David Duffy (AVD) wrote:

So apparently you're using a PIC 16, or is this just badly written PIC 18
code?

>          movlw   .1              ;

Don't do that.  The ".1" if very misleading.  Yes I know it's legal, but
that doesn't make it a good idea.  Besides, 1 is the same in any number
base.

>          subwf   f1_tmr0,f       ;decrement the low byte
>          skpc                    ;did it borrow? (0->255)
>          subwf   f1_tmr1,f       ;yes, decrement the middle byte
>          skpc                    ;did it borrow? (0->255)
>          subwf   f1_tmr2,f       ;yes, decrement the high byte
>          movf    f1_tmr0,w       ;get low byte again
>          iorwf   f1_tmr1,w       ;ior the middle byte in
>          iorwf   f1_tmr2,w       ;ior the high byte in
>          skpz                    ;is it zero (all bytes zero)
>          goto    cnt_2           ;no, tick not due yet

SKPC is also misleading here.  In this case the carry flag is the not-borro=
w
flag.  The comment is right, but the choice of macro name could cause
confusion.  For example, I have macros SKIP_CARR, SKIP_NCARR, SKIP_BORR, an=
d
SKIP_NBORR for these purposes although they emit only two different
instructions.


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