Additional 68HC11 Registers?

[Roger Heflin]

On Mon, 14 Sep 1998, Ludis Langens wrote:

> Don't expect a GM ECM to have _any_ of the 'HC11 memory mapped I/O
> registers.  The same goes for the "6801" based C3 ECMs - they don't have
> any of the standard 6801 I/O.
> 
> While we're on the subject of HC11's which aren't HC11's, has anyone
> found any GM code which uses the XGDX or XGDY opcodes?
> 

Yeah, GM could easily have had motorola make a custom 68HC11 with who knows 
what options different.  I would guess that if the registers would work
for GM as they were they would use them that way.  I would expect GM to have
requested some to be added to their custom chip.

I found both the XGDX and XGDY opcodes in my prom.  My prom is a 93 Z28 A4
prom.  What does that instruction do?

			Roger