MOV	TMOD,#2H		
						
		MOV	TH0,#-150		
AGAIN:	SETB	P1.3			
		ACALL DELAY
		ACALL DELAY
		CLR	P1.3			
		ACALL DELAY
		SJMP	AGAIN
DELAY:		
		SETB	TR0			
BACK:		JNB	TF0,BACK		
		CLR	TR0			
		CLR	TF0			
		RET