[hungpq]

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.

; 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