877ee.asm

本源码的目的是让大家熟悉单片机内部EEPROM的读写方法

   		LIST 	P=16f877
  		#INCLUDE <P16f877.INC>   
;
;- RAM LOCATIONS------
;
; Reserve RAM location 0x70 for ICD
;
Data_EE_Addr   	equ   	0X71
Data_EE_Data   	equ   	0X72

;--------VECTORS------------

         	org   	0x0 
		nop
         	goto  	START

;-------PROGRAM--------------
   
         	org  	0X20
START
        	call   	INIT
;
;----   Test the WRITE EEPROM Routine ----
;
		movlw	0x0
		movwf	Data_EE_Addr
		movlw	'0'				; Load a ASCII code "0" to W
		movwf	Data_EE_Data
EE_Write
		call	WRITE_EEPROM
		incf	Data_EE_Data,F	; 0x30+ N
		incf	Data_EE_Addr,F  ; Point to next EEPROM Address
		btfss	Data_EE_Addr,5	; Write 32 bytes ?
		goto	EE_Write
;
;----   Test the READ EEPROM Routine ----
;
		movlw	0x20		; Get back EEPROM data to RAM with start addr at 0x20
		movwf	FSR
;		
		movlw	0x0		; Point to EEPROM start address at 0x00
		movwf	Data_EE_Addr
EE_Read
		call	READ_EEPROM	; Read EEPROM data with curent address to W registre
		movwf	INDF		; move W --> RAM 
;
		incf	FSR,F
		incf	Data_EE_Addr,F  ; Point to next EEPROM Address
		btfss	Data_EE_Addr,6	; Read 32 bytes ?
		goto	EE_Read
;    
        	GOTO   	$   
;
;------ INTERNAL EEPROM READ ------
;
READ_EEPROM
		banksel	EEADR
		movf	Data_EE_Addr,W		; Load EEPROM Address into Pointer
		movwf	EEADR
;
;     		bcf     INTCON,GIE  
		banksel	EECON1
		bcf	EECON1,EEPGD
		bsf	EECON1,RD
;
		banksel	EEDATA
		movf	EEDATA,W
;       	bsf     INTCON,GIE  
;
		banksel	PORTA
		return
;	
;----INTERNAL EEPROM WRITE-----
;
WRITE_EEPROM
		banksel	EEADR		
		movf	Data_EE_Addr,W		; Load EEPROM Address & Data into Register
		movwf	EEADR
		movf	Data_EE_Data,W
		movwf	EEDATA
;		
		banksel	EECON1
		bcf	EECON1,EEPGD		; Selected Data EEPROM for Writing
		bsf	EECON1,WREN		; Enable write function

;		bcf	INTCON,GIE		; Disable Interrupt

		movlw	0x55			; Write Sequence control 
		movwf	EECON2	
		movlw	0xAA
		movwf	EECON2	
			
		bsf	EECON1,WR		; Start EEPROM write operation
;
;		bsf	INTCON,GIE		; Enable Interrupt (If used interrupt )
		bcf	EECON1,WREN		; Disable write EEPROM  
;
		btfsc	EECON1,WR		; Waiting for writing completed (4mS)
		goto	$-1			; During write period, must hold both EEADR & EEDATA until complete
;
		banksel	PORTA
		return		
;
;---------INITIAL----------------
INIT      
        	BCF     PIR2,EEIF
		banksel	PIE2
          	BCF     PIE2,EEIE
         	RETURN
;--------------------------------
            	END