Table 170. Rtc Pin Pc13 Configuration; Gpios Controlled By The Rtc - ST STM32L4x6 Reference Manual

Real-time clock (RTC)
The RTC includes:
•
Two alarms
•
Three tamper events
•
32 x 32-bit backup registers
–
•
Alternate function outputs: RTC_OUT which selects one of the following two outputs:
–
–
•
Alternate function inputs:
–
–
–
–
–
34.3.2

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. 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
00
RTC_TAMP1
00
input floating
01 or 10 or 11
00
RTC_TS and
RTC_TAMP1 00
input floating
01 or 10 or 11
1066/1693
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 170. RTC pin PC13 configuration

COE bit
(RTC_CALIB
output
enable)
Don't care
Don't care
1
0
1
0
0
1
0
DocID024597 Rev 3
RTC_OUT
RTC_ALARM
_TYPE
_RMP
bit
bit
0
0
1
0
1
1
0 Don't care
Don't care
Don't care
1
Don't care
Don't care
1
Table 170.
(1)
TAMP1E bit
(RTC_TAMP1
input
enable)
Don't care
Don't care
Don't care
1
1
RM0351
TSE bit
(RTC_TS
input
enable)
Don't care
Don't care
Don't care
0
1