Let's call it IC "C" for brevity.
I was sort of hoping for a cross reference with possibly a datasheet. But I've traced everything out except 6 pins that have vias underneath the chip. I'm leaning towards this being SPI because it has four lines direct to the cpu pins 22 (miso), 23 (mosi), 24 (sck) and 31 (pa3 - assuming device select).
It appears to have 40 general purpose i/o pins, 12 are used as outputs and I've traced the other 27 back to sources, verified, etc. The inputs labeled feedback I assume are for open circuit detection. I'll continue to work on pin 10, but here's where I think most of these registers map to in (what I assume is) ram.
It took a while to confirm $6446-$6449 because when messing with inputs, outputs become affected i.e. closing either door switch causes the courtesy lights to turn on. Likewise, when commanding outputs, some of the feedback pins change state as well.Code:inputs: register bit:
8 ign3 (e4) 8
9 ign1 (e5) 7
10 unknown (via under chip) 6
11 park lights on (d14) 5
12 disarm utd (d15) 4
13 r door sw (d16) 3
14 l door sw (c12) 2
15 key in sw (c11) 1 $6449
16 hatch sw (c10) 8
17 unlock ckt (c5) 7
18 lock ckt (c4) 6
19 arm utd (c3) 5
20 defrost req (d5) 4
21 diag mode (d6) 3
22 unused (d7) 2
23 oil float sw (f8) 1 $6448
24 turn flasher (f9) 8
25 seat belt sw (f10) 7
26 hi beam (f15) 6
27 unused (e14) 5
28 m clock feedback 4
29 data strobe feedback 3
30 data clock feedback 2
31 lcd data feedback 1 $6447
32 lcd blanking feedback 8
33 courtesy lamp feedback 7
34 defog control feedback 6
35 horn feedback 5
outputs:
36 low oil lamp (d13) 4
37 courtesy lamps (d12) 3
38 lcd blanking (d11) 2
39 rear defog (d10) 1 $6446
40 horn (c16) 8
41 chime 2 (c15) 7
42 chime 1 (c14) 6
43 seat belt lamp (c13) 5
44 check gauges lamp (c9) 4
45 change oil lamp (c8) 3
46 door ajar lamp (c7) 2
47 security lamp (c6) 1 $????
To jump straight to the chase, I don't think the reman pin is coming in this ic. The only input not accounted for is VSS, which I believe is handled by the cpu.
I know quite a bit more but will only give generalizations now. All 8 adc inputs to the cpu seem to be accounted for. There's an unused one that would connect to E8 if the components were present. I think this is to accomodate another light sensor for a DRL option that I believe was only sold in Canada. The LCD outputs are all driven directly by the cpu pins PA4-PA7.
The other PLCC52 chip labeled 'delco 16126532' which I'll refer to as ic "B" appears to handle all the PWM outputs, but that's about all I've had a chance to trace down. My guess is that it does use shared ram due to the number of lines it shares with the uveprom and what I believe is a dram chip labeled 'delco 16089396'.