twi_init();
    twi_set_addr_slave( TWI_ADDR_DS1307 );
    u8 temp = twi_read_byte( DS1307_OSCILLATOR_EN_REG );
    if( temp & (1 << 7) )
    { // часы не запущены и не выставлены
        twi_write_byte( DS1307_OSCILLATOR_EN_REG, DS1307_OSCILLATOR_ENABLE );
        twi_write_byte( DS1307_ADDR_CONTROL, DS1307_OUT_L | DS1307_SQWE_OFF );

        // 14 апреля 2008 года. 16:50
        twi_write_byte( DS1307_ADDR_YEAR,    0x08 ); 
        twi_write_byte( DS1307_ADDR_MONTH,   0x04 ); 
        twi_write_byte( DS1307_ADDR_DATE,    0x14 );
        twi_write_byte( DS1307_ADDR_HOURS,   0x16 ); 
        twi_write_byte( DS1307_ADDR_MINUTES, 0x50 ); 
    }