ST STM32L4+ Series Reference Manual page 204

Power control (PWR)
1. Optional: Jump into the SRAM and power-down the Flash by setting the RUN_PD bit in
the
2. Decrease the system clock frequency below 2 MHz.
3. Force the regulator in low-power mode by setting the LPR bit in the PWR_CR1 register.
Refer to
Exiting the Low-power run mode
To exit the Low-power run mode, proceed as follows:
1. Force the regulator in main mode by clearing the LPR bit in the PWR_CR1 register.
2. Wait until REGLPF bit is cleared in the PWR_SR2 register.
3. Increase the system clock frequency.
Refer to
Low-power run mode
Mode entry
Mode exit
Wakeup latency
5.3.3 Low-power modes
Entering low-power mode
Low-power modes are entered by the MCU by executing the WFI (Wait For Interrupt), or
WFE (Wait for Event) instructions, or when the SLEEPONEXIT bit in the Cortex
System Control register is set on Return from ISR.
Entering Low-power mode through WFI or WFE will be executed only if no interrupt is
pending or no event is pending.
Exiting low-power mode
From Sleep modes, and Stop modes the MCU exit low-power mode depending on the way
the low-power 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 is used to enter the low-power mode, the MCU exits the low-
power mode as soon as an event occurs. The wakeup event can be generated either
by:
–
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Flash access control register
Table 28: Low-power run
Table 28: Low-power run
Decrease the system clock frequency below 2 MHz
LPR = 1
LPR = 0
Wait until REGLPF = 0
Increase the system clock frequency
Regulator wakeup time from low-power mode
NVIC IRQ interrupt.
- When SEVONPEND = 0 in the Cortex
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
(FLASH_ACR).
on how to enter the Low-power run mode.
on how to exit the Low-power run mode.
Table 28. Low-power run
Description
®
-M4 System Control register. By enabling
RM0432 Rev 6
RM0432
®
-M4