R2	EQU	0x2
R3	EQU	0x3	
R4	EQU	0x4
	MOVLW 	0x55		
	MOVWF  	PORTB		
BACK	CALL 	DELAY_500MS	
	COMF	PORTB		
	GOTO 	BACK		
DELAY_500MSEC
		MOVLW		D'20'	
		MOVWF		R4			
BACK		MOVLW		D'100'	
		MOVWF		R3		
AGAIN		MOVLW		D'250'	
		MOVWF		R2		
HERE		NOP
		NOP				
		DECF		R2, F		
		BNZ		HERE		
		DECF		R3, F		
		BNZ		AGAIN	
		DECF		R4, F		
		BNZ		BACK
		RETURN