Bo,

The ".inc" file associated with the chip will define W = 0 and F = 1 so you
can use these letters instead of the numbers which just makes it a bit
easier to remember. ie:

ADDWF     val, F

will add the contents of W with the contents of the file register "val" and
put the result in "val" whereas

ADDWF     val, W

will do the same but put the result in the W register.

If you don't put either W or F the assembler will give a warning ("Using
default destination of 1 (file)") and default to the F register.

R/-

Grant


On Sun, Mar 28, 2010 at 11:46 AM, Bo Dirigo <bo.dirigo@gmail.com> wrote:

> While studying various PIC instructions' formats, I noticed a number of
> instructions that had a 'd' (destination) in the Mnemonic; e.g., MOVF
> f,d; ADDWF f,d; INCF f,d, et al.
>
> If d=0, the results are stored in the W register - ADDWF  FSR, 0
> If d=1, the results are stored in the f register - ADDWF  FSR, 1
>
> My question is "Do you need to specify the "0" value if one knows they
> want the resultant value to be stored in the W register?"  Obviously, if
> one wants the result to be stored in the f register, they must specify
> the "1" value.  I'm probably all wet here, but was thinking perhaps the
> assembler would automatically default to the "0" value if nothing
> specified.  Before you shoot me, I am in agreement it would be better to
> specify either a "0" or "1" depending on what it is one wants done.  I'm
> just curious.
>
> Bo Dirigo
>
>
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