Real Time Clock (RTC)

The purpose of an RTC or a real time clock is to provide precise time and date which can be used for various applications. RTC is an electronic device in the form of an Integrated Chip (IC) available in various packaging options. It is powered by an internal lithium battery. As a result of which even if the power of the system is turned off, the RTC clock keeps running.

It plays a very important role in the real time systems like digital clock, attendance system, digital camera etc. In applications where time stamp is needed, RTC is a good option. Using RTC for designing such application has always been a good designer’s choice although the beginning might be a bit difficult.

While designing any real time system which deals with time, there are two ways of handling the time factor. One is to generate the time internally which is done by programming the timers of the controller; and the other is to use an RTC. The following table shows the comparison of these methods while designing a real time application.

S.No.	Parameter	Internal Timers	RTC
1.	Error	High and keeps increasing with time	Almost negligible. Of the order of 1 sec in 100 years
2.	Memory space usage	High	Low
3.	CPU usage	High	Low
4.	Ease of Interfacing	Easy	Difficult
5.	Program complexity	High	Low
6.	Efficiency of system	Low	High
7.	Achieving goals of the system	Difficult	Easy
8.	Cost	Low	High

DS12C887 is a commonly used RTC by Dallas Semiconductors. It can be easily interfaced with 8051 microcontroller (AT89C51). To explore the basic operation of accessing the internal registers and extracting time from the RTC, refer interfacing RTC DS12C887 with AT89C51.

More RTC DS12C887 based projects:

Digital clock using RTC DS12C887 and 8051 microcontroller (AT89C51) with time set

Clock using RTC DS12C887 & 8051 microcontroller (AT89C51) with alarm set function

LCD based clock using RTC DS12C887 and 8051 microcontroller (AT89C51) using update interrupt

Digital clock using DS12C887 & 8051 microcontroller (AT89C51) in 12 hour mode