home *** CD-ROM | disk | FTP | other *** search
- Path: sparky!uunet!olivea!hal.com!darkstar.UCSC.EDU!cats.ucsc.edu!chonky
- From: chonky@cats.ucsc.edu (J. R. `Bob' Matthew)
- Newsgroups: comp.sys.apple2
- Subject: IRQ/video counter problem
- Message-ID: <1k2endINNjck@darkstar.UCSC.EDU>
- Date: 26 Jan 93 04:29:33 GMT
- Organization: University of California, Santa Cruz
- Lines: 29
- NNTP-Posting-Host: am.ucsc.edu
-
-
- cal info request:
-
- Is there any known problem with leaving irqs enabled while
- accessing the vertical or horizontal video counters ($e0/c02e,c02f)?
-
- I have written a custom irq handler (patching e1/0010... yes, bad
- practice, please no gs/os comapability flames) in order to play music
- with a program that uses stack-based animation. Well, the animation
- works fine, but problems arise when I try to synch it. This works:
-
- (irqs are enabled)
- ]lp ldal $e0c019
- bmi ]lp
-
- This doesn't work (it crashes after getting to the irq handler, which
- messes with various softswitches, but doesn't touch video counters):
-
- ]lp ldal $e0c02e
- cmp #$d8 (example)
- bne ]lp
-
- So, does anyone know if accessing the video counters temporarily changes
- something internal that could muck up the way irqs function?
-
- Thanks for any response,
-
- -arekusu
- ace@deeptht.armory.com
-