Real-time clocks (RTC) keep track of days, dates and time, including century, year, month, hour, minutes, and seconds. Many include battery switchover circuits, enabling them to keep time even when power is off. Other timekeeping functions offered include alarm and watchdog, and a calibration register supports high accuracy requirements.
RTC options include supervisory functions such as power-on reset/low-voltage detect, early power-fail warning, battery monitor, and more. Some parts such as the M41ST85 non-volatizor can be used as NVRAM supervisors by providing battery switchover and write protection for external low-power SRAMs.
ST's popular serial RTCs support both SPI and I2C buses, and come in packages ranging from QFN16 and TSSOP8 to ST's SNAPHAT® with removable/replaceable battery with crystal
M41ST87Securitizor - Combination Serial RTC, Microprocessor Supervisor,
and NVRAM Controller with special security functions for Tamper
Detect and RAM Clear
