Rochester, 20 April 2006.

First of all, if at all possible, avoid using the 16F84A. I believe the
16F88 has I2C built in (though using built-in I2C isn't necessarily simpler
than bit-banging I2C, it certainly is faster once the program is done, as
you can process other things while bytes are received/sent).

However, if you do want to use it, I'm sure the piclist.com website contains
various implementations of I2C. And if that is not enough, you could go to
my website, http://jen.mosha.net/PIC/ which, under "Drake 2" as a link to
base.asm. This base.asm contains all sorts of functions, some of which start
with I2C or EROM. I know that this is for the 16F628A, but the 16F628A is
very similar to the 16F84A, and porting the code should give no problems. A
more recent version of these files is available on sourceforge as
http://sourceforge.net/projects/drake-devkit which also contains the Drake 3
code, for the 16F877A, which shows how you can use the built in peripheral
(though the 16F88 peripheral might not work the same as that of the 16F877A:
I have the 16F88 but never tried to use the built-in I2C functonality).

All these implementations are in absolute mode assembly, so you might want
to make them relocatable. They do have a lot of comments.

The routines support random write, random read and sequential read. If you
also want sequential write, you might want to look at the Drake 4 project,
which is for the 16F688. These are basically the same routines, but I made
some minor modifications to allow sequential writes. Note that most memory
chips don't allow sequential writes outside of a page (256-byte boundary).
Another thing to be aware of is that the Drake 2/3 routines allow reading of
the internal EEPROM using the same routines, you might want to delete this
code (this internal EEPROM is referred to as IROM).

Greetings,
Maarten Hofman.
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