#include <avr/io.h> 
#include <avr/interrupt.h> 
#include <avr/pgmspace.h> 
#include <util/delay.h>
 
void pcint0_init(void);  

volatile unsigned char PinChange = 0;
volatile unsigned char PinState = 0x00;

int main(void) {

  DDRB = 0xF0;
  PORTB = 0x0F;
  DDRA = 0xFF;

  pcint0_init();

  while(1) {
    if(PinChange) {
      switch (PinState) {
        case 0x08:
          PORTA |= 0x08;
          _delay_ms(1000);
          PORTA &= ~0x08;
          PinChange = 0;
          PinState = 0x00;
          break;
        case 0x04:
          PORTA |= 0x04;
          _delay_ms(1000);
          PORTA &= ~0x04;
          PinChange = 0;
          PinState = 0x00;
          break;
        case 0x02:
          PORTA |= 0x02;
          _delay_ms(1000);
          PORTA &= ~0x02;
          PinChange = 0;
          PinState = 0x00;
          break;
        case 0x01:
          PORTA |= 0x01;
          _delay_ms(1000);
          PORTA &= ~0x01;
          PinChange = 0;
          PinState = 0x00;
          break;
        default:
          PinChange = 0;
          PinState = 0x00;
          break;
      }
    }
  }
}

void pcint0_init(void) {
  cli();
  PCICR |= (1 << PCIE0);
  PCMSK0 = PCMSK0 | (1 << PCINT0) | (1 << PCINT1) | (1 << PCINT2) | (1 << PCINT3);
  PCIFR |= (1 << PCIF0);
  sei();
}

ISR(PCINT0_vect) {
  PinChange = 1;
  PinState = PINB;
  PCIFR |= (1 << PCIF0);
}