P4 GM ECM using 68HC11

[Dale Ulan]

> 
> What cars was the P4 used in?  Is it in all the TPI camaros/firebirds?
> Thats the only GM ECM I've seen using a 27256.  It would be great to
> tear one of those down and figure it out.
> 
> Is the OEM code on ROM on the chip?  I know you can get 68hc11 mask
> programmed at motorolla, but considering there is an external 32k
> EPROM maybee they don't use that.

Masked programming is only done if you're making millions of the same
thing.
Most cars used the P4 ECM (post 1986). Older cars and most trucks (up to
about 1991) used the C3 which is very old...

Yes, the PROM contains code. About 20k worth of it. Have fun!!!

-Dale