DocID024597 Rev 5 1203/1830
RM0351 Real-time clock (RTC)
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Note: When the RTC_CALIB or RTC_ALARM output is selected, the RTC_OUT pin is
automatically configured in output alternate function.
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.
38.3.16 Alarm output
The OSEL[1:0] control bits in the RTC_CR register are used to activate the alarm alternate
function 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 alternate function output
The RTC_ALARM pin can be configured in output open drain or output push-pull using the
control bit RTC_ALARM_TYPE in the RTC_OR 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).
When the RTC_CALIB or RTC_ALARM output is selected, the RTC_OUT pin is
automatically configured in output alternate function.
38.4 RTC low-power modes
Table 212. Effect of low-power modes on RTC
Mode Description
Sleep
No effect
RTC interrupts cause the device to exit the Sleep mode.
Low-power run No effect.
Low-power sleep No effect. RTC interrupts cause the device to exit the Low-power sleep mode.
Stop 0
Peripheral registers content is kept.Stop 1
Stop 2
Standby
The RTC remains active when the RTC clock source is LSE or LSI. RTC alarm,
RTC tamper event, RTC timestamp event, and RTC Wakeup cause the device to
exit the Standby mode.
Shutdown
The RTC remains active when the RTC clock source is LSE. RTC alarm, RTC
tamper event, RTC timestamp event, and RTC Wakeup cause the device to exit
the Shutdown mode.
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