Path: utzoo!attcan!uunet!husc6!bloom-beacon!mit-hermes.ai.mit.edu!jpexg
From: jpexg@mit-hermes.ai.mit.edu.AI.MIT.EDU (John Purbrick)
Newsgroups: comp.sys.atari.st
Subject: Timer interrupts
Keywords: Bombs, Megamax
Message-ID: <3012@mit-hermes.ai.mit.edu.AI.MIT.EDU>
Date: 13 Jun 88 03:55:25 GMT
Organization: MIT AI Lab, Cambridge, MA
Lines: 12

I've got a program where I want to get interrupts at a fairly high frequency,
up to 1 KHz (the interrupt won't do much, so there should be time for it).
Megamax, bless them, included an example of how to do this in the Laser C
instruction book, and I copied and ran it. It interrupts at 48Hz, and works
perfectly. Unfortunately, that's the ONLY frequency it runs at. The timer
chip has various pre-divider rates (anywhere up to divide-by-200), but any
division less then 200 (the largest, therefore the slowest) causes a crash.
Then you can specify a starting point for the count-to-256 counter that
actually generates the interrupt, but if that's set to anything > 0 (0 means
count the full 256) again a crash. Is my problem with Megamax's specific
code (which seems straightforward enough) or is it that the ST simply can't
generate faster interrupts? Help would be much appreciated.