On Mon, 14 Jul 2003, Bob Blick wrote:

> Hi Everyone,
>
> I'm trying to shrink my interrupt service routine on a 16F87x program that
> has multiple interrupt sources.
> In the service routine I have a test and a service routine for each of the
> three interrupt sources I have operating.

When the IE bits and IF bits are in the same bank then you can do
something like this:

     BTFSC   flags_reg, if_bit
      BTFSS  enable_reg, ie_bit
       goto  check_next_interrupt

If you had to check several of these split banked bits then you could do
something like this:

     MOVF    PIR1,W
     BSF     STATUS,RP0    ; switch banks
     ANDWF   PIE1,W        ;the individual IE and IF bits align
                           ;if both are high then the interrupt
                           ;is enabled and it's pending.
     MOVWF   int_temp1

     BTFSS   int_temp1,CCP1IF
      goto   check_next_interrupt

or if you want to just check CCP1, then do this:

     MOVF    PIR1,W
     BSF     STATUS,RP0    ; switch banks
     ANDWF   PIE1,W        ;
     ANDLW   1<<CCP1IF
     SKPNZ
      goto   check_next_interrupt

If you can afford to cache PIE1 in INDF then you could do this:

      BTFSC  PIR1,CCP1IF
       BTFSS INDF,CCP1IE     ; FSR = PIE1
        goto check_next

Other than that, I suppose the only other option is your state-driven
interrupt enabling code that you proposed.

Scott

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