[Coco] real-time mouse cursor
robert.gault at worldnet.att.net
Sat Jan 26 20:57:30 EST 2008
Roger Taylor wrote:
> Hopefully others are paying attention to your tutes so they might can
> dive into something graphics intensive. I've known for ages most of
> what you're saying but the part about letting IRQ decide when to switch
> the screen and having the main code not accidentally get mixed up with
> the current state is something that carries a little bit of worry since
> IRQ can happen at any time during the main code execution, even if
> predictable at 60hz.
> I mostly use the following VSYNC subroutine in all of my screen updating
> VSYNC TST $FF02
> a@ TST $FF03
> BPL a@
That's the way to use the PIA interrupt but as time is crucial, I'd
suggest in-line code rather than a subroutine. That will remove the
cycles needed to BSR or JSR and RTS.
Are you writing for any Coco or just a Coco3? If the latter, you can
also use the GIME interrupts.
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