ST STM32F446 Series User Manual

RM0390 Rev 4 107/1328
RM0390 Power controller (PWR)
115
Refer to Table 19 for more details on how to enter Standby mode.
In Standby mode, the following features can be selected by programming individual control
bits:
• Independent watchdog (IWDG): the IWDG is started by writing to its Key register or by
hardware option. Once started it cannot be stopped except by a reset. See
Section 20.3: IWDG functional description.
• Real-time clock (RTC): this is configured by the RTCEN bit in the backup domain
control register (RCC_BDCR)
• Internal RC oscillator (LSI RC): this is configured by the LSION bit in the Control/status
register (RCC_CSR).
• External 32.768 kHz oscillator (LSE OSC): this is configured by the LSEON bit in the
backup domain control register (RCC_BDCR)
Exiting Standby mode
The microcontroller exits Standby mode according to Exiting low power mode. The SBF
status flag in the PWR power control/status register (PWR_CSR) indicates that the MCU
was in Standby mode. All registers are reset after wakeup from standby except for PWR
power control/status register (PWR_CSR).
Refer to Table 19 for more details on how to exit Standby mode.
Table 19. Standby mode entry and exit
Standby mode Description
Mode entry
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP is set in Cortex
®
-M4 with FPU with FPU System Control
register
– PDDS bit is set in Power Control register (PWR_CR)
– no interrupt (for WFI or event (for WFE) is pending
– WUF bit is cleared in Power Control/Status register (PWR_CR)
– the RTC flag corresponding to the chosen wakeup source (RTC Alarm A,
RTC Alarm B, RTC wakeup, Tamper or Timestamp flags) is cleared
On Return from ISR while:
– SLEEPDEEP bit is set in Cortex
®
-M4 with FPU with FPU System Control
register and
– SLEEPONEXIT = 1 and
– PDDS bit is set in Power Control register (PWR_CR) and
– no interrupt is pending and
– WUF bit is cleared in Power Control/Status register (PWR_SR) and
– the RTC flag corresponding to the chosen wakeup source (RTC Alarm A,
RTC Alarm B, RTC wakeup, Tamper or Timestamp flags) is cleared
Mode exit
WKUP pin rising edge, RTC alarm (Alarm A and Alarm B), RTC wakeup,
tamper event, time stamp event, external reset in NRST pin, IWDG reset.
Wakeup latency Reset phase.

ST STM32F446 Series Specifications

General

Brand	ST
Model	STM32F446 Series
Category	Microcontrollers
Language	English