GM PCM OBD-II HW registers

[Dave Hempstead]

Hi,
    Does anyone out there know about the OBD-II hardware interface
chips?  I'm interested in any register descriptions.  Does anyone know
what chip is used in the GM PCM's?  (I'm looking at a '96 right now).
I've got some data sheets on some Intel OBD-II chips, but I'd be
surprised if GM uses those.

Any  help would be greatly appreciated,
Dave Hempstead
dave_hempstead at agilent.com