Nigel Goodwin

Well for a start you've chosen a PIC antique to compare it with, that was obselete last century! - it was replaced by the cheaper, higher spec, 16F628 in the 1990's. However, people (rather stupidly) keep using it, so MicroChip appear to have reintroduced it at an inflated price - which can only be good for their profits.

The Scenix chips are pretty obscure, and have never managed any sort of market penetration, but may well be perfectly fine for your purposes?. However, do the Parallax chips include hardware I2C interfaces, which are really essential for I2C slave operation (the 16F84A doesn't either, but there are plenty of more modern PIC's that do).

I would suggest you don't get 'hung up' on MIPS, from the looks of your requirements high MIPS are of no use to you - and I would suggest all you need is small modern PIC's with internal 4 or 8MHz oscillators, and I2C hardware.

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justDIY

the 84 is an ancient chip, hence the high price

check out the 16F884 ... 4k, 35 IO pins, hardware I2C (or spi) port, flexible onboard clock generator (32khz-8mhz), roughly $2.50

mips aren't everything. 20 mips is hardly "slow" - speed comes from efficient programming, relying on instructions per second is just a crutch for sloppy code.

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Sceadwian

The chip runs at 75MIPS. Not the basic that's run on it.... Even 1MIPS is incredibly powerful if you have hardware level access.

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oeginc

Who codes in Basic? Assembly language all the way baby!

This is very good to know, the 16F884 sounds like it's right up my alley, I'll take another look at the Microchips and see what I can find. There are just SOOOOoo many choices it's mind boggling sometimes. I want to Keep It Super Simple.

Also, forgive me for being ignorant, but why does the i2c interface need to be hardware driven for slave applications? Scenix provides software i2c source code for "authentic i2c master/slave interface" HERE

WVProfessor

"you can do reasonably well emulating i2c timing with a software uart, but why bother when Microchip has a Philips certified I2C Master/slave interface built right into the chip."

I have a PIC16F88 and some folks are telling me that the only way to use it as an I2C master (controlling a 24LC512) is to write code that controls the pins individually (called bit banging I believe). I have such code already but it ties up the microprocessor. I need to know if it is possible to use the internal hardware to impliment an I2C master, in particular how the pic88 hardware sees the ack signal from the slave.

I am writing my code in assembly language because that is all that I know (for working with the pics).
I already wrote code (with much assistance) that uses the usart hardware to talk to the serial port. That part of the project is finished.

monkeybiter

small point from a pedant; 16f84 runs up to 20MHz, that's 5mips on a pic.
for your simple applications, the faster the processor the more times it will perform delay loops.