The RTC_B module can be configured for real-time clock (RTC) or calendar mode providing seconds, minutes, hours, day of week, day of month, month, and year. Calendar mode integrates an internal calendar which compensates for months with less than 31 days and includes leap year correction. The RTC_B also supports flexible alarm functions and offset-calibration hardware. The implementation on this device supports operation in LPM3.5 mode and operation from a backup supply.
Using the MSP430 RTC_B Module With Battery Backup Supply describes how to use the RTC_B with battery backup supply functionality to retain the time and keep the RTC counting through loss of main power supply, as well as how to handle correct reinitialization when the main power supply is restored.