R1 EQU $1201			
R2 EQU $1202
R3 EQU $1203
COUNT_1 EQU 100	
COUNT_2 EQU 100
COUNT_3 EQU 10
	MOVB	#$FF,DDRB	
	MOVB	#$55,PORTB
	MOVB	#COUNT_3,R3
LOP_3	MOVB	#COUNT_2,R2
LOP_2	MOVB	#COUNT_1,R1
LOP_1	COM	PORTB
	DEC	R1
	BNE	LOP_1
	DEC	R2
	BNE	LOP_2
	DEC	R3
	BNE	LOP_3