21.4.4 Sleep Mode Operation

The RTC will continue to operate in any sleep mode where the source clock is active. RTC interrupts can be used to wake the device from a sleep mode. RTC events can trigger other operations in the system without exiting sleep mode.

An interrupt request will be generated after wake-up if the Nested Vectored Interrupt Controller (NVIC) is configured accordingly. Refer to the NVIC – Nested Vectored Interrupt Controller section for details. Otherwise, the CPU will wake up directly, without triggering any interrupt. In this case, the CPU will continue executing from the first instruction that followed the entry into sleep.

Periodic events can also wake up the CPU through the interrupt function of the Event System (EVSYS). In this case, the event must be enabled and connected to an event channel with its interrupt enabled. Refer to the EVSYS – Event System chapter for more information.

When the device is in Standby sleep mode, the Direct Memory Access (DMA) engine is not able to write to the Counter Value (COUNT) register. To write to the COUNT register with the DMA the device must be in Active mode or Idle sleep mode. Refer to the DMAC – Direct Memory Access Controller and PM - Power Manager chapters for details.