To operate the PIT, follow these steps:
  1. 1.Configure the RTC clock CLK_RTC as described in section Configure the Clock CLK_RTC.
  2. 2.Enable the interrupt by writing a ‘1’ to the Periodic Interrupt (PI) bit in the PIT Interrupt Control (RTC.PITINTCTRL) register.
  3. 3.Select the period for the interrupt by writing the desired value to the Period (PERIOD) bit field in the Periodic Interrupt Timer Control A (RTC.PITCTRLA) register.
  4. 4. Enable the PIT by writing a ‘1’ to the Periodic Interrupt Timer Enable (PITEN) bit in the RTC.PITCTRLA register.
Note: The RTC peripheral is used internally during device start-up. Always check the Synchronization Busy bits in the RTC.STATUS and RTC.PITSTATUS registers, and on the initial configuration.