The DS1307 has a built-in power-on reset circuit that initializes the clock to a known state after power-up. However, the clock does not start running automatically. You need to write a '1' to the clock halt (CH) bit in the hours register (address 0x02) to start the clock.
The EOSC pin is used to enable or disable the internal oscillator circuit. When EOSC is high, the oscillator is enabled, and the clock starts running. When EOSC is low, the oscillator is disabled, and the clock stops. This pin can be used to save power when the clock is not needed.
The DS1307 has a year register that only stores the last two digits of the year (00-99). To handle the year 2000 bug, you need to implement a software workaround to correctly interpret the year value. One approach is to use a century register to store the century value (19 or 20) and calculate the full year value in software.
The DS1307 clock accuracy is dependent on the crystal oscillator frequency and the temperature. The datasheet specifies an accuracy of ±20 ppm (parts per million) over the operating temperature range of -40°C to +85°C. This translates to an error of approximately ±1 minute per year.
Yes, the DS1307 has a built-in battery switchover circuit that allows you to connect a battery backup to maintain the clock operation during power failures. The VBAT pin is used to connect the battery, and the device automatically switches to battery power when the main power supply (VCC) is removed.
DS1307 datasheet
by Maxim Integrated Products
