Just out of curiosity, if you're using an 18C (or 17C) part,
why wouldn't you use the CPFSEQ, CPFSLT, or CPFSGT
mnemonics?


Ryan



> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Scott Dattalo
> Sent: Wednesday, September 29, 1999 6:30 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: More snippets
>
>
> Let's see how the 18cxxx parts compare
>
> On Tue, 28 Sep 1999, Tony Nixon wrote:
>
> > Just following on from the previous snippets,
> in an effort to make
> > comparisons easier to understand, here are some
> more. The best part is,
> > the Z flag is ignored.
> >
> > if RAMx > RAMy
> >
> > movf RAMy,w
> > sublw 0xFF
> > addwf RAMx,w
> > btfsc status,carry
> > goto true
>
>   movf  RAMx,w  ;wreg = RAMx
>   subwf RAMy,w  ;wreg = RAMy - RAMx
>   bn    true    ;Branch if negative
>                 ;The N bit will be cleared if
> RAMx == RAMy or
>                 ;RAMy > RAMx, and will be set if
> RAMy < RAMx
>
> (or you could use the bnc [branch if no carry] to
> achieve the same effect.
> The negative bit has a clearer meaning in this context).
>
> 18cxxx 3*16 = 48 bits of program memory
> 16cxxx 5*14 = 70 bits of program memory
>
>
> btw, Tony's example can be shortened to:
>
>   movf  RAMx,w
>   subwf RAMy,w
>   skpc
>    goto true
>
> but there are still 4*14 = 52 bits. however this
> works on the 12bit core,
> so only 4*12 = 48 bits of program memory are
> required there.
>
>
> >
> > if RAMx < RAMy
> >
> > movf RAMx,w
> > sublw 0xFF
> > addwf RAMy,w
> > btfsc status,carry
> > goto true
> >
>
>   Same as above with RAMx and RAMy exchanged.
>
> > if RAMx >= RAMy
> >
> > movf RAMx,w
> > sublw 0xFF
> > addwf RAMy,w
> > btfss status,carry
> > goto true
> >
>
>   movf  RAMy,w    ;wreg = RAMy
>   subwf RAMx,w    ;wreg = RAMx - RAMy
>   bnn   true      ;branch if not negative
>                   ;The N bit will be cleared if
> RAMx == RAMy or
>                   ;RAMx > RAMy, and will be set
> if RAMy < RAMx
>
> Again, you could use the bc (branch on carry)
> instruction too. Also,
> Tony's sequence can be reduced by an instruction.
>
> > if RAMx <= RAMy
> >
> > movf RAMy,w
> > sublw 0xFF
> > addwf RAMx,w
> > btfss status,carry
> > goto true
>
>
>
> Scott