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NMOS HMOS 6502 accuracy #2
Description
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.
Activity
miniupnp commentedon Nov 23, 2019
I'm not sure about the Ricoh 2A03/2A07 of the NES
redcode commentedon 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 commentedon Nov 23, 2019
regarding the differences between the different 6502 versions, do you plan to add different modes for the emulator ?
redcode commentedon Nov 23, 2019
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 commentedon 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.