On Fri, 21 Dec 2001, Don Hyde wrote:

> indexlsb        equ     0x80
> indexmsb        equ     0x81            ;table index is here
> temp            equ     0x82
>
> lookup:
>         movlw   low table
>         addwf   indexlsb,w
>         movwf   temp
>         movfw   indexmsb
>         skpnc
>         incf    indexmsb,w
>         addlw   high table
>         movwf   PCLATH
>         movfw   temp
>         movwf   FSR
>
> table   retlw   1
>         retlw   2
>         ...

Why not save a couple instructions:

     movlw   HIGH(table)
     addwf   indexmsb,w
     movwf   PCLATH
     movlw   LOW(table)
     addwf   indexlsb,w
     skpnc
      incf   PCLATH,F
     movwf   PCL

But the table probably is accessed sequentially:

     incf    PCLATH,F
     incfsz  index,w
     decf    PCLATH,F
     movwf   index
     movwf   PCL

But even better IMO, is to use the 16F877 or similar flash device and
store the table directly in ROM. One word holds 14-bits, 9 words hold 16
bytes. Also, since this is a bit stream, you really don't have to worry
about artificial byte boundaries.

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body