Re: ParPort output low - hi-Z or ground?

Hmm, for some reason I don't get any of the file commands in the
files area. I've uploaded both versions of the optoisolation scheme
to the Electronics_101 files area - A3977 Stepper folder. Thats
where the schematic for my stepper controller is anyway. Have to
change that to incorporate the optos (currently has 74245s) and add
the EStop relays.

Do the parallel port inputs have internal pullup resistors when
they're high? Logically, I can't see them NOT having resistors, how
would anyone manage to pull them low without burning the port pin?
Then again, I'm no EE 8). As you can see on the drawing, I've just
run the port pin through the transistor side of the opto and
directly to ground. If I put a resistor in there, would I not just
keep the voltage on the input high?

Oh and thanks for the 3.3 volt tip. I checked mine and the outputs
are 3.3v while the input high is a full 5v. Had to adjust the led
resistors (7mA just ain't enough).