Saving variable(s) contents before power is removed

[Acetronics2]

The PIC16F628 has voltage comparators that can cause an interrupt. In the schematic the programmable reference is compared against a division of the input voltage. If input power falls dangerously low then an interrupt is generated.

I do not see a way of monitoring supply voltage with out using a pin.

Good luck!

Hi, Ron

Good analysis ...

you can even avoid using a comparator input, as the Schmitt trigger inputs High/Low thresolds of the pic are quite precise ( you can use pin polling instead of interrupts ).
If no comparator available, you also can use a To 92 case MC 33064 P5 or equivalent which will drive its output pin LOW for voltage < 4.65 v.

Alain