RE: mmu for 65c02

From: Baltissen, GJPAA (Ruud) (
Date: 2005-04-22 09:03:25

Hallo Gabor,

> STA $C023
> ...
> So CPU will get "STA $0000" to execute!
> ...
> It can be solved anyway. In case of fault, a FlipFlop ....

Unfortunately this solution won't work with a 6510. OK, I know, you will be
using a 65C02 but I can imagine that  one day you want to port it to a C64,
C128 etc. and that's why I think it is worth to mention this at least.

Hallo Jim,

> Uh oh, as now .A is corrupt, and there is no way to reset it.

So what, the CPU was tresspassing anyway. I don't think that particular
process will be allowed to continue anyway and therefore the return address,
flags and other saved registers will be erased. So no harm is done and
therefore your solution is not needed IMHO.

Hallo Gideon,

> That same FF should also disable writes to the flags. Actually,
> the FF should disable any change to the internal state of the CPU.

Eh, I must have missed something because I have no idea how such FF can
interfere with the internals of a CPU. See the above remark about the 6510
and my comment on Jims statement. 

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