Steve,

 'TABLE' is a label.  It is at the begining of the data table below.
 "OFFSET' is how deep into the table do you want to go.
 For instance, in the table listed below, lets say you had the offset
 at 2.  In this case, RETLW would return "C".
 The reason for this is that at compile time, the compiler saw the
 label 'TABLE', and set it's address to whatever.  This address can
 be found several places, but I like looking at the listing file.
 So when the table lookup routine is called, the PC is loaded with
 the address of the label table.  Next it adds the 'OFFSET' to the PC
 to come up with the final destination address.  And in this case,
 that equates to final destination address points to 'C' in the table.
 Is this clear to you now?  Basically what you have is the compiler
 locates the table somewhere in memory, and the combination of the
 base address plus the offset equals the element in the table you
 want to retrieve.

 Hope this helps you out.


                                           Regards,

                                             Jim


On Thu, 29 June 2000, "Kosmerchock, Steve" wrote:

>
> Friends,
>
> I know this question has been asked, and yes I looked at the
> PICLIST FAQ. There was good info their, but I was hoping somebody could
> explain a few things to me.
>
> In MICROCHIPs application note AN556 "Implemeting a Table Read"
> the code is as follows:
>
> movlw           LOW   Table
> addwf           offset
> movlw           HIGH  Table
> btfsc           status,c
> addlw           1
> movwf           PCLATH
> movf            offset,w
> call            Table
> ;
> ;
> ;
> Table:
> movwf           pcl
> retlw           'A'
> retlw           'B'
> retlw           'C'
> ;
> ;
> etc............
>
>
> I know that "LOW" is taking the lower byte of "Table".
> Problem is,..... what is "Table"? Do you equate it to a
> number at the beginning of the program like:
>
> Table           EQU     H'0200'
>
> This will load 0x00 into "LOW" and 0x02 into "HIGH"?
> Does it have to have the same name as the table of data?
> Also, the register labeled "offset", is it some type of
> register that is being incremented, decremented,...etc?
>
> Thank you very much!!
>
> Best regards,
> Steve
>
>
> Steven Kosmerchock
> Radio Frequency Systems
> Phoenix  Arizona  USA
> www.rfsworld.com
>
> www.geocities.com/researchtriangle/lab/6584

jim@jpes.com