The RV5C339A is a CMOS real-time clock IC connected to the CPU by three signal lines CE (Chip Enable), SCLK (Serial Clock), and SIO (Serial Input/Output), and configured to perform serial transmission of time and calendar data to the CPU. This model incorporates different functional circuits. The periodic interrupt circuit is configured to generate interrupt signals with six selectable interrupts ranging from 0.5 seconds to 1 month. The 2 alarm circuits generate interrupt signals at preset times. The oscillation circuit is driven under constant voltage so that fluctuations in oscillation frequency due to voltage are small and supply current is also small (TYP. 0.35A at 3 volts). The oscillation halt sensing circuit can be used to judge the validity of internal data in such events as poweron. The supply voltage monitoring circuit is configured to record a drop in supply voltage below two selectable supply voltage monitoring threshold settings. The 32-kHz clock output function (Nch. open drain) is intended to output sub-clock pulses for the external microcomputer. The oscillation adjustment circuit is intended to adjust time counts with high precision by correcting deviations in the oscillation frequency of the crystal oscillator. This model comes in an ultra-compact 10-pin SSOP-G (with a height of 1.20mm and a pin pitch of 0.5mm).