ST STM32F412 Reference Manual page 102

Power controller (PWR)
These RTC alternate functions can wake up the system from the Stop and Standby low-
power modes.
The system can also wake up from low-power modes without depending on an external
interrupt (Auto-wakeup mode), by using the RTC alarm or the RTC wakeup events.
The RTC provides a programmable time base for waking up from the Stop or Standby mode
at regular intervals.
For this purpose, two of the three alternate RTC clock sources can be selected by
programming the RTCSEL[1:0] bits in the
register (RCC_BDCR):
•
Low-power 32.768 kHz external crystal oscillator (LSE OSC)
This clock source provides a precise time base with a very low-power consumption
(additional consumption of less than 1 µA under typical conditions)
•
Low-power internal RC oscillator (LSI RC)
This clock source has the advantage of saving the cost of the 32.768 kHz crystal. This
internal RC oscillator is designed to use minimum power.
RTC alternate functions to wake up the device from the Stop mode
•
To wake up the device from the Stop mode with an RTC alarm event, it is necessary to:
a)
b)
c)
• To wake up the device from the Stop mode with an RTC tamper or time stamp event, it
is necessary to:
a)
b)
c)
•
To wake up the device from the Stop mode with an RTC wakeup event, it is necessary
to:
a)
b)
c)
RTC alternate functions to wake up the device from the Standby mode
•
To wake up the device from the Standby mode with an RTC alarm event, it is necessary
to:
a)
b)
•
To wake up the device from the Standby mode with an RTC tamper or time stamp
event, it is necessary to:
a)
102/1163
Configure the EXTI Line 17 to be sensitive to rising edges (Interrupt or Event
modes)
Enable the RTC Alarm Interrupt in the RTC_CR register
Configure the RTC to generate the RTC alarm
Configure the EXTI Line 21 to be sensitive to rising edges (Interrupt or Event
modes)
Enable the RTC time stamp Interrupt in the RTC_CR register or the RTC tamper
interrupt in the RTC_TAFCR register
Configure the RTC to detect the tamper or time stamp event
Configure the EXTI Line 22 to be sensitive to rising edges (Interrupt or Event
modes)
Enable the RTC wakeup interrupt in the RTC_CR register
Configure the RTC to generate the RTC Wakeup event
Enable the RTC alarm interrupt in the RTC_CR register
Configure the RTC to generate the RTC alarm
Enable the RTC time stamp interrupt in the RTC_CR register or the RTC tamper
interrupt in the RTC_TAFCR register
Section 6.3.20: RCC Backup domain control
RM0402 Rev 6
RM0402