ST STM32L4+ Series Reference Manual page 1549

RM0432
The RTC includes:
•
Two alarms
•
Three tamper events from I/Os
–
•
One timestamp event from I/O
•
Tamper event detection can generate a timestamp event
•
Timestamp can be generated when a switch to V
•
32 x 32-bit backup registers
–
•
Output functions: RTC_OUT which selects one of the following two outputs:
–
–
•
Input functions:
–
–
–
–
–
46.3.2 GPIOs controlled by the RTC
RTC_OUT, RTC_TS and RTC_TAMP1 are mapped on the same pin (PC13). PC13 pin
configuration is controlled by the RTC, whatever the PC13 GPIO configuration, except for
the RTC_ALARM output open-drain mode. In this particular case, the GPIO must be
configured as input. The RTC functions mapped on PC13 are available in all low-power
modes and in VBAT mode.
The output mechanism follows the priority order shown in
OSEL[1:0]
bits
PC13 Pin
configuration
(RTC_ALARM
and function
output
enable)
RTC_ALARM
01 or 10 or 11
output OD
RTC_ALARM
01 or 10 or 11
output PP
RTC_CALIB
00
output PP
Real-time clock (RTC) applied to STM32L4Rxxx and STM32L4Sxxx only
Tamper detection erases the backup registers.
The backup registers (RTC_BKPxR) are implemented in the RTC domain that
remains powered-on by VBAT when the VDD power is switched off.
RTC_CALIB: 512 Hz or 1Hz clock output (with an LSE frequency of 32.768 kHz).
This output is enabled by setting the COE bit in the RTC_CR register.
RTC_ALARM: This output is enabled by configuring the OSEL[1:0] bits in the
RTC_CR register which select the Alarm A, Alarm B or Wakeup outputs.
RTC_TS: timestamp event
RTC_TAMP1: tamper1 event detection
RTC_TAMP2: tamper2 event detection
RTC_TAMP3: tamper3 event detection
RTC_REFIN: 50 or 60 Hz reference clock input
Table 312. RTC pin PC13 configuration
COE bit
(RTC_CALIB
output
enable)
Don't care
Don't care
1
BAT
RTC_OUT
RTC_ALARM
_TYPE
_RMP
bit
bit
0
0
1
0
1
1
0 Don't care
RM0432 Rev 6
occurs
Table 312.
(1)
TAMP1E bit
(RTC_TAMP1
input
enable)
Don't care
Don't care
Don't care
TSE bit
(RTC_TS
input
enable)
Don't care
Don't care
Don't care
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