#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 counter = 0; 
int main(void)
{
 DDRB = 0xFE; 
 PORTB = 0x01; 
 DDRA = 0xFF; 
 pcint0_init(); 
 while(1)
 {
 if(PinChange) 
 {
 PORTA |= 0x80;
 _delay_ms(1000);
 PORTA &= ~0x80;
 PinChange = 0; 
 }
 }
}

void pcint0_init(void)
{
 cli();
 PCICR |= (1 << PCIE0);
 PCMSK0 |= (1 << PCINT0); 
 PCIFR |= (1 << PCIF0);
 sei(); // SREG = 1
}

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