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Topic: Why parallel port needs so many ground pins? Can just use one? (Read 833 times) previous topic - next topic

lightaiyee

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.

zoomkat

Quote
It wastes mechanical space.


It is what it is. Any single ground pin should work.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

majenko

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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KeithRB

It also allowed for signal grounds, chassis grounds and possibly differential pairs.

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