OUTLINE
The Rx5C348A/B are CMOS real-time clock ICs connected to the CPU by four signal lines, CE, SCLK, SI, SO, and configured to perform serial transmission of time and calendar data to the CPU. 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 interrupt circuits generate interrupt signals at preset times. As the oscillation circuit is driven under constant voltage, fluctuation of the oscillator frequency due to supply voltage is small, and the time keeping current is small (TYP. 0.35µA at 3V: Rx5C348A, TYP.0.55µA at 3V: Rx5C348B). The oscillation halt sensing circuit can be used to judge the validity of internal data in such events as power-on; The supply voltage monitoring circuit is configured to record a drop in supply voltage below two selectable supply voltage monitoring threshold settings. The 32.768kHz clock output function (N-channel open drain output) is intended to output sub-clock pulses for the external microcomputer. The 32-kHz clock circuit can be disabled by certain register settings for the Rx5C348A but cannot be disabled by any register settings for the Rx5C348B. The oscillation adjustment circuit is intended to adjust time counts with high precision by correcting deviations in the oscillation frequency of the crystal oscillator. These models come in an ultra-compact SSOP10 (RS5C348A/B), SSOP10G (RV5C348A/B), TSSOP10G (RT5C348B)

FEATURES
● Timekeeping supply voltage ranging from 1.45 to 5.5V
● Low power consumption
   Rx5C348A: 0.35µA TYP (0.8µA MAX) at VDD=3V
   Rx5C348B: 0.55µA TYP (1.0µA MAX) at VDD=3V
● Only four signal lines (CE, SCLK, SI, and SO) required for connection to the CPU.
● Maximum clock frequency of 2 MHz (with VDD = 5V)
● Time counters (counting hours, minutes, and seconds) and calendar counters
   (counting years, months, days, and weeks) (in BCD format)
● Interrupt circuit configured to generate interrupt signals
   (with interrupts ranging from 0.5 seconds to 1 month)
   to the CPU and provided with an interrupt flag and an interrupt halt
● 2 alarm interrupt circuits
   (Alarm_W for week, hour, and minute alarm settings and Alarm_D
   for hour and minute alarm settings)
● 32-kHz clock output circuit (Nch. open drain output)
● The Rx5C348A is designed to disable 32-kHz clock output in response to a command
   from the host computer and the Rx5C348B is designed to keep 32-kHz output enabled.
● Oscillation halt sensing circuit which can be used to judge the validity of internal data
● Supply voltage monitoring circuit with two supply voltage monitoring threshold settings
● Automatic identification of leap years up to the year 2099
● Selectable 12-hour and 24-hour mode settings
● Built-in oscillation stabilization capacitors (CG and CD)
● High precision oscillation adjustment circuit
● Ultra-compact SSOP10 (RS5C348A/B), SSOP10G (RV5C348A/B), TSSOP10G (RT5C348B)
● CMOS process