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Message
From: H. Peter Anvin<hpa@z...>
Date: Tue Dec 13 19:02:36 CET 2005
Subject: [oc] T80 bugfix for INI, IND, INIR, INDR, OUTI, OUTD, OTIR, OTDR
Guy Hutchison wrote:
> Hi Peter,
>
> We spoke a while back, and you mentioned the JR bug recently on the
> list. I had a little time today to look in to it, and was wondering
> if you could elaborate on what the bug is.
>
> According to the Z80 handbook, the cycle timing for a JR operation is
> 4/3 if the test fails, and 4/3/5 if the test passes. This matches the
> mcycle coding in the microcode as well as the results I see in
> simulation.
>
> Could you (re)summarize the problem for me?
>
Sorry... didn't see the message until now.
The problem is that if the test passes, the timing is 10 cycles
(presumably 4/3/3, like JP.)
-hpa
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