> > 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 <[email protected]> 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 [email protected] >
