Taken from the Turbocnc manual (hope this is ok).
On the parallel port, pins 2-9 are always available for output, which allows at least 4 axes of motion to be controlled. Pins 1,14,16, and 17 can be output also, to control spindles, coolant pumps, and tool changers.
The parallel port inputs are on pins 10,11,12,13, and 15. These are TTL level signals as well. Typical uses for these are spindle encoders, limit switches, and extra logic for detecting when youíve run out of stock.
Pins 18-25 are ground. Use some of these to shield your cables.
Hope it helps,