The DS1302 is a real time clock (RTC) contains the trickle-charge time keeping chip. It communicates with a microprocessor via a simple serial interface. The real-time clock provides seconds, minutes, hours, day, date, month, and year. In DS1302, three wires are required to communicate with the clock (CE, I/O, and SCLK). Data can be transferred to and from the clock 1 byte at a time and up to 31 bytes. The DS1302 is designed to operate on very low power and retain data and clock information on less than 1uW. The DS1302 has dual power pins, one for primary and another for backup by a battery. In this exercise, learn how to use DS1302 and control several devices in different time.