15.6.2.8.1 Idle Mode

The Idle mode allows power optimization with the fastest wake-up time.

The CPU is stopped. To further reduce power consumption, the user can disable the clocking of modules and clock sources by configuring the SLEEP.IDLE bit group. The module will be halted regardless of the bit settings of the mask registers in the Power Manager (PM.AHBMASK, PM.APBxMASK).

Regulator operates in normal mode.

• Entering Idle mode: The Idle mode is entered by executing the WFI instruction. Additionally, if the SLEEPONEXIT bit in the Arm Cortex System Control register (SCR) is set, the IDLE mode will also be entered when the CPU exits the lowest priority ISR. This mechanism can be useful for applications that only require the processor to run when an interrupt occurs. Before entering the Idle mode, the user must configure the Idle mode configuration bit group and must write a zero to the SCR.SLEEPDEEP bit.
• Exiting Idle mode: The processor wakes the system up when it detects the occurrence of any interrupt that is not masked in the NVIC Controller with sufficient priority to cause exception entry. The system goes back to the Active mode. The CPU and affected modules are restarted.