[Coco] ASM Coders - Round two!
lost at l-w.ca
Tue Aug 29 12:54:47 EDT 2006
David Roper wrote:
> *lda #$33
> *sta $FFA4 CLRSCRN ldy #HSCLEN
Now you're swapping out the interrupt handlers that the BASIC ROM uses.
$FFA4 maps $8000-$9FFF which is the Extended Basic ROM area. ECB has an
IRQ handler so within 1/60 second an interrupt fires, the service
routine isn't there anymore, and things go wonky (that's a technical
term, BTW :) )
What you'll need to do is disable interrupts around the entire section
of code that is clearing the screen if you want to map the entire screen
into the logical address space at once.
If you're looking to do things without using the BASIC ROMs, you may
want to look into writing your own IRQ service routine but simply
disabling interrupts should be sufficient for now.
finger lost at l-w.net for further information
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