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Are there any PIC microcontroller programmers here?

I'm learning some PIC microcontroller programming using a pickit2 and the 16F887 chip I'm working through trying out the various facilities at the moment. I can't able to read right byte from location. I am sharing my read and write code. Did lot of combination / read lot of data on net and sheet but not able to close this issue. My code for read:

EDREAD
        BANKSEL EEADR
        movlw   0X08            ;Read data from location 08
        movwf   EEADR
        BANKSEL EECON1
        bcf     EECON1,EEPGD
        bsf     EECON1,RD
        BANKSEL EEDATA
        movf    EEDATA,W
        BANKSEL BIN1
        movwf   BIN1
        RETURN

Write Instruction:

EDWRITE
        banksel EECON1
back    btfsc   EECON1,WR   ;Wait for
        goto    back
        banksel EEADR
        movlw   0X08
        BANKSEL EEADR
        movwf   EEADR
        BANKSEL VALUE
        movf    VALUE,W
        BANKSEL EEDATA
        movwf   EEDATA
        NOP
        NOP
        BANKSEL EECON1
        bcf     EECON1,EEPGD
        bsf     EECON1,WREN
        banksel EECON2
        MOVLW   0x55        ; Unlock-write voodoo
        MOVWF   EECON2
        MOVLW   0xAA
        MOVWF   EECON2
        BANKSEL EECON1
        
        BSF     EECON1,WR
JUMP    BTFSC   EECON1,WR   ;
        GOTO J  UMP
        BCF     EECON1,WREN
        RETURN

i write data in value resistor to EEPROM. This data comes from ADC Input value. data shown post running code is 255 despite input of ADC varies from 100 to 200.

Dan1138
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manoj Sharma
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1 Answers1

2

The sequence of instructions you have implemented does not enable writes to the EEPROM correctly. There are extra BANKSEL directives that interfere with how the EEPROM write unlock sequence works.

I would suggest that you read and understand the example 10-2 on page 113 of the PIC16F887 data sheet.

Dan1138
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