ST STM32F301 6 Series Reference Manual page 620

Real-time clock (RTC)
Note: When COSEL bit is cleared, the RTC_CALIB output is the output of the 6th stage of the
asynchronous prescaler.
When COSEL bit is set, the RTC_CALIB output is the output of the 8th stage of the
synchronous prescaler.
24.3.16 Alarm output
The OSEL[1:0] control bits in the RTC_CR register are used to activate the alarm output
RTC_ALARM, and to select the function which is output. These functions reflect the
contents of the corresponding flags in the RTC_ISR register.
The polarity of the output is determined by the POL control bit in RTC_CR so that the
opposite of the selected flag bit is output when POL is set to 1.
Alarm output
The RTC_ALARM pin can be configured in output open drain or output push-pull using
RTC_TAFCR register.
Note: Once the RTC_ALARM output is enabled, it has priority over RTC_CALIB (COE bit is don't
care and must be kept cleared).
24.4 RTC low-power modes
Mode
Sleep
Stop
Standby
24.5 RTC interrupts
All RTC interrupts are connected to the EXTI controller. Refer to
interrupts and events controller
To enable the RTC Alarm interrupt, the following sequence is required:
1. Configure and enable the EXTI line corresponding to the RTC Alarm event in interrupt
mode and select the rising edge sensitivity.
2. Configure and enable the RTC_ALARM IRQ channel in the NVIC.
3. Configure the RTC to generate RTC alarms.
To enable the RTC Tamper interrupt, the following sequence is required:
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Table 78. Effect of low-power modes on RTC
No effect
RTC interrupts cause the device to exit the Sleep mode.
The RTC remains active when the RTC clock source is LSE or LSI. RTC alarm, RTC
tamper event, RTC timestamp event, and RTC wake-up cause the device to exit the Stop
mode.
The RTC remains active when the RTC clock source is LSE or LSI. RTC alarm, RTC
tamper event, RTC timestamp event, and RTC wake-up cause the device to exit the
Standby mode.
Description
(EXTI).
RM0366 Rev 5
RM0366
Section 11.2: Extended