Whoops!, forgot about testing for 00 XX XX before
decrementing HIGH....

;
; 24 bit decrement Version 2
;
;                               ; test 1     test2
;                               ;            underflow from zero
;
        MOVF    HIGH,W          ; FF FF 01   00 00 00
        IORWF   MID,W           ; *** added ***
        SKPNZ                   ;
        DECF    HIGH,F          ; skip       FF 00 00
        MOVF    MID,W           ;
        SKPNZ                   ;
        DECF    MID,F           ; skip       FF FF 00
        DECF    LOW,F           ; FF FF 00   FF FF FF

;       8 cycles, uses W,
;

Ray Gardiner ray@hdc.com.au