9 Feb
2025
9 Feb
'25
7:27 p.m.
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"
Thanks for the clarification. Had forgotten about all that.
On Sun, Feb 9, 2025 at 5:27 PM Fred Cisin via cctalk <cctalk(a)classiccmp.org>
wrote:
> 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
>