How to control the power of attiny13a via pin change interrupt?
#define F_CPU   1200000UL

#define LED     PB2 // PB2
#define BUTTON1 PB1 // INT0
#define BUTTON0 PB0 // PCINT0

#define HIGH         1
#define LOW          0
#define INPUT        0
#define OUTPUT       1
#define INPUT_PULLUP 2
#define FALSE        0
#define TRUE         1
#define _BV(bit)    (1 &lt;&lt; (bit))

#include &lt;avr/io.h&gt;
#include &lt;avr/interrupt.h&gt;
#include &lt;avr/sleep.h&gt;
#include &lt;util/delay.h&gt;

void pinMode(uint8_t pin, uint8_t mode){
    if(mode == OUTPUT) // Pin as output
        DDRB |= _BV(pin);
    else // Pin as input or input pullup
    {
        DDRB &amp;= ~_BV(pin); // Set pin as input
        if(mode == INPUT_PULLUP)
            PORTB |= _BV(pin); // Enable pullup resistors
    }
}

void digitalWrite(uint8_t pin, uint8_t val){
  if(val)
    PORTB |= _BV(pin);  // Set pin high
  else
    PORTB &amp;= ~_BV(pin); // Set pin low
}

uint8_t digitalRead(uint8_t pin){
  return !!(PINB &amp; _BV(pin));
}

//wake up
ISR(INT0_vect){
   sleep_disable();
   //cli(); // Turn off global interrupts
   digitalWrite(LED, HIGH);
}

void blink(){
    digitalWrite(LED, LOW);
    _delay_ms(1000);
    digitalWrite(LED, HIGH);
    _delay_ms(1000);
}

// go to sleep
ISR(PCINT0_vect)
{
   //cli(); // Turn off global interrupts
   if(!digitalRead(BUTTON0)){
        cli(); // Turn off global interrupts

        blink();

        digitalWrite(LED, LOW);

        sei(); // Turn on global interrupts
        set_sleep_mode(SLEEP_MODE_PWR_DOWN);
        sleep_enable();
        sleep_cpu();
    }
}

int main(void)
{
    //enabled external interrupt
    MCUCR=0;
    //MCUCR=0b00000000;
    GIMSK|=_BV(INT0); // enabled external interrupt INT0 - PB1

    // Sets the Pin change interrupt mask
    GIMSK|=_BV(PCIE);
    PCMSK|=_BV(PCINT0);//PB0

    pinMode(LED, OUTPUT);       
    digitalWrite(LED, LOW);

    pinMode(BUTTON1, INPUT_PULLUP);//INT0 - PB1
    pinMode(BUTTON0, INPUT_PULLUP);//PCINT0 - PB0

    //Enables Interrupts globally after setup
    //SREG |= _BV(SREG_I); 
    sei(); // Turn on global interrupts
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
    sleep_enable();
    sleep_cpu();

    while(TRUE){}

    return 0;
}