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Table read for pic 18f2420

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PicChristmas

New Member
Could someone please help me setup a table read using the 18F series pic. I'm using Pic Basic pro and asm. What i am trying to do is take a value 0 to 127 stored in register vTemp and call a lookup table in program memory and have the value pointed by vTemp returned in vTemp.
I have created the table in asm with the

org LevelTable
da 0x0607 .0x1011 ....

And have 64 two byte groups

I need some help withintializing the pointer and reading the data
 

Jay.slovak

Active Member
Look at my code (not complete, too long to publish here):
Code:
fLCD	CLRF	LCDc	;LCD char counter
	CLRF	TBLPTRU	;Device does not have more 64KB of Flash!
	MOVFF	TAB_No,TBLPTRH;Determines Table to proces
	MOVFF	TAB_Pos,TBLPTRL;Determines position in Table
Fl	TBLRD*+
	INCF	LCDc,f	;Increment LCD counter
	MOVLW	H'11'   ;This is char, that is at the end of the string
	CPFSEQ	LCDc	
	GOTO	$+6	;String continues, send to LCD
	RETURN		;End of string
	MOVFF	TABLAT,LCD	;send to LCD
	CALL	LCDd	
	GOTO	Fl	;Send another char

Table	ORG	0x1100
	DW	" Line1              "
	DW	" Line2              "
	DW	" Line1              " 
	DW	" Line4              "
You have to put coordinats to TAB_No and TAB_Pos registers, and have LCDd rutine in your code.
 

motion

New Member
PicChristmas said:
Could someone please help me setup a table read using the 18F series pic. I'm using Pic Basic pro and asm. What i am trying to do is take a value 0 to 127 stored in register vTemp and call a lookup table in program memory and have the value pointed by vTemp returned in vTemp.
I have created the table in asm with the

org LevelTable
da 0x0607 .0x1011 ....

And have 64 two byte groups

I need some help withintializing the pointer and reading the data
Here is a code snippet plucked from one of my programs..

Code:
         MOVF     vTemp,W
         ANDLW    B'01111111'
         ADDLW    LOW  LevelTable
         MOVWF    TBLPTRL
;
         MOVLW    HIGH LevelTable
         BTFSC    STATUS,CARRY
         ADDLW    1
         MOVWF    TBLPTRH
         CLRF     TBLPTRU
;
         TBLRD*
         MOVFF    TABLAT,vTemp
 

PicChristmas

New Member
Thanks for the help. The vTemp value was already in range 0-127 so I didn't have to strip the 7th bit. With this code you just have to make sure the table starts with a low byte address of hex 00

Code:
   movlw	upper _lvlTable
	movwf	TBLPTRU
	movlw	high lvlTable 
	movwf	TBLPTRH
	movf	_vTemp,0               ;Points to value in table
	movwf	TBLPTRL
	TBLRD	*+ 				
	MOVFF       TABLAT, _vTemp
 
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