True, but unidirectional parallel ports can't read the data lines at all.
The question is not full vs. half duplex, but whether we can read 8 bits at
a time at all. In fact, bidirectional parallel ports are still half duplex,
but they have the ability to tristate the data lines by hooking them to +5V
across a 4.7K resistor, then the other end of the connection can pull them
down to 0V to read a 0 or leave them at +5 to read a 1, and you can read the
input in the feedback register. If you don't put the resistor there, it
will still probably work as a bidirectional port, but could pass dangerously
high currents through the signal wires.
===
Evan Jeffrey
erjeffre@artsci.wustl.edu
Let us go. Let us leave this festering hell hole. Let us think the
unthinkable, let us do the undoable. Let us prepare to grapple with the
ineffable itself, and see if we may not eff it after all.
--Dirk Gently