6 Apr
2006
6 Apr
'06
12:16 a.m.
I remember when I put the BBII together being told,
on the subject of
interfacing an ASCII keyboard, that Apple-type keyboards (and clones of
them) would specifically _not_ work because they set the high bit. Dunno if
this hardware you're looking at expects that or if it's even a consideration
at all, but figured it would't hurt to mention it.
According to the Apple ][ manual, the keyboard outputs a _7_ bit code
(makes sense, ASCII is 7 bits, after all). These are read in as the low 7
bits of an input port. The 8th bit (MSH) is the latched version of the
keyboard strobe, and is set if a key has been pressed. The strobe is
cleared by referencing another I/O location.
Surely if you want to use such a keyboard with a machine that reads 8
data bits from the keyboard, all you have to do is tie the 8th input low.
-tony