6 Apr
2010
6 Apr
'10
12:55 p.m.
... pulled out my notes from 2004: I had scoped the
lines from the 6520 to the
'145 1-of-10 decoder, the observed 4-bit scan sequence driving the 145 is
09ABCDEF0 rather than 0->9, so only 2 lines instead of 10 on one side of the
Hat it been 89ABCDEF8989ABCDEF... I would have guessed that the D input
was stuck highm possibly due to a defect in the PIA or a bad connection
(the PIA is socketed IIRC). Are you sure it's not this sequence?
keyboard matrix are being scanned.
-tony