M41ST85WMX6TR

The M41ST85W is a combination serial real-time clock, microprocessor supervisor, and NVRAM supervisor. It is built in a low-power CMOS SRAM process and has a 64-byte memory space with 44 bytes of NVRAM and 20 memory-mapped RTC registers. The RTC registers are configured in binary coded decimal (BCD) format. The M41ST85W combines a 400 kHz I2C serial RTC with an automatic backup battery switchover circuit for powering an external LPSRAM as well as the internal RTC. When power begins to fail, the switchover automatically connects to the backup battery to keep the RTC and external LPSRAM alive in the absence of system power.

• Internal serial RTC and
• External low power SRAM (LPSRAM)
• 400 kHz I2C serial interface
• 3.0/3.3 V operating voltage
• Seconds, minutes, hours, day, date, month, and year
• Century
• Tenths/hundredths of seconds
• Clock calibration register allows compensation for crystal variations over temperature
• Programmable watchdog 62.5 ms to 128 s time-out period
• Early power-fail warning circuit (PFI/PFO) with 1.25 V precision reference