Old ALDL Synchronous format

[Oliver Scholz]

Hi all

Someone a bit ago requested the information on the old GM ALDL
That was probably me...

synchronous data format.  Here is what I know about it:

>      ; The total frame length is 19 data bytes (?).

This is not necessarily true. I have an ECM that transmits 20 bytes and
one that transmits 25 bytes per frame.

>      ; A/D conversion values based on 256 counts = 5.000 volts (not 255 
>      counts!)

But multiplying by 0.2V is close enough ;-)

The newer ECM uses 8192 Baud as the basic format, *but* it still sends
frames of constant length (as opposed to later ECMs which send
variable length frames with checksums). Does anyone have any details of
those?

Best regards,

-Oliver