Summary description
The M41T81 is a low power Serial RTC with a built-in 32.768kHz oscillator (external crystal controlled).
   
Feature summary
■ Counters for tenths/hundredths of seconds,
    seconds, minutes, hours, day, date, month,
    year, and century
■ 32KHz crystal oscillator integrating load
    capacitance (12.5pF) providing exceptional
    oscillator stability and high crystal series
    resistance operation
■ Serial interface supports I2C bus (400kHz
    protocol)
■ Ultra-low battery supply current of 0.6µA
    (typ@3V)
■ 2.0 to 5.5V clock operating voltage
■ Automatic switch-over and deselect circuitry
    (for 3V application select M41T81S data sheet)
■ Power-down time stamp (HT bit) allowing
    determination of time elapsed in battery back
    up
■ Programmable alarm and interrupt function
    (valid even during battery back-up mode)
■ Accurate programmable watchdog timer (from
    62.5ms to 128s)
■ Software clock calibration to compensate
    crystal deviation due to temperature
■ Operating temperature of –40 to 85°C
■ ECOPACK® package available