4 Apr
1999
4 Apr
'99
6:28 p.m.
True. But AFAIK the AT keyboard host interface was
never implemented in
TTL (it always used a programmed 8042 microcontroller), so it's a little
harder to build from scratch.
If what you're trying to do is interface the AT keyboard to some custom
controller that doesn't need to be otherwise AT-compatible, there's no
reason why you need the 8042. The AT keyboard interface is not particularly
harder to implement than the XT interface was. I've written code for several
products that bit-banged it on a microcontroller.
The AT keyboard interface protocol is really a pathetic design, though. It's
a pain in the ass to deal with, and it's not well documented anywhere (even
in the otherwise excellent AT Technical Reference, now available as a
reprint from Annabooks).