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Old 14th Jul 2019, 10:49 am   #170
NealCrook
Triode
 
Join Date: May 2019
Location: Reading, Berkshire, UK.
Posts: 18
Default Re: Gemini 80-Bus System

Just for grins I considered the effect of a d0/d1 short on my test loop. The only opcodes that have d0/=d1 are

21 Id hl xxxx
7e ld a (hl)

7e could turn into 7f (ld a,a) or 7c (ld l,h)
21 could turn into 20 (jr nz xx) or 23 (inc hl) but in either case would mess with the program flow.

I'm kind of intrigued because the code did seem to be looping and the in instruction should have been uncorrupted so I still don't understand why no /iorq.

Neal
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