Ensamblador - Encender un led cada 0.5 segundos usando temporizador

LIST		P=16F84A

	INCLUDE		<P16F84A.INC>

	CBLOCK  	0x0C				; In this position starts user´s RAM.

	ENDC

	#DEFINE  LED	PORTB,0

;**********************************************************************************************

	ORG	0x00

INICIO

	bsf		STATUS,RP0			; Access to bank 1

	bcf		LED					; LED line configurated like OUTPUT

	bcf		STATUS,RP0			; Access to Bank 0.

PRINCIPAL

	bsf		LED					; Turn on the LED

	call	Retardo_200ms		; while the sum of this time

	call	Retardo_200ms

	bcf		LED					; It turns off while the sum of the next retardos

	call	Retardo_200ms

	call	Retardo_100ms

	goto 	PRINCIPAL

; Subrutinas "Retardo_200ms" y "Retardo_100ms"-------------------------------------------

	CBLOCK

			R_ContA				; Counters for the retardos

			R_ContB

	ENDC

			Retardo_200ms		; The named "call" aports 2 machine cycles.

	movlw	d'200'				; It Aports 1 machine cycle. This is the value of "M".

	goto	Retardos_ms			; It aports 2 machine cycles.

			Retardo_100ms		; The named "call" aports 2 machine cycles.

	movlw	d'100'				; It aports 1 machine cycle.This is the value of "M".

	goto	Retardos_ms			; It aport 2 machine cycles.

			Retardo_1ms			; The named "call" aports 2 machine cycles.

	movlw	d'1'				; It aports 1 machine cycle. This is the value of "M".

			Retardos_ms

	movwf	R_ContB				; It aports 1 machine cycle.

			R1ms_BucleExterno

	movlw	d'249'				; It aports Mx1 machine cycles. This is the value of "K".

	movwf	R_ContA				; It aports Mx1 machine cycles.

			R1ms_BucleInterno

	nop							; It aports KxMx1 machine cycles.

	decfsz	R_ContA,F			; (K-1)xMx1 cm (when it doesn´t jump) + Mx2 cm (when it jumps).

	goto	R1ms_BucleInterno 	; It aports (K-1)xMx2 machine cycles.

	decfsz	R_ContB,F			; (M-1)x1 cm (when it doesn´t jump) + 2 cm (when it jumps).

	goto	R1ms_BucleExterno 	; It aports (M-1)x2 machine cycles.

	return						; The return Jump aports  2 machine cycles.

	END