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NMOS HMOS 6502 accuracy #2

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miniupnp opened this issue Nov 23, 2019 · 5 comments
Open

NMOS HMOS 6502 accuracy #2

miniupnp opened this issue Nov 23, 2019 · 5 comments

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@miniupnp
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ASL, INC and possibly other read/write instructions do two writes on an original 6502.
They first write the original value, then the modified one.
The CMOS 65C02 behave differently.

That can cause issues when working on memory mapped I/O, such as what is done on the C64.

@miniupnp
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I'm not sure about the Ricoh 2A03/2A07 of the NES

@redcode
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redcode commented Nov 23, 2019

Thanks, I've made several changes on the emulator since last version, I'll upload them to a new branch soon. I'm checking all instructions, memory access and cycles too.

@miniupnp
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regarding the differences between the different 6502 versions, do you plan to add different modes for the emulator ?

@redcode
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redcode commented Nov 23, 2019

regarding the differences between the different 6502 versions, do you plan to add different modes for the emulator ?

Yes, of course. I'm working on my NES emu, and I want to use this core for other machines too. I'll add support for the undocumented opcodes and for other 6502 models.

@redcode
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redcode commented Nov 23, 2019

I've uploaded my most recent code to the branch WIP (it uses the "v0.1" branch of Z). I'll release a new version of this core in January 2020.

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