Suggested Pin for VFD Error Input

Hello.
Is there a standard/typical/nominal Hal pin for a VFD error input? I don't really want to add it to estop because my motors would loose position. Is there a standard pin for this like "ah, stop everything now, somethings not right, but don't let the motors go limp".

I don't think so, but what you want to achieve depends greatly how your hardware is connected, and what hardware do you have.

You can connect the error so that you request a feedhold, that is probably the most simple approach, or if your hardware allows it, you can place your machine in "stop program" and disable your drives (if your drives have an enable/disable mode, that do not loose position).
I think that there are many other possibility's to your problem.

For the hardware, I've got an I/O pin which will go low if there is any fault with the VFD. I don't want the motors to be disabled, because if the fault occurs during a rapid move, the motors will coast to an uncontrolled stop. At that point, they will be out of position.

Not specifically. I connected the fault signal from my VFDs to "motion.enable". But it may or may not do exactly what your asking of it. (I don't know if it stops, then places the machine in off, or if it just goes strait to off)

in pre linuxcnc 2.6:

motion.feed-hold
careful because it can be masked by mcode.

in 2.6+

motion.feed-inhibit
motion.spindle-inhibit

these are non maskable, but feed-inhibit will wait till the end of a spindle synch move, so I think adding the spindle inhibit would cover that.

adding a message would be a nice touch too.

Chris M