Problem with onboard EEPROM on 16f628A

[clueless123]

I am trying to use the onboard EEPROM of a 16f628A, and no matter
what address I specify, only the first byte is being modified. My .asm
file is appended at the end.

In my program, I am trying to modify location 0x03, but only 0x00 is
getting modified. Could somebody please clue me in?

Thank you.

; This file is a basic code template for assembly code generation *
; on the PICmicro PIC16F628A. This file contains the basic code *
; building blocks to build upon. *
; *
; If interrupts are not used all code presented between the ORG *
; 0x004 directive and the label main can be removed. In addition *
; the variable assignments for 'w_temp' and 'status_temp' can *
; be removed. *
; *
; Refer to the MPASM User's Guide for additional information on *
; features of the assembler (Document DS33014). *
; *
; Refer to the respective PICmicro data sheet for additional *
; information on the instruction set. *
; *
;**********************************************************************
; *
; Filename: xxx.asm *
; Date: *
; File Version: *
; *
; Author: *
; Company: *
; *
; *
;**********************************************************************
; *
; Files required: *
; *
; *
; *
;**********************************************************************
; *
; Notes: *
; *
; *
; *
; *
;**********************************************************************

list p=16f628A ; list directive to define processor
#include <p16F628A.inc> ; processor specific variable definitions

errorlevel -302 ; suppress message 302 from list file

__CONFIG _CP_OFF & _DATA_CP_OFF & _LVP_OFF & _BOREN_OFF & _MCLRE_OFF & _WDT_OFF & _PWRTE_ON & _INTOSC_OSC_NOCLKOUT

; '__CONFIG' directive is used to embed configuration word within .asm file.
; The lables following the directive are located in the respective .inc file.
; See data sheet for additional information on configuration word settings.




;***** VARIABLE DEFINITIONS
w_temp EQU 0x71 ; variable used for context saving
status_temp EQU 0x72 ; variable used for context saving





;**********************************************************************
ORG 0x000 ; processor reset vector
goto main ; go to beginning of program


ORG 0x004 ; interrupt vector location
movwf w_temp ; save off current W register contents
movf STATUS,w ; move status register into W register
movwf status_temp ; save off contents of STATUS register

; isr code can go here or be located as a call subroutine elsewhere


movf status_temp,w ; retrieve copy of STATUS register
movwf STATUS ; restore pre-isr STATUS register contents
swapf w_temp,f
swapf w_temp,w ; restore pre-isr W register contents
retfie ; return from interrupt


main

; remaining code goes here

bsf STATUS, RP0 ; read from the onboard EEPROM
movlw 0x03
movfw EEADR
bsf EECON1, RD
incf EEDATA, 1

bsf EECON1, WREN ; now increment this value by 1
bcf INTCON, GIE
movlw 0x55
movwf EECON2
movlw 0xAA
movwf EECON2
bsf EECON1,WR
bsf INTCON, GIE

Stop goto Stop ;endless loop


; initialize eeprom locations

ORG 0x2100
DE 0x00, 0x01, 0x02, 0x03


END ; directive 'end of program'

 

[Mike - K8LH]

You probably wanted to do a movwf EEADR instead of a movfw EEADR...

Good luck... Regards, Mike

 

[clueless123]

I'm still unable to get my code to work. Now I have created a
write eeprom subroutine but it still does not write the desired value
into the desired location. I am sure it is a minor error of some kind.

Could somebody clue me in? My code is below:

; This file is a basic code template for assembly code generation *
; on the PICmicro PIC16F628A. This file contains the basic code *
; building blocks to build upon. *
; *
; If interrupts are not used all code presented between the ORG *
; 0x004 directive and the label main can be removed. In addition *
; the variable assignments for 'w_temp' and 'status_temp' can *
; be removed. *
; *
; Refer to the MPASM User's Guide for additional information on *
; features of the assembler (Document DS33014). *
; *
; Refer to the respective PICmicro data sheet for additional *
; information on the instruction set. *
; *
;**********************************************************************
; *
; Filename: xxx.asm *
; Date: *
; File Version: *
; *
; Author: *
; Company: *
; *
; *
;**********************************************************************
; *
; Files required: *
; *
; *
; *
;**********************************************************************
; *
; Notes: *
; *
; *
; *
; *
;**********************************************************************

list p=16f628A ; list directive to define processor
#include <p16F628A.inc> ; processor specific variable definitions

errorlevel -302 ; suppress message 302 from list file

__CONFIG _CP_OFF & _DATA_CP_OFF & _LVP_OFF & _BOREN_OFF & _MCLRE_OFF & _WDT_OFF & _PWRTE_ON & _INTOSC_OSC_NOCLKOUT

; '__CONFIG' directive is used to embed configuration word within .asm file.
; The lables following the directive are located in the respective .inc file.
; See data sheet for additional information on configuration word settings.

cblock 0x20 ;start of general purpose registers
eeprom_addr
eeprom_value
endc



;***** VARIABLE DEFINITIONS
w_temp EQU 0x71 ; variable used for context saving
status_temp EQU 0x72 ; variable used for context saving





;**********************************************************************
ORG 0x000 ; processor reset vector
goto main ; go to beginning of program


ORG 0x004 ; interrupt vector location
movwf w_temp ; save off current W register contents
movf STATUS,w ; move status register into W register
movwf status_temp ; save off contents of STATUS register

; isr code can go here or be located as a call subroutine elsewhere


movf status_temp,w ; retrieve copy of STATUS register
movwf STATUS ; restore pre-isr STATUS register contents
swapf w_temp,f
swapf w_temp,w ; restore pre-isr W register contents
retfie ; return from interrupt


main

; remaining code goes here

movlw 0x70
movwf EEADR
movlw 0xAA
movwf EEDATA
call Write_EEPROM

Stop goto Stop ;endless loop


Read_EEPROM ; put address in w; result is returned in w
bsf STATUS, RP0 ; read from the onboard EEPROM
movwf EEADR
bsf EECON1, RD
movfw EEDATA
bcf STATUS, RP0
return

Write_EEPROM ; put value in eeprom_value and address in eeprom_addr
bsf STATUS, RP0
bsf EECON1, WREN
bcf INTCON, GIE
movlw 0x55
movwf EECON2
movlw 0xAA
movwf EECON2
bsf EECON1, WR
bsf INTCON, GIE
return


; initialize eeprom locations

ORG 0x2100
DE 0x00, 0x01, 0x02, 0x03


END ; directive 'end of program'

 

[ym2k]

Write_EEPROM ; put value in eeprom_value and address in eeprom_addr
bsf STATUS, RP0
bsf EECON1, WREN
bcf INTCON, GIE
movlw 0x55
movwf EECON2
movlw 0xAA
movwf EECON2
bsf EECON1, WR
bsf INTCON, GIE
return

Try to put a loop until the write is finish and switch back your bank to 0 like this :

Write_EEPROM ; put value in eeprom_value and address in eeprom_addr
bsf STATUS, RP0
bsf EECON1, WREN
bcf INTCON, GIE
movlw 0x55
movwf EECON2
movlw 0xAA
movwf EECON2
bsf EECON1, WR
btfsc eecon1,wr
goto $-1
bcf eecon1,wren ;disable eeprom write
bcf status,rp0
bsf INTCON, GIE
return