EPROM emulator

[Andrew K. Mattei]

Bruce Plecan wrote:
> 
> I thinks we may be over the $50, so just one depending on price for CSH, HQ,
> but with the staff we got here might have to get a spare, anyway.

Looking at the design I have in mind (seems like we have quite a few
differing ideas :) ), I added up the raw costs, and it fell out at
~$150. :( Most of that ($90) was for the NVRAM I had in mind. (128k x 8)
Dallas Semiconductor DS1245Y/AB. About $45/each from Newark. They grow
on trees around here where I work (that's why I had them in mind ;^D),
but for a "buy in" part, that's too expensive.

Here's how "my" parts list broke out:

(2) DS1245Y/AB 128kx8 NVSRAMs: $90
(1) 17C742 Microchip PIC: $21 (I think that's the part number; from
DigiKey)
(12) 74HC245 Tri-state octal bus: $12
(1) 74HC125 Tri-state quad bus: $1
(1) Printed circuit board: $25 (?)
(misc stuff): a few more $ ;)

So, I know I need to take some cost out of this. I like the idea of the
one-wire "emulator", but am not quite sure about it - can it be done on
a 165 or 730? Can you really change operating parameters with only the
components available in the over the counter ECM? (I notice that there
are definitely "open" IC spots). I'm currently working with two
different cars - my '94 LT1 (which I know can be changed with one wire),
and my '89 L98 - which has the removable EPROM that I'd be building this
emulator for. I have no intent of messing with the LT1 memory at this
point.

So, any suggestions on removing cost? Flash may be cheaper, but take
some of the flexibility out of this. Any thoughts?

Thanks!

-Andrew