Index pulse home

OK so I’ve searched  for a topic But didn’t find anything.
my set up is a two axis lathe running a 5I25 with 7I76. 
Connected to DMM servos Using Position command
my question is I want to be able to use the index pulse given by the servo driver as a home switch. However since I am not using encoders into LinuxCNC  I have not found a way to get Linux to recognize the Index pulse since I have no encoder tied to the axis.. 
DMM Drivers have the ability to output a open collector index Pulse that is completely isolated. 
I want  LinuxCNC to Home to the switch and then find the pulse just like it normally would with an encoder

Yes I was very concerned about the index pulse not being long enough to be detected on a normal input of the 7I76. I need to throw my Oscilloscope on it and measure it my hunch is it’s a standard index pluse.
I have one other option to achieve accurate homing on this machine. The DMM servos have the ability to return to absolute zero upon a command to a pin on the drives however I could never figure a way to actually work that into Linux. Because there can be no motion command a single pin would be activated and the drive themselves will home

So I tried my oscilloscope when I was home unfortunately the battery was dead so I pulled up HalScope.. and did not see the pulse. so my guess is it to fast for the input to see..
this leads to the second question is there a why to use the go home lead for the servo drive with linuxcnc

I not even sure how that would work because linuxcnc what's do to the motion and in this case the drive would be moving the servos to ABS-0

any thoughts?

One possibility is to use firmware that implements index on the stepgen.
You would need to access the other 5I25 connector for this (unless the encoder
inputs on the 7I76 are free) and LinuxCNC master.

All of the 7I76 encoders inputs are used. To expand on that topic. What if I got 7I85 and use that for the pluse input? Would it possible to just use the z input with out doing closed loop in LinuxCNC

Yes, you could use a 7I85 or 7I75 or a inexpensive parallel port BOB
Bare 5I25 inputs can also be used but you have to be careful and at the minimum
add a 220 Ohm series resistor to prevent overcurrent from negative inputs
damaging the ESD protection diodes on the 5I25 I/O pins

Ok so I was checking some more things on my drives and wiring and the type of output is not compatible. If I interpret the schematic correctly it’s looking for sourcing host side. I will put up the drawing. I think that the 7I85 is my best bet.  The Drive outputs 2  independent Z index one a individual open collector and the other a set of A B Z Emulated encoder output. 
I will need some guidance on how to just pick the index pulse from the encoder input and use it as a homing index.