From: Ullrich von Bassewitz (uz_at_musoftware.de)
Date: 2003-08-23 20:49:21
On Sat, Aug 23, 2003 at 08:10:08PM +0200, Rainer Buchty wrote:
> If I recall correctly, the NMI is level driven like a latch not
> level-change triggered like a flip-flop. To prevent false triggers from
> the 6551, wouldn't it be possible to "lock" the NMI using the CIA's
> timer IRQ, then do the changes and finally release the timer IRQ?
Won't an ACIA NMI get lost in this case? Assume this order:
1. CIA NMI triggered
2. CIA NMI gets handled, but still stays active
3. ACIA NMI occurs, since /NMI is already active, nothing happens
4. CIA NMI released. /NMI still active (from ACIA), nothing happens
Regards
Uz
--
Ullrich von Bassewitz uz@musoftware.de
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