ORG	0
BACK:	MOV 	A,#55H	
	MOV  	P1,A		
	LCALL 	DELAY	
	MOV 	A,#0AAH	
	MOV	P1,A		
	LCALL	DELAY	
	SJMP 	BACK		
	ORG	300H		
DELAY:	MOV	R5,#0FFH	
AGAIN:	DJNZ 	R5,AGAIN	
	RET			
	END