The M41T81M6F is a Real Time Clock (RTC) circuit manufactured by STMicroelectronics. It features a 2-wire, I2C, serial interface and has an SRAM of 20b. The power supply range is 2÷5.5V and the packaging of the chip is SO8. It is used in applications where precise time keeping is required, such as in timing control, precision synchronizing, and event logging. The M41T81M6F is a low power CMOS device with backup battery operation in the event of power failure, fast access time and advanced function, and includes an embedded alarm, periodic time-stamp and programmable square-wave output.