correct EEPROM code

I spent quite some time trying to be able to write data to EEPROM, but no matter what I did it wouldn't work. Even when I copied the exact same code the book provides, it didn't do anything. I emailed Prof. Emami about it today and this is his response:

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Hi Andrew, the reason why it doesn't write to the EEPROM is that you do not disable the EEPROM write mode at the end.Also the EEPROM write interrupt flag must be cleared. (These lines are dropped in the textbook by mistake.) Try the following code and let me know if it works:

BCF INTCON, GIE ; Only disable interrupts

; if already enabled,

; otherwise discard

BCF STATUS, RP0 ;

BSF STATUS, RP1 ; Bank 2

MOVF ADDR, W ; Address to

MOVWF EEADR ; Write to

MOVF VALUE, W ; Data to

MOVWF EEDATA ; Write

BSF STATUS, RP0 ; Bank 3

BCF EECON1, EEPGD ; Point to Data memory

BSF EECON1, WREN ; Enable writes

MOVLW 0x55 ; Write 55^th to

MOVWF EECON2 ; EECON2

MOVLW 0Xaa ; Write AAh to

MOVWF EECON2 ; EECON2

BSF EECON1, WR ; Start write operation

BTFSC EECON1, WR ; Wait for

GOTO $-1 ; Write to finish

BCF EECON1, WREN ; Disable writes

BCF STATUS, RP0

BCF STATUS, RP1 ; Bank0

BCF PIR2, EEIF ; Clear write interrupt flag

BSF INTCON, GIE ; Only enable interrupts

; if using interrupts,

; otherwise discard

_MRE

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Also, here is how to check what was written to EEPROM without any code:

-Open PICusb and write your code to the chip.

-Click on "Read" <- Important!!

-View "EEPROM Memory"

Remember that it won't work if you don't read first.

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Comment by Andrew Ferrazzutti on February 19, 2012 at 1:32am: Tip: when using this code, the registers VALUE and ADDR may not work if you declared them with cblock. I just spent 40 minutes debugging, and for some reason, using udata works while cblock 0x20 doesn't do anything. Interestingly, cblock 0x70 does work, but that's a bad idea for other reasons.

Comment by Tatsuhiro Onodera on February 5, 2012 at 11:35am: Hi andrew thanks for this.
It really helped :)