I wrote:


>Andy:
>
>Opps. I should have said a test case of 0x00FFxx where xx is anything
>but 00. Using 0x00FF01 and your outline:
>
>                        ;HI MD LO
>                        ;
>                        ;00 FF 01
>        DECF    HI      ;FF FF 01
>        DECF    MID     ;FF FE 01
>        DECF    LO      ;FF FE 00
>
>        INCFSZ  LO,W    ;FF FE 00    W = 01
>        INCF    MID     ;FF FF FF    MID = 0xFF, so far so good.
>
>        INCFSZ  MID,W   ;FF FF FF    W = 00, thinks overflow occured.
>        INCF    HI      ;01 FF FF    result off by 0x010000 now.
>
>Chip

I messed up the last few lines, I seem to be a bit tired today:
        INCFSZ LO,W    ; FF FE 00    W = 01
        INCF   MID     ; FF FF 00    (I mess-up last byte.)
        INCFSZ MID,W   ; FF FF 00    W = 00, so thinks overflow
occurred.
        INCF   HI      ; FF FF 00    This instruction is skipped.
The results are off by 0x010000, but in the other direction. Sorry about
any confusion.

Chip.