Real-time clock (RTC) - definition
Real-time clock (RTC) - definition
The Real-Time Clock (RTC, or Real-Time Clock) is a specialised electronic circuit used to maintain accurate real time, regardless of the operating state of the main digital system. The RTC is designed for continuous timekeeping - seconds, minutes, hours, days, and often months and years - even in situations where power to the main microprocessor system is off. This function is enabled by the use of an independent power supply, usually in the form of a backup battery or capacitor.
RTC circuits typically integrate a clock generator based on a 32.768 kHz Quartz crystals resonator, which provides high stability and timing accuracy. In addition, they contain registers storing timing data, and often a calendar with leap year correction, as well as timing alarms and interrupt functions. Communication with the microcontroller or processor is via standard serial interfaces such as I²C, SPI or sometimes parallel buses.
RTC is used in a wide range of electronic devices, from personal computers, embedded systems, data loggers, medical equipment to industrial automation and smart measurement systems. In personal computers, the RTC is responsible for maintaining system time between power cycles, and can also interact with the BIOS or operating system. In energy-saving systems, the RTC allows the device to be cycled out of sleep mode or to schedule events over time.
From an electronics design point of view, the choice of RTC takes into account parameters such as current consumption in standby mode, timing accuracy, operating temperature range and availability of additional functions. For high reliability applications, temperature compensation mechanisms are also often used, as well as synchronisation with external time sources, e.g. via GPS or network NTP protocols.
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