From: "Mcgee, Mark" <mark.mcgee@csfb.com>

> Hi
>
> I'm using PIC16F628A.
>
> I've been wondering how would you move along a buffer/array, reading or
> writing to each location in a loop?  I can't see any obvious indirect 
> memory
> access instructions in the reference manual.
>
> In my old 6502/'6510 assembler days I'd do something like (IIRC);
> LDA #0
> LDX #5
> loop:
> STA buffer_start,X
> DEX
> BNE loop
> ...
>
> Obviously, PIC only has the W register, and doesn't have index 
> registers...Is
> there some 16-bit address to set, and some indirect instruction or 
> something?
>
> cheers,
> Mark

Mark:

Take a look at the description of FSR and INDF. This is what you need to 
use. A PIC equivalent of your code would be something like this:

    movlw    buffer    ; get addr of buffer
    movwf    FSR      ;into FSR
    movlw    5           ;get count
    movwf    temp     ;into a working reg
loop:
    clrf        INDF    ; store info mem pointed to be FSR
    incf        FSR      ; point to next mem location
    decfsz    temp     ; any more to do?
    goto       loop

; Of course, for this short buffer at a known location, I would just write:

    clrf    buffer
    clrf    buffer+1
    clrf    buffer+2
    clrf    buffer+3
    clrf    buffer+4

Bob Ammerman
RAm Systems

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