GM ECM IO

[peter paul fenske]

Hi GUYs (and gals) sori
Been playing with IO on 730 ECM. Well there is this monstrous
block of IO from about 3FC0 to 401F. Trying to untangle this
mess is interesting.
In the 730 the GMP-4 communicates with the ECU directly.
This is probably some of the IO. Also via a High Speed internal
serial buss with the A.D and FMD. This explains some
of the two byte io instructions. The one around 3FFC and 3FFA seem
to be of this order. The high byte is the serial address and
the low byte the data. FB1A means don't use backup. FB12 means
use backup. Stuff like that.
There appear to be general Io from 4000H to 4007.
4001 to 4004 appear to be simple outputs. Things like PN switch ect.
4007 has multiple commands. Could be stepper control for all I know.
All the interchanges around 3FCX seem to be counter timers.
A/D around 3FEA with A/D control at 3FDA???????
Now comes the clincher. I am not sure but I am beginning to 
suspect the low ram of the co-processor the ECU is mapped into
the IO of the GMP-4. By alternating E clocks such an arrangement
could be possible.
Anyways If someone wants to tell me I am on drugs I would
appreciate the criticism. Also if someone wished to reveal
this fudge caramel puzzle well please.
Tnx all: peter
PS yes still working at it.