sleepmode:

//start timer0
  TCNT0 = 0;
  TCCR0 |= 0x07; //Set 1024 prescaler for timer0 and normal mode
  TIMSK |= 0x01; //Enable interrupt from timer0 overflow

//set Sleep Enable bit
  MCUCR |= 0x20;
  
  asm("sleep");
  
//clear Sleep Enable bit
  MCUCR &=~ 0x20;

//stop timer0
  TCCR0 &=~ 0x07; //Switch off timer0
  TIMSK &=~ 0x01; //Disable interrupt from timer0 overflow

  timer_++;
  if (timer_ < 25)
       goto sleepmode;

    #define SLEEP_MODE_IDLE         (0)
    #define SLEEP_MODE_ADC          _BV(SM0)
    #define SLEEP_MODE_PWR_DOWN     _BV(SM1)
    #define SLEEP_MODE_PWR_SAVE     (_BV(SM0) | _BV(SM1))
    #define SLEEP_MODE_STANDBY      (_BV(SM1) | _BV(SM2))
    #define SLEEP_MODE_EXT_STANDBY  (_BV(SM0) | _BV(SM1) | _BV(SM2))

    #define set_sleep_mode(mode) \
    do { \
        _SLEEP_CONTROL_REG = ((_SLEEP_CONTROL_REG & ~(_BV(SM0) | _BV(SM1) | _BV(SM2))) | (mode)); \
    } while(0)

      set_sleep_mode(<mode>);
      cli();
      if (some_condition)
      {
        sleep_enable();
        sei();
        sleep_cpu();
        sleep_disable();
      }
      sei();