Description
●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 (see Table 2 on page 20). The RTC registers are configured in binary coded decimal (BCD) format.
●Features
●■ Automatic battery switchover and WRITE protect for:
●– Internal serial RTC and
●– External low power SRAM (LPSRAM)
●■ 400kHz I2C serial interface
●■ 3.0/3.3V operating voltage
●–VCC= 2.7 to 3.6V
●■ Ultra-low battery supply current of 500nA (max)
●■ RoHS compliant
●– Lead-free second level interconnect
●Serial RTC features
●■ 400kHz I2C
●■ 44 bytes of general purpose NVRAM
●■ Counters for:
●– Seconds, minutes, hours, day, date, month, and year
●–Century
●– 10ths/100ths of seconds
●– Clock calibration register allows compensation for crystal variations over temperature
●■ Programmable alarm with repeat modes
●– Functions in battery back-up mode
●■ Power-down timestamp (HT Bit)
●■ 2.5 to 5.5V oscillator operating voltage Microprocessor supervisor features
●■ Programmable watchdog
●– 62.5ms to 128s time-out period
●■ Early power-fail warning circuit (PFI/PFO) with 1.25V precision reference
●■ Power-on reset/low voltage detect
●– Open drain reset output
●– Reset voltage, VPFD= 2.60V (nom)
●– Two reset input pins
●– Watchdog can be steered to reset output
