LIST p=16F873A
	#INCLUDE "P16F873A.INC"

ERT	EQU	H'20'
MOZ	EQU	H'2C'
ABB	EQU	H'24'
ABA	EQU	H'25'

	ORG	0000
	GOTO	START
	ORG	0004
	GOTO	MEG

START	CLRF	PORTA
	CLRF	PORTB
	CLRF	PORTC
	MOVLW	B'11000000'
	MOVWF	TMR0
	BSF	STATUS,5
	MOVLW	B'01000000'
	MOVWF	OPTION_REG
	MOVLW	B'10111000'
	MOVWF	INTCON
	MOVLW	B'00000001'
	MOVWF	PIE1
	CLRF	PIE2
	MOVLW	B'00000101'
	MOVWF	ADCON1
	MOVLW	B'00001111'
	MOVWF	TRISA
	MOVLW	B'11111111'
	MOVWF	TRISB
	CLRF	TRISC
	BCF	STATUS,5
	MOVLW	B'00111100'
	MOVWF	T1CON
	MOVF	PORTB,0
	MOVWF	ERT
ELSO	BSF	PORTC,7
	BTFSS	ERT,0
	GOTO	ELSO
	BTFSC	PORTC,0
	GOTO	EGY
	BSF	PORTC,0
	CLRF	ERT
	GOTO	ELSO
EGY	BTFSC	PORTC,1
	GOTO	KET
	BSF	PORTC,1
	CLRF	ERT
	GOTO	ELSO
KET	BTFSC	PORTC,2
	GOTO	HAR
	BSF	PORTC,2
	CLRF	ERT
	GOTO	ELSO
HAR	BTFSC	PORTC,3
	GOTO	NEG
	BSF	PORTC,3
	CLRF	ERT
	GOTO	ELSO
NEG	CLRF	PORTC
	CLRF	ERT
	GOTO	ELSO

MEG	BSF	ERT,0
	BCF	INTCON,0
	BCF	INTCON,1
	BCF	INTCON,2
	RETFIE
	END