A Real Time Clock is like a watch – it runs on a battery and keeps time even when there is a power outage.
- DS1307 is an I2c based serial real time clock (RTC).
- RTC keep track of seconds, minutes, hours, date of month, month, day of month and year with leap year compensation which is valid upto year 2100.
- The clock can be programmed to operate either in 12-hour or 24-hour format.
- DS1307 requires very less number of components to operate.
- RTC DS1307 operate in frequency of crystal oscillator 32.768kHz.
- DS1307 uses I2C Protocol.
- RTC act as a slave device and I2C Master can read/write register of RTC.
- To communicate with the slave device, master need the slave address of device connected on bus.
- DS1307 has fixed slave address.
- Slave Address
- 7-Bit format: 0b1101000 = 0x68
- Slave address for I2C Write: 0b11010000 = 0xD0
- Slave address for I2C Read: 0b11010001 = 0xD1.
Application
- Digital Clock.
Hardware Required

- DS1307.
- 3.3v Cmos battery.
- 8051 MicroController.
Pinout
- SCL and SDA to port pins.
- Gnd: Gnd.
Circuit
