Re: Marko's IRQ loader routine

From: Marko Mäkelä (
Date: 1998-12-29 11:14:33

On Mon, 28 Dec 1998, Ojala Pasi 'Albert' wrote:

> You could make a hack in the interrupt routine to check where the
> loader was interrupted (read the return address from the stack) and
> fix the A register value (in the stack), but that would take in the
> order of hundreds of cycles (100-200?) for each interrupt.

A better solution could be to disable interrupts right before the
lda $dd00 and enable them right after the sta $dd00.  If the interrupt
routine is timing-critical, you will need to have the interrupt triggered
earlier to get rid of the jitter.  If you're using raster interrupts, one
raster line should be enough.  Timer interrupts let you waste less cycles.


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