29 Sep
2009
29 Sep
'09
4:02 p.m.
Hi Sean,
I've got the tech ref and have the pages handy. I've been staring at
the NMI keyboard handler, but I can't figure out what the machine might
be doing that would cause keyboard handling to fail.
If NMI is the highest priority, then nothing about decoding the keyboard
should fail except for the keyboard sending out bad bits. The call to
INT 0x48 will still be done under the NMI interrupt, so nothing else can
interrupt it and hose it.
So the big question is, given the NMI setup, how can keyboard decoding
ever fail due to something else the system might be trying to do? All
other INTS are suppressed.
The fact that I'm messing with a timer that it is not even using (0)
bothers me even more .. Same code with the standard clock tick rate
from timer 0 works just fine with the keyboard. Change
the clock rate,
and the keyboard goes nuts (can't decode anything) and the
system
becomes unstable. Lock the keyboard out with the faster rate, and
everything is golden.
Still have your Jr?
Mike