Re: IRQ/video counter problem

[jmk3@crux2.cit.cornell.edu (Jay Krell)]

I don't know what is wrong with your program but something to
definitely watch out for when using the video counters is that
(the) fact that you might never see certains values.
Heartbeat (VBL) interrupts trigger at line 192. You are not likely
to ever see 192-??? (depends on how many heartbeat tasks and
how long they take.)

Interrupts would not mess with the video counters. Be sure to
access them 8-bits at a time (unless you know what the next location
is, it might be safe. The video counters are two neighboring bytes,
aren't they.) And using the video counters would not mess up interrupts.
(I forget which you asked.) Also, be sure that cmp #$xx is only
8-bit if the accumulator is 8-bits then. That is an easy way
to get a brk instruction in your code.
 
 J