Also, for servo systems, an uncontrolled e-stop is downright unsafe. I made a custom 1800IPM gantry system for a client this year using a National Instruments motion card, servomotors and Gecko G340 drivers. Controlled motion on e-stop and soft limit events were a requirement. Suddenly stopping the pulse stream resulted in a drive error/shut-down allowing the carriage to freewheel and do (more) damage. (I wrote my own g-code CAM software in LabView for this project - - a far cry from Mach in features but not bad, I think).
Ok so your typical home-build machine doesn’t do 1800IPM. But the speeds are getting to the point where controlled stops are going to be an important requirement (especially w/ the G100).
I think most controll the motion on e-stops and limits by using enable pins to fault or disable the drives.
I don't know if the index pulse of an encoder could be used as a home switch. I would think it would be possible with some VB codeing, not sure though.
I'm not certain if the encoder dros are consistent across an e-stop. I wouldn't think so. Maybe someone else will reply with this info.
Brett