L297 / L298 Help Required Pls!

Hello All (Sorry for the post without subject ... Half a sleep today!)

Could someone please explain how to connect a L297 / L298 Stepper
driver to the PC parallel port?

The parallel port send Step / Direction info. Hi/Low signals ... on
two pins.

What I don't understand is how this works and where the GND / + side
comes from the PC.

Additional info ....

I have three stepper cards that control X ,Y, Z axis of a mill.
When I use a logic probe on the card connectors I find the step pin is
high by default (from the stepper card). When I turn the jog button
this flashes the Grn (low) led on the probe then returns to high
(red) and the stepper motor turns.
This is running on an old machine that would be sent information in
blocks at a time via an rs232 port.

I am attempting to bypass this logic and go direct to the cards via a
PC printer port.

TIA
Steve