal Name Description
SWDCLK Serial wire clock pin
SWDIO Serial wire bidirectional data pin
RESET Target device reset pin, active low
VTref Target voltage sense, should be connected to the device VDD
GND Ground
1
VTref
GND
GND
NC
NC
SWDIO
SWDCLK
NC
NC
nRESET
10 Pin Debug Header (SWD)
GND
SWDIO
SWCLK
RESET
VDD
608
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
34.7.2 20-way SAM-ICE Serial Wire Debug Interface
Figure 34-11.20-way Serial Wire Debug Connections
Table 34-10. 20-way Serial Wire Debug Connections (SAM-ICE)
Signal Name Description
SWCLK Serial wire clock pin
SWDIO Serial wire bidirectional data pin
nTRST Target device reset pin, active low
VTref Target voltage sense, should be connected to the device VDD
GND Ground
GND* These pins are reserved for firmware extension purposes. They can be left open or connected to GND
in normal debug environment. They are not essential for SWD in general.
1
VTref
NC
NC
SWDIO
SWCLK
NC
NC
nTRST
NC
NC
NC
GND
GND
GND
GND
GND
GND*
GND*
GND*
GND*
SAM -ICE 20 Pin Header (SW D)
GND
SWDIO
SWCLK
RESET
VDD
609
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
35. Errata
35.1 Revision B
35.1.1 Device
1 - If APB clock is stopped and GCLK clock is running, APB read access to
read-synchronized registers will freeze the system. The CPU and the DAP
AHB-AP are stalled, as a consequence debug operation is impossible.
Errata reference: 10416
Fix/Workaround:
Do not make read access to read-synchronized registers when APB clock is
stopped and GCLK is running. To recover from this situation, power cycle the
device or reset the device using the RESETN pin.
2 - DFLLVAL.COARSE, DFLLVAL.FINE, DFLLMUL.CSTEP and
DFLLMUL.FSTEP bit groups are not correctly located in the register map.
Errata reference: 10988
DFLLVAL.COARSE is only 5 bits and located in DFLLVAL[12..8]. DFLLVAL.FINE
is only 8 bits and located in DFLLVAL[7:0]. DFLLMUL.CSTEP is only 5 bits and
located in DFLLMUL[28..24]. DFLLMUL.FSTEP is only 8 bits and located in
DFLLMUL[23:16]
Fix/Workaround:
DFLLVAL.COARSE, DFLLVAL.FINE, DFLLMUL.CSTEP and DFLLMUL.FSTEP
should not be used if code compatibility is required with future device revisions.
35.1.2 PM
1 - If a clock failure is detected (INTFLAG.CFD = 1) on the crystal oscillator
connected to GCLKMAIN, and the INTFLAG.CFD bit and CTRL.BKUPCLK bit
is cleared to switch the clock back to GCLKMAIN while the clock failure is
still present, the INTFLAG.CFD bit will not be set again and the
INTFLAG.XOSCRDY flag will not be cleared. Errata reference: 10858
Fix/Workaround:
If a clock failure is detected on the crystal oscillator connected to GCLKMAIN, th e
device should be reset after the failure condition has been resolved.
2 - The SysTick timer do not generate wake up signal to the Power Manager,
and therefore cannot be used to wake up the CPU from sleep mode Errata
reference: 11012
Fix/Workaround:
None.
610
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
35.1.3 GCLK
1 - When the GCLK generator is enabled (GENCTRL.GENEN = 1), set as
output (GENCTRL.OE = 1) and use a division factor of one (GENDIV.DIV = 1
or 0 and GENCTRL.DIVSEL=0), the GCLK_IO might not be set to the
configured GENCTRL.OOV value after disabling the GCLK generator
(GENCTRL.GENEN=0). Errata reference: 10716
Fix/Workaround
Disable the OE request of the GCLK generator (GENCTRL.OE = 0) before
disabling the GCLK generator (GENCTRL.GENEN = 0).
2 - The GCLK Generator clock is stuck when disabling the generator and
changing the division factor from one to a different value while the GCLK
generator is set as output. Errata reference: 10686
When the GCLK generator is enabled (GENCTRL.GENEN=1), set as output
(GENCTRL.OE=1) and use a division factor of one (GENDIV.DIV=1 or 0 and
GENCTRL.DIVSEL=0), if the division factor is written to a value different of one or
zero after disabling the GCLK generator (GENCTRL.GENEN=0), the GCLK
generator will be stuck.
Fix/Workaround
Disable the OE request of the GCLK generator (GENCTRL.OE=0) before
disabling the GCLK generator (GENCTRL.GENEN=0).
3 - When a GCLK is locked and the generator used by the locked GCLK is
not GCLK generat or 1, issuing a GCLK software reset will lock up the GCLK
with the SYNCBUSY flag always set. Errata reference: 10645
Fix/Workaround
Do not issue a GCLK SWRST or map GCLK generator 1 to ""locked"" GCLKs.
35.1.4 XOSC32K
1 - The automatic amplitude control of the XOSC32K do not work. Errata
reference: 10933
Fix/Workaround:
Use the XOSC32K with Automatic Amplitude control disabled
(XOSC32K.AAMPEN = 0)
35.1.5 DFLL48M
1 - If the firmware writes to the DFLLMUL.MUL register in the same cycle as
the closed loop mode tries to update it, the fine calibration will first be reset
to midpoint and then incremented/decremented by the closed loop mode.
Then the coarse calibration will be performed with the updated fine value. If
this happens before the dfll have got a lock, the new fine calibration value
can be anything between 128-DFLLMUL.FSTEP and 128+DFLLMUL.FSTEP
611
Atmel SAM D20 [Preliminary DATASHEET]
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which could give smaller calibration range for the fine calibration. Errata
reference: 10634
Workaround:
Always wait until the DFLL48M has locked before writing the DFLLMUL.MUL
register
2 - Changing the DFLLVAL.FINE calibration bits of the DFLL48M Digital
Frequency Locked Loop might result in a short output frequency overshoot.
This might occur both in open loop mode while writing DFLLVAL.FINE by
software and closed loop mode when the DFLL automatically adjusts its
output frequency. Errata reference: 10537
Fix/Workaround
- When using DFLL48M in open loop mode, be sure the DFLL48M is not used by
any module while DFLLVAL.FINE is written.
- When using DFLL48M in closed loop mode, be sure that DFLLCTRL.STABLE is
written to 1. The DFLL clock should not be used by any modules until the DFLL
locks are set.
If the application requires on-the-fly DFLL calibration (temperature/VCC drift
compensation), the firmware should perform, either periodically or when the
DFLL48M frequency differ too much from target frequency (indicated by
DFLLVAL.DIFF), the following:
o Switch system clock/module clocks to different clock than DFLL48M
o Re-initiate a DFLL48M closed loop lock sequence by disabling and re-enabling
the DFLL48M
o Wait for fine lock (PCLKSR.DFLLLCKF set to 1)
o Switch back system clock/module clocks to the DFLL48M
Better accuracy is achieved using a high multiplier for the DFLL48M, using a
scaled down or slow clock as reference. A multiplier of 6 will have a theoretical
worst case frequency deviation from the reference clock of +/- 8.33%. A multiplier
of 500 will have a theoretical worst case frequency deviation from the reference
clock of +/- 0.1%.
3 - If the DFLL48M reaches the maximum or minimum COARSE or FINE
calibration values during the locking sequence, an out of bounds interrupt
will be generated. These interrupts will be generated even if the final
calibration values at DFLL48M lock are not at maximum or minimum, and
might therefore be false out of bounds interrupts. Errata reference: 10669
Fix/Workaround:
Check that the lockbits: DFLLLCKC and DFLLLCKF in the SYSCTRL Interrupt
Flag Status and Clear register (INTFLAG) are both set before enabling the
DFLLOOB interrupt.
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35.1.6 EVSYS
1 - Using synchronous or resynchronized paths, some channels (0,3,6,7)
detect an overrun on every event even if no overrun condition is present.
Errata reference: 10895
Fix/Workaround:
Ignore overrun detection bit for channels 0,3,6,7.
Use channels 1,2,4,5 if overrun detection is required.
2 - Changing the selected generator of a channel can trigger a spurious
interrupt/event. Errata reference: 10443
Fix/Workaround:
To change the generator of a channel, first write with EDGESEL written to zero,
then perform a second write with EDGESEL written to its target value.
35.1.7 SERCOM
1 - The SERCOM SPI CTRLA register bit 17 (DOPO Bit 1) will always be zero,
and cannot be changed. Therefore the SERCOM SPI cannot be switched
between master and slave mode on the same DI and DO pins. Errata
reference: 10812
Fix/Workaround:
Connect the alternate DI and DO pins externally and use the port MUX to switch
between pin configurations for master and slave functionality.
2 - When the SERCOM is in slave SPI mode, the BUFOVF flag is not
automatically cleared when CTRLB.RXEN is set to zero. Errata reference:
10563
Fix/Workaround:
The BUFOVF flag must be manually cleared by software.
3 - The sercom SPI BUFOVF status bit is not set until the next character is
received after a buffer overflow, instead of directly after the overflow has
occurred. Errata reference: 10551
Fix/Workaround:
None.
In the sercom SPI the CTRLA.IBON bit will always be zero, and cannot be
changed.
Fix/Workaround:
None.
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35.1.8 ADC
1 - The automatic right shift of the result when accumulating/averaging ADC samples does
not work. Errata reference: 10530
Fix/Workaround:
To accumulate or average more than 16 samples, one must add the number of automatic right
shifts to AVGCTRL.ADJRES to perform the correct number of right shifts. For example, for
averaging 128 samples, AVGCTRL.ADJRES must be written to 7 instead of 4, as the automatic
right shift of 3 is not done. For oversampling to 16 bits resolution, AVGCTRL.ADJRES must be
written to 4 instead of 0 as the automatic right shift of 4 is not done.
The maximum number of right shifts that can be done using ADJRES is 7. This means that when
averaging more than 128 samples, the result will be more than 12 bits, and the additional right
shifts to get the result down to 12 bits must be done by firmware.
35.1.9 Flash
1 - When cache read mode is set to deterministic (READMODE=2), setting CACHEDIS=1
does not lead to 0 wait states on Flash access. Errata reference: 10830
Fix/Workaround:
When disabling the cache (CTRLB.CACHEDIS=1), the user must also set READMODE to 0
(CTRLB.READMODE=0).
2 - When NVMCTRL issues either erase or write commands and the NVMCTRL cache is not
in LOW_POWER mode, CPU hardfault exception may occur. Errata reference: 10804
Fix/Workaround
Either:
- turn off cache before issuing flash commands by setting the NVMCTRL CTRLB.CACHEDIS bit to
one.
- Configure the cache in LOW_POWER mode by writing 0x1 into the NVMCTRL
CTRLB.READMODE bits.
35.2 Revision A
Not Sampled
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36. Datasheet Revision History
Please note that the referring page numbers in this section are referred to this document. The referring revision in this
section are referring to the document revision.
36.1 Rev. D – 08/2013
Description Updated the whole Atmel SAM D20 “Description” on page 1
General Fixed different typos throughout the datasheet and applied correctly the template
Block Diagram Updated the “Block Diagram” on page 7
zAdded 2KB RAM and 16KB FLASH
DSU Updated the Figure 12-1
zRemoved HRAM from the block diagram
Clock System Updated “Clock System” on page 72
zThe description of the Basic Read Request has been updated
zUpdated the Figure 13-3
SYSCTRL z“Continuous Mode” on page 136: Added information about Continues mode not being
available for BOD12 when running in standby sleep mode.
zUpdated the writing of the interrupts sources in “Interrupts” on page 137
zAdded the reference to INTFLAG
zBOD12: Bit 6: RUNSTDBY removed and set to reserved.
NVMCTRL Updated the Fig ur e 20 -2
zRemoved the blue mark from the figure
PORT z“CPU Local Bus” on page 286: IOBUS address 0x60000000 added
zRemoved RWM from the description
EVSYS Channel register (CHANNEL):
zBits 25:24: CHANNEL:PATH description updated.
Schematic Checklist Upd at ed the “Schematic Checklist” on page 600
zUpdated “Introduction” on page 600
zReplaced all TDB by their respective values
zWrote correctly the Ohm symbol in “External Reset Circuit” on page 603
Electrical
Characteristics
zUpdated “Electrical Characteristics” on page 562
zRemoved the colors from “Electrical Characteristics” on page 562
zAdded footnote in the Figure 32-17. fADC = 6 * CLKADC
Table Of Contents zApplied correctly the template for the TOC
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36.2 Rev. C – 07/2013
Description Updated the front page:
zRemoved the “Embedded Flash” from the title and from the description on the page 1
zReplaced “speeds” by “frequencies” on the page 1
zAdded a sub-bullet on PTC in feature list (256-Channel capacitive touch and proximity
sensing) on the page 2
zReplaced IO lines by IO pins on the page 2
Configuration
Summary Updated the table
zThe RTC
zI/O lines changed to I/O pins
zChanged 32.768kHz high-accuracy oscillator to 32.768kHz oscillator
zChanged 32.768kHz ultra-low power internal oscillator to 32kHz ULP oscillator
zChanged 8MHz internal oscillator to 8MHz high-accuracy internal oscillator
zUpdated SW Debug Interface
zUpdated the WDT
Ordering
information
zReplaced “base line” by “general purpose”
zCentered the tables except the ordering code table.
About the
Document
zRenamed the chapter to Appendix A and Appendix B
zMoved the two Appendixes at the end of the datasheet
zChanged the tag of the tables to the tag of appendix tables
Pinout zUpdated the description of “Multiplexing Signals”
zReplaced “PORT controller” by “PORT”
zSet the Table 5-1 as a continuing table
zUpdated the table notes of the Table 5-1
zReplaced I/O lines by I/O pins on the page 17
Signal Description zRemoved the column “Comment” from the table
Power Supply zRemoved “nominal” from power supplies
zUpdated the description of vector regulator
zAdded link to the “Schematic Checklist”
Clock System Added the link in the description of “Write-Synchronization” on page 74
Power Manager Updated the Table 15-4:
zThe column “Clock Sources” has been updated with new commands
zThe table note 2 replaced by a reference to “On-demand, Clock Requests” on page 76
System Controller zRemoved “ENABLE bit” from “VREG register”
ADC Interrupt Flag Status and Clear register (INTFLAG):
zBit 2: INTFLAG.WINMON description updated
zBit 1: INTFLAG.OVERRUN description updated
zBit 0: INTFLAG.RESRDY description updated
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36.3 Rev. B – 07/2013
DAC z“Register Summary” on page 549: DATA and DATABUF bit fields updated.
zDATA register: Bit fields and description updated.
zDATABUF register: Bit fields and description updated.
Electrical Chara Added “Electrical Characteristics” on page 562
Package Informati on Replaced the 64 pins QFN drawing by the correct one
Block Diagram “Block Diagram” on page 7: Added output from Analog Comparator block
Signal Description “Signal Descriptions List” on page 14: Signal Description table cleaned up
Memories “NVM Software Calibration Row Mapping” on page 22: Added OSC32K Calibrati on to Table 9-4
DSU Die Identification register (DID):
zBit 15:12: Added DIE[3:0] bit group
zBit 11:8: Added REVISION[3:0] bit group
EVSYS “Features” on page 309: Number of event generators updated from 59 to 58
SERCOM SPI Control A register (CTRLA):
zBit 16: CTRLA.DOPO updated to Bit17:16: CTRLA.DOPO[1:0]
zBit 17:16 - DOPO[1:0] description updated
Status register (STATUS):
zBit 2 - STATUS.BUFOVF description updated
ADC “Accumulation” on page 483: Section add ed
“Averaging” on page 483: Section updated
“Oversampling and Deci mation” on page 484: Section updated
AC “Starting a Comparison” on page 518: Heading updated from Basic Operation.
“Synchronization” on page 525: Updated with list of write-synchronized bits and registers
Register property updated to “Write-Synchronized”:
zCTRLA, Comparator Control n
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36.4 Rev. A – 06/2013
SYSCTRL zRemoved VDDMON and ENABLE bits from registers.
zUpdated start-up time tables for XOSC32K and OSC32K:
zXOSC register: Table 16-2
zXOSC32K register: Table 16-4
zOSC32K register: Table 16-5
Errata Rev. B “Revision B” on page 609 updates:
z“Device” on page 609: Two erratas added (10988 and 10537)
z“PM” on page 609: Two erratas added (10858 and 11012)
z“XOSC32K” on page 610: One errata added (10933)
z“DFLL48M” on page 610: Two erratas added (10634, 10537), one errata updated (10669)
z“EVSYS” on page 612: One errata added (10895)
z“SERCOM” on page 612: Two erratas added (10812 and 10563), one errata removed
(10563)
z“ADC” on page 613: One errata updated (10530)
z“Flash” on page 613: One errata updated (10804)
Errata Rev. A Status changed to “Not Sampled”
1. Initial revision
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Appendix A. Conventions
A.1 Numerical Notation
A.2 Memory Size and Type
A.3 Frequency and Time
Table A-1. Numerical Notation
Symbol Description
165 Decimal number
0b0101 Binary number (example 0b0101 = 5 decimal )
0101 Binary numbers are given without suffix if unambiguous
0x3B24 Hexadecimal number
XRepresents an unknown or don't care value
ZRepresents a high-impedance (floating) state for either a signal or a bus
Table A-2. Memory Size and Bit Rate
Symbol Description
KB (kbyte) kilobyte (210 = 1024)
MB (Mbyte) megabyte (220 = 1024*1024)
GB (Gbyte) gigabyte (230 = 1024*1024*1024)
bbit (binary 0 or 1)
Bbyte (8 bits)
1kbit/s 1,000 bit/s rate (not 1,024 bit/s)
1Mbit/s 1,000,000 bit/s rate
1Gbit/s 1,000,000,000 bit/s rate
word 32 bit
half-word 16 bit
Table A-3. Frequency and Time
Symbol Description
kHz 1kHz = 103Hz = 1,000Hz
MHz 106 = 1,000,000Hz
GHz 109 = 1,000,000,000Hz
ssecond
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A.4 Registers and Bits
ms millisecond
µs microsecond
ns nanosecond
Table A-3. Frequency and Time (Continued)
Symbol Description
Table A-4. Register and Bit Mnemonics
Symbol Description
R/W Read/Write accessible register bit. The user can read from and write to this bit.
RRead-only accessible register bit. The user can only read this bit. Writes will be ignored.
WWrite-only accessible register bit. The user can only write this bit. Reading this bit will return an
undefined value.
BIT Bit names are shown in uppercase. (Exa mple ENABLE)
FIELD[n:m] A set of bits from bit n down to m. (Example: PINA[3:0] = {PINA3, PINA2, PINA1, PINA0}
Reserved Reserved bits are unused and reserved for future use. For compatibility with future devices, always
write reserved bits to zero when the register is written. Reserved bits will always return zero when
read.
PERIPHERALiIf several instances of a peripheral exist, the peripheral name is followed by a number to indicate the
number of the instance in the range 0-n. PERIPHERAL0 denotes one specific instance.
Reset Va lue of a register after a power reset. Th is is al so the value of registers in a peripheral after
performing a software reset of the peripheral, except for the Debug Control registers.
SET/CLR
Registers with SET/CLR suffix allows the user to clear and set bits in a register without doing a read-
modify-write operation. These registers always come in pairs. W riting a one to a bit in the CLR
register will clear the corresponding bi t in both registers, while writing a one to a bit in the SET
register will set the corresponding bit in both registers. Both registers will return the same value when
read. If both registers are written simultaneously, the write to the CLR register will take precedence.
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Appendix B. Acronyms and Abbreviations
Table B-1 contains acronyms and abbreviations used in this document.
Table B-1. Acronyms and Abbreviations
Abbreviation Description
AC Analog Comparator
ADC Analog-to-Digital Converter
ADDR Address
AHB AMBA Advanced High-performance Bus
AMBA®Advance Microcontroller Bus Architecture
APB AMBA Advanced Peripheral Bus
AREF Analog reference voltage
BLB Boot Lock Bit
BOD Brown-out de te ctor
CAL Calibration
CC Compare/Capture
CLK Clock
CRC Cyclic Redundancy Check
CTRL Control
DAC Digital-to-Analog Converter
DAP Debug Access Port
DFLL Digital Frequency Locked Loop
DSU Device Service Unit
EEPROM Electrically Erasable Programmable Read-Only Memory
EIC External Interrupt Controller
EVSYS Event System
GCLK Generic Clock Controller
GND Ground
GPIO General Purpose Inpu t/Output
I2CInter-Integrated Circuit
IF Interrupt flag
INT Interrupt
MBIST Memory built-in self-test
MEM-AP Memory Access Port
NMI Non-maskable interrupt
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NVIC Nested Vector Interrupt Controller
NVM Non-Volatile Memory
NVMCTRL Non-Volatile Memory Controller
OSC Oscillator
PAC Peripheral Access Controller
PC Program Counter
PER Period
PM Power Manager
POR Power-on reset
PTC Peripheral Touch Controller
PWM Pulse Width Modulation
RAM Random-Access Memory
REF Reference
RTC Real-Time Counter
RX Receiver/Receive
SERCOM Serial Communication Interface
SMBus™System Management Bus
SP Stack Pointer
SPI Serial Peripheral Interface
SRAM Static Random-Access Memory
SYSCTRL System Controller
SWD Serial Wire Debug
TC Timer/Counter
TX Transmitter/Transmit
ULP Ultra-low power
USART Universal Synchronous and Asynchronous Serial Receiver and Transmitter
VDD Common voltage to be applied to VDDIO, VDDIN and VDDANA
VDDIN Digital supply voltage
VDDIO Digital supply voltage
VDDANA Analog supply voltage
VREF Voltage reference
WDT Watchdog Timer
XOSC Crystal Oscillator
Table B-1. Acronyms and Abbreviations (Continued)
Abbreviation Description
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Table of Contents
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
1. Configuration Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
2. Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2.1 SAM D20E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 SAM D20G. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 SAM D20J . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
4. Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
4.1 SAM D20J . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2 SAM D20G. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3 SAM D20E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. I/O Multiplexing and Considerations . . . . . . . . . . . . . . . . . . . . . . . . .11
5.1 Multiplexed Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.2 Other Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. Signal Descriptions List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
7. Power Supply and Start-Up Considerations . . . . . . . . . . . . . . . . . . .16
7.1 Power Domain Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.2 Power Supply Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.3 Power-Up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.4 Power-On Reset and Brown-Out Detector. . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8. Product Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
9. Memories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
9.1 Embedded Memories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.2 Physical Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.3 Non-Volatile Memory (NVM) User Row Mapping. . . . . . . . . . . . . . . . . . . . . . 21
9.4 NVM Software Calibration Row Mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
10. Processor and Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
10.1 Cortex-M0+ Processor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
10.2 Nested Vector Interrupt Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
10.3 High-Speed Bus Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
10.4 AHB-APB Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
10.5 PAC – Peripheral Access Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
10.6 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
11. Peripherals Configuration Overview . . . . . . . . . . . . . . . . . . . . . . . . .34
12. DSU – Device Service Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
12.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
12.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
12.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
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12.4 Signal Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
12.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
12.6 Debug Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
12.7 Chip-Erase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
12.8 Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
12.9 Intellectual Property Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
12.10 Device Identification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
12.11 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
12.12 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
12.13 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
13. Clock System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
13.1 Clock Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
13.2 Synchronous and Asynchronous Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
13.3 Register Synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
13.4 Enabling a Peripheral. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
13.5 On-demand, Clock Requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
13.6 Power Consumption vs Speed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
13.7 Clocks after Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
14. GCLK – Generic Clock Controller . . . . . . . . . . . . . . . . . . . . . . . . . . .78
14.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
14.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
14.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
14.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
14.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
14.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
14.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
14.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
15. PM – Power Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
15.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
15.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
15.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
15.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
15.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
15.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
15.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
15.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
16. SYSCTRL – System Controller . . . . . . . . . . . . . . . . . . . . . . . . . . .127
16.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
16.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
16.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
16.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
16.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
16.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
16.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
16.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
17. WDT – Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179
17.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
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17.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
17.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
17.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
17.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
17.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
17.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
17.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
17.9 Asynchronous Watchdog Clock Characterization . . . . . . . . . . . . . . . . . . . . 197
18. RTC – Real-Time Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198
18.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
18.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
18.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
18.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
18.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
18.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
18.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
18.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
19. EIC – External Interrupt Controller . . . . . . . . . . . . . . . . . . . . . . . . .242
19.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
19.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
19.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
19.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
19.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
19.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
19.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
19.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
20. NVMCTRL – Non-Volatile Memory Controller . . . . . . . . . . . . . . . .261
20.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
20.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
20.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
20.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
20.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
20.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
20.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
20.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
21. PORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .284
21.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
21.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
21.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
21.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
21.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
21.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
21.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
21.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
22. EVSYS – Event System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .309
22.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
22.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
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22.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
22.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
22.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
22.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
22.7 Register Summary
316
22.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
23. SERCOM – Serial Communication Interface . . . . . . . . . . . . . . . . .332
23.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
23.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
23.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
23.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
23.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
23.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
24. SERCOM USART – SERCOM Universal Synchronous and Asynchronous Receiver and
Transmitter 340
24.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
24.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
24.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
24.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
24.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
24.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
24.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
24.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
25. SERCOM SPI – SERCOM Serial Peripheral Interface . . . . . . . . . .364
25.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
25.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
25.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
25.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
25.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
25.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
25.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
25.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
26. SERCOM I2C – SERCOM Inter-Integrated Circuit . . . . . . . . . . . . .389
26.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
26.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
26.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
26.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390
26.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390
26.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391
26.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403
26.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407
27. TC – Timer/Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .436
27.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436
27.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436
27.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437
27.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438
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27.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438
27.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
27.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449
27.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452
28. ADC – Analog-to-Digital Converter . . . . . . . . . . . . . . . . . . . . . . . .476
28.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476
28.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476
28.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477
28.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477
28.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478
28.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479
28.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488
28.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490
29. AC – Analog Comparators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .515
29.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515
29.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515
29.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516
29.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516
29.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516
29.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517
29.7 Additional Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524
29.8 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
29.9 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528
30. DAC – Digital-to-Analog Converter . . . . . . . . . . . . . . . . . . . . . . . .544
30.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
30.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
30.3 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
30.4 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
30.5 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545
30.6 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546
30.7 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549
30.8 Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550
31. PTC - Peripheral Touch Controller . . . . . . . . . . . . . . . . . . . . . . . . .561
31.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561
31.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561
31.3 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561
31.4 Product Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561
32. Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .562
32.1 Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562
32.2 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562
32.3 General Operating Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562
32.4 Supply Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563
32.5 Maximum Clock Frequencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564
32.6 Power Consumption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566
32.7 I/O Pin Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568
32.8 Analog Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571
32.9 NVM Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 580
628
Atmel SAM D20 [Preliminary DATASHEET]
42129D–SAM–08/2013
32.10 Oscillators Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582
32.11 Timing Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587
33. Packaging Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .592
33.1 Thermal Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592
33.2 Package Drawings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593
33.3 Soldering Profile. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599
34. Schematic Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .600
34.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600
34.2 Power Supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600
34.3 External Analog Reference Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . 601
34.4 External Reset Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603
34.5 Unused or Unconnected Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603
34.6 Clocks and Crystal Oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
34.7 Programming and Debug Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607
35. Errata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 09
35.1 Revision B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609
35.2 Revision A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613
36. Datasheet Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .614
36.1 Rev. D – 08/2013. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614
36.2 Rev. C – 07/2013. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 615
36.3 Rev. B – 07/2013 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616
36.4 Rev. A – 06/2013 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617
Appendix A. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .618
A.1 Numerical Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .618
A.2 M emory Size and Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .618
A.3 Frequency and Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .618
A.4 Registers and Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .619
Appendix B. Acronyms and Abbreviations . . . . . . . . . . . . . . . . . . . . . .620
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .623
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