ST STM32G474 User Manual

Power control (PWR) RM0440
254/2126 RM0440 Rev 4
6.3.10 Auto-wakeup from low-power mode
The RTC can be used to wakeup the MCU from low-power mode without depending on an
external interrupt (Auto-wakeup mode). The RTC provides a programmable time base for
waking up from Stop (0 or 1) or Standby mode at regular intervals. For this purpose, two of
the three alternative RTC clock sources can be selected by programming the RTCSEL[1:0]
bits in the RTC domain control register (RCC_BDCR):
• Low-power 32.768 kHz external crystal oscillator (LSE OSC)
This clock source provides a precise time base with very low-power consumption.
• Low-power internal RC Oscillator (LSI)
This clock source has the advantage of saving the cost of the 32.768 kHz crystal. This
internal RC Oscillator is designed to add minimum power consumption.
To wakeup from Stop mode with an RTC alarm event, it is necessary to:
• Configure the EXTI Line 17 to be sensitive to rising edge
• Configure the RTC to generate the RTC alarm
To wakeup from Standby mode, there is no need to configure the EXTI Line 17.
To wakeup from Stop mode with an RTC wakeup event, it is necessary to:
• Configure the EXTI Line 20 to be sensitive to rising edge
• Configure the RTC to generate the RTC alarm
To wakeup from Standby mode, there is no need to configure the EXTI Line 20.
Table 48. Shutdown mode
Shutdown mode Description
Mode entry
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP bit is set in Cortex
®
-M4 with FPU System Control
register
– No interrupt (for WFI) or event (for WFE) is pending
– LPMS = “1XX” in PWR_CR1
– WUFx bits are cleared in power status register 1 (PWR_SR1)
On return from ISR while:
– SLEEPDEEP bit is set in Cortex
®
-M4 with FPU System Control
register
– SLEEPONEXT = 1
– No interrupt is pending
– LPMS = “1XX” in PWR_CR1 and
– WUFx bits are cleared in power status register 1 (PWR_SR1)
– 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 WKUPx pin edge, RTC event, external Reset in
NRST pin
Wakeup latency Reset phase

ST STM32G474 Specifications

General

Brand	ST
Model	STM32G474
Category	Microcontrollers
Language	English