2001 Microchip Technology Inc. DS39563A
PICDEM.netTM
USER’S GUIDE
DS39563A - page ii 2001 Microchip Technology Inc.
“All rights reserved. Copyright © 2001, Microchip Technology
Incorporated, USA. Information contained in this publication
regarding device applications and the like is i ntended t hrough
suggestion only and may be superseded by updates. No rep-
resentation or warranty is given and no liability is assumed by
Microchip Technology Incorporated with respect t o the accu-
racy or use of s uch information, or infringement of patents or
other intellectual property rights arising from s uch us e or oth-
erwise. Use of M icrochip’s products as c ritical components in
life support systems is not authorized except with express
written approval by Microchip. No licenses are conveyed,
implicitly or otherwise, under any intellectual property rights.
The Microchip logo and name are registered trademarks of
Microchip Technology Inc. in the U.S.A. and ot her countries.
All rights reserved. All other trademarks mentioned herein are
the property of their respective companies. No licenses are
conveyed, implicitly or otherwise, under any intellectual prop-
erty rights.”
Trademarks
The Microchip name, logo, PIC, PICmicro, PICMASTER, PIC-
START, PRO MATE, KEELOQ, SEEVAL, MPLAB and The
Embedded Control Solutions Company are registered trade-
marks of Microchip Technology Incorporated in the U.S.A. and
other countries.
Total Endurance, I CSP, In-Circuit S erial Programming, Filter-
Lab, MXDEV, microID, FlexROM, fuzzyLAB, MPASM,
MPLINK, MPLIB, PICDEM, PICDEM.net, ICEPIC, Migratable
Memory, FanSense, ECONOMONITOR, Select Mode and
microPort are trademarks of Microchip Technology Incorpo-
rated in the U.S.A.
Serialized Quick Term Programming (SQTP) is a service mark
of Microchip Technology Incorpora ted in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2001, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Microchip received QS-9000 quality system
certification for its worldwide headquarters,
design and wafer fabrication facilities in
Chandler and T empe, Arizona in July 1999. The
Company’s quality system processes and
procedures are QS-9000 compliant for its
PICmicro® 8-bit MCUs, KEELOQ® code ho pp in g
devices, Serial EEPROMs and microperipheral
products. In addition, Microchip’s quality
system for the design and manufacture of
development systems is ISO 9001 certified.
Iosoft S peci al Software License Agre ement
The software supplied as part of the PICDEM.net board is Copyright © 2001 by Iosoft, Ltd. All rights are reserved. This software is
owned by Iosoft, and is only licensed for distribution with the book 'TCP/IP Lean' and the PICDEM.net board, and may only be used
for personal experimentation by the purchaser of that book or the PICDEM.net kit, on condition that this copyright notice is retained.
Any use in violation of the foregoing restrictions may subject the user to criminal sanctions under applicable laws, as well as to civil
liability for the breach of the terms and conditions of this license. For commercial licensing, contact license@iosoft.co.uk
THIS IS EXPERIMENTAL SOFTWARE, PROVIDED IN AN “AS IS” CONDITION. NO WARRANTIES, WHETHER EXPRESS,
IMPLIED OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FIT-
NESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. IOSOFT SHALL NOT, IN ANY CIRCUMSTANCES, BE
LIABLE FOR SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
2001 Microchip Technology Inc. DS39563A-page iii
PICDEM.netTM USER’S GUIDE
Table of Contents
Table of Contents
General I nformation
Introduction................................................................................................ 1
Highlights................................................................................................... 1
About This Guide....................................................................................... 1
Warranty Registration................................................................................ 3
Recommended Reading............................................................................ 3
Troubleshooting .........................................................................................4
The Microchip Internet Web Site............................................................... 4
Development Systems Customer Notification Service.............................. 5
Customer Suppo rt.............. .............. ..... .............. ..... .............. .... .............. . 6
Chapter 1. Introduction to the PICDEM.net Board
1.1 Introduction..................................................................................... 7
1.2 Highlights........................................................................................ 7
1.3 The Demonstration Kit: What’s In The Box..................................... 7
1.4 The PICDEM.net Demonstration Board.......................................... 8
1.5 The Developmen t Manual.. .... ..... ..... .............. .... ..... .............. ..... ... 10
1.6 The Internet Solutions CD ............................................................ 10
Chapter 2. Getting Started with the PICDEM.net Board
2.1 Highlights............. .... ..... ..... .............. .... .............. ..... .............. ..... ... 11
2.2 Limitations on Networking............................................................. 11
2.3 Host Computer Requirements...................................................... 12
2.4 Setting Up the Test System.......................................................... 12
2.5 Establishing Communications....................................................... 18
Chapter 3. Exploring The ChipWebTM Page
3.1 Highlights.......................................................................................21
3.2 Structure of the Page.................................................................... 21
PICDEM.netTM User’s Guide
DS39563A-page iv 2001 Microchip Technology Inc.
Chapter 4. Reconfiguring and Restoring the Firmware
4.1 Highlights ...................................................................................... 23
4.2 Reconfiguring the PICDEM.net Hardware .................................... 23
4.3 Reconfiguring the PICDEM.net Firmware..................................... 23
4.4 Clearing the Controller Firmware.......... .... ..... ..... .... .............. ..... ... 26
Chapter 5. ChipWeb, the Miniature Ethernet Server
5.1 Overview....................................................................................... 27
5.2 Hardware....................................................................................... 27
5.3 Ethernet Driver........................ .... .............. ..... .............. ..... .... ........ 34
5.4 LCD Driver ................ .... ..... .............. ..... .............. .... .............. ..... ... 41
5.5 Other Drivers................................................................................. 43
5.6 Protocols....................................................................................... 44
5.7 User Interface................................................................................ 54
5.8 Configuration................................................................................. 58
5.9 Source Code................................................................................. 63
Chapter 6. Troubleshooting
6.1 Highlights ...................................................................................... 65
6.2 Common Issues............................................................................ 65
Appendix A. PICDEM.net Board Schematics
A.1 PICDEM.net Board Schematics.................................................... 69
Appendix B. PICDEM.net Internet Solutions CD
B.1 Highlights ...................................................................................... 71
B.2 What’s on the CD.......................................................................... 71
Index......................................................................................................... 73
Worldwide S al e s a nd Se rvice . .. ........ .. .. ........ .. .. ........ .. .. ........ .. .. ........ .. .. .. 76
2001 Microchip Technology Inc. DS39563A-page 1
PICDEM.netTM USER’S GUIDE
General Information
Introduction
This chapter contains general information about this manual and contacting
customer support.
Highlights
Topics covered in this chapter:
•About this Guide
•Recommended Reading
•W arranty Registration
•Troubleshooting
•The Microchip Internet Web Site
•Development Systems Customer Notification Service
•Customer Support
About This Guide
Document Layout
This document describes how to use PICDEM.net as an evaluat ion tool for
embedded connectivity solutions using PICmicro® devices. The manual
layout is as follows:
•Chapter 1: Introduction to the PICDEM.net Board – What
PICDEM.net is, and what features are available on the board.
•Chapter 2: Getting Started with the PICDEM.net Board – Describes
how to connect and begin to use the PICDEM.net board.
•Chapter 3: Exploring The ChipW ebTM Page – Describes the demon-
stration Web page provided with the PICDEM.net firmwar e.
•Chapter 4: Reconfiguring and Restoring the Firmware – Provides
instructions on loading a Web page into the on-board EEPROM, and
reconfiguring the network settings.
•Chapter 5: ChipWeb, the Miniature Ethernet Server – Provid es an
introduction to EthernetTM communications and TCP/IP, and an over-
view of how the custom TCP/IP stack firmware is implemented.
•Chapter 6: Troubleshooting – Provides information on solving
common problems.
PICDEM.netTM User’s Guide
DS39563A-page 2 2001 Microchip Technology Inc.
•Appendix A: PICDEM.net Board Schematics – Provides schematic
diagrams of the PICDEM.net board.
•Appendix B: PICDEM.net Internet Solutions CD – Provides a sum-
mary of the software solutions on the accompanying CD-ROM.
•Worldwide Sales an d Service – Lists Microchip Sales and Service
locations and telephone numbers, worldwide.
Conventions Used in this Guide
This manual us es the fol lowi ng docum entatio n conventions:
Documentation Conventions
Description Represents Examples
Code (Courier font):
Plain characters Sample code
Filenames and paths #define START
c:\autoexec.bat
Angl e br ack ets: < > Variables <label>, <exp>
Square br ackets [ ] Optiona l arguments MPASMWIN
[main.asm]
Curly brackets and
pipe character: { | } Choice of mutually exclusive
arguments
An OR selection
errorlevel {0|1}
Lower case charac-
ters in quotes Type of data “filename”
Ellipses... Used to imply (but not show)
additional text that is not
relevant to the example
list
[“list_option...
, “list_option”]
0xnnn A hexadecimal number where
n is a hexadecimal digit 0xFFFF, 0x007A
Italic characters A variable argument; it can be
either a type of data (in lower
case characters), or a specific
example (in uppercase
characters)
char isascii
(char ch);
Interface (Arial font):
Underlined, italic
text with right arrow A menu selection from the
menu bar File > Sa ve
Bold ch arac ters A window or dialo g button to
click OK, Cancel
Char acters in angle
bracke ts < > A key on the keyboard <Tab>, <Ctrl-C>
Documents (Arial font):
Italic characters Referenced books MPLAB ® IDE User’s
Guide
2001 Microchip Technology Inc. DS39563A-page 3
General Information
Documentation Updates
All documentation becomes dated, and this user’s guide is no excepti on.
Since MPLAB IDE, MPLAB C1X and other Microchip tools are constantly
evolving to meet customer needs, some actual dialogs and/or tool
descriptions may differ from those in this document. Please refer to our web
site to obtain the latest documentation available.
Documentat ion Numbering Conve ntions
Documents are number ed with a “DS” number. The number is located on the
bottom of each page, in front of the page number. The numbering convention
for the DS Number is: DSXXXXXA,
where:
Warranty Registration
Please complete the enclosed Warranty Registration Card and mail it
promptly. Sending in your Warranty Registration Card entitles you to receive
new product updates. Interim software releases are available at the Microchip
web site.
Recom mended Re ading
This user’s guide describ es how to use the PICDEM. net Ethernet/I nterne t
Demonstration Kit. The data sheets contain current information on
programming the specific microcontroller devices.
MPLAB® IDE, Simulator, Editor User’s Guide (DS5102 5)
Comprehensive guide that describes installation and features of Microchip’s
MPLAB Integrated Development Environment (IDE), as well as the editor and
simulator functions in the MPLAB environment.
MPASM™ User’s Guide with MPLINK™ and MPLIB™ (DS33014)
Describes how to use Microchip Universal PICmicro Microcontroller
Assembler (MPASM), Linker (MPLINK), and Librarian (MPLIB).
Technical Library CD-ROM (DS00161)
This CD-ROM contains comprehensive data sheets for Microchip PICmicro®
MCU devices available at the time of print. To obtain this disk, contact the
nearest Microchip Sales and Service location (see back page), or
download individual data sheet files from the Microchip web site
(http://www.microchip.com).
XXXXX = The document number.
A = The revi sion level of the docum ent.
PICDEM.netTM User’s Guide
DS39563A-page 4 2001 Microchip Technology Inc.
Embedded Control Handbook (DS00711)
This handbook consists of several documents that contain a wealth of
information about microcontroller applications. To obtain these documents,
contact the nearest Microchip Sales and Service location (see back page).
The application notes described in these manuals are also obtainable from
Microchip Sales and Service locations, or from the Microchip web site
(http://www.microchip.com).
PICmicro Mid-Range MCU Family Reference Manual (DS33023) and
PICmicro 18C MCU Family Reference Manual (DS39500)
These manuals explain the general details and operation of the mid-range
and advanced MCU family architecture and peripheral modules. They are
designed to complement the device data sheets.
Microsoft® Windows® Manuals
This manual assumes that users are familiar with Microsoft Windows
operating system. Many excellent references exist for this software program,
and should be consulted for general operation of Windows.
Troubleshooting
See Chapter 6 for information on common problems.
The Microchip Internet Web Site
Microchip provides online support on the Microchip World Wide Web (WWW)
site.
The web site is used by Microchip as a means to make files and information
easily available to customers. To view the site, the user must have access to
the Internet and a web browser, such as Netscape® Communicator or
Microsoft® Internet Explorer®. Files are also available for FTP download from
our FTP site.
Connecting to the Microchip Internet Website
The Microchip web site is available by using your favorite Internet browser
to attach to:
http://www.microchip.com
The file transfer site is available by using an FTP program/client to connect to:
ftp://ftp.microchip.com
2001 Microchip Technology Inc. DS39563A-page 5
General Information
The web site and file transfer site provide a variety of services. Users may
download files for the latest Development Tools, Data Sheets, Application
Notes, User’s Guides, Articles, and Sample Programs. A variety of Microchip
specific business information is also available, including listings of Microchip
sales offices, distributors and factory representatives. Other data available for
consideration is:
•Latest Microchip Press Releases
•Technical Support Section with Frequently Asked Questions
•Design Tips
•Device Errata
•Job Postings
•Microchip Consultant Program Member Listing
•Links to other useful web sites related to Microchip Products
•Conferences for products, Development Systems, technical information
and more
•Listing of seminars and events
Development Systems Customer Notification Service
Microchip started the customer notification service to help our customers
keep current on Microchip products with the least amount of effort. Once you
subscribe, you will receive email notification whenever we change, update,
revise or have errata related to your specified product family, or development
tool of interest.
Go to the Microchip WWW web page (http://www .microchip.com) and click on
Customer Change Notification under Items of Interest. Follow the instructions
to register.
The Development Systems product group categories are:
•Compilers
•Emulators
•In-Circuit Debuggers
•MPLAB IDE
•Programmers
Here is a description of these categories:
Compilers - The latest information on Microchip C compilers, linkers and
assemblers. These include MPLAB C17 C compiler, MPLAB C18 C compiler,
MPLINK Object Linker (as well as the MPLIB Object Librarian) and MPASM
Assembler.
Emulators - The latest information on Microchip in-circuit emulators. These
include the MPLAB ICE 2000 and PICMASTER® Emulator.
PICDEM.netTM User’s Guide
DS39563A-page 6 2001 Microchip Technology Inc.
In-Circuit Debuggers - The latest information on Microchip in-circuit
debuggers. This includes the MPLAB ICD.
MPLAB - The latest information on Microchip MPLAB IDE, the Windows
Integrated Development Environment for development systems tools. This list
is focused on the MPLAB IDE, MPLAB SIM simulator, MPLAB IDE Project
Manager and general editing and debugging features.
Programmers - The latest information on Microchip PICmicro device
programmers. These include the PRO MATE® II device programmer and
PICSTART® Plus development programmer.
Customer Support
Users of Microchip products can receive assistance through several
channels:
•Distributor or Representative
•Local Sales Office
•Field Application Engineer (FAE)
•Corporate Applications Engineer (CAE)
•Hotline
Customers should call their distributor, representative, or field application
engineer (FAE) for support. Local sales offices are also available to help
customers. See the back cover for a listing of sales offices and locations.
Corporate applications engineers (CAEs) may be contacted at
(480) 792-7627.
In addition, there is a Systems Information and Upgrade Line. This line
provides system users a listing of the latest versions of all of Microchip's
development systems software products. Plus, this line provides information
on how customers can receive any currently available upgrade kits.
The Hotline Numbers are:
1-800-755-2345 for U.S. and most of Canada, and
1-480-792-7302 for the rest of the world.
2001 Microchip Technology Inc. DS39563A-page 7
PICDEM.netTM USER’S GUIDE
Chapter 1. Introduction to the PICDEM.net Board
1.1 Intr oduction
The PICDEM.net Demonstration Board Kit has been created to allow
developers to examine the possibilities of embedded connectivity solutions for
Ethernet and Internet. Using the custom-developed Iosoft TCP/IP stack,
developers can experiment with the simple Web page-based server. Users
can explore even more possibilities with the solutions offered by other
vendors.
1.2 Highlights
This chapter covers the following:
•PICDEM.net Demonstration Kit contents
•PICDEM.net Demonstration Board features
•The Development Manual
•The Internet Solutions CD
1.3 The Demonstration Kit: What’s In The Box
Your Demonstration Kit contains the following items:
1. The PICDEM.net Embedded Internet/Ethernet Demonstration Board
2. A universal power supply (110-230 VAC input, 9 VDC output) for the
Demonstration Board
3. A serial cable (DB9, M/F connectors) for use in programming the board
4. A CAT5 “crossover” network cable (RJ45 connectors) for networking the
board
5. T he m anual “TCP/I P Lean: Web Servers for Emb edded Sys tems”, with
accompanying software on CD-ROM
6. The “PICDEM .net Inte rnet Sol utions ” CD-ROM, which c ontains various
connectivity solutions provided by Microchip’s partners
7. This manual
8. A Warranty Registratio n card
PICDEM.netTM User’s Guide
DS39563A-page 8 2001 Microchip Technology Inc.
1.4 The PICDEM.net Demonstration Board
The PICDEM.net board has all the features to begin developing Internet
connectivity applications over an Ethernet connection. The pre-programmed
firmware allows users to begin investigating and developing applications right
out of the box, with no additional programming or configuration. All that is
required to begin exploring the board is a PC-compatible computer with an
Ethernet card and Internet browser software. (See the “Getting Started”
chapter for more specific information.)
Figure 1.1: PICDEM.net Board
Features on the PICDEM.net board include:
1. MICR OCONTROLLER SOCKET: A 40-pin DIP socket (600 mil) is pro-
vided for the u ser ’s choi ce of M icroc hip PI Cmicro m icr ocontrol lers. T he
board i s equip ped fr om th e fac tory wi th a P IC16F 877 m id-rang e micr o-
controller, clocked at 19.6608 MHz and pre-programmed with custom
TCP/IP stack firmware.
The board also supports other Microchip pin-compatible controllers,
such as the PIC18C452 and PIC18F452.
2. MEMORY: A Microchip 24LC256 serial EEPROM provides 256 Kbit
(32 Kbyte) of storage for Web pages. The 24LC256 is programmable via
a two-wire serial I2CTM interface.
1
2
3
4
5
67
10
8
9
11
12
13
14
15
6a
16
2001 Microchip Technology Inc. DS39563A-page 9
Introduction to the PICDEM.net Board
3. LCD DISPLAY: This two-line by 16-character dot matrix display shows
diagnostic and error messages with the factory programmed firmware. It
may be used for other applications with appropriate re-programming.
4. ET HERNET CONTROLLER: T he PICDEM.net b oard uses the Real tek
RTL8019AS single chip Ethernet controller and transceiver to provide
network co nnec tivi ty.
5. STATUS LEDs: Four LEDs are provided:
•SYSTEM – flashes to show the board is powered up and connected correctly .
•LINK STATUS – flashes to indicate a Collision Detect state on Revision
4 versions of the board. On Revision 5 and later versions, this LED
lights to show that the Ethernet connection is active.
•XMIT and RX – when the board is connected correctly, these are nor-
mally lit, and flash OFF (inverted logic), when the board is transmitting
or receiving a packet (respectively).
6. USER-DEFINED LEDs: These two LEDs are driven by digital I/O pins of
the controller , and may be used to simulate a digital output to an embed-
ded devic e. They ma y also be ena bled or disab led by jump er selectio n
on the board (located at 6a).
7. US ER-DEFINED PUSH BUTTON: Thi s switch is connec ted to a digital
I/O pin on the microcontroller , and may be used to simulate a digital input
in an embedded application.
8. USER-DEFINED POTENTIOMETERS: Two 10 kOhm potentiometers
are connected to analog I/O pins of the microcontroller. These can be
used to simulate analog inputs in an embedded application.
9. RESET PUSH BUTTON: This switch is tied to the MCLR pin on the con-
troller, and is used to reset the board.
10. RJ-45 (10-Base T) MODULAR CONNECTOR: This provides standard
Ethernet connectivity.
1 1. RJ-1 1 (SIX-WIRE) MODULAR CONNECTOR: This allows the demonstra-
tion board to be connected to Microchip MPLAB ICD (In-Circuit Debugger)
systems for advanced microcontroller emulation and debugging.
1 2. RS-232 (DB9M) CONNECTOR: This allows the demonstration board to be
configured for IP and Ethernet address through a standard serial connection.
This interface also allows users to download new Web pages to the EEPROM.
13. PROTOTYPE AREA: A 24x27 grid is p rovided for users to breadboard addi-
tional circuitry for development. Connections are provided for +5 VDC, ground,
and fo ur dif ferent I/O por ts (RA <5:0>, R B<4:0>, RC <7:0> an d RD<7:0>) .
14. ON-BOARD POWER: An on-board full-wave bridge allows for AC or DC
power input. An on-board regulator provides 5 VDC at 1 A.
15. ETHERN ET ID: This u nique serial number repre sent s the t wo least signif -
icant bytes of the Media Access Control (MAC), which is used by the
Ethern et transce iver to iden tify and f ilter pa ckets. Th e Ethernet ID bytes of
the PICDEM.net board can be changed in firmware.
16. REVISION LEVEL INDICA T OR (BACK SIDE): The silk-screened text on
the reverse (trace) side of the board, directly beneath the Prototype
Area, indicates the hardware revision level.
PICDEM.netTM User’s Guide
DS39563A-page 10 2001 Microchip Technology Inc.
1.5 The Development Manual
Also included in this kit is the book “TCP/IP Lean: Web Servers for Embedded
System”. Written by Jeremy Bentham of Iosoft, Ltd., “TCP/IP Lean” provides a
comprehensive introduction to the many protocols embedded in TCP/IP, and
how to custom tailor the “stack” for specific microcontroller based connectivity
applications.
In addition to the manual, Mr. Bentham has also provided an overview of the
custom TCP/IP stack and software already programmed on the PICDEM.net
board. The discussion is in Chapter 5 of this User’s Manual.
1.6 The Internet Solutions CD
Although the Iosoft TCP/IP firmware has been provided with the board, it is
important to note that Iosoft is just one of several companies that support
Internet connectivity solutions with Microchip components. This is why
Microchip has also provided the Internet Solutions CD with the PICDEM.net
kit.
The CD provides sample software solutions and additional information for
several different vendors. Specifically included are examples from
LiveDevices and Y ipee, which may used in exploring connectivity solutions for
both the PIC16C and PIC18C families of microcontrollers. Additional details
are provided in Appendix B.
More information on these and other solution providers is available from the
Design Center at the Microchip Web site. The address for the PICDEM.net
Connectiv i ty Sol uti on s page is
http://www.microchip.com/internet.
2001 Microchip Technology Inc. DS39563A-page 11
PICDEM.netTM USER’S GUIDE
Chapter 2. Getting Started with the PICDEM.net Board
2.1 Highlights
This chapter will cover the following topics:
•Limitations on Networking the PICDEM.net Board
•Hardware and Software Requirements for the Host Computer
•Setting Up the Test System
•Establishing Communications
2.2 Limitations on Networking
The PICDEM.net board provided in your kit has been designed to
demonstrate the possibilities of networking with embedded Microchip
controllers over Ethernet and the Internet. As with any custom TCP/IP
implementation, however, some precautions are in order.
Whenever new hardware or software is added to a network, it is always
advisable to create a separate test network, isolated from the LAN. This
allows testing the new system in a controlled atmosphere, and minimizes the
possibilities of network interference from the new equipment. The major
sources include:
•ADDRESSING – Each device on the network must have a unique
address. Networks using Dynamic Host Configuration Protocol (DCHP)
may not permit single devices with fixed IP addresses without major
configuration changes.
•TRAFFIC LEVELS – While the Ethernet transceiver hardware will filter
out unwanted messages, a highly loaded network with many broadcast
messages may place a sizable burden on the PICDEM.net board.
•DATA SECURITY – Although it is unlikely that the addition of a single
device will compromise the integrity or privacy of sensitive information,
it is always a good idea to perform extensive testing with new equip-
ment before adding it to a secure network.
•EXPERIMENTATION – Even as a simple microcontroller based device,
the PICDEM.net board is capable of generating a high volume of net-
work traffic, which may severely disrupt normal network operations.
For these rea sons , it is recomm end ed that the PICDEM.net evaluation board
be used only in one of two controlled configurations:
•connected directly to a dedicated host system, using the supplied
cros so ver cable ; or
•connected via a standard Ethernet cable to a single Ethernet hub,
which has no connections to any other LAN.
PICDEM.netTM User’s Guide
DS39563A-page 12 2001 Microchip Technology Inc.
2.3 Host Computer Requirements
To configure and communicate with the PICDEM.net card, you must have a
system that meets the following hardware and software requirements:
•PC-compatible system with an Intel Pentium® class, or highe r
processor, or equivalent
•4 MB RAM (16 MB or more, recommended)
•CD-ROM drive (for use with the accompanying CD)
•Standard Ethernet card (10 Mbps) with RJ45 (10-Base T) connector
•One available standard serial port, with a matching COM port available
through the operating system
•Microsoft Windows 95, Windows 98, Windows NT 4.0 or Windows 2000
Professional Desktop (any version)
•Microsoft Internet Explorer, or Netscape Navigator (version 3.0 or
higher for either)
•Any terminal emulation package, such as HyperTerminal® (for optional
serial programming of the PICDEM.net board)
2.4 Setting Up the Test System
For evaluating the PICDEM.net board, the simplest configuration uses a
single host computer connected directly to the board using a crossover cable.
Creating this isolated test system involves the following steps:
1. Hooking up the PICDEM.net board to the host system
2. Obtaining (or configuring) the host IP address
3. Configuring the PICDEM.net IP address
Note: This section assumes that an Ethernet card has already been
installed and is working properly, and that the TCP/IP protocol has
been installed and bound to the card. If this has not been done, or
if you are uncertain if this has been done, please contact your Infor-
mation Systems support person for further assistance.
2001 Microchip Technology Inc. DS39563A-page 13
Getting Started with the PICDEM.net Board
2. 4.1 Hookin g U p the Boa r d
The basic connections are shown in Figure 2.1.
Figure 2.1: Connections between the PICDEM.net Board and the Host Computer
1. Power down the host system. If it currently connected to a LAN, discon-
nect the network cable.
2. Unbox and unwrap the board, and set it on a non-conductive surface
near the host compute r.
3. Connect the serial cable (supplied in the kit) to the board, then to the
open serial port on your computer.
Host Computer
Ethernet
Card
Serial Port
(CO M1 or
COM2)
9 VDC from
Power Supply
PICDEM.net Board
Serial Cable
Network Cable
Serial Port
(DB 9 to D B 9)
(10-Base T)
Ethernet Port
Crossover
Note: Most PC-compatible desktop computers have two serial ports: one
is a DB9 male (pin) connector , while the other may be either a DB9
male, or DB25 male connector. If your available serial port is the
latter, you will ne ed to u se a DB 25 F-to -D B9M po rt ada pter, some-
times known as an “external modem adapter”. Check with your
local electronics parts store or your Information Services provider
for additional information.
PICDEM.netTM User’s Guide
DS39563A-page 14 2001 Microchip Technology Inc.
4. Con nec t the 10- B as e T Et her ne t cr oss ov er ca bl e (su ppl ied in the k i t) to
the board, then to the computer.
5. Con nect th e bar rel plu g of the power supp ly to the Power Input jack on
the board.
6. Plug the power adapter into your wall socket or power strip.
7. Check the PICDEM.net board. You should verify all of the following:
•The System LED is blinking
•The User LEDs are dark
•In Rev 4 boards, the LINK LED is dark; in later revisions, the LINK LED
is lit
•The XMIT and RX LEDS should be solidly lit or flickering
•The LCD display shows the message:
ChipWeb v1.03
10.10.5.15
If your PICDEM.net board does not show all of these things, check all
connections with the power supply and the board. For additional assistance,
refer to Chapter 6 ("Troubleshooting").
8. Power up the host system.
2.4.2 Obtaining (or Configuring) the Host IP Address
The process in this section varies, depending on the operating system used
on the host system and the absence or presence of DHCP configuration on
the host system. If you are unsure if your LAN uses DHCP to assign individual
machine IP addresses, contact your network support group.
These steps only need to be done once, before using the PICDEM.net card
for the first time.
Note: The Revision Label is on the reverse (trace) side of the board,
directly underneath the Prototype Area grid (see Figure 1.1, item
16). For additional information on the LINK Led, refer to Chapter 6
("Troubleshooting").
Note 1: The actual version of the firmware will be reflected in the first
line of the LCD display. Version 1.03 is the revision available at
the time this manual was prepared. Your display may differ.
2: The IP address “10.10.5.15” is valid when the board is first
unboxed and configured. After that, the IP address displayed
will be the address you have reprogrammed into the board (see
the following sections for more de tails).
2001 Microchip Technology Inc. DS39563A-page 15
Getting Started with the PICDEM.net Board
Obtaining Host IP Address (Windows 95:)
1. Fro m the Start menu, se lect Run, then type the command winipcfg.
Press <ENTER>. The IP Configuration window will appear with the IP
Configuration of the host system (Figure 2.2).
•If the IP address is 0.0.0.0, or if the system is using DCHP:
Continue with Step 2.
•If the IP address is anything except 0.0.0.0: Make a note of the IP
address, and continue with the procedure for "Configuring the
PICDEM.net IP Address" (page 17).
.
Figure 2.2: IP Configuration Window (Windows 95)
2. Click “Release”. The IP Address and Subnet mask are both now
"0.0.0.0". Close the IP Configuration dialog.
3. F rom the Start menu, selec t Settings>Co ntrol Panel. Click on the Net-
work applet icon.
4. At the Network dialog box, select the "Configuration" tab.
5. Select "TCP/IP" from the list of installed components. Click "Properties".
6. Select the "xxx" tab. Select the "Specify an IP Address" option.
7. Enter "10.10.5.1" for the IP Address, and "255.255.255.0" for the Subnet
Mask. Click "Ap ply".
8. Close the Network dialog box, and reboot the system.
9. Close the dialog box, then re-run the winipcfg command. The IP
address is now a non-zero address; make a note of it.
PICDEM.netTM User’s Guide
DS39563A-page 16 2001 Microchip Technology Inc.
Obtaining Host IP Address (Windows 98 and NT):
1. Open a DOSTM (or command prompt) window. From the Start menu,
select Programs>Accessories>MS-DOS Prompt (Windows 98) or
Progra ms>Ac cessor ies>C omma nd Prompt (W indows NT 4.0 and 200 0
Professional).
2. At the DOS win dow, type t he command ipconfig. This will re turn the
IP Configuration for the host system, including the IP address tied to the
Ethernet card (Figure 2.3).
•If the IP address is 0.0.0.0, or the system is configured for DHCP:
Continue with Step 3.
•If the IP address is anything except 0.0.0.0: Make a note of the IP
address, and continue with the procedure for "Configuring the
PICDEM.net IP Address" (page 17).
3. Type the command ipconfig/release, and press <ENTER>. You
may receive a message that addresses were automatically configured
and cannot be released; this is normal.
4. Type the command ipconfig/renew, and press <ENTER>. Wait for
about one minute for the system to return a command prompt. You may
receive a message that the DHCP server was unavailable; this is also
normal.
5. Close the DOS window, then open a new DOS window.
6. Type the command ipconfig, and press <ENTER>. The new IP
address is now a non-zero address. Make a note of this.
Figure 2.3: The ipconfig Screen (Windows 2000)
2001 Microchip Technology Inc. DS39563A-page 17
Getting Started with the PICDEM.net Board
2.4.3 Conf iguri n g the PICDEM.n et IP Address
1. From the Start menu, select Programs>Accessories>Com-
munications>HyperTerminal (for some operating systems,
Programs>Accessories>HyperTerminal).
2. At the initial “Connection Description” dialog box, enter a name for the
connection. You may call the terminal session any name that you will
easily remember. Click “OK”.
3. At the “Connect To” dialog box that follows, choose the appropriate COM
port from the drop-down menu. Click “OK”.
4. At the COM Properties dialog box that follows, select the settings:
•Bits per second: 9600
•Data bits: 8
•Parity: none
•Stop bits: 1
•Flow Control: none
Click “OK”. The terminal window opens with a flashing cursor. The
message “Connected” appears in the status bar at the bottom of the
terminal window, along with an elapsed time display.
5. Press and hold button RB5 on the PICDEM.net board. While holding
RB5, press and release the MCLR button. The terminal responds with:
ChipWeb v1.0.3
Config
Serial num?
The LCD also displays “ChipWeb v1.0.3 Config”.
Note: The example shown in Figure 2.3 is specific to Windows 2000. The
prompts and command responses shown differ slightly for other
Windows operating syste ms; however, the IP Address wil l always
be clearly identified as such.
Note: These instructions are written specifically for use with the Hyper-
Terminal emulator package that ships with Windows operating sys-
tems. If you are using another terminal emulation package, the
procedure you use to configure a terminal session may vary
slightly. Please consult the documentation for the terminal software
for additional information.
PICDEM.netTM User’s Guide
DS39563A-page 18 2001 Microchip Technology Inc.
6. En ter the seri al number (Eth ernet ID number) printed on the sticker on
the board. Press <ENTER>.
7. At the response IP addr?, enter your host system’s IP address,
INCREMENTED BY ONE IN THE FINAL POSITION. For example, if the
original host IP address is 169.225.150.10, enter “169.225.150.11”.
Press <ENTER>.
8. The terminal responds with XMODEM?, followed by a series of characters
appearing approximately once per second. Press and release the MCLR
button. The terminal res ponds with ChipWeb v1.0.3 an d the new IP
address entered in Step 7.
The LCD also displays “ChipWeb v1.0.3” and the new IP address.
9. Close the terminal session. For your convenience, you may save the
terminal session when prompted.
2.5 Establishing Communications
Your PICDEM.net board has already been programmed with the custom TCP/
IP stack and a special interactive page written in HTML. Once it is hooked up,
it is ready to go – no further software programming is required. At this point,
all that remains is to “log on”.
With your host system disconnected from a LAN, however, it will be
necessary to make some minor changes to your browser’s configuration.
1. Access the browser’s configuration settings in one of two ways:
•From the Start menu, select S ett ing s>C on trol Pan e l, then click on the
Internet Options applet; or
•Launch the browser, then select Tools>Internet Options from the menu.
2. Select the “Connections” tab, then click on the “LAN Settings” button.
3. Verify that the “Use a Proxy Server” box is deselected.
4. Click “OK”, then “OK” to close the Internet Properties dialog box.
Note: The actu al versio n of the firmwar e will be re flected in the first li ne
of the display. Version 1.03 is the revision available at the time this
manual was prepared. Your display may differ.
Note: These instructions are written specifically for use with Internet
Explorer. If you are using Netscape Navigator, or another Web
browser, the procedure you use will vary. Please consult the docu-
mentation for your browser for additional information.
2001 Microchip Technology Inc. DS39563A-page 19
Getting Started with the PICDEM.net Board
5. Launch the Web browser (if not running already).
6. At the URL address line, enter “http://”, and the IP a ddress of the
PICDEM.net board. Press <Enter>.
7. After several seconds, the ChipWeb page appears:
You are now ready to experiment with PICDEM.net.
Note: For users of later versions of Internet Explorer, the message will
begin with “No c on nectio n to th e Inte rn et i s curre ntl y avai la bl e....”.
There will be a choice of two buttons, “Work Offline” or “Try Again”.
Always choos e “Try Ag ain ”. If you choose “Wor k O ffli ne ”, you will
not be able to establish an external connection, and will need to
close and restart Explorer.
PICDEM.netTM User’s Guide
DS39563A-page 20 2001 Microchip Technology Inc.
NOTES:
2001 Microchip Technology Inc. DS39563A-page 21
PICDEM.netTM USER’S GUIDE
Chapter 3. Exploring The ChipWebTM Page
3.1 Highlights
This chapter will cover the following topics:
•Structure of the ChipWeb page
•Contents of the Center Frame
•Contents of the Left Frame
•Contents of the Right Frame
3.2 Structure of the Page
It’s nice to know that the PICDEM.net evaluation board can send a real Web
page to your computer. But the important question needs to be, “What can
this page do in the real world?”
The ChipWeb page is not meant to demonstrate a typical Internet-type Web
application – looking up information, buying something, checking a bank
account balance, what have you. The idea is to show how an embedded
system can send device-state and control information over an Ethernet
connection – information that is useful to other systems, as well as human
users. The ChipWeb page provides a simple demonstration of several
important concepts for an embedded control system:
•Display of analog and digital information
•Real-time control of remote devices
•Use r-fr ie ndl y inf or mati on .
The initial ChipWeb "home page" is actually an HTML "frameset"; this is a
common technique where two or more pages are displayed simultaneously to
give the appearance of a single page. The ChipWeb page is really three
different “frames”: center, left and right. Each one is implemented using
simple HTML, and demonstrates a different concept.
Additional details on the construction of the ChipWeb page’s individual
elements are provided in Chapter 5 (ChipWeb, the Miniature Ethernet
Server).
3.2.1 The Center Frame
The largest area of the page is devoted entirely to displaying graphics and
fixed content text, describing one of four general topics related to the
ChipWeb server. The actual contents shown here are selected by the user by
clicking on one of the four hyperlinks in the upper area of the left frame (see
Section 3.2.2). When the PICDEM.net board is initialized, the “Home” content
page is displayed as the default.
PICDEM.netTM User’s Guide
DS39563A-page 22 2001 Microchip Technology Inc.
3.2.2 The Left Frame
This area demonstrates real-time interactive control of the PICDEM.net
board. It has two functional groups:
1. HYPERLINKS: As already discussed, these are conventional HTML
hyperlinks that select one of four pages of information for the center
pane. The options are Home (default), Analog(ue), Digital, and Software.
2. VIRTUAL SWITCHES: This group shows a representation of two toggle
switches and associated pilot lights, representing digital inputs. Clicking
on either switch will change its state (Up or Down), while turning its light
On or Off. At the same time, clicking a switch will also turn the appropri-
ate User LED On or Off.
3.2.3 The Right Frame
This area demonstrates the feedback of analog and digital data from the
board, which is updated about every five seconds. It has three areas:
1. ANALOG INPUT: Two vertical sliding scales are displayed, along with a
digital translation of their values. These scales represent the current set-
tings of the user potentiometers, displaying the voltage across each
(range of 0 to 5V). As the setting of the potentiometers changes, the dis-
played value is updated.
2. DIGITAL OUTPUT: This area ha s two numeric displays, each showing
the value of eit her ‘0’ or ‘1’. As th e user chan ges t he vi rtual s witch es i n
the left pane, the state of the matching digit display changes.
3. DIG ITAL INPUT: Thi s area has a single nume ric displ ay, as above, th e
value of which is linked to the User push button on the board. When the
button is pushed, the value is ‘1’; when it is rel eased, the value retur ns
to the default of ’0’.
2001 Microchip Technology Inc. DS39563A-page 23
PICDEM.netTM USER’S GUIDE
Chapter 4. Reconfiguring and Restoring the Firmware
4.1 Highlights
This chapter covers the following:
•Reconfiguring the PICDEM.net hardware
•Reconfiguring t he PICDEM.net firmware
•Entering Configuration mode
•Changing the Network Configuration
•Loading (or Reloading) the Web Page into EEPROM
•Changing the Contr olle r Firmwa re
4.2 Reconfiguring the PICDEM.net Hardware
The basic hardware of the PICDEM.net board, as shipped from Microchip, is
a fixed configuration. Outside of disabling the User LEDs by removing the
associated jumper , there are no features on the board that can be changed by
the user.
4.3 Reconfiguring the PICDEM.net Firmware
To be ready for use out of the box, the PICDEM.net board is shipped with pre-
loaded firmware. The firmware has three different components:
•The ChipWeb page, written in compiled HTML and stored in the
EEPROM
•The Network Configuration, written in binary and stored in Data EEPROM
memory on the PIC16F877 controller
•The PICDEM.net operating firmware (including the TCP/IP stack), stored
in the Program Memory of the microcontroller.
The Web page can be reloaded, or a new page loaded in its place, without
affecting the operating firmware on the microcontroller. Reloading the
Network Configuration, however, requires that the Web page be reloaded.
Note: These instructions are valid only with the ChipWeb firmware pro-
vided by Iosoft Ltd., as originally configured on the PICDEM.net
board. If you have si nce loaded a di fferent firm war e package fr om
another vendor, consult that vendor’s instructions for how to
proceed.
PICDEM.netTM User’s Guide
DS39563A-page 24 2001 Microchip Technology Inc.
4.3.1 Entering Configuration Mode
In order to change the Web page or the network settings, it is necessary to
first put the board into Configuration mode. To do this, connect the board to
the host system as described in Chapter 2. Then:
1. Press and hold the User push button (RB5).
2. While holding RB5, press and release the MCLR push button.
The terminal responds with:
ChipWeb v1.0.3
Config
Serial num?
The LCD also displays “ChipWeb v1.0.3 Config”.
The PICDEM.net board will also enter the Configuration mode automatically,
whenever an EEPROM checksum failure occurs (e.g., when the EEPROM is
cleared or its contents are corrupted).
4.3.2 Changing the Network Configuration
At this point, the PICDEM.net board’s network configuration can be changed.
1. At the Serial num? prompt, enter the serial number from the Ethernet
ID sticker on the board, or a new Ethernet ID number . Alternatively , press
<ESC> to leave the ID unchanged.
2. At the IP addr? prompt, enter the new IP address in dotted-decimal
notation. Alternatively, press <ESC> to leave the IP address unchanged.
The factory default address is 10.10.5.15. For peer-to-peer connections
as described in Chapter 2, the address is a single increment from the
host system’s IP address. In other settings, the IP address must be
unique within the local domain.
3. Press <ENTER>. The new network configuration is now programmed
into the controller’s EEPROM .
4. The terminal responds with XMODEM?. To continue configuration by load-
ing a new Web page, go to step 3 of "To Load a Web Page" (page 25).
To return to normal PICDEM.net operation, briefly press and release the
MCLR button. The terminal and LCD returns with "ChipWeb v1.0.3" and
the IP address.
2001 Microchip Technology Inc. DS39563A-page 25
Reconfiguring and Restoring the Firmware
NOTES ON IP ADDRESS CONFIGURATION:
•If more than one PICDEM.net board is being evaluated, give each
board a different IP address – even if one is connected at a time. The
system may become confused with different Ethernet IDs being linked
to a single IP address.
•Rapid changes in Ethernet IDs and/or IP addresses, especially when
more than one PICDEM.net board is being evaluated, may cause a sit-
uation where the boards respond erratically. This is likely due to ARP
caching by the host system, where it retains a mapping of MACs and IP
addresses.
•For experienced users: the configuration of the PICDEM.net board
does not include either a net mask, or gateway IP address. This is
because the current implementation of ChipWeb does not include rout-
ing capabilities; all responses are returned directly to the IP and MAC of
the sender. Routing capabilities will be added to subsequent versions.
4.3.3 Loading (or Reloading) the Web Page
Before loading the Web page, the HTML file(s) must be translated into the
appropriate binary format using the Webpage tool. The software is included
with the CD accompanying the book “TCP/IP Lean”. In general, creating a
new Web page involves the following:
1. Create the HTML or GIF files using the appropriate software tools.
Remember that the total size of any single file (including HTML header)
must be no more than 1460 bytes.
2. Place the files into a single directory.
3. Merge the files with the WEBROMTM tool (see Chapters 5 and 11 of
"TCP/IP Lean").
4. Verify that the size of the finished file is within the capacity of the
EEPROM (32 Kbyte).
If you are reloading the original ChipWeb page, it is available in the proper
format on the PICDEM.net Internet Solutions CD. The path is
/iosoft/chipweb/pcm/webpage.rom..
Note: Your terminal emulation software must support the standard
XMODEM protocol. Variants such as XMODEM-1K or any of the
CRC variants will not work. HyperTerminal supports both XMODEM
and XMODEM-1K.
PICDEM.netTM User’s Guide
DS39563A-page 26 2001 Microchip Technology Inc.
To Load a Web Page:
1. Enter Configuration mode (Section 4.3.1, page 24).
2. Change the Ethernet ID and IP address as needed (Section 4.3.2,
page 24), or press <ESC> twice to bypass changes.
3. At the XMODEM? prom pt, select Transfer>Send File from the ma in menu
for HyperTerminal (the "Send File" command for other terminal emula-
tors). Specify the location of the file, and select "XMODEM" for the
Transfer Protocol.
4. When the transfer has finished, the PICDEM.net board will return to
normal operation automatically. The terminal and LCD return with
"ChipWeb v1.0.3" and the IP address.
If the t rans fer did not com pl ete su cc ess full y, the PICDEM .ne t bo ar d will
return to Configuration mode. There may also be an error message from
the termi nal e mulato r, no ting t hat the file tr ansf er di d not com plete su c-
cessfu lly. It is also po ssible that the con troller EE PROM check sum has
failed, and the network configuration needs to be reloaded.
4.4 Clearing the Controller Firmware
After investigating the PICDEM.net board and the ChipWeb server, you may
be ready to design your own embedded application. To do this, it will be
necessary to clear the existing TCP/IP stack in FLASH Program Memory of
the PIC16F877 microcontroller.
The PICDEM.net. Ethernet/Internet Demonstration Board does not include
the tools for clearing and reprogramming the microprocessor. To do this, you
must use an appropriate device programmer. You may also use the MPLAB
ICD Development System, which provides a complete development suite for
device emulation and programming.
If you already have the development tools, you have everything you need to
begin immediately . The PICDEM.net Internet Solutions CD, enclosed with the
PICDEM.net Development kit, includes sample software to assist you in
developing embedded Ethernet solutions.
Note: The MPLAB Development System and the PICDEM.net Internet
Solution s CD c on tain too ls a nd sol uti ons f or both the P IC1 6C a nd
PIC18C famil ies of m icrocontr ollers . You wil l need to ob tain a pin-
compatible P ICm ic ro 18 C or 18 F de vi ce (su ch as th e PI C1 8C 45 2)
to evaluate the full range of these Ethernet solutions.
2001 Microchip Technology Inc. DS39563A-page 27
PICDEM.netTM USER’S GUIDE
Chapter 5. Chip Web, the Miniature Ethernet Serve r
5.1 Overview
In the book “TCP/IP Lean: Web Servers for Embedded Systems”, I describe
software techniques to create small Web servers. To show how small these
can get, I conclude by implementing a complete Web server on a PICmicro®
PIC16C76 microcontroller.
This miniature server uses dynamic Web pages to display the current
temperature, time and digital input status, and allows the user to control the
digital outputs and set a real-time clock. In many ways, it is a useful little
system; the only bar to its use in a Local Area Network (LAN) environment is
that it only communicates using a serial (SLIP) link.
The next step is to adapt the server for use with Ethernet, and this chapter
describes those adaptations. As a hardware plat form, I will be using the
Microchip PICDEM.net board, which has a small amount of analog and digital
I/O, an LCD display, and the all-important Ethernet interface.
5.2 Hardware
5.2.1 Ethernet Interface
Ethernet allows a large number of computers to be connected together, so
that a transmission from one computer is received by all the others. Early
Ethernet implementations tended to use a single backbone cable linking the
systems together, in a bus topology. This has largely been replaced by the
star topology, where each computer is connected to an electronic repeater
(hub), and several hubs can be interconnected to form a large Local Area
Network, or LAN (see Figure 5.1).
Fortunately, we can ignore the differences between these topologies, since a
hub usually retransmits the message from one computer to all others in a
relatively unintelligent manner. The hardware arbitrates between the
compu t ers o n t h e net w or k (nodes) so they can transmit when necessary, with
a high probability that the message will be received by all the other nodes.
Note: The following chapter has been provided by Jeremy Bentham,
author of the ac companyin g book “TCP/IP Le an: Web Serv ers for
Embedded Systems”. All material in this chapter is copyright
© 2000 by Jeremy Bentham, and is reproduced with permission.
PICDEM.netTM User’s Guide
DS39563A-page 28 2001 Microchip Technology Inc.
Figure 5.1: Serial Link and Network Topologies
If every node had to handle all messages on the network, there would be a
very significant drain on their resources. For this reason, each computer has a
6-byte Ethernet address (usually known as a Media Access and Control, or
MAC address). All messages carry a destination MAC address and a source
MAC address, and the message is only processed by the intended recipient.
This one-to-one addressing is known as unicast. Under some circumstances,
it is necessary to send a message to all nodes on the network, which is a
broadcast. Ethernet uses a special all-ones MAC address for broadcast
messages.
The need for address filtering, and the requirement to handle the 10 Mbps
data rate, dictates the use of Ethernet specific hardware. One day, there may
be microcontrollers with built-in Ethernet interfaces, but until then, it is
necessar y to use dedicated net work int erfac e har dware
Serial Link
Network - Bus Topology
Network - Star Topology
2001 Microchip Technology Inc. DS39563A-page 29
ChipWeb, the Miniature Ethernet Server
5.2.2 Ethernet Hardware
The design of most network interface chips (Network Interface Controllers, or
NICs) owes much to the constraints imposed by the PC architecture. The
original PC 8-bit bus, used by all add-on cards, was capable of handling just
under one megabyte per second, yet the Ethernet interface transfers ten
megabits per second. This means that an old style (Industry Standard
Architecture, or ISA) PC network card had to buffer all incoming and outgoing
messages in a packet buffer, to avoid overloading the PC bus.
Modern PC cards need less buffering, since they can interface directly with
the PC main memory over a fast 32-bit bus. Such techniques are unsuitable
for microcontrollers, since they have an even greater restriction on I/O data
rates than the original PC, so the old style ISA buffered interface will be
needed.
Figure 5.2: Ethernet Hardware Block Diagram
The Ethernet hardware we’ll be using is a derivative of the original National
Semiconductor DP8390 Network Interface Controller (NIC). Figure 5.2 shows
the main functional blocks. The main points to note are:
•The CPU can read and write the control registers. These registers are
organised in banks (known as reg ist er p ages) , so that a large number o f
registers can be accessed using only four address bits.
•In this design, the CPU cannot access the packet buffer RAM directly;
data accesses are done using a remote DMA cont roll er in the NIC. The
control registers are used to set up the desired packet buffer address
and byte count, then the CPU repeatedly reads or writes a data latch, to
transfer a block of data to or from the packet buffer RAM. The latch is
not included in the set of control registers, so an additional address line
is needed for it, making a total of five (A0-4).
Packet buffer
RAM
Receive
de-serialiser 16-byte
FIFO
Transmit
serialiser
Control
registers
NETWORK
INTERFACE
CPU
INTERFACE
Local
DMA
Remote
DMA
PICDEM.netTM User’s Guide
DS39563A-page 30 2001 Microchip Technology Inc.
•Once set up, the NIC can automatically transfer data between the
network interface and the packet buffer RAM, using a small First-In/
First-Out (FIFO) buffer, and a second (local) DMA channel. The NIC is
sufficiently intelligent that it can receive several network messages
(Ethernet frames) in succession without any intervention from the host
CPU. To achieve this, the NIC has a sophisticated ring-buffer manage-
ment capability, based on 256-byte pages in RAM.
The terms local and remote DMA (Direct Memory Access) are used to keep in
line with the NIC data sheets. It is important to note that this refers to the way
the NIC handles internal transfers to and from its packet buffer RAM, and has
nothing to do with the way the CPU (in our case, the microcontroller) will
handle the data.
The Novell NE2000TM was a very well known PC card employing the DP8390
chipset. Such was its success, that it spawned a wide variety of 'clone' cards,
and the creation of highly integrated chips that incorporate the NIC, serialiser ,
buffer RAM, and support for PC 'plug-and-play' configuration. One such chip
is the Realtek RTL8019AS, which achieves a remarkably high level of
integration; very little external logic is needed to implement an ISA bus PC
networking card.
Figure 5.3: Ethernet Controller Interfaces
There are a sufficiently large number of options on the Ethernet controller, so
that it is usually equipped with an external non-volatile serial EEPROM
device. This device is programmed with the option values; on RESET, the
controller loads these values into its configuration registers. In the absence of
an external ROM, the controller boots up with sensible default settings, so it is
possible to omit the ROM.
Ethernet
Controller
NETWORK
INTERFACE
CPU
INTERFACE
Tx
Rx
Read
Write
RESET
Addr
0-4
Data
0-7
CONTROLLER
CONFIGURATION
ROM
Micro-
controller
2001 Microchip Technology Inc. DS39563A-page 31
ChipWeb, the Miniature Ethernet Server
5.2.3 Microcontroller Interface
To drive the Ethernet Controller, the microcontroller has to simulate the read
and write cycles of a PC ISA bus. This is not as difficult as it sounds; the steps
for a single cycle are
1. Set the address. Although the Ethernet controller has 20 address lines
(A0-A19); all but five of these can be fixed by being hard-wired to supply or
ground. The remaining five lines are used to select the register of interest.
2. Set the data lines. In a read cyc le, the microcontro ller data lines must
act as inputs; in a write cycle, they must be outputs, and be set with the
data byte value.
3. Assert the Read or Write signals. The signals are active-low , so either
Read or Write must be set low.
4. If Read cycle, fetch the data. If the Read line is asserted, and the
address is correct, the Ethernet controller will be driving the data bus, so
the data can be read.
5. Negate both Read and Write signals. If a Read cycle, the Ethernet
control ler will sto p driving th e data bus. If a Write cycle, it will la tch the
data received from the microcontroller.
6. Unset the data lines. The microcontrol ler out put driver s should be di s-
abled, so as to free up the data bus for other uses.
Figure 5.4: Ethernet Controller Access Cycles
The following I/O lines are needed on the microcontroller:
•One Read output and one Write output.
•Five address outputs. These are only significant while the Ethernet chip
is being accessed, so could be used for other duties as well.
•Eight bi-directional data lines. Again, these are only significant during
Ethernet chip accesses.
It is remarkable that only 15 I/O lines are needed to drive the 100-pin Ethernet
controller, and only two of those lines are dedicated full time to driving this
interface.
Write
Read
Address
Data
CPU Read Cycle CPU Write Cycle
PICDEM.netTM User’s Guide
DS39563A-page 32 2001 Microchip Technology Inc.
It is possible to use the PIC16C76 device to drive the Ethernet controller, but
on their PICDEM.net board, Microchip has chosen to step up to a PIC16F877
device. This has the following enhancements:
•Increased number of I/O pins, through the use of a 40-pin package.
•FLASH based program memory, which can be reprogrammed without
removing the device from the board (as on the PIC16F876).
•Built-in non-volatile EEPROM data memory (as on the PIC16F876).
•Built-in debug capability (as on the PIC16F876).
In all other respects, the device is very similar to the PIC16C76 used in the
previous project, so the same development tools can be employed, most
notably the Custom Computer Services PCM compiler.
5.2.4 LCD Interface
An alphanumeric Liquid Crystal Display (LCD) has also been included on the
demonstration board. This uses a different bus structure with a single read/
write line, a 4-bit data bus (connected to D4:D7 on the LCD), and an Enable
that is used to synchronise the accesses.
Figure 5.5: Liquid Crystal Display Interface
The Register Select line is essentially a single-bit address, set low to select
the 'instruction' (control) register and high for the 'data' (character) register.
The read/write line is low for writes to the LCD, and high for reads from the
LCD. The cycles are synchronised by the Enable signal; on the rising edge,
the read/write and register select signals are latched, and on the falling edge,
the data is transferred.
Figure 5.6: LCD Access Cycles
Alphanumeric
Liquid Crystal
Display
CPU
INTERFACE
Rd/Wr
Enable
RegSel
Data
4-7
Microcontroller
Enable
Read/Write
RegSel
Data
CPU Read Cycle CPU Write Cycle
2001 Microchip Technology Inc. DS39563A-page 33
ChipWeb, the Miniature Ethernet Server
The LCD can be treated as a write only device, since the main purpose of the
read-back is to check whether the LCD is ready to accept the next byte, and
this can be achieved using simple time delays instead. The steps for a write
cycle are:
1. Set the data lines as outputs, and the data on them.
2. Set the Register Select and Read/Write lines.
3. Set the Enable line high, and ensure it remains high for at least 500
nanoseconds.
4. Set the enable line low.
5. Uns et the data lines .
Despite their differences, the Ethernet controller and LCD can share a
common data bus, but it is important to establish a correct idle state for both
devices before attempting any communications.
Many LCD interfaces are equipped with a potentiometer to adjust the display
contrast and viewing angle. If this is set incorrectly, the display will always
remain blank – a problem that may cause hours of fruitless debugging, trying
to find a non-existent hardware or software fault. The PICDEM.net board
avoids this danger by using a fixed-resistor potential divider for the LCD
contrast.
5.2.5 Other Peripherals
The PICDEM.net board has the following peripheral devices:
•Two potentiometers connected to analog inputs. The voltage generated
by these (approximately 0 - 5V) can be sampled by the on-chip analog
to digital converter (ADC).
•One push button connected to a digital input
•Two light-emitting diodes (LEDs) connected to digital outputs
•RS-232 interface with handshake lines
•32 Kbyte I2C serial EEPROM memory device
There is also a convenient prototyping area for adding your own peripheral
devices.
PICDEM.netTM User’s Guide
DS39563A-page 34 2001 Microchip Technology Inc.
5.3 Ethernet Driver
5.3.1 NIC Initialization
The fundamental building blocks of the Ethernet device driver are a single
read or write cycle to the Network Interface Controller (NIC).
#BIT NIC_IOW_ = PORTE.1
#BIT NIC_IOR_ = PORTE.0
#BYTE NIC_DATA = PORTD
#define DATA_TO_NIC set_tris_d(ALL_OUT);
#define DATA_FROM_NIC set_tris_d(ALL_IN);
/* Input a byte from a NIC register */
BYTE innic(int reg)
{
BYTE b;
DATA_FROM_NIC;
NIC_ADDR = reg;
NIC_IOR_ = 0;
delay_cycles(1);
b = NIC_DATA;
NIC_IOR_ = 1;
return(b);
}
/* Output a byte to a NIC register */
void outnic(int reg, int b)
{
NIC_ADDR = reg;
NIC_DATA = b;
DATA_TO_NIC;
NIC_IOW_ = 0;
delay_cycles(1);
NIC_IOW_ = 1;
DATA_FROM_NIC;
}
The DATA_FROM and DATA_TO macros are used to set the microcontroller
data port direction (’TRIS’) register. To ensure the Read and Write signals
remain low for a sufficient time, a single CPU cycle delay has been introduced
into both the read and write functions.
Initiali zi ng the NIC consi sts of long string s of outnic calls, such as the
following:
outnic(CMDR, 0x21); /* Stop, DMA abort, page 0 */
delay_ms(2); /* ..wait to take effect */
outnic(DCR, DCRVAL); /* Data configuration */
outnic(RBCR0, 0); /* Clear remote byte count */
outnic(RBCR1, 0);
outnic(RCR, 0x20); /* Rx monitor mode */
outnic(TCR, 0x02); /* Tx internal loopback */
2001 Microchip Technology Inc. DS39563A-page 35
ChipWeb, the Miniature Ethernet Server
There is little point in analyzing these settings in great detail; as with any
complex chip, it is largely a fill-in-the-blanks exercise, complicated by the
overlapping register pages and the state machines for reception, transmission
and DMA (hence the ’stop, DMA abort’ command in the code above).
A few initialization parameters are worthy of note:
•Ethernet MAC Address: This 6-byte value must be supplied to the NIC,
so that it can filter incoming packets. Normally, this is in a non-volatile con-
figuration ROM attached to the NIC, but this has been omitted from the
board to save on component costs. It is stored in the microcontroller’s on-
chip EEPROM, from whence it is copied into RAM, and then into the NIC.
•Address Filtering: Putting the NIC into Promiscuous mode disa bl es
address filtering. This is useful during initial development and testing of
the driver software; it is useful to receive some packets, even if they are
not actually intended for this node. Promiscuous mode must be dis-
abled when working on a real network, since the large number of pack-
ets would tend to swamp the network controller.
•RAM Size: The size of the NIC packet buffer RAM is 16 Kbytes, but I
have consistently experienced problems when attempting to use the
whole RAM. A data sheet for anothe r NE2 000 co mpatibl e con tro ll er
suggests that only 8 Kbytes should be used when in 8-bit mode. Of this,
1.5K (6 pages of 256 bytes) is needed for the transmit buffer, leaving
6.5K (26 pages) for the receive buffer.
5.3.2 Accessing the Packet Buffer
Normally, the CPU would transfer the incoming Ethernet packets to its RAM
before attempting to process them. Since one packet is much larger than the
microcontroller RAM, it will be necessary to fetch and process the incoming
packets in small chunks. The NIC remote DMA controller is quite useful for
this, since it can accept an arbitrary packet buffer address and byte count,
even as small as one byte.
/* Set the ’remote DMA’ address in the NIC’s RAM to be accessed */
void setnic_addr(WORD addr)
{
outnic(ISR, 0x40) /* Clear remote DMA interrupt flag */
outnic(RSAR0, (BYTE)addr); /* Data addr */
outnic(RSAR1, addr>>8);
}
/* Get data from NIC’s RAM into the given buffer (up to 255 bytes) */
void getnic_data(BYTE *data, int len)
{
BYTE b;
outnic(RBCR0, len); /* Byte count */
outnic(RBCR1, 0);
outnic(CMDR, 0x0a); /* Start, DMA remote read */
while (len--) /* Get bytes */
{
b = innic(DATAPORT);
*data++ = b;
}
}
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DS39563A-page 36 2001 Microchip Technology Inc.
You may think that the setting of the byte count is largely redundant; why not
set this to an arbitrary large value, so that data bytes can be fetched as, and
when necessary? I have found the NIC to be highly intolerant of mismatched
DMA settings, to the extent that it can lock up a PC if too many bytes are
fetched. For this reason, I always set the length correctly before attempting
any transfer.
Writing to the packer buffer is a very similar exercise.
/* Put the given data into the NIC’s RAM (up to 255 bytes) */
void putnic_data(BYTE *data, int len)
{
outnic(ISR, 0x40); /* Clear remote DMA interrupt flag */
outnic(RBCR0, len); /* Byte count */
outnic(RBCR1, 0);
outnic(CMDR, 0x12); /* Start, DMA remote write */
while (len--) /* O/P bytes */
outnic(DATAPORT, *data++);
len = 255; /* Done: must ensure DMA complete */
while (len && (innic(ISR)&0x40)==0)
len--;
}
The last few lines of code ensure that the DMA transaction is complete before
any other NIC accesses are made. This has proved necessary on high speed
PCs, so it has been included for safety. It is probably unnecessary on a
microcontroller, due to the delays inherent in the bus interface.
5.3.3 Packet Recepti on
This involves:
•Checking for over-runs of t he packet buffer
•Detecting that one or more packets have been received
•Checking the error status of the packet
•Establishing the start address of the packet in the buffer
•Establishing the length of the packet
•Freeing up the buffer RAM used by the packet
The process is made more complicated by the splitting of the RAM space into
256-byte pages, and the wrapping of these pages to form a circular (ring)
buffer. There is little point in exploring the algorithms here; for more
information, refer to the source code and the Ethernet controller
manufacturer's data sheets. Any modifications to the software must be tested
very thoroughly under the following conditions:
•High packet rates
•Excessive packet rates (recovery from a buffer overflow)
•Mix of packet sizes
•Fetching one packet from the buffer while others are being received
2001 Microchip Technology Inc. DS39563A-page 37
ChipWeb, the Miniature Ethernet Server
It might be thought that using the drivers in a Web server represents a good
test, but this is not true for simple Web pages, since the transactions with the
Web client can be simple lock-step exchanges, with unvarying block sizes.
The fetching of a Web page, containing a variety of other objects (e.g.,
graphics), is more taxing, as the browser will tend to issue several parallel
requests to fetch the embedded content.
On the front of every Ethernet packet (frame) is a header containing the
6-byte destination and source addresses; these are known as Media Access
and Control (MAC) addresses.
Figure 5.7: Ethernet Frame
A structure is used to reference the Ethernet header.
#define MACLEN 6
typedef struct { // Ethernet frame header
BYTE dest[MACLEN]; // Dest & srce MAC addresses
BYTE srce[MACLEN];
WORD pcol; // Protocol
} ETHERHEADER;
The total frame size, including the header and a 4-byte CRC, is between 64
and 1518 bytes, so the actual data length is between 46 and 1500 bytes. If
less than the minimum, the data is padded to fit.
When receiving a frame, the NIC adds its own hardware-specific header on to
the front, so that the length and error status are known.
typedef struct { // NIC hardware packet header
BYTE stat; // Error status
BYTE next; // Pointer to next block
WORD len; // Length of this frame incl. CRC
} NICHEADER;
Destination
6 bytes Source
6 bytes Data
46-1500 bytes
Type
2 bytes CRC
4 bytes
Ethernet Frame
64 - 1518 bytes
PICDEM.netTM User’s Guide
DS39563A-page 38 2001 Microchip Technology Inc.
As a result, the frame in the NIC buffer RAM has two headers in front of the
data. To simplify access to the headers, the driver copies them into local RAM.
typedef struct { // NIC and Ethernet headers combined
NICHEADER nic;
ETHERHEADER eth;
} NICETHERHEADER;
...
NICETHERHEADER nicin; // Buffer for incoming NIC & Ether hdrs
WORD get_ether()
{
WORD len=0, curr;
...
getnic_data((BYTE *)&nicin, sizeof(nicin));
len = nicin.nic.len; /* Take length from stored header */
...
len -= MACLEN+MACLEN+2+CRCLEN;
...
return(len); /* Return length excl. CRC */
}
5.3.4 Packet Analysi s
Due to shortage of local on-chip RAM, the incoming packet must be analysed
in-place, in the NIC buffer RAM. The packet data is fetched a byte at a time,
and a checksum is computed for IP verification.
/* Get a byte from network buffer; if end, set flag */
BYTE getch_net(void)
{
BYTE b=0;
atend = rxout>=rxin;
if (!atend)
{
b = getnic_byte();
rxout++;
check_byte(b);
}
return(b);
}
BYTE ungot_byte;
BOOL ungot;
/* Get an incoming byte value, return 0 if end of message */
BOOL get_byte(BYTE &b)
{
if (ungot)
b = ungot_byte;
else
b = getch_net();
ungot = 0;
return(!atend);
}
2001 Microchip Technology Inc. DS39563A-page 39
ChipWeb, the Miniature Ethernet Server
A simple 1-byte pushback buf fer is included, so that a byte may be returned to
the buffer for rematching.
/* Unget (push back) an incoming byte value */
void unget_byte(BYTE &b)
{
ungot_byte = b;
ungot = 1;
}
The ampersand ‘&’ in the argument of get_byte() and unget_byte()
signifies a call-by-reference; any changes to the parameter are returned back
to the caller , rather than being discarded. This allows the compiler to generate
shorter code than the more conventional technique of passing in a pointer to
the value.
The packet analysis is performed using get_, match_ and skip_ calls, as
in the previous microcontroller implementation. For example:
/* Get an incoming word value, return 0 if end of message */
BOOL get_word(WORD &w)
{
BYTE hi, lo;
hi = getch_net();
lo = getch_net();
w = ((WORD)hi<<8) | (WORD)lo;
return(!atend);
}
/* Match an incoming word value, return 0 not matched,
/* or end of message */
BOOL match_word(WORD w)
{
WORD inw;
return(get_word(inw) && inw==w);
}
/* Skip an incoming word value, return 0 if end of message */
BOOL skip_word(void)
{
getch_net();
getch_net();
return(!atend);
}
PICDEM.netTM User’s Guide
DS39563A-page 40 2001 Microchip Technology Inc.
5.3.5 Packet Transmission
This is much simpler than reception; the driver has to
•Write the Ethernet header (destination & source addresses, and proto-
col word) into the packet buffer
•Write the packet data into the buffer
•Set the length of the packet in the NIC registers, rounding up if less than
64 bytes
•Start the NIC state machine
The NIC will automatically retry the transmission if it fails due to a collision,
but the transmission could still fail if the network is heavily loaded. The low
level drivers take no action in the event of failure, since it is usual for the
higher layers (TCP) to initiate a retry.
The packet data comes from a series of put_ calls, and these cou ld wr ite
directly into the NIC buffer area set aside for transmit, but this causes a
problem when get_ and put_ calls are intermixed; the NIC DMA controller has
to continually reprogram to read or write the packet buffer . A compromise is to
maintain a small local transmit data buffer, and use this to store outgoing
packet headers while they are being assembled.
#define TXBUFFLEN 64
BYTE txbuff[TXBUFFLEN]; // Tx buffer
int txin, txout;
/* Put a byte into the network buffer */
void putch_net(BYTE b)
{
if (txin < TXBUFFLEN)
txbuff[txin++] = b;
check_byte(b);
}
The put_ether function copies the NIC header and a data block into the
packet buffer; often, the data block will be the transmit buffer.
/* Send Ethernet packet given payload len */
void put_ether(void *data, WORD dlen)
{
outnic(ISR, 0x0a); /* Clear interrupt flags */
setnic_addr(TXSTART<<8);
putnic_data(nicin.eth.srce, MACLEN);
putnic_data(myeth, MACLEN);
swapw(nicin.eth.pcol);
putnic_data(&nicin.eth.pcol, 2);
putnic_data(data, dlen);
}
If the volume of data to be transferred is larger than the transmit buffer, it is
copied from the source (e.g., the Web page ROM) directly to the NIC packet
buffer.
2001 Microchip Technology Inc. DS39563A-page 41
ChipWeb, the Miniature Ethernet Server
5.4 LCD Driver
5.4.1 LCD Data Transfers
The four LCD data bits and the two select lines (read/write, and register
select) are all on PORTD (the Ethernet address bus), so it is convenient to
create a bitfield structure, and map it onto the port.
struct {
BYTE data:4;
BYTE regsel:1;
BYTE read:1;
} LCD_PORT;
#BYTE LCD_PORT = 8
#BIT LCD_E = PORTA.5
#define LCD_RD LCD_PORT.read
#define LCD_RS LCD_PORT.regsel
#define LCD_DATA LCD_PORT.data
Bytes are transferred to the LCD in the form of two 4-bit nibbles. After the
transfer , the microcontroller data port is returned to being an input, so the bus
is free for use by other devices. To simplify the interface, crude time delays
have been used to space the byte-transactions apart.
/* Send a command byte to the LCD as two nybbles */
void lcd_byte(BYTE &b)
{
lcd_nybble(b >> 4);
lcd_nybble(b);
DATA_FROM_LCD;
delay_us(40);
}
/* Send a byte to the LCD as two nybbles */
void lcd_nybble(BYTE b)
{
DATA_TO_LCD;
LCD_E = 1;
LCD_DATA = b;
LCD_E = 0;
}
PICDEM.netTM User’s Guide
DS39563A-page 42 2001 Microchip Technology Inc.
To write a command or character to the LCD, it is only necessary to set or
clear the register select line. A check is made to see if a display initialization
command is being sent; if so, a delay is introduced to allow the display time to
process the com ma nd.
/* Send a command byte to the LCD as two nybbles */
void lcd_char(BYTE b)
{
DATA_TO_LCD;
LCD_RD = 0;
LCD_RS = 1;
lcd_byte(b);
}
/* Send a command byte to the LCD as two nybbles */
void lcd_cmd(BYTE b)
{
DATA_TO_LCD;
LCD_RD = LCD_RS = 0;
lcd_byte(b);
if ((b & 0xfc) == 0)
delay_ms(2);
}
5.4. 2 L CD In it ia li za t ion
After power-up, the display must be given time to stabilise, before the
transactions can begin. The initialization is rather long-winded, since the LCD
must be forced into 8-bit mode before being set to 4 bits, and initialized.
/* Initialise the LCD */
void init_lcd(void)
{
int i;
LCD_E = 0; /* Clear LCD clock line */
DATA_FROM_LCD; /* Ensure RS and RD lines are O/Ps */
LCD_RD = LCD_RS = 0;
delay_ms(15); /* Ensure LCD is stable after power-up */
for (i=0; i<4; i++) /* Force into 8-bit mode */
lcd_nybble(0x3);
delay_ms(5);
}
lcd_cmd(0x28); /* Set 4-bit mode, 2 lines, 5x7 dots */
lcd_cmd(0x06); /* Incrementing cursor, not horiz scroll */
lcd_cmd(0x0e); /* Display on, cursor on, not blinking */
lcd_cmd(0x01); /* Clear display, home cursor */
}
2001 Microchip Technology Inc. DS39563A-page 43
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5.4.3 LCD Characters
Once initialized, it is easy to position the cursor and display a character.
#define LCD_SETPOS 0x80
#define LCD_LINE2 0x40
/* Go to an X-Y position on the display, top left is 1, 1 */
void lcd_gotoxy(BYTE x, BYTE y)
{
if (y != 1)
x += LCD_LINE2;
lcd_cmd(LCD_SETPOS - 1 + x);
}
/* Send a character to the LCD */
void lcd_char(BYTE b)
{
DATA_TO_LCD;
LCD_RD = 0;
LCD_RS = 1;
lcd_byte(b);
}
5.5 Other Drivers
5.5.1 Analog Inputs
The PCM compiler provides library functions for driving the ADCs;
initialization consists of setting the appropriate pins as analog inputs, the
clock rate for the conversion, and the channel to be sampled.
setup_adc_ports(RA0_ANALOG);
setup_adc(ADC_CLOCK_DIV_32);
SET_ADC_CHANNEL(0);
It would be better to set both RA0 and RA1 as analog inputs, however, this is
not possible without sacrificing some other I/O pins, as well - see the
Microchip data sheet for more information. To access both channels, we have
to briefly sacrifice digital output RA3, which is connected to a LED.
WORD adc1, adc2; // Current ADC values
/* Read both ADC values */
void read_adcs(void)
{
adc1 = READ_ADC(); // Read 1st channel
setup_adc_ports(RA0_RA1_RA3_ANALOG);
SET_ADC_CHANNEL(1); // Change channel & settle
delay_us(10);
adc2 = READ_ADC() // Read 2nd channel
setup_adc_ports(RA0_ANALOG);
SET_ADC_CHANNEL(0); // Back to 1st channel
}
The LED connected to RA3 will flicker very briefly every time it becomes an analog
input, but in practice, this isn’t at all noticeable. If RA3 were connected to a switching
device, such as a solid-state relay , this transient behavior could be a problem, and it
would be necessary to rea rrange the microco ntroller I /O pin a ssignment s.
PICDEM.netTM User’s Guide
DS39563A-page 44 2001 Microchip Technology Inc.
5.6 Protocols
5.6.1 Address Resolution Pr otocol: ARP
All Ethernet messages use a 6-byte Media Access and Control (MAC)
address, yet Internet Protocol (IP) addresses are commonly expressed as
4-byte numbers in dotted notation, e.g., 123.45.67.89. The client needs to be
able to translate (resolve) the IP address into a MAC address, and it uses
Address Resolution Protocol (ARP) for this purpose.
Chapter 3 of TCP/IP Lean discusses ARP in the context of a PC
implementation. Until now, it hasn’t been necessary to include it in the
microcontroller implementation, since the Serial Line IP (SLIP) protocol uses
IP addresses alone. Now that we have Ethernet, it is necessary to include an
ARP server, but this is relatively simple. Each ARP transaction consists of a
single resolution request, which generates a single reply.
Figure 5.8: ARP Packet Format
Protocol
type
H/W
address
length Operation
Sender hardware address
0 2
Bytes
6 8
4
0
8
16
24
Hardware
type
Pcol
address
length
Sender IP
address
Sender IP
address Target hardware address
Target IP address
2001 Microchip Technology Inc. DS39563A-page 45
ChipWeb, the Miniature Ethernet Server
Analysis of the incoming message is implemented using a series of match_
and skip_ calls, as in the previous server, and then the response is
formulated using a series of put_ calls, culminating in a call to put_ether to
copy the transmit buffer into the NIC packet buffer, then xmit_ether to send
the packet.
/* Handle an ARP message */
BOOL arp_recv(void)
{
BOOL ret=0;
if (match_byte(0x00) && match_byte(0x01) &&// Hardware type
match_byte(0x08) && match_byte(0x00) &&// ARP protocol
match_byte(6) && match_byte(4) && // Hardware & IP lengths
match_word(ARPREQ) && // ARP request
skip_lword() && skip_word() && // Source MAC addr
get_lword(remip.l) && // Source IP addr
skip_lword() && skip_word() && // Dest MAC addr
match_lword(myip.l))
{
ret = 1;
txin = 0;
put_word(0x0001);
put_word(0x0800);
put_byte(6);
put_byte(4);
put_word(ARPRESP);
put_data(myeth, MACLEN);
put_lword(myip.l);
put_data(nicin.eth.srce, MACLEN);
put_lword(remip.l);
put_ether(txbuff, txin);
xmit_ether(txin);
}
return(ret);
}
PICDEM.netTM User’s Guide
DS39563A-page 46 2001 Microchip Technology Inc.
5.6.2 Internet Protocol: IP
The IP decoder remains unchanged.
/* Get an IP datagram */
BOOL ip_recv(void)
{
BYTE b, hi, lo;
int n=0;
BOOL ret=1;
checkflag = 0; // Clear checksum
checkhi = checklo = 0;
if (match_byte(0x45) && skip_byte() && // Version, service
get_word(iplen) && skip_word() && // Len, ID
skip_word() && skip_byte() && // Frags, TTL
get_byte(ipcol) && skip_word() && // Protocol, checksum
get_lword(remip.l) && match_lword(myip.l) && // Addresses
checkhi==0xff && checklo==0xff) // Checksum OK?
{
if (ipcol == PICMP) // ICMP?
icmp_recv(); // Call ping handler
else if (ipcol == PTCP) // TCP segment?
tcp_recv(); // Call TCP handler
else
discard_data(); // Unknown; discard it
}
else
discard_data();
return(ret);
}
Due to ROM space restrictions, only two higher level protocols are supported:
ICMP and TCP.
2001 Microchip Technology Inc. DS39563A-page 47
ChipWeb, the Miniature Ethernet Server
5.6.3 Internet Control Message Protocol: ICMP
The ICMP echo request ( generally know n as ping) is an impor tant dia gnostic tool,
so it should be included. On receipt of an echo request, the Web server has to send
an echo reply, with a duplicate of the incoming dat a. The data may be larger than
the available R AM, so it is copied dir ectly from tran smit to receive packet buf fer.
Since the ICM P request and reply he aders are almost identica l, the che cksum
need not b e recompu ted, but can be adjusted to t ake account of the chang es.
/* Respond to an ICMP message (e.g. ping) */
BOOL icmp_recv(void)
{
BOOL ret=0;
WORD csum;
rpdlen = 0;
if (match_byte(8) && match_byte(0) && get_word(csum))
{
while (skip_byte()) // Check data
rpdlen++;
ret = (checkhi==0xff) && (checklo==0xff);
if (ret && rpdlen<=MAXPING_LEN)
{ // If OK and not bcast..
DEBUG_PUTC(’>’);
checkhi = checklo = 0; // Clear checksum
put_ip(); // IP header
put_word(0); // ICMP type and code
csum += 0x0800; // Adjust checksum for resp
if (csum < 0x0800) // ..including hi-lo carry
csum++;
put_word(csum); // ICMP checksum
put_ether(txbuff, txin); // Send ICMP response
copy_rx_tx(txin, IPHDR_LEN+ICMPHDR_LEN, rpdlen);
xmit_ether(IPHDR_LEN+ICMPHDR_LEN+rpdlen);
}
}
return(ret);
}
The received ICMP data is copied a byte at a time into the transmit packet
buf fe r. This crud e meth od serv es it s purp ose (af ter all, ICMP is onl y bein g used
for diagnostics), but results in a slower than necessary ping response time.
/* Copy a block from NIC Rx to Tx buffers */
void copy_rx_tx(BYTE dest, BYTE srce, BYTE len)
{
BYTE b;
outnic(ISR, 0x40);
dest += sizeof(ETHERHEADER);
srce += sizeof(NICETHERHEADER);
while (len--)
{
outnic(RSAR0, srce);
outnic(RSAR1, curr_rx_page);
b = getnic_byte();
outnic(RSAR0, dest);
outnic(RSAR1, TXSTART);
putnic_byte(b);
srce++;
dest++;
}
}
PICDEM.netTM User’s Guide
DS39563A-page 48 2001 Microchip Technology Inc.
5.6.4 Transmission Control Protocol: TCP
The TCP decoder remains largely unchanged.
/* Respond to an TCP segment */
BOOL tcp_recv(void)
{
int hlen, n;
BOOL ret=0;
WORD addr;
checkhi = checklo = 0;
if (get_word(remport) && get_word(locport) &&// Source & dest ports
get_lword(rseq.l) && get_lword(rack.l) && // Seq & ack numbers
get_byte(hlen) && get_byte(rflags) && // Header len & flags
skip_word() && skip_lword()) // Window, csum, urgent ptr
{
iplen -= IPHDR_LEN; // Get TCP segment length
check_word(iplen); // Check pseudoheader
check_lword(myip.l);
check_lword(remip.l);
check_byte(0);
check_byte(PTCP);
rxout = (hlen>>2) + IPHDR_LEN; // Skip over options
rpdlen = iplen - rxout + IPHDR_LEN;
addr = getnic_addr();
check_rxbytes(IPHDR_LEN+TCPHDR_LEN, iplen-TCPHDR_LEN);
setnic_addr(addr);
ret = (checkhi==0xff) && (checklo==0xff);
if (ret)
tcp_handler();
}
return(ret);
}
You will note the calls to getnic_addr() and setnic_addr(), which are
used to temporarily save and restore the NIC address pointer. This allows the
code to scan ahead for the checksum computation, and then go back for the
detailed analysis of the TCP data.
/* Handle an incoming TCP segment */
void tcp_handler(void)
{
BOOL tx=1; // Set transmission flag
tpdlen = tpxdlen = 0; // Assume no Tx data
d_checkhi = d_checklo = 0;
checkflag = 0;
tflags = TACK; // ..and just sending an ack
if (rflags & TRST) // RESET received?
tx = 0; //..do nothing
else if (rflags & TSYN) // SYN received?
{
add_lword(rseq.l, 1); // Adjust Tx ack for SYN
if (locport==DAYPORT || locport==HTTPORT)
{ // Recognised port?
rack.w[0] = 0xffff;
rack.w[1] = concount++;
tflags = TSYN+TACK; // Send SYN ACK
2001 Microchip Technology Inc. DS39563A-page 49
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}
else // Unrecognised port?
tflags = TRST+TACK; // Send reset
}
else if (rflags & TFIN) // Received FIN?
add_lword(rseq.l, rpdlen+1); // Ack all incoming data + FIN
else if (rflags & TACK) // ACK received?
{
if (rpdlen) // Adjust Tx ack for Rx data
add_lword(rseq.l, rpdlen);
else // If no data, don’t send ack
tx = 0;
if (locport==HTTPORT && rpdlen)
{ // HTTP ’get’ method?
http_recv(); // Call handler..
tx = 0; // ..which does its own Tx
}
else if (locport==DAYPORT && rack.w[0]==0)
{ // Daytime request?
daytime_handler(); // Prepare daytime data
tx = 1; // ..and send it
}
}
if (tx) // If transmission required
tcp_xmit(); // ..do it
}
The TCP implementation supports two higher level protocols:
•HTTP (for the Web server)
•Daytime (to demonstrate a simple TCP transaction)
HTTP is described in Section 5.6.5.
The Daytime protocol returns a string with the current date and time.
/* Respond to an Daytime request */
BOOL daytime_handler(void)
{
checkhi = checklo = 0;
txin = IPHDR_LEN + TCPHDR_LEN;// O/P data to buffer, calc checksum
printf(put_byte, DAYMSG);
tpdlen = DAYMSG_LEN; // Data length of response
d_checkhi = checkhi; // Save checksum
d_checklo = checklo;
tflags = TFIN+TACK; // Ack & close connection
}
The non-standard CCS compiler call with a function argument
printf(put_byte, ...) has been used so that the function put_byte()
is called once for every character in the output string, which stores the string
in the transmit buffer and computes its checksum. Unfortunately, we don’t
have a real-time clock chip, so a dummy message is put out instead.
#define DAYMSG "No daytime msg\r\n"
#define DAYMSG_LEN 16
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DS39563A-page 50 2001 Microchip Technology Inc.
The transmit buffer is 64 bytes in length, so it is sufficient for short messages
such as these (the total length of the above response is 20 + 20 + 16 = 56
bytes). Longer messages, such as the HTTP page data, are transferred direct
from ROM to the NIC packet buffer; this will be described later.
Due to the absence of a state machine, the TCP implementation is known as
stateless, i.e., the server stores no state information about any of the clients.
As described in the book, the server can only send one frame in response to
each request from the client, otherwise the lock-step nature of the transaction
is broken, and the server would need to implement a retry strategy. Aside
from simplicity, the huge advantage of the stateless approach is that the
server can accommodate very large numbers of simultaneous connections,
which makes it very responsive when handling multiple requests.
When responding to an incoming message, the server should perform an
ARP cycle to resolve:
1. The return IP address, if in the current domain, or
2. The router’s IP address, if the return address is outside the current domain.
A much more compact approach is to re-use the incoming IP and MAC
addresses for the return message. Providing the network routing has been
kept simple, this approach will work fine.
/* Put out a TCP segment. Data checksum must have already been computed
*/
void put_tcp(void)
{
WORD len;
checkflag = 0; // Ensure we’re on an even byte
checkhi = d_checkhi; // Retrieve data checksum
checklo = d_checklo;
put_word(locport); // Local and remote ports
put_word(remport);
put_lword(rack.l); // Seq & ack numbers
put_lword(rseq.l);
put_byte(tflags&TSYN ? TCPSYN_LEN*4 : TCPHDR_LEN*4); // Header len
put_byte(tflags);
put_byte(0x0b); // Window size word
put_byte(0xb8);
len = tpdlen + tpxdlen + TCPHDR_LEN;
if (tflags & TSYN) // If sending SYN, send MSS option
{
txin += 4; // Put MSS in buffer after TCP header
len += TCPOPT_LEN;
put_byte(2);
put_byte(4);
put_word(TCP_MSS);
txin -= TCPOPT_LEN + 4; // Go back to checksum in header
}
check_lword(myip.l); // Add pseudoheader to checksum
check_lword(remip.l);
check_byte(0);
check_byte(PTCP);
check_word(len);
put_byte(~checkhi); // Send checksum
put_byte(~checklo);
put_word(0); // Urgent ptr
if (tflags & TSYN) // Adjust Tx ptr if sending MSS option
txin += TCPOPT_LEN;
}
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5.6.5 Hypertext Transfer Protocol: HTTP
The TCP/IP Lean microcontroller HTTP implementation was dominated by
the problem of the TCP checksum; it must be computed before the Web page
goes out, yet there was insufficient RAM to buffer the page prior to
transmission. As a result, a complex scheme of counter-balancing HTTP t ags
was employed, so that the checksum was known in advance, even when the
page was being changed on the fly.
The good news is that the Ethernet controller stores a complete page in its
packet buffer prior to transmission, so we remove the need for a
pre-computed checksum, using the following method:
1. Cop y data (i.e., Web page) to packet buffer, comp uting checksum as it
is copied.
2. Prepare TCP header in local RAM, using data checksum value.
3. Copy TCP header from local RAM to packet buffer.
4. Transmit whole packet in buffer.
/* Receive an incoming HTTP request (’method’), return 0 if invalid */
BOOL http_recv(void)
{
int len, i;
BOOL ret=0;
char c;
WORD blen;
tpxdlen = 0; // Check for ’GET’
DEBUG_PUTC(’h’);
if (match_byte(’G’) && match_byte(’E’) && match_byte(’T’))
{
ret = 1;
match_byte(’ ’);
match_byte(’/’); // Start of filename
memset(romdir.f.name, 0, ROM_FNAMELEN);
for (i=0; i<ROM_FNAMELEN && get_byte(c) && c>’ ’ && c!=’?’; i++)
{ // Name terminated by space or ’?’
romdir.f.name[i] = c;
} // If file found in ROM
if (find_file())
{ // ..check for form arguments
check_formargs();
}
else // File not found, get index.htm
{
romdir.f.name[0] = 0;
find_file();
}
checkhi = checklo = 0;
txin = IPHDR_LEN + TCPHDR_LEN;
if (!fileidx) // No files at all in ROM - disaster!
{
setnic_addr((TXSTART<<8)+sizeof(ETHERHEADER)
+IPHDR_LEN+TCPHDR_LEN);
printf(putnic_checkbyte, HTTP_FAIL);
tflags = TFIN+TACK;
d_checkhi = checkhi;
PICDEM.netTM User’s Guide
DS39563A-page 52 2001 Microchip Technology Inc.
d_checklo = checklo;
tcp_xmit();
}
else // File found OK
{
open_file(); // Start i2c transfer
setnic_addr((TXSTART<<8)+sizeof(ETHERHEADER)
+IPHDR_LEN+TCPHDR_LEN);
while (tx_file_byte())// Copy bytes from ROM to NIC
;
close_file();
tflags = TFIN+TPUSH+TACK; // Close connection when sent
d_checkhi = checkhi; // Save checksum
d_checklo = checklo;
tcp_xmit(); // Do header, transmit segment
}
}
return(ret);
}
The tx_file_byte() function copies the data from ROM to packet buffer,
performing EGI (Embedded Gateway Interface) variable substitution as it
goes.
/* Transmit a byte from the current i2c file to the NIC
** Return 0 when complete file is sent
** If file has EGI flag set, perform run-time variable substitution */
BOOL tx_file_byte(void)
{
int ret=0, idx;
BYTE b;
if (romdir.f.len) // Check if any bytes left to send
{
b = i2c_read(1); // Get next byte from ROM
if ((romdir.f.flags&EGI_ATVARS) && b==’@’)
{ // If ’@’ and EGI var substitution..
b = i2c_read(1); // ..get 2nd byte
romdir.f.len--;
idx = b - 0x30;
if (idx == 1) // Scaled ADC value for slider 1
printf(putnic_checkbyte, "%u", (BYTE)(adc1/11)+6);
else if (idx == 2) // Scaled ADC value for slider 2
printf(putnic_checkbyte, "%u", (BYTE)(adc2/11)+6);
else if (idx == 3) // Voltage value for ADC 1
putnic_volts(adc1);
else if (idx == 4) // Voltage value for ADC 2
putnic_volts(adc2);
else if (idx == 5) // User O/P LED 1 state
putnic_checkbyte(USERLED1 ? ’0’ : ’1’);
else if (idx == 6) // User O/P LED 2 state
putnic_checkbyte(USERLED2 ? ’0’ : ’1’);
else if (idx == 7) // I/P button state
putnic_checkbyte(USER_BUTTON ? ’0’ : ’1’);
else // Unknown variable
printf(putnic_checkbyte, "??");
}
else // Non-EGI byte; send out unmodified
putnic_checkbyte(b);
romdir.f.len--; // Decrement length
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ChipWeb, the Miniature Ethernet Server
ret = 1;
}
return(ret);
}
/* Send the voltage string for the given ADC to the NIC */
void putnic_volts(WORD val)
{
BYTE v;
v = (BYTE)(val / 21);
putnic_checkbyte(v/10 + ’0’);
putnic_checkbyte(’.’);
putnic_checkbyte(v%10 + ’0’);
}
The EGI variables are prefixed with an ‘@’ character , and are used as follows:
•@1, @2: scaled ADC values for slider animation (see next section).
•@3, @4: voltage values for ADCs.
•@5, @6: O/P LED states.
•@7, @8: I/P button state.
When one of these variables is encountered in the file, it is changed into the
corresponding real-time data value. This is done using the non-standard CCS
imple men tation of printf() with a function call printf
(putnic_checkbyte, ...) to copy the characters into the packet buffer
RAM, while keeping track of the checksum.
5.6.6 Protocol Debugging
To help in debugging the TCP/IP stack, a simple diagnostic output can be
enabled on the serial port using the DEBUG compile-time definition.
#define DEBUG 1 // Set non-zero to enable diagnostic
printout
The output owes more to brevity than clarity; the display for a simple HTTP
request might look like:
Rx46>a>A Rx46>i>t>T Rx46>i>t> Rx56>i>t>h index.htm>T Rx46>i>t>T Rx72>i
Each received packet is indicated by ‘Rx’, the length (in decimal), and a right-
arrow ‘>’. Subsequent protocol decodes are indicated by lower case letters:
•a: ARP
•i: IP
•c: ICMP
•t: TCP
•h: HTTP
PICDEM.netTM User’s Guide
DS39563A-page 54 2001 Microchip Technology Inc.
Transmissions are indicated by the corresponding upper case letters, so
Rx46>a>A
Indicates that a 46-byte ARP request was received, and a response was sent.
For HTTP requests, the filename is displayed, so
Rx56>i>t>h index.htm>T
shows that INDEX.HTM was requested, and a TCP (strictly speaking,
HTTP-TCP-IP) response was sent.
Although it is a poor substitute for a Protocol Analyser, this diagnostic
capability can be very useful for resolving simple protocol problems.
5.7 User Interface
5.7.1 Dynamic Web Pages: HTML
Due to the SLIP serial link, the TCP/IP Lean Web server couldn’t handle
complicated Web pages (those with a lot of embedded graphics), since the
browser will issue multiple parallel GET requests, one for each graphic, which
causes an overflow of the small serial buffer. Although the browser’s retry
mechanism will ensure that all the graphics arrive, it does make for
frustratingly slow Web page updates.
The Ether net controll er removes the b ottleneck caused b y the serial bu ffer , so it is
possible t o create quite ela borate displays within th e const raint of ea ch indivi dual
file, fitting within one Ethernet frame (file plus HTTP header must fit in 1460
bytes). Th e h ome page for th e P ICDEM. ne t boa r d is sh own i n F ig ure 5.9.
Figure 5.9: Home Page for PICDEM.net
2001 Microchip Technology Inc. DS39563A-page 55
ChipWeb, the Miniature Ethernet Server
Aside from using this opportunity to include cute graphics, we can use HTTP
frames to segregate the user’s screen into three areas: the main center
section (that changes according to the user’s selections), and the two
sidebars (one for navigation and control, the other for showing the I/O status).
This achieves several objectives:
1. Provides a clearer layout for user navigation.
2. Splits the screen area into several smaller files, rather than one large
one.
3. Al lo ws the use of simple tech ni que s for the toggle swi t ch cont ro ls .
4. Li mits the si ze of the dynami c upda te area, since thi s can flic ker du ring
updates.
The home page INDEX.HTM is just a shell that contains the three frames:
<HTML>
<HEAD>
<TITLE>ChipWeb server</TITLE>
</HEAD>
<FRAMESET cols="120,*,120" border=0>
<FRAME name="left" src="digout00.htm" marginheight=2 marginwidth=2>
<FRAME name="middle" src="main1.htm" marginheight=5 marginwidth=5>
<FRAME name="right" src="stat1.egi" marginheight=5 marginwidth=5>
</FRAMESET>
</HTML>
5.7.2 Status Display Frame
The right hand status frame uses a client pull instruction so that the browser
will re-fetch it from the server every five seconds.
<html><meta http-equiv="refresh" content="5">
<head><title>ChipWeb status</title></head>
<body bgcolor=#d0d0ff><font face=helvetica>
<h3><center>I/O status</center></h3>
...
This technique is acceptable for Local Area Network (LAN) use, but is
unusable over the Internet; random delays in the path between client and
server can cause a backlog of requests at the client, and annoyingly
inconsistent update times.
The analog display uses variable GIF block sizes to vertically position the
indicators, as discussed in the book. Some browsers flicker when updating
dynamic graphics, so it is best to keep the area small, and offer the user a
more accurate (and flicker-free) text indication of the value as well.
PICDEM.netTM User’s Guide
DS39563A-page 56 2001 Microchip Technology Inc.
...
<b>Analog I/P</b>
<table border=0 cellpadding=1 cellspacing=0 bgcolor=#e0e0ff>
<tr><th colspan=5 align=center><small>Volts</small></th></tr>
<tr align=center valign=bottom>
<td><img src="v5_100n.gif"><br><img src="clr.gif" height=10 width=10></
td>
<td><img src="lptr.gif"><br><img src="clr.gif" height=@1 width=10></td>
<td><img src="clr.gif" height=1 width=25></td>
<td><img src="v5_100n.gif"><br><img src="clr.gif" height=10 width=10></
td>
<td><img src="lptr.gif"><br><img src="clr.gif" height=@2 width=10></td>
</tr><tr>
<td colspan=2 align=center>@3</td>
<td> </td>
<td colspan=2 align=center>@4</td>
</tr>
</table><br>
The display of digital inputs and outputs is text-only:
<b>Digital O/P</b><br>
<table cellpadding=6 bgcolor=#e0e0ff vspace=0>
<tr><th align=center colspan=2><small>O/P states</small></th></tr>
<tr><td align=center>@5</td> <td align=center>@6</td> </tr>
</table><br>
<b>Digital I/P</b><br>
<table cellpadding=6 bgcolor=#e0e0ff vspace=0>
<tr><th align=center colspan=1><small>I/P state</small></th></tr>
<tr><td align=center>@7</td></tr>
</table>
</body></html>
5.7.3 Navigation Frame
This frame contains links that select what is to be displayed in the central
area. This is achieved using HREF entries that specify a target location; the
possible targets are ‘left’ ‘middle’ and ‘right’, as specified within the frameset
definition of INDEX.HTM.
<HTML><HEAD></HEAD>
<BODY bgcolor=#d0d0ff><font face=helvetica>
<h3><center>Navigation</center></h3>
<CENTER>
<A href="main1.htm" target=middle>Home</A><P>
<A href="maina.htm" target=middle>Analogue</A><P>
<A href="maind.htm" target=middle>Digital</A><P>
<A href="mains.htm" target=middle>Software</A><P>
</CENTER>
...
2001 Microchip Technology Inc. DS39563A-page 57
ChipWeb, the Miniature Ethernet Server
The navigation frame also has the toggle switches and LEDs for controlling
the outputs. This grouping not only helps the user to navigate using a
minimum of mouse movement, but also helps us by permitting the use of a
very simple technique for animating the toggle switches. At the start of TCP/IP
Lean, chapter 8, I describe how a toggle switch and lamp can be animated
using two Web pages; one showing ‘off’, and the other ‘on’; clicki ng th e swi tch
on one page causes the other page to be loaded. Since the PICDEM.net
board has two outputs, this principle has been expanded to four pages, one
for each stat e. The switch URLs are cross-linked, as shown below:
File digout00.htm:
...
<h3><center>Control</center></h3>
<center><table>
<tr valign=middle>
<td><a href="digout10.htm"><img src="sw0.gif"></a></td>
<td><a href="digout01.htm"><img src="sw0.gif"></a></td>
</tr><tr valign=middle>
<td align=center><img src="led0.gif"></td>
<td align=center><img src="led0.gif"></td>
</tr></table>
...
File digout01.htm:
...
<table>
<tr valign=middle>
<td><a href="digout11.htm"><img src="sw0.gif"></a></td>
<td><a href="digout00.htm"><img src="sw1.gif"></a></td>
</tr><tr valign=middle>
<td align=center><img src="led0.gif"></td>
<td align=center><img src="led1.gif"></td>
</tr></table>
...
Same logic for digout10.htm and digout11.htm...
Rudimentary parsing of the input filename is used to propagate the on/off
states to the hardware, bearing in mind the hardware inversion; the LED is on
when the output line is low.
#bit USERLED1 = PORTA.2 // User LEDs
#bit USERLED2 = PORTA.3
...
/* Check for arguments in HTTP request string
** Simple version: just check last 2 digits of filename, copy to 2 LEDs
*/
void check_formargs(void)
{
if (romdir.f.name[6]==’0’ || romdir.f.name[6]==’1’)
USERLED1 = (romdir.f.name[6] == ’0’);
if (romdir.f.name[7]==’0’ || romdir.f.name[7]==’1’)
USERLED2 = (romdir.f.name[7] == ’0’);
}
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DS39563A-page 58 2001 Microchip Technology Inc.
5.7.4 LCD Display
The 2-line LCD is used to display a sign-on message (including the software
version number) and the IP address of the server. In Configuration mode, the
second display line is changed to reflect the off-line state of the server.
To save space, a singl e ‘print’ character handler is used, with flags to
determine whether the output will be directed to the serial port, the LCD, or
both.
BOOL disp_lcd, disp_serial; // Flags to enable display O/Ps
...
disp_lcd = disp_serial = TRUE; // Set display flags
printf(displays, SIGNON); // ..and sign on
...
/* Display handler; redirects to LCD and/or serial */
void displays(BYTE b)
{
if (disp_lcd)
{
if (b == ’\r’)
lcd_cmd(LCD_SETPOS);
else if (b == ’\n’)
lcd_cmd(LCD_SETPOS + LCD_LINE2);
else
lcd_char(b);
}
if (disp_serial)
{
if (b == ’\n’)
putchar(’\r’);
putchar(b);
}
}
5.8 Configuration
The following configuration items need to be stored in non-volatile memory:
•4-byte IP address
•6-byte MAC address
•Web pages
The first two will be stored in the PIC16F877 on-chip EEPROM, while the last
will be in the separate serial EEPROM. To simplify production, and to allow
the user to alter the values on-site, they need to be programmable over the
serial link.
To configure the system, the user connects a serial terminal (e.g., Windows
HyperTerminal) to the board. A simple checksum is used to see if the CPU is
uninitialized, and if so, it automatically enters Configuration mode. If not, the
user has to manually initiate the mode by holding down the user I/P push
button, while the CPU is coming out of RESET. As with the LED outputs, there
is an I/O inversion in the hardware, so the input reads zero when the button is
pressed.
2001 Microchip Technology Inc. DS39563A-page 59
ChipWeb, the Miniature Ethernet Server
#bit USER_BUTTON=PORTB.5 // User pushbutton
...
while (!read_nonvol() || !USER_BUTTON) // If csum error, or button
{
printf(displays, "Config ");
user_config(); // ..call user config
}
...
/* Read in the nonvolatile parameters, return 0 if error */
BOOL read_nonvol(void)
{
int i;
myeth[4] = read_eeprom(0);
myeth[5] = read_eeprom(1);
myip.b[3] = read_eeprom(2);
myip.b[2] = read_eeprom(3);
myip.b[1] = read_eeprom(4);
myip.b[0] = read_eeprom(5);
return (csum_nonvol() == read_eeprom(6));
}
/* Do a 1’s complement checksum of the non-volatile data */
BYTE csum_nonvol(void)
{
int i;
BYTE sum=0;
for (i=0; i<6; i++)
sum += read_eeprom(i);
return(~sum);
}
5.8.1 Address Configuration
The first three bytes of the 6-byte Media Access and Control (MAC) address
identify the board vendor; for Microchip, these are 00 04 A3. It is important
that the remaining three bytes are unique amongst all Microchip products, so
each board is allocated a serial number , and the user is prompted to enter this
number on the serial interface. This value is used directly as the last three
MAC bytes. So long as all the serial numbers are unique, and the user enters
the number properly, there is no danger of two boards having the same MAC
address. Although acceptable on a prototype board, this method could not be
used on production equipment; the MAC address should be machine
programmed on manufacture, and not be changeable by the user.
The IP address is the other user-configured item; it must be set to reflect the
network (domain) the Web server is connected to, and be a unique value
within that domain.
To configure both these settings, the user must enter Configuration mode, and
is then prompted for the required values; the escape key can be used to
bypass a setting, in case it is already correct.
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DS39563A-page 60 2001 Microchip Technology Inc.
Originally, the user interface was coded using a conventional get-line-then-
parse approach, but a parse-on-the-fly approach was much smaller. The
absence of a loop might also be surprising, but it must be understood that the
compiler can resolve an array reference with a constant index (such as
myip.b[1]) to a fixed memory location, so the ‘unrolled’ loop can be more
economical in terms of code and data space.
BOOL escaped;
...
/* User initialisation code; get serial number and IP address
** Skip if user hits ESC */
void user_config(void)
{
WORD w;
BYTE t1, t2;
escaped = 0;
printf("\r\nSerial num? ");
w = getnum();
if (!escaped)
{
myeth[4] = w >> 8;
myeth[5] = w;
}
escaped = 0;
printf("\r\nIP addr? ");
USERLED1 = USERLED2 = 1;
myip.b[3] = getnum();
putchar(’.’);
if (!escaped)
myip.b[2] = getnum();
putchar(’.’);
if (!escaped)
myip.b[1] = getnum();
putchar(’.’);
if (!escaped)
myip.b[0] = getnum();
if (!escaped)
write_nonvol();
printf("\r\nXmodem? ");
xmodem_recv();
}
5.8.2 Web Page Download
The TCP/IP Lean book includes a utility, WEBROM, which takes all the files
out of a given directory, adds the HTTP headers, and merges them into a
single ROM file, ready for transfer to the Web page EEPROM, e.g.,
webrom webpage.rom c:\chipweb\pcm\romdocs
2001 Microchip Technology Inc. DS39563A-page 61
ChipWeb, the Miniature Ethernet Server
To transfer the file down the serial link, the simplest file transfer protocol is
employed: XMODEM. This sends the file in 128-byte blocks with a simple
header and a checksum trailer (which is ignored in this implementation). A
minor complication is that the EEPROM isn’t able to accept the whole 128
bytes at once; it must be broken up into chunks, with a pause between them
to allow the device to program itself. Fortunately, the programming time
(5 milliseconds) allows the use of a relatively small serial buffer to cover this
delay. A detailed discussion of the XMODEM protocol is outside the scope of
this document; ther e ar e copious refer ences on the Web that analyse the
byte-structure and timing in detail. This implementation employs a few
Boolean flags and a timer to construct a simple state-machine. The timer is
used to handle any interruptions in the transfer, but other errors (such as
single character corruption) are not handled; it is assumed that there is a short
cable link to the PC, not a noisy modem connection.
#define SOH 0x01
#define EOT 0x04
#define ACK 0x06
#define NAK 0x15
#define CAN 0x18
#define ROMPAGE_LEN 32
#define XBLOCK_LEN 128
/* Handle incoming XMODEM data block */
void xmodem_recv(void)
{
BYTE b, len=0, idx, blk, i, oset;
BOOL rxing=FALSE, b1=FALSE, b2=FALSE, b3=FALSE;
timeout(ledticks, 0);
while (1)
{
while (!kbhit())
{
restart_wdt(); // Kick watchdog
geticks() // Check for timeout
if (timeout(ledticks, LEDTIME))
{
SYSLED = !SYSLED;
USERLED1 = 1;
if (!rxing // Send NAK if idle
{
len = 0;
b1 = b2 = b3 = FALSE;
putchar(NAK);
}
rxing = FALSE;
}
}
b = getchar(); // Get character
rxing = TRUE;
if (!b1) // Check if 1st char
{
if (b == SOH) // ..if SOH, move on
b1 = TRUE;
else if (b == EOT) // ..if EOT, we’re done
{
PICDEM.netTM User’s Guide
DS39563A-page 62 2001 Microchip Technology Inc.
putchar(ACK);
break;
}
}
else if (!b2) // Check if 2nd char
{
blk = b; // ..block num
b2 = TRUE;
}
else if (!b3) // Check if 3rd char
{
if (blk == ~b) // ..inverse block num
{
b3 = TRUE;
blk--;
}
}
else if (len < XBLOCK_LEN) // Rest of chars up to block len
{ // Buffer into ROM page
idx = len & (ROMPAGE_LEN - 1);
len++;
txbuff[idx] = b; // If end of ROM page..
if (idx == ROMPAGE_LEN-1) // ..write to ROM
{
i2c_start();
i2c_write(EEROM_ADDR);
i2c_write(blk >> 1);
oset = len - ROMPAGE_LEN;
if (blk & 1)
oset += 0x80;
i2c_write(oset);
for (i=0; i<ROMPAGE_LEN; i++)
i2c_write(txbuff[i]);
i2c_stop();
}
}
else // End of block, send ACK
{
putchar(ACK);
timeout(ledticks, 0);
SYSLED = !SYSLED;
len = 0;
b1 = b2 = b3 = FALSE;
}
}
}
2001 Microchip Technology Inc. DS39563A-page 63
ChipWeb, the Miniature Ethernet Server
5.9 Source Code
The following source files are provided. They have been compiled with
Custom Computer Services ’PCM’ C compiler version 2.693, and should still
be compatible with later versions. The compiler doesn’t use a linker, so library
files are included in the main source file.
p16web.c Main Program
p16_drv.h Low Level Driver
p16_eth.h Ethernet Interface
p16_ip.h IP and TCP
p16_lcd.h LCD Interface
p16_usr.h User Interface and Configuration
p16_http.h HTTP and Web Page Processing
webrom.h ROM Filesystem Definitions
It is intended that the source files reside in the directory \chipweb\pcm.To
maintain compatibility with a variety of software tools, P16WEB.C has
absolute file paths for the ‘include’ files; these will have to be changed if a
different directory is used.
The compiler output file, CHIPWEB.HEX, should be programmed into a
PIC16F77 device.
The Web documents are located in the directory \chipweb\pcm\romdocs.
To reload them into the Web page ROM, they must first be merged using the
utility from TCP/IP Lean:
cd \chipweb\pcm
\tcplean\webrom webpage.rom romdocs
They must then be downloaded using the XMODEM protocol (not
XMODEM-1k). Details of this procedure are given in Chapter 4 of the User’s
Guide.
PICDEM.netTM User’s Guide
DS39563A-page 64 2001 Microchip Technology Inc.
NOTES:
2001 Microchip Technology Inc. DS39563A-page 65
PICDEM.netTM USER’S GUIDE
Chapter 6. Troubleshooting
6.1 Highlights
This chapter discusses common operational issues, and how to resolve them.
6.2 Common Issues
1. The System LED is not lit or flashing
Check the PICDEM.net board for power :
•Verify that the power supply is plugged in, and the wall outlet has power.
•Check that voltage is available (9 VDC) at the barrel plug.
•Check that the regulated voltage (5 VDC) is available at the connectors at
the prototype area of the board.
2. The LINK LED is not lit, or only lights intermittently
Check the Revision Level of the PICDEM.net board:
•On Revision 4 boards, the LINK LED is tied to pin LED0 of the Ethernet
transceiver. With the Iosoft firmware provided, this pin functions as an
Ethernet Collision Sense indicator; it will normally be dark unless a packet
collision is detected.
•On Revision 5 and later boards, the LINK LED is tied to pin LEDBNC of
the transceiver; the LED functions as a Link Status indicator, and should
be lit if the board is configured and connected correctly to the host
system.
If the PICDEM.net board is Revision 5 or higher:
Check the board for power (see Issue 1, above).
3. The LCD doesn’t disp lay a message whe n power is applied t o the
PIC D E M .net boar d
Check the board for power (see Issue 1, above).
If the board functions normally otherwise (including connectivity to the host
system), the LCD display itself may be faulty. Contact Customer Service for
additional assistance.
Note: The Revision Label is on the reverse (trace) side of the board,
directly underneath the Prototype Area grid (see Figure 1.1,
item 16).
PICDEM.netTM User’s Guide
DS39563A-page 66 2001 Microchip Technology Inc.
4. The PICDEM.net board will not communicate with the host system
A. Verify that the correct Ethernet cable is being used:
•When the PICDEM.net board is directly connected to the host system
as described in Chapter 2, a crossover cable must be used
•When the PICDEM.net board is connected to the host system
through an Ethernet hub, a standard ("straight-through") cable must
be used
Verify that the Ethernet cable is connected and undamaged.
B. If the board fails when connected through a hub, verify that the hub is
working properly. If it is, try connecting the host system directly to the
Ethernet board, as described in Chapter 2. Also check that the right cable
is being used (see above).
C. Check TCP/IP connectivity with the ping command:
1. Launch a DOS (or Command Prompt) window.
2. Type ping <IP address>, where "IP address" is that of the
PICDEM.net board.
If ping returns the message "Request timed out", check the RECEIVE
LED on the PICDEM.net board:
•If the LED bl in ks du rin g at t empt ed com muni cat io ns , t he IP addressing
may be wrong ( i. e. , th e bo ard and t he hos t ar e no t in th e sa me
domain). Refer to Chapter 3 of the book "TCP/IP" for more informati on.
•If the LED does NOT blink, the Ethernet cable is defective or the
wrong type, or the host system has not been properly configured for
TCP/IP.
D. Check the Device Manager to verify the Ethernet card (Windows 95,
Windows 98 and Windows 2000 only):
1. From the Windows Start Menu, choose Sett ing s>C on trol Pan e l.
2. Select the "System" applet icon.
3. Select the “Device Manager” tab (for Windows 2000, the “Hardware”
tab, then the “Device Manager” button).
Note: If you suspect that the Ethernet cable supplied with the kit is dam-
aged, be certain to replace it only with an Ethernet crossover cable.
A conv entiona l CAT5 cable will not work if th e PICDE M.net b oard
is directly connected to the host system.
2001 Microchip Technology Inc. DS39563A-page 67
Troubleshooting
4. Verify that the host system’s Ethernet adapter is working properly
(the card is present in Device Ma nager, and th ere are no excl amatio n
points or question ma rks associat ed wi th th e ca rd’s icon).
E. Check the PICDEM.net board for power (see Issue 1, above).
F. If all else fails, reconfigure the PICDEM.net board’s network setting s,
using the default Ethernet ID and IP address. See Section 4.3.1 and
Section 4.3.2 for more information.
5. T he host syste m communicates with the board, but the Web pa ge
is not present or does not function correctly
If the Web page EEPROM is blank or absent, any attempt to access the
ChipWeb page will result in the message "No Web pages!". If this message
appears, reload the Web page to the EEPROM from the Internet Solutions
CD (see Section 4.3.3 for more information).
If th e ChipW e b p age displ ay is "b roken " (d isjointe d dis play, frames not w ork ing,
error mess ag es d isplayed), u se yo ur b row se r’s "Reload" command to refresh
the page. If the page is still broken, reload the EEPROM (Section 4.3.3).
6. The board will not communica te with the host syst em after chang-
ing the IP address and/or Ethernet ID
Check the PICDEM.net board and host system as in Issue 3, above.
If these steps don’t work, restore the PICDEM.net board’s default network
configuration to see if communications can be re-established. See
Section 4.3.1 and Section 4.3.2 for more information.
7. Unable to initiate a serial connection with the PICDEM.net board
Carefully review the instructions for the terminal emulation software you are
using. Make certain that the software is correctly installed, and that you are
able to successfully configure a session.
Verify that you are using the correct serial port. Check that the COM port you
have selected in the terminal software is actually the physical port that the
serial cable is connected to.
Verify that the serial cable is properly connected at the host system and the
PICDEM.net board, and that the cable is undamaged.
Note: Microsoft Windows NT 4.0 does not permit a direct diagnostic view
of network hardware. Some Ethernet cards may have an applet
installed in the Control Panel, which gives the device status. For
most, however , the only way to determine if a card is working prop-
erly is to ex am in e the state of the devic e dr i vers and ins talle d net -
work components. The name and particular configuration of device
drivers varie s wid el y from dev i ce to de vi ce . For inf or mat ion partic -
ular to your s ituation, c on sult the doc um entatio n f or y our E th er net
card, or your local system support provider.
DS39563A-page 68 2001 Microchip Technology Inc.
PICDEM.netTM User’s Guide
NOTES:
2001 Microchip Technology Inc. DS39563A-page 69
PICDEM.netTM USER’S GUIDE
Appendix A. PICDEM.net Board Schematics
Figure A.1: PICDEM.net Board Schematic, Part 1 (Main Board)
PICDEM.netTM User’s Guide
DS39563A-page 70 2001 Microchip Technology Inc.
Figure A.2: PICDEM.net Board Schematic, Part 2 (Etherne t Transceiver Detail)
U5
RTL8019
2001 Microchip Technology Inc. DS39563A-page 71
PICDEM.netTM USER’S GUIDE
Append ix B. PICDEM.n et Inter net Solutions CD
B.1 Highlights
This chapter summarizes the contents of the PICDEM.net Internet Solutions
CD-ROM. This includes connectivity solutions provided by Microchip’s
partners, such as:
•Iosoft
•LiveDevices
•Yipee
B.2 What’s on the CD
The PICDEM.net Internet Solutions CD includes software solutions from
these vendors.
B.2.1 Iosoft
The full source code for the ChipWeb page (as installed on the PICDEM.net
board) is included in this folder, as well as the Web pages used and the
WEBROM page merging utility.
Additional Iosoft demonstration code and utilities are provided on the CD
accompanying the book “TCP/IP Lean: Web Systems for Embedded
Servers”.
B.2.2 LiveDevices
LiveDevices has provided a copy of its small TCP/IP stack, developed for the
PIC18C family and either Ethernet or modem (PPP) connectivity. This folder
also contains demonstration software and information on other LiveDevices
solutions.
B.2.3 Yipee
Yipee has provided an evaluation version of its TCP/IP stack developed for
the PIC16F877 microcontroller and Ethernet connectivity. This folder also
contains demonstration software, a movie file, and detailed information on
their so luti on .
DS39563A-page 72 2001 Microchip Technology Inc.
PICDEM.netTM User’s Guide
NOTES:
2001 Microchip Technology Inc. DS39563A-page 73
PICDEM.netTM USER’S GUIDE
A
Address Resolution Protocol (ARP) ........................ 44
ARP Caching .......................................................... 25
B
Bus Topology .......................................................... 27
C
Changing Network Configuration ............................ 24
Changing the Routing Table ................................... 17
ChipWeb Page ..................................................19, 21
Structure .......................................................... 21
Center Pane ............................................. 21
Communication Protocols ....................................... 44
Address Resolution Protocol (ARP) ................. 44
Debugging ....................................................... 53
Dynamic Host Configuration Protocol
(DCHP) ..................................................... 11
Hypertext Transfer Protocol (HTTP) ................ 51
Internet Control Message Protocol
(ICMP) ...................................................... 47
Internet Protocol (IP) ....................................... 46
Transmission Control Protocol (TCP) .............. 48
Configuration Mode ................................................ 24
Configuring the Host System .................................. 12
Connectors
10-Base T .......................................................... 9
DB9 (Serial) ....................................................... 9
RJ-11 (six-wire) ................................................. 9
RJ-45 ................................................................. 9
Customer Notification Service ................................... 5
Customer Support ..................................................... 6
D
Development Manual .............................................. 10
Document Conventions ............................................ 2
Document Layout ...................................................... 1
Documentation
Numbering Conventions .................................... 3
Updates ............................................................. 3
Dynamic Host Configuration Protocol
(DCHP) ............................................................ 11
E
Ethernet Card ..........................................................12
Ethernet Controller ....................................................9
Ethernet Crossover Cable ...................................7, 14
Ethernet Driver
Accessing the Packet Buffer ............................35
NIC Initialization ...............................................34
Packet Analysis ...............................................38
Packet Reception .............................................36
Packet Transmission .......................................40
Ethernet Hardware ..................................................29
Ethernet ID ................................................................9
Ethernet Interface ...................................................27
Ethernet MAC Address ...........................................35
F
Firmware ................................................8, 10, 23, 65
Source Code ....................................................63
H
Hooking Up the Board .............................................13
Host Computer Requirements ................................12
Hypertext Transfer Protocol (HTTP) .......................51
I
Internet Control Message Protocol (ICMP) .............47
Internet Protocol (IP) ...............................................46
Internet Solutions CD ........................................10, 71
Contents ..........................................................71
Iosoft, Ltd ......................................................ii, 10, 71
L
LCD Display ........................................................9, 65
LCD Driver
LCD Characters ...............................................43
LCD Data Transfers .........................................41
LCD Initial iz ati on ..............................................42
LCD Interface ..........................................................32
LEDs
LINK Status ........................................................9
Rev 4 vs Rev 5 and Later .........................65
Status .................................................................9
User-Defined ......................................................9
Limitations on Networking .......................................11
LiveDevices .......................................................10, 71
Loading the Web Page ...........................................25
Index
PICDEM.netTM User’s Guide
DS39563A-page 74 2001 Microchip Technology Inc.
M
Media Access and Control Address
(MAC) ..........................................................9, 59
Memory
EEPROM .....................................................8, 23
MCU Program Memory ....................................23
Microchip Internet Web Site ......................................4
Conne cti vi ty Solutions Web page ....................10
Microcontroller Interface ..........................................31
Microcontroller Socket ...............................................8
MPLAB ICD Develo pm ent Sys tem ..........................26
N
Network Interface Controller (NIC) ..........................29
Initialization ......................................................34
O
Obtaining Host IP Address
Wind ows 95 .....................................................15
Wind ows 98 and NT ........................................16
Other Hardware Drivers
Analog Inputs ...................................................43
P
PIC16F877 ................................................................8
PIC18C452 ...............................................................8
PIC18F452 ................................................................8
PICDEM.net Board Schematics ..............................69
Ethernet Transceiver .......................................70
Main Board ......................................................69
PICDEM.net Demonstration Board ...........................8
PICDEM.net Demonstration Kit .................................7
PIDEM.net Configuration ........................................58
Address Configurati on .....................................59
Web Page Download .......................................60
Potentiometers, User-d efin ed ...................................9
Prototype Area ..........................................................9
Push Button
Reset .................................................................9
User-Defined ......................................................9
R
Recomm ended Reading ...........................................3
Reconfiguring PICDEM.net
Clearing the Controller Firmware .....................26
Configuration Mode ..........................................24
Firmware ..........................................................23
Hardware .........................................................23
Loading a Web Page .......................................26
Network C onfi gu rati on .....................................24
Web Page ........................................................25
Revision Level Indicator ......................................9, 65
S
Serial Port ...............................................................13
Star Topology ..........................................................27
T
TCP/IP Lean: Web Servers for
Embedded System (book) ...............................10
TCP/IP Lean: Web Servers for
Embedded Systems (book) ..............................27
Transmission Control Protocol (TCP) .....................48
Troubleshooting
Comm uni ca tio n s Iss ue s .............................66, 67
LCD Display .....................................................65
Link LED ..........................................................65
Serial Port
Serial Port .................................................67
System LED .....................................................65
U
User Interface
Dynamic Web Pages .......................................54
LCD Display .....................................................58
Navigation Frame .............................................56
Status Display Frame .......................................55
W
WWW Address ..........................................................4
Y
Yipee .................................................................10, 71
2001 Microchip Technology Inc. DS39563A-page 75
Index
NOTES:
Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by
update s. It i s your respo nsibilit y to en sure t hat you r app licatio n mee ts with y our sp ecifica tions. N o re presen tation or warra nty is given and n o liability is
assumed by M icroc hip Techno log y Incor porate d with respe ct t o the accuracy or u se of such infor mation, or infrin gemen t of patents or other in tellectua l
property rights arising from such use or otherwise. Use of Microchip’s products as critical components in life support systems is not authorized except with
express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, except as maybe explicitly expressed herein, under any intellec-
tual p roperty rights. The M icrochip logo an d name are reg istered tradema rks of Microchip Technolo gy Inc. in the U.S.A . and other countries. All rights
reserved. All other trademarks mentioned herein are the property of their respective companies.
DS39563A-page 76 2001 Microchip Technology Inc.
All rights reserved. © 2001 Microchip Technology Incorporated. Printed in the USA. 5/01 Printed on recycled paper.
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