Problem with ASM IRQ using FSR0 on PIC18F252

[Darrel Taylor]

Hey Michael,

This doesn't really explain your problem, but in this section...

; save the FSR value because it gets changed below
    movf       Low FSR0, W
    movwf      fsave
    movf       High FSR0, W
    movwf      fsave+1

It's really just saving address 00 instead of saving the contents of the FSR0 registers. (FE9 and FEA)

The symbol FSR0 equates to 0x0h. It's for use with LFSR etc.

I believe it should be like this.

; save the FSR value because it gets changed below
    movf       FSR0L, W
    movwf      fsave
    movf       FSR0H, W
    movwf      fsave+1

It's the same again when trying to restore it.

HTH,
   Darrel