9 Feb
2025
9 Feb
'25
3:27 p.m.
On Sun, 9 Feb 2025, Steve Lewis via cctalk wrote:
BTW, every "DB25" connector in the PC world
I've
seen, it's got 8-pins for data. Even the UserPort in the Commodore world
has that - I've not commonly seen 4-data-pin parallel cables?
The stock IBM 5150 parallel port has 8 pins of data. BUT, that's 8 pins
of OUTPUT (plus 4 pins of handshake)
The "handshake" lines could be used as input, but not the data lines.
THAT is why you hear "only 4 pins of data input"
BUT, there is a trivial hardware modification that you can make to the IBM
5150 parallel port to make the 8 data pins usable as bi-directional.
(Many aftermarket parallel ports doo not need that nodification)
The need for that modificaation is WHY you keep hearing that the parallel
port only has four bits of input.
IFF you make a "Centronics" TO parallel port adapter (36 pin female blue
ribbon input to 25 pin DB25 male output with appropriate wiring in the
adapter, then it is possible to be able to take a machine that has
parallel [Centronics compatible] output, but no serial port, etc. (there
did used to be such!)
And tell it that it is connected to a printer. The PC would then need to
act as a "printer emulator", to take incoming data from the parallel port
and save it. I built such 30+ years ago, but I never got the software to
be adequate to make it a commercial product. Hardly anybody could even
uderstand what or why it was.
'course, you could accomplish the same task with an external parallel to
serial printer buffer, and come in through the serial port.
--
Grumpy Ol' Fred cisin(a)xenosoft.com