RM0444 Rev 5 889/1390
RM0444 Real-time clock (RTC)
926
When the TAMPOE control bit is set is the RTC_CR, all external and internal tamper flags
are ORed and routed to the TAMPALRM output. If OSEL = 00 the TAMPALRM output
reflects only the tampers flags. If OSEL ≠ 00, the signal on TAMPALRM provides both
tamper flags and alarm A, B, or wakeup flag.
The polarity of the TAMPALRM output is determined by the POL control bit in RTC_CR so
that the opposite of the selected flags bit is output when POL is set to 1.
TAMPALRM output
The TAMPALRM pin can be configured in output open drain or output push-pull using the
control bit TAMPALRM_TYPE in the RTC_CR register. It is possible to apply the internal
pull-up in output mode thanks to TAMPALRM_PU in the RTC_CR.
Note: Once the TAMPALRM output is enabled, it has priority over CALIB on RTC_OUT1.
When TAMPALRM output is selected, the RTC_OUT1 pin is automatically configured but
the RTC_OUT2 pin must be set as alternate function. In case the TAMPALRM is configured
open-drain in the RTC, the RTC_OUT1 GPIO must be configured as input.
30.4 RTC low-power modes
The table below summarizes the RTC pins and functions capability in all modes.
Table 151. Effect of low-power modes on RTC
Mode Description
Sleep
No effect
RTC interrupts cause the device to exit the Sleep mode.
Stop
The RTC remains active when the RTC clock source is LSE or LSI. RTC interrupts
cause the device to exit the Stop mode.
Standby
The RTC remains active when the RTC clock source is LSE or LSI. RTC interrupts
cause the device to exit the Standby mode.
Shutdown
The RTC remains active when the RTC clock source is LSE. RTC interrupts cause the
device to exit the Shutdown mode.
Table 152. RTC pins functionality over modes
Functions
Functional in all low-
power modes except
Standby and Shutdown
modes
Functional in Standby
and Shutdown mode
Functional in V
BAT
mode
RTC_TS Yes Yes Yes
RTC_REFIN Yes No No
RTC_OUT1 Yes Yes Ye s
RTC_OUT2 Yes Yes No
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