[Coco] DAC sound output and keyboard input

[Mark McDougall]

Hi Gurus,

I have a strange problem and I'm not sure whether it is an issue with my 
code, the Coco, or MESS.

If I configure the Coco3 for DAC sound output, occasionally I get incorrect 
results when reading the keyboard to detect if *ANY* key is pressed (ie, the 
column select is zero (0) which ordinarily would return the results for all 
rows). In some cases - and there's seemingly no pattern to it - bit 7 is 
reset, indicating a key has been depressed in that column. And once on, it 
is stuck on. It also *seems* to happen more often when I use <F10> (toggle 
throttle) in MESS, which suggests that it's perhaps an emulation problem).

This *only* happens when I use the DAC for sound output. It has *never* 
happened when using 1-bit sound output or no sound output at all.

Any ideas? I can post the relevant code snippets if required.

TIA
Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"