Programming The Rtc Alternate Functions To Wake Up The Device From The Stop And Standby Modes; Table 22. Standby Mode Entry And Exit - ST STM32F412 Reference Manual

RM0402
Refer to
Standby mode
Mode entry
Mode exit
Wakeup latency
I/O states in Standby mode
In Standby mode, all I/O pins are high impedance except for:
•
Reset pad (still available)
•
RTC_AF1 pin (PC13) if configured for tamper, time stamp, RTC Alarm out, or RTC
clock calibration out
•
WKUP pin (PA0/PC0/PC1), if enabled
Debug mode
By default, the debug connection is lost if the application puts the MCU in Stop or Standby
mode while the debug features are used. This is due to the fact that the Cortex
FPU core is no longer clocked.
However, by setting some configuration bits in the DBGMCU_CR register, the software can
be debugged even when using the low-power modes extensively. For more details, refer to
Section 30.16.1: Debug support for low-power
5.3.7 Programming the RTC alternate functions to wake up the device from
the Stop and Standby modes
The MCU can be woken up from a low-power mode by an RTC alternate function.
The RTC alternate functions are the RTC alarms (Alarm A and Alarm B), RTC wakeup, RTC
tamper event detection and RTC time stamp event detection.
Table 22 for more details on how to exit Standby mode.

Table 22. Standby mode entry and exit

WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP is set in Cortex
– 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 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
and
– SLEEPONEXIT = 1, and
– PDDS bit is set in Power Control register (PWR_CR), and
– No interrupt is pending,
– WUF bit is cleared in Power Control/Status register (PWR_SR),
– The RTC flag corresponding to the chosen wakeup source (RTC Alarm
A, RTC Alarm B, RTC wakeup, Tamper or Timestamp flags) is cleared.
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.
Reset phase.
Description
®
-M4 with FPU System Control register,
modes.
RM0402 Rev 6
Power controller (PWR)
®
-M4 with FPU System Control register,
®
-M4 with
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