Posted By
Crown
on 2005-09-29
06:50:09
|  Re: emulators bug
Standard kbd irq only puts $ff into $fd30 when it is doing a full scan, but before it does that, it checks if any button is pressed at all writing $00 into $fd30, and that's the state this particular program expects. Full scan is only performed if this particular check come back as any key being pressed.
When you are not touching the keyboard, the standard keyboard routine writes the following sequnce into $fd30 at every frame
$7f $7f $00
at every 5th frame it writes
$7f $7f $7f $7f $00
This is probably when it checkes for repeating keys...
The turbo assembler instuctions actually turns off the writing of the $7f $7f sequences, and the irq only writes $00 into $fd30 at every frame. Most likely it turns off keyboard repeating, I believe there is a zero page or low memory area variable where you can turn that off...
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