From: Groepaz (groepaz_at_gmx.net)
Date: 2005-11-28 07:51:08
On Monday 28 November 2005 00:02, Ullrich von Bassewitz wrote:
> After lots of try&error I noticed that this piece of code prevents the
> driver from working. It seems as if reading register $d03f doesn't give the
> last value written to it. Typing in ?PEEK(53311) from BASIC proves this: It
> prints 255. Can this really be true? There's a similar issue with the
> register bank: There's no way to read the old setting. How are subroutines
> or drivers supposed to work if they cannot read and save the old settings
> before changing anything?
mmmh i have seen that kinda behaviour before (might have been on the gameboy
or then NES....dont remember :=P). it can (must) be handled by maintaining a
shadow-register "manually"....as in
.macro pokeD03F
sei
sta shadow
sta $d03f
cli
.endmacro
.macro peekD03F
lda shadow
.endmacro
mmmh that said, i think the original action replay hardware has a simelar
problem too :)
--
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<Steve Wright>
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