> -----Original Message-----
> From: Olin Lathrop [SMTP:olin_piclist@EMBEDINC.COM]
> Sent: Wednesday, April 03, 2002 1:56 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [PIC]:16F873 PortC bit 5 revisited
>
> > >         bsf Portc,3             ;port C bit 5 low
> > >         bcf portc,3             ;so pulse bit 3 four times
> > >         bsf Portc,3
> > >         bcf portc,3
> > >         bsf Portc,3
> > >         bcf portc,3
> > >         bsf Portc,3
> > >         bcf portc,3
> > >         goto MAIN
> >
> > This sort of coding is not recommended in PICs.
> >
> > I think you are better off doing something like this, or keeping a
> > shadow register for portc.
> >
> > ; xxxx  = bits that are previously set or cleared.
> >
> >         movlw b'xxxx1xxx'       ; PORTC,3 = 1
> >         movwf PORTC
> >         movlw b'xxxx0xxx'       ; PORTC,3 = 0
> >         movwf PORTC
> >
> >         etc
>
> There is nothing wrong with successive BCF BSF as long as you understand
> the
> implications.  It is better to learn the issues than to blindly always use
> a
> shadow register.  Many times you won't need that.
>
This is one of the times it will very likely be needed however.  I have had
problems with this type of code running at only 4MHz and driving the gate of
a MOSFET.

Mike

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