that's what i found in the gali pluging Manual:
The Galil PlugIn is capable of using a probe for various probing
functions. This is accomplished using the Galil high speed position
latch functions. Unfortunately, the latch inputs share general purpose
inputs on the Galil ICM. Galil axes A, B, C, and D use inputs 1, 2, 3,
and 4 and Galil axes E, F, G, and H use inputs 9, 10, 11, and 12 for the
latch inputs.
IMPORTANT!!!! A probe should be wired to ALL latch inputs for any
moving axis on your machine! For example, if you have a 3 axis mill
and you are using Galil axes A, B, and C to drive them, then the probe’s
output should be wired to inputs 1, 2, and 3. This is because the G31
probe command will move in all 3 dimensions. If you have 3 axis mill
with a 4th axis rotary driven from Galil axes A, B, C, and D, then the
probe’s output should be wired to inputs 1, 2, 3, and 4.
When setting up Mach for probing, it is imperative that the “Probe”
signal is enabled in “Ports and Pin” on the “Input Signals” tab and the
port and pin should be mapped to one of the Galil latch input pins. For
example, if your 3 axis mill uses Galil axes A, B, and C to drive Mach
axes X, Y, and Z, then the probe’s output signal should be wired to Galil
inputs 1, 2, and 3 and the Mach Probe signal should be enabled and
mapped to port 1, and one of pins 25, 26, or 27. Which pin is mapped
really does not matter since all of the inputs will be active upon a probe
hit.