23.4.1.2 Configure RTC

To operate the RTC, follow these steps:

  1. Set the compare value in the Compare (RTC.CMP) register, and/or the overflow value in the Period (RTC.PER) register.
  2. Enable the desired interrupts by writing to the respective interrupt enable bits (CMP, OVF) in the Interrupt Control (RTC.INTCTRL) register.
  3. Configure the RTC internal prescaler by writing the desired value to the Prescaler (PRESCALER) bit field in the Control A (RTC.CTRLA) register.
  4. Enable the RTC by writing a ‘1’ to the RTC Peripheral Enable (RTCEN) bit in the RTC.CTRLA register.
Note: The RTC peripheral is used internally during device start-up. Always check the Synchronization Busy bits in the Status (RTC.STATUS) and Periodic Interrupt Timer Status (RTC.PITSTATUS) registers, and on the initial configuration.