Re: MOnSter 6502

From: Segher Boessenkool <*segher_at_kernel.crashing.org*> Date: Mon, 30 May 2016 10:18:48 -0500 Message-ID: <20160530151848.GA31938@gate.crashing.org> · segher_at_kernel.crashing.org

On Mon, May 30, 2016 at 04:52:23PM +0200, Gerrit Heitsch wrote:
> >   -- T2
> >   DL -> ADL -> ABL
> >   00 -> ADH -> ABH
> >   (this does a dummy read from the zp)
> >   X  -> SB  -> ADD
> >   DL -> ADL -> ADD
> >   compute the sum
> >
> >   -- T3
> >   ADD -> ADL -> ABL
> >   (and this now reads the correct address)
> >
> >   -- T0
> >   (fetch the first byte of the next instruction)
> >   DL -> DB -> SB -> AC
> >   (set flags NZ from DB)
> 
> T0 doesn't quite fit...  Shouldn't
> DL -> DB -> SB -> AC
> 
> be part of T3 or am I missing something?

No, it then would store the result of the dummy read to the accumulator.
The result of a read is available to the *next* cycle.

Segher

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