Arduino/AVR sleep function kicked by Pin Change Interrupt(GPIO interrupt).

sleep.c

#include <avr/sleep.h>

void setup()
{
  pinMode(6, INPUT);
  pinMode(13, OUTPUT);
	Serial.begin(9600);
  digitalWrite(13, HIGH);
}

void pm_sleep()         // here we put the arduino to sleep
{
    /* Now is the time to set the sleep mode. In the Atmega8 datasheet
     * http://www.atmel.com/dyn/resources/prod_documents/doc2486.pdf on page 35
     * there is a list of sleep modes which explains which clocks and 
     * wake up sources are available in which sleep mode.
     *
     * In the avr/sleep.h file, the call names of these sleep modes are to be found:
     *
     * The 5 different modes are:
     *     SLEEP_MODE_IDLE         -the least power savings 
     *     SLEEP_MODE_ADC
     *     SLEEP_MODE_PWR_SAVE
     *     SLEEP_MODE_STANDBY
     *     SLEEP_MODE_PWR_DOWN     -the most power savings
     *
     * For now, we want as much power savings as possible, so we 
     * choose the according 
     * sleep mode: SLEEP_MODE_PWR_DOWN
     * 
     */  
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);   // sleep mode is set here

    sleep_enable();          // enables the sleep bit in the mcucr register


		sei();

    sleep_mode();
		/*- long time passed -*/
    sleep_disable();

}

ISR(PCINT2_vect) {
	cli();
	digitalWrite(13, HIGH);
	sei();
	Serial.println("fuga");
}

void loop()
{
	Serial.println("hoge");
	sei();
	digitalWrite(13, LOW);
	delay(1000);
	/*- PCINT22 is Arduino pin6.
	 *  This is corresponding to PCI2.-*/
	PCMSK2 = 1 << 6;
	PCICR = 1 << 2;
	Serial.println("hoge");
	delay(100);
	pm_sleep();
	while(1);
}