The attached helped but - - I can get the if block to work but my switch simply falls through

Is it possible to use a string for the switch function?

Thought:
Such a simple idea, but it would be nice to incorporate either automatic or manual file backups.

Did we resolve this?

Maybe an easier method would be to simply connect a dual optical isolator via resistor directly to the micro controller transformer on the secondary ac side. Your open collector outputs will switch at every zero crossing.
That signal is connected to the hardware interrupt which services the routine ...

See below

Did this get sorted?

Martin! Thank you... Happy New Year.

Using PIC18f27q10. FC11
I have two interrupts. One is a hardware input interrupt. The other is a timer0 interrupt. I believe that priorities are settable but requires a few c code register adjustments such as (maybe):
IPR0bits.INT0IP = 1; // High priority
IPR0bits.TMR0IP = 0; // Low priority
I don't ...

Thank you. I think I have selected the correct register number for the osc? Maybe not? I have attached my file

If the system timing is correct at 20mhz, would that not indicate internal oscillator to be correct?