Hi Artem,
Tanks for your help.

I=B4m looking for retlw instead tblrd (table-read instructions)
becouse I have some codes writes for the 16Fxxx and I have
to change for the 18Fxxx series, Then In this case,
it will be easier for me.


I=B4ve found 2 ways to do it:
Can I use the example 1 of Bob Amerman without problems?
To me it look like simpler.


Thanks in advanced

Luis F.



1-) I=B4ve found this :
http://www.piclist.com/techref/microchip/tables.htm

Bob Ammerman of Ram Systems says:
Here is a trick I use to avoid problems with PCLATH/PCLATU and interrupts o=
n =

18C chips:
  given:

MOVF OFFSET,WRLNCF OFFSET,1  ;here, you have to adjust de OFFSET mpy by 2
                ;Now the program counter addresses bytes instead words.rcal=
l =

lookup_func
instead of: ;align to page start if needed
lookup_func:
addwf    PCL,Fretlw      1
retlw      2....................................................
I have used: ;align to page start if needed
lookup_func:
rcall    lookup_index
retlw    1
retlw    2

lookup_index:
addwf    TOSL,F
return

; For large tables you can:

lookup_index:
addwf    TOSL,F
btfsc      STATUS,C
incf        TOSH,F
return........................................................
2-)I=B4ve found in DS00716A page 3

    movf OFFSET,W
    call TABLE

    ......

TABLE:
    movwf TABOFF        ;save table offset
    rlncf TABOFF,1      ;mpy by 2

    movlw HIGH(TAB_ST)
    btfsc STATUS,C
    incf WREG,W
    movwf PCLATH        ;modify PCLATH if required

    movlw LOW(TAB_ST)   ;get low byte of table address
    addwf TABOFF,W      ;add in offset
    btfsc STATUS,C
    incf PCLATH,1       ;inc if needed
    movwf PCL           ;make jump

TAB_ST:
    retlw 1
    retlw 2
    retlw 3
    ...
    ...




Hi, Luis.

I've found this :
http://www.piclist.com/techref/microchip/bigtable.htm

It work fine for my application. I use litle and big tables in
relocatable code and i have crossing of page boundary.
For avoid error in calculation You need to check the crossing by adding
Offset to StartTableAdress and if result > 256 simply increment the
PCLATH (high byte of adress)

        movlw Low(TableStart)
        addwf OffsetL,W
        skpnc
          incf PCLATH,F
        movwf   PCL     ;computed goto with right PCLATH
...
TableStart
Retlw d'0'
        Retlw d'255'
        Retlw d'9'
        ....
        etc

Best Regards

Artem


antoniasse a =E9crit :
> Hi,
>
> How is the correct form (or best way) to create a table lookup with
> RETLWs and don=B4t cross 256 byte page boundary on PIC18Fxxxx?
>
> Any suggestion?
>
> Regards
>
> Luis F.
>

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