Programming |  PIC's |  16F84A |  Data EEPROM Memory


Reading EEPROM DATA

        BCF     STATUS, RP0         ; Bank 0
        MOVLW   CONFIG_ADDR         ;
        MOVWF   EEADR               ; Address to read
        BSF     STATUS, RP0         ; Bank 1
        BSF     EECON1, RD          ; EE Read
        BCF     STATUS, RP0         ; Bank 0
        MOVF    EEDATA, W           ; W = EEDATA

Writing EEPROM DATA

        BSF     STATUS, RP0         ; Bank 1
        BCF     INTCON, GIE         ; Disable INTs.
        BSF     EECON1, WREN        ; Enable Writes
        
        ; the following steps must be performed in the order shown without interuption
        MOVLW   55h                 ;
        MOVWF   EECON2              ; Write 55h
        MOVLW   AAh                 ;
        MOVWF   EECON2              ; Write AAh
        BSF     EECON1,WR           ; Set WR bit
        ; write begins
        BCF     EECON1, WREN        ; Disable writes
        BSF     INTCON, GIE         ; Enable INTs.

Verifing EEPROM DATA

        BCF STATUS,RP0              ; Bank 0
        :                           ; Any code
        :                           ; can go here
        MOVF EEDATA,W               ; Must be in Bank 0
        BSF STATUS,RP0              ; Bank 1
READ
        BSF EECON1, RD              ; YES, Read the value written
        BCF STATUS, RP0             ; Bank 0
                                    ;
                                    ; Is the value written
                                    ; (in W reg) and
                                    ; read (in EEDATA)
                                    ; the same?
                                    ;
        SUBWF EEDATA, W             ;
        BTFSS STATUS, Z             ; Is difference 0?
        GOTO WRITE_ERR              ; NO, Write error