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Question & Answer
Classification:
Date: Apr 20, 1999
PC - XS40/XS95/XSP Parallel Port Interface
Q:
The normal way to comunicate with the XS board is via the Parallel Port. D0..D7 can be sent from the pc to the xs board. Now my question, is it possible to invert the direction and read D0-D7 from the PC? if I configure my Partallel Port as an ECP/EPP shouldn't this be posssible.
A:
This is possible for the upper six data bits if you have a bidirectional parallel port (almost all current PCs do). But the lower two bits pass through a 74LS14 inverter which will always drive the FPGA/CPLD pins regardless of the state of the parallel port.