RTC Interrupt

#include <avr/sleep.h>
#include <Wire.h>
#include "Sodaq_DS3231.h"

static uint8_t prevSecond=0;

void setup ()
{
/*Initialize INT0 for accepting interrupts */
PORTD |= 0x04;
DDRD &=~ 0x04;

Serial.begin(57600);
Wire.begin();

rtc.begin();
attachInterrupt(0, INT0_ISR, FALLING);

//Enable Interrupt
rtc.enableInterrupts(EveryMinute); //interrupt at EverySecond, EveryMinute, EveryHour
// or this
//rtc.enableInterrupts(18,4,0); // interrupt at (h,m,s)
}

void loop ()
{

DateTime now = rtc.now(); //get the current date-time
if((now.second()) != prevSecond )
{
//print only when there is a change in seconds
Serial.print(now.year(), DEC);
Serial.print('/');
Serial.print(now.month(), DEC);
Serial.print('/');
Serial.print(now.date(), DEC);
Serial.print(' ');
Serial.print(now.hour(), DEC);
Serial.print(':');
Serial.print(now.minute(), DEC);
Serial.print(':');
Serial.print(now.second(), DEC);
Serial.println(' ');
}
prevSecond = now.second();
rtc.clearINTStatus();

}

//Interrupt service routine for external interrupt on INT0 pin conntected to /INT
void INT0_ISR()
{
//Keep this as short as possible. Possibly avoid using function calls