Selection Of Rtc_Af1 And Rtc_Af2 Alternate Functions; Table 30. Rtc_Af1 Pin - ST STM32F40 Series Reference Manual

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General-purpose I/Os (GPIO)

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

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

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

configuration

and function

Calibration out

TAMPER1 input

input floating

input floating

Standard GPIO

1. OD: open drain; PP: push-pull.

Doc ID 018909 Rev 4

ALARMOUTTYPE

configuration

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