aijma@castle.ed.ac.uk (John Mather) (04/18/91)
Does anyone know anything about the protocols/speeds these things use? Are IIC microprocessors avaiable? and RAM? Any info at all would be greatly appreciated. Thanks, John.
stevem@specialix.co.uk (Steven Murray) (04/19/91)
aijma@castle.ed.ac.uk (John Mather) writes: >Does anyone know anything about the protocols/speeds these things use? >Are IIC microprocessors avaiable? and RAM? >Any info at all would be greatly appreciated. >Thanks, >John. You would certainly be best off getting some data from Philips themselves, there is a data book available from them that deals specifically with i2c. i2c has a 'fast' mode and a 'slow' mode. I personally have stuck to using their chips in 'Fast' mode at 100khz bit timing - that is 10us for each bit. The protocol is a little bit involved (buy the book :-) but basically there are two lines, SCL and SDA, both O.C. Normally the data is put on SDA and a positive going 5us pulse on SCL clocks it into the receiving device, however there is a special case when the SDA line changes while the SCL line is still high - this is the 'Start' and 'Stop' signal for each data transmission. The first byte of a tx is the address of the device on the bus you want to talk to, followed by (for memories, like RAMs) the address WITHIN the device, followed by (Basically) the data transfer. You can implement i2c master communications on just about any microprocessor with a couple of bidirectional I/O pins, but Philips make a whole range of micro's that include hardware on the chip to make life a little easier. They also publish appl. note describing drivers. I have used the 87C751, (2k PROM, 64by RAM) and the 87C552 (8k PROM and 256 bytes RAM). i2c drivers programs are unfortunately not trivial, but the chips sure are dinky. You were after a RAM - the PCF8570 is a 256 x 8 ram in an 8 pin DIP. I have no connection with Philips other than being an addicted customer. Some other people make i2c chips too. Regards, Steven Murray -- Steven Murray uunet!slxsys!stevem stevem@specialix.co.uk I am speaking, but | If these are your opinions, then we are in agreement!! not for my employer.| Flames, spelling errors, complaints > /dev/null
rtm1@thumper..bellcore.com (Ravi Masand) (04/19/91)
In article <9647@castle.ed.ac.uk> aijma@castle.ed.ac.uk (John Mather) writes: >Does anyone know anything about the protocols/speeds these things use? >Are IIC microprocessors avaiable? and RAM? >Any info at all would be greatly appreciated. >Thanks, >John. I2C is a serial protocol implemented by a bunch of Philips/Signetics devices. Signetics has (used to have ?) a data book exclusively for I2C devices. Specifications for the protocol however, were in their microprocessor data book. Yes, they do have I2C microprocessors. About RAMS - i don't know. Ravi Masand
sze@enel.ucalgary.ca (Peter Sze) (04/22/91)
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