Author: Vincent Himpe
E-mail: Vincent.himpe@ping.be
Last-modified: 08 Jul 1995
Version: 1.3
Archive-name: I2C-BUS-FAQ
My signature:
--------------------------------------------------------------
Vincent Himpe
/////
Internet: O *)
vincent.himpe@ping.be /
vi_himpe@mietec.be \__/
Fido:
2:291/1912.8
You can visit my Homepages: http://www.ping.be/~ping0751
God has put me on earth to do a certain number of things.
Right now I'm so far behind I'll probably never die.
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"Extracted from The I2CFaq (c) Vincent Himpe. Posted in SCI.ELECTRONICS"
Some sections have been re-arranged or partially re-written. Some new sections give an address list and roadmap to I2C devices (which is not complete for the moment. Only Philips devices are incorporated. More to come in the next release).
[filipg - the next paragraph does NOT apply to THIS HTML version of this FAQ. This version comes in ONE part]
Furthermore the FAQ has been split into 2 pieces. This is due to the fact that some Usenet tools have problems accessing files larger then 64Kbyte. (Current FAQ is over 75 Kbytes long).
There is also a Q&A section and troubleshooting guide. These two are based on questions I got from people who start to use the bus.
I get lots of replies from people that want to know if this faq has been archived yet. Well it hasn't. I have two problems here.
The 'hull' of this FAQ was taken from the 8051-FAQ by Russ Hersh. Also check out that one. It's a great lead for people interested in I2C. Lot's of 8051 clones have an I2C controller on board. Hope its useful to you guys and girls out there.
Keep those replies coming
Regards,
Vincent
English is not my natural language but I guess you figured that one out already.
You can contact me:
By e-mail: Internet : Vincent.himpe@ping.be (preferred)
vi_himpe@mietec.be
Fido : 2:291/1912.8
By Snail-Mail: Vincent Himpe
A.De Taeyelaan 12
8792 Desselgem
Belgium
If you are a manufacturer and have an anonymous ftp site or BBS available that has information and/or tools for the I2C Bus please let me know by EMail so that I can add it to this FAQ. Also, please feel free to update me on new products.
comp.protocols.misc
sci.electronics
The schedule for posting will be once a month. I can't promise that it will be on time, but I hope to post it by the end of each month.
For this reason I have appended a copyright statement to the end of this FAQ. I feel pretty silly doing this, but I just want to protect myself. The copyright does not limit the use of this FAQ for non-commercial purposes. I hereby give my permission to one and all to pass this FAQ around and post it wherever you want - as long as it is not for financial gain.
You are allowed to distribute portions of the FAQ as long as you incorporate the following note:
"Taken from The I2C FAQ as posted in SCI.ELECTRONICS."
Thank you.
Subject: PIC microcontrollers
Newsgroups: comp.realtime
comp.robotics
sci.electronics
Maintainer: Tom Kellett
Tom@takdsign.demon.co.uk
Subject: 68hc11 microcontrollers
Newsgroups: comp.realtime
comp.robotics
sci.electronics
Archive: rtfm.mit.edu: <plus all mirror sites>
/pub/usenet/comp.answers/microcontroller-faq/68hc11
/pub/usenet/sci.answers/microcontroller-faq/68hc11
/pub/usenet/news.answers/microcontroller-faq/68hc11
Maintainer: Russ Hersch
Email: sibit@datasrv.co.il
Subject: Microcontroller primer and FAQ
Newsgroups: comp.sys.intel
comp.realtime
comp.robotics
sci.electronics
alt.comp.hardware.homebuilt
Archive: rtfm.mit.edu: <plus all mirror sites>
/pub/usenet/comp.answers/microcontroller-faq/primer
/pub/usenet/sci.answers/microcontroller-faq/primer
/pub/usenet/news.answers/microcontroller-faq/primer
Maintainer: Russ Hersch
Email: sibit@datasrv.co.il
Subject: Robotics
Newsgroups: comp.robotics
Maintainer: Kevin Dowling
(412)268-8830
Email: nivek@ri.cmu.edu
Smail: Carnegie Mellon University
The Robotics Institute
Pittsburgh, PA 15213
Subject: Electronics
Newsgroups: sci.electronics
Comments: There are a number of FAQs available in this newsgroup
on various subjects. Among some of the subjects covered
are: LCDs, stepper motors, etc
FAQ subject: Real-time
Newsgroups: comp.realtime
comp.answers
news.answers
Archive: rtfm.mit.edu: pub/usenet/comp.realtime
Maintainer: Mark Linimon
Lonesome Dove Computing Services
Roanoke, Virginia
Email: linimon@nominil.lonesome.com
Subject: Motorola 68K microprocessor line
Newsgroups: comp.sys.m68k
Archive: bode.ee.ualberta.ca : pub/motorola/general
ftp.luth.se : /pub/misc/motorola/faq
file name of archive is m68kfaq?.zip (? is version)
Maintainer: Robert Boys - Ontario, Canada
Email: r.boys@genie.geis.com
or
fboys@uoguelph.ca
Normal Computer systems use ByteWide buses to accomplish this task. This results in lots of copper tracks on PCB's to route the Address and datalines. Not to mention a bunch of address decoders and glue logic to connect everything. In mass production items such as TV-sets, VCR's and audio equipment this is not acceptable. Furthermore lots of control lines implies that the systems is more susceptible to disturbances by EMC and ESD. The research done by Philips Labs in Eindhoven (The Netherlands) resulted in a 2 wire communication bus called the I2C bus.
I2C is an acronym for Inter-IC bus. It's name literally explains it's purpose: to provide a communication link between Integrated Circuits.
Nowadays the extent of the bus goes much further than Audio and Video equipment. The bus is generally accepted in industry. Offspring like D2B and ACCESS bus find their ways into computer peripherals like keyboards, mice, printers, monitors, etc. The I2C BUs has been adopted by several leading chip manufacturers like Xicor, SGS-Thomson, Siemens, Intel, TI, Maxim, Atmel, and Analog Devices.
Every component hooked up to the bus has its own unique address whether it is a CPU, LCD driver, memory, or complex function chip. Each of these chips can act as a receiver and/or transmitter depending on it's functionality. Obviously an LCD driver is only a receiver, while a memory or I/O chip can both be transmitter and receiver. Furthermore there may be one or more BUS MASTER's.
The BUS MASTER is the chip issuing the commands on the BUS. In the I2C protocol specification it is stated that the IC that initiates a data transfer on the bus is considered the BUS MASTER. At that time all the others are regarded to as the BUS SLAVEs.
As mentioned before, the IC bus is a Multi-MASTER BUS. This means that more than one IC capable of initiating data transfer can be connected to it. As MASTERs are generally microcomputers let's take a look at a general 'inter-IC chat' on the bus.
Lets consider the following setup:
-------- ------------
| CPU |-----------o--------| I/O port |
-------- | ------------
|
| ------------
+--------| Memory |
------------
The CPU will issue a START condition (see further on for description of all these conditions) This acts as an 'ATTENTION' signal to all of the connected ic's. ALL IC's on the bus will listen to the bus for incoming data.
Then the CPU sends the address of the device