Accessing EEPROM in PIC16F877

[hunzaboy]

Hello

I have been studying and implementing EEPROM tutorials and forums from last 5 hours and no one had solved my problem.

I hope i'll fine the answer here.

PROBLEM:
The problem is " I am trying to store data and retrieve data from EEPROM of PIC16F877". But i can't find the simplest way. I have studied the DataSheet and tried the given thing many times but i haven't got the results.

Please tell me the simplest way to PUT DATA at a specific address and RETRIEVE DATA from a specific Address.

I'll be thankful to you.

Regards,
Aslam

 

[Nigel Goodwin]

From my PIC tutorials, an example:

EE_Read		bsf 	STATUS,	RP0 		; Bank 1
		movlw 	EEPROM_Addr
		movwf 	EEADR			; Address to read
		bsf 	EECON1,	RD 		; EE Read
		movf 	EEDATA,	W 		; W = EEDATA
		bcf 	STATUS,	RP0 		; Bank 0
		movwf	LED_PORT		; restore previous value
		retlw	0x00

EE_Write	movf	LED_PORT,	w	; read current value
		bsf 	STATUS,	RP0 		; Bank 1
		bsf	EECON1,	WREN 		; Enable write
		movwf	EEDATA			; set EEPROM data
		movlw	EEPROM_Addr
		movwf	EEADR			; set EEPROM address
		movlw	0x55
		movwf	EECON2 			; Write 55h
		movlw	0xAA
		movwf	EECON2 			; Write AAh
		bsf	EECON1,	WR 		; Set WR bit
						; begin write
		bcf 	STATUS,	RP0 		; Bank 0
		
		btfss	PIR1,	EEIF		; wait for write to complete.
		goto	$-1
		bcf	PIR1,	EEIF		; and clear the 'write complete' flag
		bsf 	STATUS,	RP0 		; Bank 1
		bcf	EECON1,	WREN 		; Disable write
		bcf 	STATUS,	RP0 		; Bank 0
		retlw	0x00

Basically you follow what the datasheet says.

 

[hunzaboy]

Thank you for the reply!! I will run this code and update with the issues..

What Address can i use for EEPROM? As per my knowledge i can use the EMPTY MEMORY IN EACH BANK..

 

[hunzaboy]

**broken link removed**

THE SAME PROBLEM .. the code doesn't go beyond this point
btfss PIR1, EEIF ; wait for write to complete.
goto $-1
and no changes in the EECON1 and EECON2 as shown in the attached image.

Please helpp me ..

 

[Nigel Goodwin]

I've no idea if it works in the simulator, as I never use it - but the EEPROM data memory is a specific size, and entirely separate to the rest of the memory.

 

[Pommie]

EEIF is in PIR2.

Mike.

 

[hitch]

Hi hunzaboy,
download oshonsoft pic simulator, it is a basic lang. and it takes most of the guess work out of the equation. if you like ASM you can use that 2. I have recently used the demo version to implement i2c interface from a 16f84 - 24lc256 (search the post) and with the help of eric we sorted that out in no time. I too have some ASM exp. but i prefer the basic lang. especially when you have a limited time to complete. I will def. be purchasing the oshonsoft ide.