Nascom 2 keyboard connector
ard at p850ug1.demon.co.uk
Sat Jun 4 16:30:18 CDT 2005
> My Nascom is almost impossible to get to at the moment, can you remind me
> as to what chips are on the keyboard? I am going to guess at at least one
> TTL decoder chip, and maybe not a lot else.
I've had a look at the NAS-SYS 3 source listing. I mamnaged to find the
keyboard scanning routine, and it would appear that the keyboard
incorporates a hardware scan counter. It's reset by one of the Q outputs
(Q1, I think) and incremented by one of the others (Q0?). The keyboard
row lines are read in on the bottom 7 of the D inputs. What the D7 input
is used for (shift???) and what the other 2 Q outputs do is something
I've not worked out yet.
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