The real time clock module in the FR59xx family, provides clock counters with calendar mode, a flexible programmable alarm, and the ability to perform calibration. The RTC module is functional in LPM3.5 when the core LDO is turned off allowing for extremely low current consumption while maintaining the RTC count. Wakeup from this mode can be in the form of event interrupts or alarms. On wakeup from LPM3.5 the device undergoes a reset similar to a Brownout reset and the RTC registers such as the interrupts need to be re-enabled on startup.

