Lookup table using RETLW

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leojose
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2004/11/03 07:59:46 (permalink)
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Lookup table using RETLW

Hi all,

I have been trying to set up a look up table using the RETLW instruction for a couple of hours but I just can't get it to work correctly. It seems to pass the simulation test, but when I run it on the controller it kind of misbehaves. I think it is the manner that I am treating the PC registers.
I am posting the specific look up table here.


 	CALL	COS_TABLE	;this instruction is somewhere in the Main routine 
 	.
 	.	
 	ORG	0x2000
 COS_TABLE:				;
 	MOVFF	PCL,TEMP		;to read the program counter in the PCLATH
 	MULLW	.2			;to create an offset
 	MOVF	PRODL,W		;putting the calculated value back in WREG
 	ADDWF	PCL,F			;adding the offset to the PCL
 	RETLW	0x01
 	RETLW	0x02
 	RETLW	0x03
 	RETLW	0x04
 	RETLW	0x05
 	.
 	.
 	.


I am using the PIC18f452
Kindly help...

Kind Regards.
< Message edited by leojose -- Nov. 3, 2004 1:03:16 AM >

***ljose***
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    whsiung
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    RE: Lookup table using RETLW 2004/11/03 08:38:07 (permalink)
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    Hi Leo,

    Try this:


     ; with offset in W
     bcf WREG, 7
     rlnc WREG, f
     addwf PCL, f
     retlw ....
     ....


    Good luck.
    WH Tan

    Sorry, typing mistake.


     ; with offset in W
     bcf WREG, 7
     rlncf WREG, f
     addwf PCL, f
     retlw ....
     ....
    < Message edited by whsiung -- Nov. 3, 2004 11:41:45 PM >
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