Selection Of Rtc_Af1 And Rtc_Af2 Alternate Functions - ST STM32F405 Reference Manual

RM0090
8.3.15

Selection of RTC_AF1 and RTC_AF2 alternate functions

The STM32F4xx feature two GPIO pins RTC_AF1 and RTC_AF2 that can be used for the
detection of a tamper or time stamp event, or RTC_ALARM, or RTC_CALIB RTC outputs.
•
The RTC_AF1 (PC13) can be used for the following purposes:
RTC_ALARM output: this output can be RTC Alarm A, RTC Alarm B or RTC Wakeup
depending on the OSEL[1:0] bits in the RTC_CR register
•
RTC_CALIB output: this feature is enabled by setting the COE[23] in the RTC_CR
register
•
RTC_TAMP1: tamper event detection
• RTC_TS: time stamp event detection
The RTC_AF2 (PI8) can be used for the following purposes:
•
RTC_TAMP1: tamper event detection
•
RTC_TAMP2: tamper event detection
•
RTC_TS: time stamp event detection
The selection of the corresponding pin is performed through the RTC_TAFCR register as
follows:
•
TAMP1INSEL is used to select which pin is used as the RTC_TAMP1 tamper input
•
TSINSEL is used to select which pin is used as the RTC_TS time stamp input
•
ALARMOUTTYPE is used to select whether the RTC_ALARM is output in push-pull or
open-drain mode
The output mechanism follows the priority order listed in
Pin
RTC_ALARM
configuration
enabled
and function
Alarm out
1
output OD
Alarm out
1
output PP
Calibration
0
out output PP
TAMPER1
0
input floating
TIMESTAMP
and
0
TAMPER1
input floating
TIMESTAMP
0
input floating
Standard
0
GPIO
1. OD: open drain; PP: push-pull.
Table 37. RTC_AF1 pin
RTC_CALIB Tamper
enabled enabled
Don't
Don't care
care
Don't
Don't care
care
Don't
1
care
0 1
0 1
0 0
0 0
RM0090 Rev 18
Table 37
(1)
Time TAMP1INSEL
stamp TAMPER1
enabled pin selection
Don't
Don't care
care
Don't
Don't care
care
Don't
Don't care
care
0 0
1 0
1 Don't care
0 Don't care
General-purpose I/Os (GPIO)
and Table 38.
TSINSEL
ALARMOUTTYPE
TIMESTAMP
RTC_ALARM
pin
configuration
selection
Don't care
Don't care
Don't care Don't care
Don't care Don't care
0 Don't care
0 Don't care
Don't care Don't care
0
1
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