Description
The M41T56 is a low power, serial real-time clock with 56 bytes of NVRAM. A built-in 32,768Hz oscillator (external crystal controlled) and the first 8 bytes of the RAM are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. Addresses and data are transferred serially via a two-line, bidirectional bus. The built-in address register is incremented automatically after each WRITE or READ data byte.
The M41T56 clock has a built-in power sense circuit which detects power failures and automatically switches to the battery supply during power failures. The energy needed to sustain the RAM and clock operations can be supplied from a small lithium coin cell.
Typical data retention time is in excess of 10 years with a 50mAh, 3V lithium cell. The M41T56 is supplied in an 8-lead plastic SOIC package.

Features
■ Counters for seconds, minutes, hours, day, date, month, years, 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 (100kHz protocol)
■ Ultra-low battery supply current of 450nA (typ at 3V)
■ 5V ±10% supply voltage
■ Timekeeping down to 2.5V
■ Automatic power-fail detect and switch circuitry
■ 56 bytes of general purpose RAM
■ Software clock calibration to compensate crystal deviation due to temperature
■ Automatic leap year compensation
■ Operating temperature of –40°C to 85°C
■ Available in an 8-lead, 150mil, plastic SOIC (SO8)
■ RoHS compliant
   – Lead-free second level interconnect