PICers,

OK, thanks to James Cameron, Wayne H. et al for that advice about
indexed addressing. I'm starting to see the light.

Let's say you want to send 4 bytes of data to a serial tx routine. How
I'd *now* go about it looks like so :-


 CBLOCK 0x0C
data_0
data_1
data_2
data_3
txbuf
ByteCount
 ENDC

 PAGE
         org       0x00
start    goto      main

;*********************************************************
;PROCEDURES SECTION
;*********************************************************
clear   clrw
        clrf      FSR           ;Start with null values
        clrf      INDF          ;for FSR & INDF.
        movlw     0x0fe         ;Put some random values
        movwf     data_0        ;in the data registers
        movlw     0x05a
        movwf     data_1
        movlw     0x032
        movwf     data_2
        movlw     0x0dc
        movwf     data_3
        retlw     0x00

tx_out  nop                      ;A dummy serial tx routine
        return

;*******************************************************
;Begin MAIN PROGRAMME
;*******************************************************
main     call      clear          ;Set up the registers
         movlw     0x04           ;Initialise the counter
         movwf     ByteCount
         movlw     data_3         ;Initialise the pointer
         movwf     FSR
loop     movf      INDF,0         ;Get [FSR], the current data byte
         movwf     txbuf          ;Load it and ...
         call      tx_out         ;... then send it.
         decf      FSR,1          ;Point to next data item down
         decfsz    ByteCount      ;At end of the data count?
          goto     loop           ;No  - loop around
fin      goto      $              ;Yes - stop here.
         end


This works OK, the 4 data bytes are sent to tx_out in proper order.
I'm not too happy about using ByteCount to keep track of things but
testing for when data_0 is reached involves AND comparisons and more
code.

What I REALLY don't get is how you use dt or db or whatever to feed a
block of bytes to an indexed routine like this one. Could one of you
guys please explain like *exactly* what goes on with DT/DB ? Would you
define data_0,1,2,3 and then fill'em individually (mighty clumsy) or
define a block of contents or what?

Yeah, I read the MPASM User's Guide but it still don't make a lotta
sense.

Ian

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