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parallel port and 8255A PPI

Posted on 1998-11-23
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Last Modified: 2007-12-19
I'd like to know in a PC, how are the 8255A pins connected to the LPT's 25 D-connector pins. According what I know, 8255A PPI is the chip used to implment parallel port. Any detailed information about how the implementation is accomplished is welcomed.
Thank you!
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Question by:f22
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jhance earned 450 total points
ID: 1129586
The original IBM PC and PC-AT did not use an 8255 to implement the parallel port.  To save a few pennies, these were implemented using 74LS374 and 74LS174 latches for holding the outputs and 74LS244 and 74LS240 for reading inputs.  Believe it or not, I've got original users manuals for both the IBM PC and PC-AT and will be glad to scan the schematic for you if you need it.
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by:f22
ID: 1129587
Yes, may I have a copy of the manual?
Thank you very much!
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