CNC is just a hobby for me.  It grew out of a hobby of computer programming in Visual Basic, which led to Programmable Integrated Circuits ("PIC") with PIC Basic.  PIC lingo has the term "watchdog" also, but there it's called a "watchdog timer".  I suppose it has something to do with synchronization, but I have yet to have a problem that is solved by a "watchdog", so I know very little about it.

I do know how to capture a signal on a PIC pin.  It would be much easier if it was simply an on or off.

PIC from Microchip is great stuff! I use a whole range of them in automation. I like the 16bit ones. How is your electronic knowledge? I can help you with the chargepump decoupled signal, or there is a different version in the "download" section of art's website.

Whacko

I'm using a Microchip 16F877A.  I would say my electronics knowledge is as good as a Techenical College degree.  By decoupling the signal do you mean having a capacitor between the signal input and ground?

I didn't know there was a "decoupled signal" example in the downloads.

Yes, a capacitor arranged so that you have a charge pump circuit. Only a signal that changes rapidly will build up a charge good enough to switch a comparator. Inductive decoupling would be like a pulse transformer, again only a signal that changes state rapidly can cross the isolated barrier via magnetic flux variance in the transformer. You have to implement this through a current limiting resistor so that if the port state is active high, you will not damage the switching device, like a mosfet, or bipolar transistor.
The example in the download page is apparently good, but I have not used that one.

Whacko