Debouncing; What is it and what is used for? Well, if you ever looked at the current through (or the voltage across) a mechanical switch or a relay as it was changing states you would notice that the transition is not always a nice, clean step function. Often there are several changes before the switch makes its transition. In this case, the switch is said to be "bouncing". However, the same behavior can be observed in dirty switches or switches that are switching a heavy load.
Debouncing routines sample the switch's state at a fairly high rate. When a change in the state is detected, the routine will count anywhere from 1 to whatever the debounce number is set to. Mach samples to make sure the transition was not a glitch and that the switch has settled to its new state. The higher the number the longer it waits to verify that the switch has indeed been triggered and is not just noise from servo,spindle, etc.
As hood pointed out "debounce interval" I believe applies to every input except the spindle sensor (index debounce). The spindle sensor is used for rigid tapping, motor speed control, and turning and css on a lathe.
Chad