Cám ơn bác namqn đã quan tâm giúp đỡ. Tôi dùng hợp ngữ để lập trình cho PIC và dùng Mplap để mô phỏng. Tôi sử dụng đoạn Code dưới đây trong datasheet của con pic16f877a để thực hiện, nhưng mô phỏng chẳng thấy nó chạy đúng gì cả. Không hiểu là nó sai hay mình mô phỏng không đúng. Mong bác chỉ giúp.
Code:
; This write routine assumes the following:
;
; 1. A valid starting address (the least significant bits = ‘00’)is loaded in ADDRH:ADDRL
; 2. The 8 bytes of data are loaded, starting at the address in DATADDR
; 3. ADDRH, ADDRL and DATADDR are all located in shared data memory 0x70 - 0x7f
;
BSF STATUS,RP1 ;
BCF STATUS,RP0 ; Bank 2
MOVF ADDRH,W ; Load initial address
MOVWF EEADRH ;
MOVF ADDRL,W ;
MOVWF EEADR ;
MOVF DATAADDR,W ; Load initial data address
MOVWF FSR ;
LOOP MOVF INDF,W ; Load first data byte into lower
MOVWF EEDATA ;
INCF FSR,F ; Next byte
MOVF INDF,W ; Load second data byte into upper
MOVWF EEDATH ;
INCF FSR,F ;
BSF STATUS,RP0 ; Bank 3
BSF EECON1,EEPGD ; Point to program memory
BSF EECON1,WREN ; Enable writes
BCF INTCON,GIE ; Disable interrupts (if using)
MOVLW 55h ; Start of required write sequence:
MOVWF EECON2 ; Write 55h
MOVLW AAh ;
MOVWF EECON2 ; Write AAh
BSF EECON1,WR ; Set WR bit to begin write
NOP ; Any instructions here are ignored as processor
; halts to begin write sequence
NOP ; processor will stop here and wait for write complete
; after write processor continues with 3rd instruction
BCF EECON1,WREN ; Disable writes
BSF INTCON,GIE ; Enable interrupts (if using)
BCF STATUS,RP0 ; Bank 2
INCF EEADR,F ; Increment address
MOVF EEADR,W ; Check if lower two bits of address are ‘00’
ANDLW 0x03 ; Indicates when four words have been programmed
XORLW 0x03 ;
BTFSC STATUS,Z ; Exit if more than four words,
GOTO LOOP ; Continue if less than four words