并行io端口扩充键盘.asm

基于Proteus的51系列单片机设计与仿真

       ORG    00H
PORTA  EQU    0000H
PORTB  EQU    4000H
PORTC  EQU    0C000H
CONTA  EQU    7FFFH
       AJMP   START
       ORG    20H
START: MOV    A,#90H
       MOV    DPTR,#PORTC
       MOVX   @DPTR,A
       MOV    DPTR,#PORTA
       MOVX   A,@DPTR       
       MOV    DPTR,#PORTB
       MOVX   @DPTR,A
       CALL   DELAY
       LJMP   START
DELAY: MOV    R7,#05H
DELA:  MOV    R6,#28H
DEL:   MOV    R5,#5AH
       DJNZ   R5,$
       DJNZ   R6,DEL
       DJNZ   R7,DELA
       RET
       END