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Topic: Why parallel port needs so many ground pins? Can just use one? (Read 826 times) previous topic - next topic


I am using the parallel port connector DB25. I am surprised the parallel port has so many ground pins. Why so many ground pins (pins 18 to 25)? It wastes mechanical space.

As I am using a breadboard, can I just tie one pin to ground instead of all the pins? Hate spiderwebs.


It wastes mechanical space.

It is what it is. Any single ground pin should work.
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It stems from the days when a parallel printer cable was a ribbon cable.  Using IDC connections (Insulation Displacement Connection) the ground signals line alternately in between the signal connections providing a measure of shielding and cross-talk protection.

As the parallel port has evolved over the years some of the ground connections have been re-appropriated to other uses, but all the remaining ground connections have remained for backwards compatability.
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It also allowed for signal grounds, chassis grounds and possibly differential pairs.

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