arduino - pin change interrupts (analog pins)

#include <avr/interrupt.h>

#define sbi(sfr, bit) ((sfr) |= (1 << (bit)))
#define cbi(sfr, bit) ((sfr) &= ~(1 << (bit)))

/* Pin to interrupt map:
 * D0-D7 = PCINT 16-23 = PCIR2 = PD = PCIE2 = pcmsk2
 * D8-D13 = PCINT 0-5 = PCIR0 = PB = PCIE0 = pcmsk0
 * A0-A5 (D14-D19) = PCINT 8-13 = PCIR1 = PC = PCIE1 = pcmsk1
 */

volatile int state;

void setup()
{
  Serial.begin(9600);

  sbi(PCICR, PCIE1);
  sbi(PCMSK1, PCINT8);
  sbi(PCMSK1, PCINT9);
}

void loop()
{
  if (state == 1) {
    Serial.println("ISR was triggered");
    state = 0;
  }
}

ISR(PCINT1_vect)
{
  state = 1;
}