A newbie question ... I have the X & Y running fine. But I'm trying to get my Z axis control circuit working in a "2.5" configuration. Given my stepper output board layout, it would be a lot easier if I could map the 2.5D output, normally set up "6" to another pin. Say 15. Is there a way to do this in Mach 3? Or am I locked into pin 6 for the Z axis control? Thx ...

You can map any signal to any pin.  Just go to Config->Ports & Pins.

Regards,
Ray L.

If you are using the LPT1 port, then you can't use pin 15  which is an input and cannot be changed to output. The other outputs are 1,14,16 and 17.

If you are using some configurable input/output board, then yes.