On Wed, 30 Jul 1997 19:26:29 -0700 Ravindra Divekar <ravindra@HAL.COM>
writes:
>I want to use the FSR register as a data pointer on 16C84.
>
>i.e.
>        if FSR = h'0c',
>
>        movf    @fsr,w   ( correct syntax)
>
>should load data in h'0c' into w.
>
>What is the syntax for this in MPASM (using MPLAB) ?
Instead of '@FSR' use INDF.  INDF is a directly accessable special
function register that causes an indirect access.

In a 14-bit PIC like the 16C84, register 0 has a special function, it
always holds a copy of the data in the register pointed to by register 4.
 (actually, register 0 doesn't exist, attempting to access it triggers
address substitution logic that uses the contents of register 4 as the
address instead)  Microchip calls register 4 "FSR" (File Select Register)
and register 0 "INDF" (INDirect File) and equates them as such in the
.inc file for the particular chip in use.  So to read register 0c into W
indirectly, use:

        movlw   h'0c'
        movwf   FSR             ;Point FSR at RAM 0c
        movfw   INDF            ;or "movf INDF,w" - Get byte
@FSR

-Mike