SKPNC is a synonym for BTFSC STATUS,C

MPASM recognizes a bunch of such special mnemonics in an attempt to make
code clearer.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

----- Original Message -----
From: Sam Linder <SamL@IN-INC.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, September 18, 2000 6:11 PM
Subject: Re: [PIC]: usec delay routine


> Where does "skpnc" come from? It's not part of the Mid-Range Instruction
> Set.
>
>
>
> -----Original Message-----
> From: Scott Dattalo [mailto:scott@DATTALO.COM]
> Sent: Friday, September 15, 2000 12:24 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: usec delay routine
>
>
> On Fri, 15 Sep 2000, Sam Linder wrote:
>
> > unsigned char delayU, delayL;   // C code
> > #asm
> > Delay10bit              // delay is 10 bit value + 7 cycles ( + call +
> > return, if any)
> >     incf    _delayU,f   // correct for dec & test instead of test & dec
> > Dly10bLoop:
> >     comf    _delayL,w   // invert LSBs
> >     decfsz  _delayU,f
> >     goto    Dly10bLoop  // coarse delay to closest 4 cycles
> >     andlw   3
> >
> >     // this additional code checks for the
> >     // page boundary and sets pclath correctly
> >     // ****
> >     movwf   _delayL
> >     movlw   low offset
> >     addwf   _delayL
> >     movlw   high offset
> >     btfsc   status,C
> >     addlw   1
> >     movwf   pclath
> >     movf    _delayL,w
> >     // ****
> >
> >     addwf   pcl,f
> > offset:
> >     nop
> >     nop
> >     nop
> >     return
> > #endasm
>
>
> It's little more efficient to do this:
>
>
>
>
> > unsigned char delayU, delayL;   // C code
> > #asm
> > Delay10bit              // delay is 10 bit value + 7 cycles ( + call +
> > return, if any)
> >     incf    _delayU,f   // correct for dec & test instead of test & dec
> > Dly10bLoop:
> >     comf    _delayL,w   // invert LSBs
> >     decfsz  _delayU,f
> >     goto    Dly10bLoop  // coarse delay to closest 4 cycles
> >     andlw   3
>
>       addlw   offset
>       skpnc
>        incf   pclath,f
>
>       movwf   pcl
> offset:
>
> >     nop
> >     nop
> >     nop
> >     return
> > #endasm
>
>
> Looks like 3 more cycles than the original
>
> Scott
>
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