MOVB	#$FF,DDRB		
	MOVB	#$7F,DDRA		
	CLC
 	LDAA	#$66  		
	STAA	PORTB   		
TURN 	BRCLR	PORTA,$80,CW 	
  	LSRA        		
  	BCC	OVER
  	ORAA	#$80
OVER	JSR	DELAY   		
  	STAA	PORTB      	
 	BRA	TURN     		
CW	LSLA          		
  	BCC 	OV1
  	ORAA #$01
OV1 	JSR	DELAY  		
  	STAA 	PORTB    		
  	BRA	TURN