14 Jan
1999
14 Jan
'99
11:57 p.m.
I can't remember how the Apple ][ centronics card
does it. I remember 8
outputs. I can't remember if that was 8 data bits and a strobe in
hardware or 7 data bits and a software strobe (remember that 7 bits are
enough for text characters). The busy input actually fiddled with the
ROM addresses on the card, so the Apple executed different instructions
when the printer became ready. Neat!.
Depends on the Card - some Cards used 6522 devices and here the
(programmable) handshake functionality of the 6522 was used. Some
cards had dedicated logic for unidirectional paralell output and
did the generation via a monoflop.
Gruss
H.
--
Ich denke, also bin ich, also gut
HRK