ORG	0000H
		LJMP	MAIN		
		ORG	001BH		
		ORG	0030H  	
MAIN:		MOV	TMOD,#10H	
	  	MOV	P0,#0FFH	
		MOV	TL1,#018H	
		MOV	TH1,#0FCH	
		MOV	IE,#88H	
		SETB	TR1		
BACK:		MOV	A,P0		
		MOV	P1,A		
		SJMP	BACK		
ISR_T1:	CLR	TR1		
		CLR	P2.1		
		MOV	R2,#4		
HERE:		DJNZ	R2,HERE	
		MOV	TL1,#18H	
		MOV	TH1,#0FCH	
		SETB	TR1		
		SETB	P2.1		
		RETI			
		END