Diagnostics

[Peter Gargano]

Swayze wrote:
> 
> a post not too long ago in regards to axxc.s bin on incoming, discussion by
> John Gwynne in regards to NVRAM on '730 and ALDL Mode11. wish I had more
> details, but should be in the archives.

Yep, seen that! That is (becoming) a standard way to change 
tables that exist in NVRAM, and is used by John, Kalmaker, 
myself, etc. The ALDL command(s) modify data table, or if you 
like, they modify the calibration data, not the code.

What I was really after was information on factory diagnostics
that are downloaded into the ECU - into the small RAM area
between 0 .. 1FF, and are then executed there. These are not
tables, but are 68xx instructions that are loaded from a PC's
(or other diagnostic tool) disk (or cartridge) etc. Note that
I'm only inferring the existence of these diagnostic bits of 
code from the fact that I've disassembled ALDL commands that
set up RAM with ALDL data (well, code actually) and jump there
to execute it.

I wouldn't be surprised if no-one has seen these diagnostics, 
but GM put that code in (some) ECUs for a reason...

Peter
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