On Wed, 30 Jun 1999, Bill Sudbrink wrote:
> I also looked at the MPU-A. Sure enough, on the 16 pin header
> to the front panel, pins 1-8 are connected to pins D0-D7 on
> the 8080, in order (pin1-D0, pin2-D1, etc). They also go a
> bunch of other places I have not tried to figure out yet.
Actually, (working from memory) they should go to the 8212 latch which
then will feed thru to the CPU chip. Might go another place or two as
well, but I'm not in front of a schematic either...
> It's
> probably just going to the data lines on the S-100 connector.
Not directly... (IIRC)
> Given the C3 instruction, I don't see why everything goes so
> wacky when I reverse the header.
Given the 'C3' by itself, there would be no effect, but if you consider
that the entire three byte jump sequence is jammed onto the CPU thru the
cable (inst/hi addr/lo addr) ((watch, I probably got the byte sequence
backwards and will get flamed)) it gets real interesting when the bytes
are assembled and the jump executed...
-jim
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Received on Wed Jun 30 1999 - 16:24:45 BST