ORG	0
		LJMP	MAIN
		ORG	23H
		LJMP	SERIAL		
		ORG	30H
MAIN:		MOV	P1,#0FFH		
		MOV	TMOD,#20H		
		MOV	TH1,#0FDH		
		MOV	SCON,#50H		
		MOV	IE,#10010000B	
		SETB	TR1			
BACK:		MOV	A,P1			
		MOV	SBUF,A  		
		MOV	P2,A			
		SJMP	BACK			
		ORG	100H
SERIAL:	JB	TI,TRANS		
		MOV	A,SBUF		
		CLR	RI			
		RETI				
TRANS: 	CLR	TI			
		RETI				
		END