M41T81SM6F Datasheet PDF - ST Microelectronics

The M41T81SM6F is a low-power serial Real-time Clock (RTC) IC with a built-in 32.768kHz oscillator (external crystal controlled). 8 bytes of the SRAM are used for the clock/calendar function and are configured in binary-coded decimal (BCD) format. An additional 12 bytes of SRAM provide status/control of alarm, watchdog and square wave functions. Addresses and data are transferred serially via a two line, bidirectional I²C interface. The built-in address register is incremented automatically after each WRITE or READ data byte. It has a built-in power sense circuit which detects power failures and automatically switches to the battery supply when a power failure occurs. The energy needed to sustain the clock operations can be supplied by a small lithium button supply when a power failure occurs. Functions available to the user include a non-volatile, time-of-day clock/calendar, alarm interrupts, watchdog timer and programmable square wave output.

● Counters for tenths/hundredths of seconds, minutes, hours, day, date, month, year and century

● Oscillator stop detection (monitors clock operation)

● 0.6µA (typical) Ultralow battery supply current

● 2 to 5.5V Clock operating voltage

● Power-down time-stamp (HT bit) which allows determination of time elapsed in battery backup

● Battery low flag

● Programmable alarm and interrupt function

● Accurate programmable watchdog timer

● Software clock calibration