As noted in my previous message you could use the routine from the
piclist.com faq:
http://www.piclist.com/techref/microchip/math/bit/mask.htm

; Convert 3-bit number (0-7) in INDEX to a 8-bit mask (00000001 ...
; 10000000) in BitP.
        movfw   INDEX
        andlw   b'00000011'     ;Start with half of the mask.
        movwf   BitP
        incf    BitP, W         ;The 4-bit converter
        btfsc   BitP, 1
        iorwf   BitP, F
        incf    BitP, F
        btfsc   INDEX, 2        ;Is it high 4 bits?
        swapf   BitP, F

So you make your number into a mask, then you can apply that mask to the
number from the port.  Your value (set or clear) will show up in the
status register, zero bit.

-Adam

Gonzalo Jimenez Yamasaki wrote:
>
>     Well I4ve found FSR and INDF, but that can solve half my problem... with
> this I can select porta, portb or portc easily, but what about bits, how can
> I choose between them?
>
>     Petra: I should use any port, and any bit... my idea is to make a
> subrutine to read a bit using sofware filter...
>
>     Regards,
>
>     Gonzalo
>
> ----- Mensaje original -----
> De: "Olin Lathrop" <olin_piclist@EMBEDINC.COM>
> Para: <PICLIST@MITVMA.MIT.EDU>
> Enviado: Jueves 4 de Enero de 2001 2:31 PM
> Asunto: Re: [PIC]: Not use the address but what is inside that address
>
> | >     What I want to do exactly is to have to variables, one with the port
> I
> | > want to use (let4s call it "port") and another one with the bit I want
> to
> | > read (let4s call it "bit") then use the instruccion btfss.
> | >
> | >     Something like this:
> | >
> | >     porta --> port
> | >     3 -->    bit
> | >
> | >     btfss    port, bit
> | >
> | >     What should mean btfss porta, 3
> | >
> | >     Is it possible?
> |
> | If "bit" and "port" are assembler variables, then yes.  No matter how you
> | may try to disguise it, the register and bit referenced by a BTFSS
> | instruction are hard coded into the instruction, and therefore must be
> known
> | at assembly time.
> |
> | If you need to dynamically select a register at runtime, use an FSR.
> There
> | are more options for dynamically selecting a bit, most of which require
> bit
> | shifting or mask selecting.
> |
> |
> | *****************************************************************
> | Olin Lathrop, embedded systems consultant in Devens Massachusetts
> | (978) 772-3129, olin@embedinc.com, http://www.embedinc.com
> |
> | --
> | http://www.piclist.com hint: The PICList is archived three different
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> |
> |
> |
>
> --
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