So basically what I was doing was passing the address of
the register rather than its contents ?

I could write this so much easier in C but I'am
determined to get to grips with asm.

Ok thanks guys, I'll keep at it.

Russ.

> -----Original Message-----
> From: Bob Ammerman [mailto:RAMMERMAN@PRODIGY.NET]
> Sent: Monday, June 26, 2000 1:47 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: asm question
>
>
> The bit manipulation insturctions (BTFxx, BSF and BCF) all
> include the bit
> number as an immediate value within the instruction. You
> cannot pass a bit
> number to these instructions in  a register.
>
> However, you can get the same effect by using a bit _mask_
> rather than a bit
> _number_ and using the ANDWF or IORWF instructions. You can
> convert a bit
> number to a bit mask using a short table lookup function.
>
> Bob Ammerman
> RAm Systems
> (high performance, high function, low-level software)
>
> ----- Original Message -----
> From: Russell Farnhill <r.farnhill@STOR-WAVE.CO.UK>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Monday, June 26, 2000 6:17 AM
> Subject: [PIC]: asm question
>
>
> > Hi all,
> >
> > I have just started learning asm and playing around with a
> 16f84. I've
> > already read
> > a couple of tutorials from the net and now have a question. How do I
> create
> > a function
> > that uses a bit orientated command and pass its arguments
> via a register.
> I
> > have
> > included a small piece of code to try and illustrate.
> >
> > #include        "p16f84.inc"
> > #DEFINE PAGE0 bcf STATUS,5
> > #DEFINE PAGE1 bsf STATUS,5
> >
> > RBpin equ 0x0C          ; Port B pin number
> >
> >
> >         org 4
> >         goto start
> >
> > start
> >         clrf    PORTB           ; clear portb
> >         PAGE1                   ; select bank 1
> >         clrf    PORTB           ; portb all output's
> >         PAGE0                   ; select bank 0
> >
> > loop    movlw   0               ; bit 0 portb
> >         movwf   RBpin           ; move bit select into register
> >         call    foobar  ; test function
> >         goto loop
> >
> > foobar
> >
> >         bsf     PORTB,RBpin
> >         return
> >
> >         END
> >
> > When I compile this I get the error "Argument out of range.  Least
> > significant bits used".
> > I guess this is because bsf expects a single bit arg but I
> pass it a byte.
> I
> > tried loading
> > W with my bit number and then read W from within my
> function which worked
> > fine, but if I
> > need to pass 2 args I can't use W as one arg overwrites the other.
> >
> > Any suggestions ?
> >
> > Thanks Russell.
>