On Wed, 26 Apr 2000, Laurens Holst wrote:
> The IM mode 2 is used very often on MSX (though not
> supported by any hardware). A lot of programs running
> in the Basic memory-layout (with BIOS on page 0), but
> still wanting to have their own interrupt routines use
> IM 2 to achieve that.
I don't think IM2 is used that often. For example, I used it only once.
And what Daniel Caetano said about analysing incoming IM1/IM2 instructions
will probably work. I'm not sure yet if it is possible to simulate the
"always #FF" behaviour that most MSXes have, but at least it can get the
vector from somewhere in the I*#100..I*#100+#FF range, so any well-written
IM2 program will work.
> The problem with I/O registers is also unsolvable,
> remapping or any other trick won't work because the
> problem is INSIDE the processor. The only solution is
> to debug the programs not working, and there are just
> too much.
The internal I/O ports take up #40 port numbers. There are very few MSX I/O
devices that use ports in the range #00..#3F. So I don't think there will
be that many programs not working. You can try to convince me otherwise by
naming the programs and the reasons they need to do I/O in the #00..#3F
range...
Bye,
Maarten
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