ST STM32F446 Series User Manual

Power controller (PWR) RM0390
102/1328 RM0390 Rev 4
5.3.3 Low power mode
Entering low power mode
Low power modes are entered by the MCU executing the WFI (Wait For Interrupt), or WFE
(Wait For Event) instructions, or when the SLEEPONEXIT bit in the Cortex
®
-M4 System
Control register is set on Return from ISR.
Exiting low power mode
From Sleep and Stop modes the MCU exits low power mode depending on the way the
mode was entered:
• If the WFI instruction or Return from ISR was used to enter the low power mode, any
peripheral interrupt acknowledged by the NVIC can wake up the device
• If the WFE instruction was used to enter the low power mode, the MCU exits the mode
as soon as an event occurs. The wakeup event can by generated either by:
– NVIC IRQ interrupt
- When SEVEONPEND=0 in the Cortex
®
-M4 System Control register.
By enabling an interrupt in the peripheral control register and in the NVIC. When
the MCU resumes from WFE, the peripheral interrupt pending bit and the NVIC
peripheral IRQ channel pending bit (in the NVIC interrupt clear pending register)
have to be cleared.
Only NVIC interrupts with sufficient priority will wakeup and interrupt the MCU.
- When SEVEONPEND=1 in the Cortex
®
-M4 System Control register.
By enabling an interrupt in the peripheral control register and optionally in the
NVIC. When the MCU resumes from WFE, the peripheral interrupt pending bit and
(when enabled) the NVIC peripheral IRQ channel pending bit (in the NVIC
interrupt clear pending register) have to be cleared.
All NVIC interrupts will wakeup the MCU, even the disabled ones.
Only enabled NVIC interrupts with sufficient priority will wakeup and interrupt the
MCU.
- Event
Configuring a EXTI line in event mode. When the CPU resumes from WFE, it is
not necessary to clear the EXTI peripheral interrupt pending bit or the NVIC IRQ
channel pending bit as the pending bits corresponding to the event line is not set.
It may be necessary to clear the interrupt flag in the peripheral.
From Standby and Shutdown modes the MCU exits Low power mode through an external
reset (NRST pin), an IWDG reset, a rising edge on one of the enabled WKUPx pins or a
RTC event (see Figure 240: RTC block diagram).
5.3.4 Sleep mode
Entering Sleep mode
The Sleep mode is entered according to Entering low power mode, when the SLEEPDEEP
bit in the Cortex
®
-M4 System Control register is cleared.
Refer to Table 16 for details on how to enter the Sleep mode.

ST STM32F446 Series Specifications

General

Brand	ST
Model	STM32F446 Series
Category	Microcontrollers
Language	English