On Fri, 17 Oct 2003, Ken Pergola wrote:

> Hi Harold,
>
> How about something like this?:
>
> (Not the fastest and does not use DECFSZ, but can easily be expanded for
> multi-byte variables)
>
>
>
>
> LOOP_ITERATIONS EQU .257        ; # of loop iterations
>
>     ; *** LoopIteration = LOOP_ITERATIONS
>     MOVLW  high LOOP_ITERATIONS
>     MOVWF  LoopIteration_MSB
>
>     MOVLW  low LOOP_INTERATIONS
>     MOVWF  LoopIteration_LSB
>     ; ***
>
>
> Loop
>
>      ; { Your favorite loop action code goes here }
>
>
>      ; *** Decrement composite loop iteration variable by 1
>      ;     ( LoopIteration = LoopIteration - 1 )
>      DECF       LoopIteration_LSB, F
>      BTFSS      STATUS, C
>      DECF       LoopIteration_MSB, F

CAUTION: this only works on the 18F series (the midrange pics DECF
instruction does not disturb C).

Of course, a better approach is this:

beginning_of_loop:

     ; stuff

      decf    LoopIteration_LSB,F
      skpnz
       decfsz LoopIteration_MSB,F
        goto  beginning_of_loop

Or even better for the 18f series:

     dcfsnz   LoopIteration_LSB,F
       decfsz LoopIteration_MSB,F
        goto  beginning_of_loop

Scott

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