Eprom Emulator

[Andrew K. Mattei]

Well, I did a little more thinking, and some price lookup, and I think the
Dual Port SRAM (from IDT or Cypress) puts us over our price target. I priced
the IDT chips at between $39 and $45 each.

OK, new thought (for me). Standard SRAM. From DigiKey. $6.75 for a 1 Mbit
32-pin DIP. Still need all the buffer IC's I mentioned earlier (at least 12
74245's and one 74125). Use Flash (1 Mbit = $8.55) as the "semi-permanent"
program storage (that the computer will use by default when the key is
turned "on"). One PIC, still, with a bunch (35?) of outputs, RS232 input,
and flash memory for the program.

OK, here's a question. Where does the ECM store the parameters that it
"learns"? Is that in some sort of low-power RAM, that's maintained after the
car is turned "off" (I know that they are retained)? How would those react
to a sudden change in program without power cycling the ECM? Just curious...

By using the above IC's, we can get the cost under $50, and can run a
standard, stock program in the Flash.

Any thoughts, ideas, or flames?

-Andrew