>All my examples seem a little bit more obvious
>in their intentions than the example from the docs,
>although they're certainly helpful.
None of them (including the one from the SCTECH file) would work,
because the timing isn't right. It would have to be like
LDX #$3f
CMP $F000,X
NOP
CMP $F77B
that would have the same timing as
LDX #$3f
CMP $F000,X
CMP ($80),Y
if the pointer at $80 plus the contend of Y is $F77B. That way both
addressing modes are possible. Instead of CMP you can use any
intruction, that allows theese addressing modes, since only the
accesses at the two addresses are important.
CMP $F03F
NOP
CMP $F77B
would also be possible, but not as flexible, since LDX in the above
example could also read from a variable.
>Is there a good reason to make the instructions even
>less comprehensible? Is it necessary?
It is not necessary, but an easy way to manipulate bits. For example,
if you don't clear the RAM in your program, $80 contains the control
byte of the current load. That way
LDX $80
CMP $F002
CMP $FFF8
would enable SC writing by setting the RAM bit.
LDX $80
CMP $F000
CMP $FFF8
would disable writing by clearing the RAM bit. (No NOPs needed for
writes to the control byte at $FFF8)
>Another question - what's the point in being able
>to power up/down the Supercharger's ROM? It's not
>like extra RAM is available if the ROM is powered
>down... is there some other effect I don't know
>about - some side effect of having it enabled
>that would make you want to disable it?
I'm not sure about this one, but I think someone mentioned that
the ROM chip in the SC gets very hot, if it is powered up.
Therefore it might be better, to turn it off, when you don't need it,
to avoid, that it gets damaged, when it is on for too long.
Ciao, Eckhard Stolberg
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