Hi Rolf,

I believe that the context saving is not right in your code. You likely to
overwrite Z flag, however, I can't see any section of your code that would
use the zero flag so it might not be the case.

Tamas



;------------------------------------------------------------------------------
> ; INTERRUPT SERVICE ROUTINE
>
> ;------------------------------------------------------------------------------
>
> INT_VECTOR    CODE    0x0004  ; interrupt vector location
>        MOVWF   W_TEMP        ; save off current W register contents
>        MOVF    STATUS,w      ; move status register into W register
>        MOVWF   STATUS_TEMP   ; save off contents of STATUS register
>
>
Should be:

INT_VECTOR    CODE    0x0004  ; interrupt vector location
       MOVWF   W_TEMP        ; save off current W register contents
       SWAPF    STATUS,w      ; move status register into W register
       MOVWF   STATUS_TEMP   ; save off contents of STATUS register


i_end
>
>        MOVF    STATUS_TEMP,w ; retrieve copy of STATUS register
>        MOVWF   STATUS        ; restore pre-isr STATUS register contents
>        SWAPF   W_TEMP,f
>        SWAPF   W_TEMP,w      ; restore pre-isr W register contents
>        RETFIE                ; return from interrupt
>

Should be:

i_end

       SWAPF    STATUS_TEMP,w ; retrieve copy of STATUS register
       MOVWF   STATUS        ; restore pre-isr STATUS register contents
       SWAPF   W_TEMP,f
       SWAPF   W_TEMP,w      ; restore pre-isr W register contents
       RETFIE                ; return from interrupt

Tamas


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