[Opps! I forgot to put the [PIC]: at the start of the subject line when I first sent this. Sorry!]

I am having trouble writing to the EEPROM in a on 16F873.

Using the "RomZAP Bootloader III" I put in the following code to read a value from an analog input, then display the value on some LEDs and store the value in EEPROM. The program does all this except it only does it once - ie it doesn't go around the LOOP. It seems to hang on the last instruction before "goto LOOP".

NOTE: if I remove all the code from EWRITE onwards the LOOP works perfectly.

NOTE2: the code after EWRITE routine is more or less straight out of the 16F87x datasheet, except I have modified it so it just writes the value which is in W to EEPROM address 0x00. Also, I have not enable interrupts so I have commented out the relevant bits as required.

(I will more EWRITE out to be a subroutine, but I have put it in the main loop for now in order to just get it going...)

Any suggestions greatly appreciated!

John



        org 0x0003

        bsf     STATUS,RP0      ; select register bank 1
        bcf     STATUS,RP1      ;

        movlw   H'00'
        movwf   TRISC           ; set PORTC [7-0] all outputs
        clrf    ADCON1          ; set PORTA [7-0) all analogue inputs

        bcf     STATUS, RP0     ; select register bank 0

        movlw   B'01000001'     ; bits [7-6] = select Fosc/8; bits [5-3] select analogue input from RA0/AN0
        movwf   ADCON0          ;     bit [0] = activate A2D converter


LOOP    bsf     ADCON0,GO       ; start A2D conversion
Adwait  nop                     ; wait for conversion to complete
        btfsc   ADCON0,GO       ;
        goto    Adwait          ;

        movf    ADRESH,W

        MOVWF   PORTC

EWRITE  bsf     STATUS, RP1
        bsf     STATUS, RP0     ; select register bank 3
Ewait   btfsc   EECON1, WR      ; wait for any previous write_
        goto    $-1             ;   to finish
        bcf     STATUS, RP0     ; select register bank 2
;       movf    VALUE, W        ; set EEDATA to value you want to write_
        movwf   EEDATA          ;   to EEPROM
;       movf    ADDR, W ; set EEADR to the EEPROM address_
        movlw   0x00
        movwf   EEADR           ;   that you want to write to
        bsf     STATUS, RP0     ; select register bank 3
        bcf     EECON1, EEPGD   ; Point to data memory
        bsf     EECON1, WREN    ; Enable writes
;       bcf     INTCON, GIE     ; Only disable interrupts if already enabled_
;                               ;   otherwise discard
        movlw   0x55            ; Write 55h to_
        movwf   EECON2          ;   EECON2
        movlw   0xAA            ; Write AAh to_
        movwf   EECON2          ;   EECON2
        bsf     EECON1, WR      ; Start write operation
;       bsf     INTCON, GIE     ; Only disable interrupts if already enabled_
;                               ;   otherwise discard
        bcf     EECON1, WREN    ; Disable writes

        goto LOOP


_______________________________________________________________________
John Brown
PhD (Clinical Psychology) candidate
                                      Email:  john.brown@anu.edu.au
School of Psychology                  Phone:  (02) 6125-3827
Room 124, Building 39, Psychology     Fax:    (02) 6125-0499
The Australian National University    Mobile: 0429 455 504
ACTON ACT 0200   Web: http://www.anu.edu.au/psychology/staff/BrownJ.htm

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