Re: VIC-registers
Date: 1998-02-25 19:51:32

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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