Hi Neil,

I guess you can use these operations (hope someone has better algorithm for
you):


Initialize table pointer (traditional way):
    movlw   upper ( table )
    movwf   TBLPTRU
    movlw   high ( table )
    movwf   TBLPTRH
    movlw   low ( table )
    movwf   TBLPTRL

Initialize table pointer (cheat way, when you are absolutely sure that the
table is in the page 0...):
    clrf    TBLPTRU
    clrf    TBLPTRH
    movlw   low ( table )
    movwf   TBLPTRL

Initialize table pointer (cheat way, when you use a separate section in the
linker script for the table):
    clrf    TBLPTRU          ; assume that the table is on below that range
    movlw   high ( table )   ; load the section address only
    movwf   TBLPTRH
    clrf    TBLPTRL          ; table starts at the offset 0 on that section

incrementing by one (efficient way)
    TBLRD*+
    ; we do not use the value of TABLAT here so we only incremented the
pointer...

incrementing manually by one (math operations way, you do not need this...)=
:
    INCF    TBLPTRL
    CLRF    WREG
    ADDWFC  TBLPTRH
    ADDWFC  TBLPTRU

incrementing by another number:
    MOVLW   0x10 ; or other incrementals
    ADDWF   TBLPTRL
    CLRF    WREG
    ADDWFC  TBLPTRH
    ADDWFC  TBLPTRU ; you can leave out this if you absolutely sure it will
never overflow

incrementing by another number (silly thing, slightly smaller prog mem
footprint but much slower):
    MOVLW   0x10 ; or other incrementals
    TBLRD*+
    DECFSZ  WREG,F
    BRA     $-4

Tamas



On 17 January 2012 05:28, PICdude <picdude3@narwani.org> wrote:

> Put a bit of time into this tonight, and partially answering my own
> question, I found that I can do it this way (simplified)...
>
> // Define data...
> unsigned char rom LookupTable[10] =3D { 1,2,3,5,7,9,11,13,17,19 };
> // Access/retrieve data...
> a =3D LookupTable[5];
>
> But still wondering, is there a more space-efficient way to do this if
> I directly manipulate TBLPTRU/H/L etc ?
>
> Cheers,
> -Neil.
>
>
>
>
> Quoting PICdude <picdude3@narwani.org>:
>
> > I should also point out that this is for an 18F PIC.
> >
> >
> >
> > Quoting PICdude <picdude3@narwani.org>:
> >
> >> On the subject of tables in C18, as I've been tinkering with C
> >> (instead of asm) for PICs, I'm going to get into tables soon.
> >>
> >> Off the top of my head right now, I can see how I'd use TBLPTRU/H/L to
> >> point to the correct data, but not sure yet how data is declared and
> >> held in memory efficiently, and how these will be 256-byte boundary
> >> aligned (though I would think that that's not necessary here).  These
> >> will be pre-determined values.
> >>
> >> Anyone care to share an example of how this is done with C18?  AFAIK,
> >> the mchip app notes all show this in assembly.
> >>
> >> Cheers,
> >> -Neil.
> >>
> >>
> >> --
> >> http://www.piclist.com PIC/SX FAQ & list archive
> >> View/change your membership options at
> >> http://mailman.mit.edu/mailman/listinfo/piclist
> >>
> >
> >
> >
> > --
> > http://www.piclist.com PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
> >
>
>
>
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>



--=20
int main() { char *a,*s,*q; printf(s=3D"int main() { char *a,*s,*q;
printf(s=3D%s%s%s, q=3D%s%s%s%s,s,q,q,a=3D%s%s%s%s,q,q,q,a,a,q); }",
q=3D"\"",s,q,q,a=3D"\\",q,q,q,a,a,q); }
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.