Posted By
siz
on 2022-03-12
06:09:48
|  Re: MemBankP4/cc65: demo prg won't load data to expansion RAM
I tried to read your code but it's pretty hard due to forum formatting. And a lot of symbols are referenced but I can only guess what they mean. What _can_ be a problem though is that you write values 2 and 3 to $fd16 which is ... how to put it... not recommended. For the Csory expansion the upper two bits select the 16k address space of the CPU you want to see the expansion memory window selected by the lower 4 bits.
So if you set it to 2 or 3 it will replace the memory from $0000-$3fff which contains the zero page and the stack and that can cause problems. (and perhaps your own code gets mapped out which is also not that good).
If you insist on using the Csory expansion I would recommend using $4000-$7fff or $8000-$bfff address spaces as your window (the latter only when ROM is switched off).
Be aware of two things:
1) Csory RAM expansion is controlled by a MOS 6529B IC meaning it's default value is $ff
2) I'm pretty sure that NONE of the emulators handle Csory expansion correctly. And I'm not aware of anyone having a computer with original Csory expansion to test it. (although TLC built one several years ago for himself) But if your intended audience is yourself using VICE then good luck.
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