Register goes from 0x00 to 0xFF... ? - Electronic Circuits Projects Diagrams Free

RobertD · 19th August 2008, 04:42 AM

Hi folks,

I have a register that has 0 in it, when I move the content of this register to the W register, the 0x00 becomes 0xFF.

Can anyone tell me what is going on?

kchriste · 19th August 2008, 04:48 AM

Post your code and state what PIC you are using. DECF temp,W or COMF temp,W could do this.

Pommie · 19th August 2008, 05:08 AM

You could be reading from the wrong bank.

Mike.

RobertD · 20th August 2008, 03:10 AM

I could be reading from the wrong bank indeed. I'm reading the value from EEPROM, and when I switch it over from the EEPROM register to the W register to work with it, it pops.

Mike, K8LH · 20th August 2008, 03:13 AM

Quote:

when I switch it over from the EEPROM register to the W register to work with it, it pops

What does that mean?

Mike

Gayan Soyza · 20th August 2008, 05:18 AM

Quote:

Originally Posted by RobertD

I could be reading from the wrong bank indeed. I'm reading the value from EEPROM, and when I switch it over from the EEPROM register to the W register to work with it, it pops.

Did you assign EEPROM locations in the last part of your program?

RobertD · 20th August 2008, 09:59 PM

Yes, I have assigned 0x75 for the EEPROM location, and reading from it. It's moved from the EEDATA register to the W register then from the W to the SELECT register, which is where I need it, and that's when it goes from 0x00 to 0xFF.

I'm using the 16F88 data sheet EEPROM code for read/write. I get a value from AD which I "andf" with "00001111" and rotate right.

I think I read something about "and" masks that was someting there I had to watch for.

And it doesn't move the W register to the SELECT register when I call for it. Now that's puzzling. I included the SELECT register in the cblock in the beginning. It is at 0x02c, while NEW is at 0x075.

Code:

read
        banksel EEADR 
		movf 	NEW, W ;
		movwf 	EEADR ; Data Memory Address to read
		banksel EECON1 
		bcf 	EECON1, EEPGD; Point to Data memory
		bsf 	EECON1, RD ; EE Read
		banksel EEDATA ; Select Bank of EEDATA
		movf 	EEDATA, W ; W = EEDATA                
	            
        return                       

write
        banksel EECON1 ; Select Bank of EECON1
		btfsc 	EECON1, WR ; Wait for write
		goto 	$-1 ; to complete
		banksel EEADR ; Select Bank of EEADR
		movf 	NEW, W ;
		movwf 	EEADR ; Data Memory Address to write
		movf 	NEW, W ;
		movwf 	EEDATA ; Data Memory Value to write
		banksel EECON1 ; Select Bank of EECON1
		bcf 	EECON1, EEPGD ; Point to DATA memory
		bsf 	EECON1, WREN ; Enable writes
		bcf 	INTCON, GIE ; Disable INTs.
		movlw 	h'55' ;
		movwf 	EECON2 ; Write 55h
		movlw 	h'AA' ;
		movwf 	EECON2 ; Write AAh
		bsf 	EECON1, WR ; Set WR bit to begin write
		bsf 	INTCON, GIE ; Enable INTs.
		bcf 	EECON1, WREN ; Disable writes

       
        return                  ;    

 
;coming from A/D going to EEPROM

            swapf	ADRESH
	movlw	B'00001111'
	andwf	ADRESH
	rrf		ADRESH
	movfw	ADRESH
	movwf	NEW

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19th August 2008, 04:42 AM	(permalink)
RobertD	Register goes from 0x00 to 0xFF... ? Hi folks, I have a register that has 0 in it, when I move the content of this register to the W register, the 0x00 becomes 0xFF. Can anyone tell me what is going on?

19th August 2008, 04:48 AM	(permalink)
kchriste	Post your code and state what PIC you are using. DECF temp,W or COMF temp,W could do this. __________________ --- The days of the digital watch are numbered. --- Last edited by kchriste; 19th August 2008 at 04:50 AM.

19th August 2008, 05:08 AM	(permalink)
Pommie	You could be reading from the wrong bank. Mike.

20th August 2008, 03:10 AM	(permalink)
RobertD	I could be reading from the wrong bank indeed. I'm reading the value from EEPROM, and when I switch it over from the EEPROM register to the W register to work with it, it pops.