ORG		00H
PORTA	EQU		7CFFH 			;A口
PORTB	EQU		7DFFH 			;B口
PORTC	EQU		7EFFH 			;C口
CADDR	EQU		7FFFH 			;控制字地址
		SJMP	START
		ORG		30H
START:	MOV		A,#82H   		;方式0,PA,PC輸出，PB輸入
		MOV		DPTR,#CADDR
		MOVX    @ DPTR,A
		MOV     DPTR,#PORTB
		MOVX    A,@ DPTR      	;讀入B口
		MOV     DPTR,#PORTA
		MOVX    @DPTR,A   		;輸出到A口
        CALL	DELAY 
		LJMP	START
DELAY:	MOV		R6,#0
        MOV		R7,#0
DELAYLOOP:
		DJNZ	R6,DELAYLOOP
		DJNZ	R7,DELAYLOOP
		RET
		END