From: Gideon Zweijtzer (gideonz_at_dds.nl)
Date: 2005-04-22 06:58:26
> Gábor Lénárt wrote:
>
> >
> >It can be solved anyway. In case of fault, a FlipFlop (FF for short)
> >should be set. Any further memory operation (either
> read/write) should
> >be ignore by the MMU if that FF is set! In this way, we isolates CPU
> >from the memory after a fault, to be sure that it will not corrupt a
> >bogus memory locaton. The only task left is to clear that FF
> after the
> >opcode when the NMI taken, as fault handler.
> >
> >
> It gets worse. The opcode in question could have updated an internal
> register:
>
> $67ff and #$10
>
> 67ff (and) gets pulled.
>
> $6800 is page fault, so force 0. Uh oh, as now .A is
> corrupt, and there
> is no way to reset it.
>
That same FF should also disable writes to the flags. Actually, the FF
should disable any change to the internal state of the CPU.
Gideon
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