ST STM32F301 6 Series Reference Manual page 84

Power control (PWR)
Refer to
When exiting Stop mode by issuing an interrupt or a wake-up event, the HSI RC oscillator is
selected as the system clock.
When the voltage regulator operates in low-power mode, an additional startup delay is
incurred when waking up from Stop mode. By keeping the internal regulator ON during Stop
mode, the consumption is higher although the startup time is reduced.
Stop mode
Mode entry
Mode exit
Wakeup latency
6.3.5 Standby mode
The Standby mode allows to achieve the lowest power consumption. It is based on the
Cortex-M4 deepsleep mode, with the voltage regulator disabled. The 1.8 V domain is
consequently powered off. The PLL, the HSI oscillator and the HSE oscillator are also
switched off. SRAM and register contents are lost except for registers in the RTC domain
and Standby circuitry (see
Caution: In the STM32F318x8 devices, the Standby mode is not available.
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Table 16 for more details on how to exit Stop mode.
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– Set SLEEPDEEP bit in Arm
– Clear PDDS bit in Power Control register (PWR_CR)
– Select the voltage regulator mode by configuring LPDS bit in PWR_CR
Note: To enter Stop mode, all EXTI Line pending bits (in
(EXTI_PR1)), all peripherals interrupt pending bits and RTC Alarm flag
must be reset. Otherwise, the Stop mode entry procedure is ignored and
program execution continues.
If the application needs to disable the external oscillator (external clock)
before entering Stop mode, the system clock source must be first switched
to HSI and then clear the HSEON bit.
Otherwise, if before entering Stop mode the HSEON bit is kept at 1, the
security system (CSS) feature must be enabled to detect any external
oscillator (external clock) failure and avoid a malfunction when entering
Stop mode.
If WFI was used for entry:
– Any EXTI Line configured in Interrupt mode (the corresponding EXTI
Interrupt vector must be enabled in the NVIC).
– Some specific communication peripherals (USART, I2C) interrupts, when
programmed in wakeup mode (the peripheral must be programmed in
wakeup mode and the corresponding interrupt vector must be enabled in
the NVIC).
Refer to .
If WFE was used for entry:
Any EXTI Line configured in event mode. Refer to
up event management
HSI RC wakeup time + regulator wakeup time from Low-power mode
Figure
Table 16. Stop mode
Description
®
Cortex
6).
RM0366 Rev 5
®
-M4 System Control register
Pending register
Section 11.2.3: Wake-
RM0366