aldl codes

[Lou Faustini]

      I have worked on the ALDL serial data stream. There are two "flavors" 
of GM data streams. On later models the data rate is 8192 baud. This is the 
only data stream I have worked with. The earlier stuff worked at approx 166 
baud (-I think-). I never actually cracked either data format. I can tell 
you hardware wise you will need a level-shifter/inverter to interface to the 
PC. I used a MAX233 serial line driver. You can program the 8250 UART in the 
PC to get close enough to 8192 baud to work without errors. You will have to 
program the 16-bit divisor in the 8250 with port-IO commands. If its not too 
much trouble, please let me know if you get anywhere on decoding the GM data 
stream. 

                                  ------- Lou