EPROM emulator

[Stuart Bunning]

Sorry if this is a few days behind but I think it is worth mentioning anyway.
It's a bit long (sorry) but I really think this could be the best approach
for some of us anyway.

As mentioned below use a ALDL command to write to RAM/memcal. Well there
allready is a ALDL command to read from memory so maybe there is a
undocumented write command that allows to write to memory.

The factory may have??? used a development memcal with a s-ram chip on it
instead of eprom with a write line coming from somewhere else on the ECM ???

So maybe the micro code is allready there to do such a thing. and a custom
memcal re-write is not even needed. Out of a possible 253 ALDL commands I
have only heard of about 3 that actually do anything.

As I have been in the service dept of a company that imports electronic test
and measurment equipment for 10 years I have seen plenty of fancy
calibration devises that work on the standard product with a simple bridge
of two tracks and some serial commands that were otherwise listed as not
used. I have been amazed time and time again of what can be done if you know
how.

The programmers at GM are not dumb they think of these things when the
system was origionally designed to aid development and 99% of the time these
(back doors) are never deleted in the production code...

The big question is has one of this list or diyefi out there allready
decompiled the ALDL routine section of a 8192 ALDL ECM bin file to see if it
is or isn't implemented.

EFI DIRECT in AUSTRALIA allready do this with a simple 1 wire modification
and replaced the eprom with a battery backed s-ram on what they call a
development board. There is also a security device they have installed to
stop people like us copying there technique. But I bet by #$%% that is was
based on what the origional engineer used when the code was origionally written.

Now this may not help every GM EFI tinkerer but just maybe every one with
8192 ALDL ??

Think about it.
if you are serious about his email me off list
stuart at kenelec.com.au



>Instead, how about a board with RAM and logic that plugs between a
>MEMCAL and a P4 ECM - which uses the P4's CPU and ALDL commands to write
>to the RAM.  The MEMCAL doesn't get the processor R/~W signal, but I've
>come up with a jumperless solution using a medium sized EPLD.  Of
>course, any ALDL based design requires a custom code fragment in the
>EPROM.  This may reduce the usefulness of such a board.
>
>-- 
>Ludis Langens                               ludis (at) cruzers (dot) com
>Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
>
>

Stuart 
Australia
1 * 1988 VN Commodore Buick 3.8l V6 (Aussie GM Vehicle 808)
1 * 1976 Chrysler Charger 4.3l Hemi 6 with DELCO P4 808
1 * Bench ECU for testing and playing 808

Email: stuart at kenelec.com.au
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