ORG	 0
		MOV 	 A,#55H	
BACK:	MOV 	 P1,A	
		ACALL DELAY	
		CPL	 A		
		SJMP	 BACK	
DELAY:
		MOV	 R5,#0FFH	
AGAIN:	DJNZ	 R5,AGAIN	
		RET			
		END