Summary description
The M41T6x Serial Access TIMEKEEPER® is a low power Serial RTC with a built-in 32.768 kHz oscillator (external crystal controlled). Eight registers (see Table 3 on page 19) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. An additional 8 registers provide status/control of Alarm, 32KHz output, Calibration, and Watchdog functions. Addresses and data are transferred serially via a two line, bi-directional I2C interface. The built-in address register is incremented automatically after each WRITE or READ data byte.

FEATURE summary
■ Counters for tenths/hundredths of seconds,
   seconds, minutes, hours, day, date, month,
   year, and century
■ 32 KHz crystal oscillator integrating load
   capacitance and high crystal series resistance
   operation
■ Oscillator stop detection monitors clock
   operation
■ Serial interface supports I2C bus (400kHz)
■ 350nA timekeeping current @ 3V
■ Low operating current of 35µA (@400kHz)
■ Timekeeping down to 1.0V
■ 1.3V to 4.4V I2C bus operating voltage
■ 32KHz square wave on power-up to drive a
   microcontroller in low power mode
   (M41T62/63/64)
■ Programmable (1Hz to 32KHz) square wave
   (M41T63/64)
■ Programmable alarm with interrupt function
   (M41T62/65)
■ Accurate programmable watchdog
   (from 62.5ms to 31 min)
■ Software clock calibration to compensate
   deviation of crystal due to temperature
■ Automatic leap year compensation
■ Operating temperature of –40 to 85°C
■ Lead-free 16-pin QFN package
■ Lithium ion rechargeable operation