GM Serial Data

[Tom Hussey]

There is a gap between messages. This is what the UART uses to
synchronize on. When the line goes low there are circuits inside the
UART that oversample the signal to de-glitch it. Once the start bit is
recognized that starts a state machine that samples the rest of the
bits. Half way through each bit it is sampled and shifted in. There is a
good description in most UART manuals. As I remember the PC uart is an
8250 intel or you can look up the one inside the 68HC11 from data sheets
available at mot.com.

-Tom

Ross Myers wrote:
> 
> Hi All,
> 
> So it is that GM uses 8192baud, 1Stop & no Parity for Comms on later
> PCM's.
> If I am looking at a data stream of this, how can I pick out the start
> and
> stop bits from a data capture?. I've scanned the net for info on
> serial
> comms but to no avail.
> 
> Thanks
> 
> Ross Myers