Real time clock chip (RTC) is a high-performance, low-power circuit with RAM memory, mainly used for timing and calendar functions. It can accurately time years, months, days, Sundays, hours, minutes, and seconds, and has leap year compensation function. The RTC chip communicates synchronously with the CPU or SoC through the IIC communication interface, supporting burst mode transmission of multiple bytes of clock signals or RAM data. Internally integrated RAM registers are used for temporary storage of data.

Working principle
The working principle of clock chips is based on crystal oscillators, which generate stable frequency signals. Adjust the signal of the crystal oscillator to the desired clock frequency through frequency division and multiplication circuits. A crystal oscillator is a device that uses mechanical vibrations of crystals to generate electrical signals, and its frequency is very stable, usually between tens of thousands to tens of millions of hertz.

Typical applications
Taking the FH8563 clock chip as an example, its application diagram is as follows:
The SCL and SDA pins need to be connected to the I2C bus of the controller.
The battery BAT (marked as CR1220 in the figure) serves as a backup power source. When VDD is lower than the battery voltage, the battery supplies power to the chip.
It is recommended to reserve capacitors (marked as C1/C2 positions in the figure) for the OSCI/OSCO (marked as XI/XO in the figure) pins of the chip to fine tune the clock frequency. The CLKOUT and INT pins can be connected to the circuit according to actual needs and remain suspended when not in use.

precautions
When the system is powered on, please ensure that the power supply sequence of the pull-up resistor on the I2C bus is not earlier than the power supply of FH8563 to ensure the normal operation of the system.