The G214 needs both GND and +5V to operate all the signals of its interface.
You can use PCgnd and PC+5V from the J1, J2, J3, and J4 terminal strips of
the PMDX-126 for this purpose.
The ENABLE input of the G214 will allow the drive to run when there is no
connection. When you want to "freewheel" the motor, you can either tie the
ENABLE input to PCgnd or use a logic signal to drive it low. The outputs on J5
or J6 are suitable for this function.
The RESET input is similar to the ENABLE input, but it will also reset the
microstep counters to the same state as initial power up.
The FAULT output is a totem pole output. This means that you will
need to add a diode in series before you can combine the signal
from several drives into the one ERR input on the PMDX-126.
Each diode should have its cathode connected to the FAULT signal
of the G214 drive. All of the anodes could connect together and to
the ERR- on J13 of the PMDX-126.
The ERR+ from J13 of the PMDX-126 should connect to the PC+5
on J5 or J6 of the PMDX-126.
The return path will be through the G214's OptoIsolator Ground
that is already connected to PCgnd on the PMDX-126.
The diodes can be any switching diode rated for 5 volts or more.