Rtc Main Features - ST STM32F40 Series Reference Manual

RM0090
23.2

RTC main features

The RTC unit main features are the following (see
●
Calendar with subseconds , seconds, minutes, hours (12 or 24 format), day (day of
week), date (day of month), month, and year.
●
Daylight saving compensation programmable by software.
● Two programmable alarms with interrupt function. The alarms can be triggered by any
combination of the calendar fields.
●
Automatic wakeup unit generating a periodic flag that triggers an automatic wakeup
interrupt.
● Reference clock detection: a more precise second source clock (50 or 60 Hz) can be
used to enhance the calendar precision.
●
Accurate synchronization with an external clock using the subsecond shift feature.
● Maskable interrupts/events:
–
–
–
–
–
●
Digital calibration circuit (periodic counter correction)
–
–
● Timestamp function for event saving (1 event)
●
Tamper detection:
–
●
20 backup registers (80 bytes). The backup registers are reset when a tamper
detection event occurs.
● Alternate function output (RTC_OUT) which selects one of the following two outputs:
–
–
●
RTC alternate function inputs:
–
–
–
–
Refer to
Alarm A
Alarm B
Wakeup interrupt
Timestamp
Tamper detection
5 ppm accuracy
0.95 ppm accuracy, obtained in a calibration window of several seconds
2 tamper events with configurable filter and internal pull-up.
RTC_CALIB: 512 Hz or 1 Hz clock output (with an LSE frequency of 32.768 kHz).
This output is enabled by setting the COE[23] bit in the RTC_CR register. It is
routed to the device RTC_AF1 function.
RTC_ALARM (Alarm A, Alarm B or wakeup).
This output is selected by configuring the OSEL[1:0] bits in the RTC_CR register.
It is routed to the device RTC_AF1 function.
RTC_TS: timestamp event detection. It is routed to the device RTC_AF1 and
RTC_AF2 functions.
RTC_TAMP1: TAMPER1 event detection. It is routed to the device RTC_AF1 and
RTC_AF2 functions.
RTC_TAMP2: TAMPER2 event detection.
RTC_REFIN: reference clock input (usually the mains, 50 or 60 Hz).
Section 7.3.15: Selection of RTC_AF1 and RTC_AF2 alternate
Doc ID 018909 Rev 4
Real-time clock (RTC)
Figure 222: RTC block diagram):
functions.
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