9 Aug
2000
9 Aug
'00
7:33 p.m.
At 09:27 PM 8/9/00 -0400, Allison wrote:
Read up on parallel ports for PC first, the M8027 WILL
NOT be sufficient.
Most parallel ports ahve enough bidirectional lines and the 8bit data is
bidirectional (only the old XT ports aren't).
I have, and they are, _if_ they are CENTRONICs compatible. There are 11
output bits and 6 input bits. When you have such a port on your PC (and
even PC/AT and some 386 machines had them) you could use them in "nybble"
mode. In this mode four of the 8 data bits are outputs, Busy/SLCT/Paper
Out/Fault are inputs, strobe is "write nybble", ACK is "read nybble",
and
the upper four bits are used to control things like interface direction and
turn around. In this way a general 4 bit bi-directional interface is
created that can run and 400KBits/sec on some machines! (typically closer
to 300Kbits but still)
Ports that aren't Centronics compatible _really_ don't always work. However
I could also try it with a M7941.
--Chuck