--- Tony Nixon <Tony.Nixon@ENG.MONASH.EDU.AU> wrote:
> Morgan Olsson wrote:
> >
> > In the thread "A-D on PIC 16C73B" , table boundary
> problem was mentioned.
>
>
> If a value in ram is specified for a 256 element
> lookup table then this
> may help deal with boundary issues. There are
> probably better methods
> around also.
>
>
>         movlw high ($ + 8)
>         movwf pclath
>         movf RAMx,w
>         addlw low ($ + 6)
>         btfsc Status,Carry
>         incf pclath
>         movf RAMx,w
>         addwf pcl
>         retlw 0h
>         retlw 1h
>         etc...
>


Here's a method that's better. I first saw something
like this posted by mike kietz about 2 years ago.

   movlw  high   (TABLE_START)
   movwf  pclath
   movf   index,w
   addlw  TABLE_START
   skpnc
    incf  pclath,f
   movwf  pcl
TABLE_START
   retlw  ...

If the table is called such that W is the index:

   addlw  TABLE_START
   movwf  temp
   rlf    known_zero,w
   addlw  high(TABLE_START)
   movwf  pclath
   movf   temp,w
   movwf  pcl
TABLE_START

.lo
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