Posted By
Mad
on 2017-03-10
19:49:00
|  Re: Commodore Server .com -- Porting C64 code to Plus/4 code (V-1541)
I am not really sure, what to answer. The thing is, everything above $8000 (as far as I know) will lie under the rom. You can enable ram by sta $ff3f and enable rom by sta $ff3e (you can write any value there, to get it function). If ram is enabled you can not use the rom functions, as I know so far. Normally I would put any resident programm directly below $fd00, which is the highest memory without getting in trouble with the io area. However, if you place your programm there you have to enable ram to call any function of it. If your programm runs in an interrupt that should be an easy task. You can put the sta $ff3f and later sta $ff3e into the irq handler before calling your programm.
The ram/rom thingy is my assumption of what get wrong with your program [$c000 on C64 is ram]. If it's some other stuff, please write what is going wrong with the program. If you just want to test if it's working perhaps you could try to place it somehow below $8000 so there is no ram/rom problem. Just for testing.
So what exact is the problem? If it's just the memory area, then I would suggest taking an area directly below $fd00. But perhaps there are already some rules about this and other people do know some more..
btw: you could check the Ultimate Map for any plus/4 related details
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