list P=PIC18F458
#include P18F458.INC
R1 equ 0x07
R2 equ 0x08
ORG 0
	CLRF	TRISB		
	CLRF	TRISC		
	CLRF	TRISD		
	MOVLW	0x55		
	MOVWF	PORTB		
	MOVWF	PORTC		
	MOVWF	PORTD		
L3	COMF	PORTB,F	
	COMF	PORTC,F	
	COMF	PORTD,F	
	CALL	QDELAY	
	BRA	L3
QDELAY
	MOVLW D'200'
	MOVWF R1
D1	MOVLW D'250'
	MOVWF R2
D2	NOP
	NOP
	DECF R2, F
	BNZ D2
	DECF R1, F
	BNZ D1
	RETURN
	END