Hallo allemaal, > > at $d02f and a 2MHz mode/test mode selection register at $d030. The $d030 > > register must be initialized with $fc for normal operation. Also, I've > > understood that the SuperCPU accelerator card misuses these addresses for > > something. > > To the best of my knowledge, SCPU uses $D07x, $D0Bx, and $D200-$D3FF and > nothing else. > > -Steve Thanks for the info you all. It seems that somebody already used "my" idea :-( The next is for the sound gurus amongst you: what happens if you write something to a read-only register? (I hope to hear 'nothing') Good question which can cause a lot of trouble for my design and the SCPU: You can disable the I/O area and select the CHARROM or RAM in its place. You can write to RAM of course. What happens with the SCPU if you write to $D07X ???? If the SCPU emulates the 6510-port as well, then it is save. In my case writing to $D031 puts the 6510 in DMA-mode. The question is how many and what kind of PRGs use the RAM under the I/O area; If there are too many or they are too important (like GEOS) then I can forget this idea :-( So if anybody else has another idea of creating an extra I/O area not using IO1 and IO2 and wants to share it with me, (s)he is welcome. Groetjes, Ruud
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