Datasheet

Functional overview STM32H743xI
38/226 DocID030538 Rev 3
3.29 Real-time clock (RTC), backup SRAM and backup registers
The RTC is an independent BCD timer/counter. It supports the following features:
• Ca
lendar with subsecond, seconds, minutes, hours (12 or 24 format), week day, date,
month, year, in BCD (binary-coded decimal) format.
• Automatic correction for 28, 29 (leap year), 30, and 31 days of the month.
• Two programmable alarms.
• On-the-fly correction from 1 to 32767 RTC clock pulses. This can be used to
synchronize it with a master clock.
• Reference clock detection: a more precise second source clock (50 or 60 Hz) can be
used to enhance the calendar precision.
• Digital calibration circuit with 0.95 ppm resolution, to compensate for quartz crystal
inaccuracy.
• Three anti-tamper detection pins with programmable filter.
• Timestamp feature which can be used to save the calendar content. This function can
be triggered by an event on the timestamp pin, or by a tamper event, or by a switch to
V
BAT
mode.
• 17-bit auto-reload wakeup timer (WUT) for periodic events with programmable
resolution and period.
The RTC and the 32 backup registers are supplied thr
ough a switch that takes power either
from the V
DD
supply when present or from the V
BAT
pin.
The backup registers are 32-bit registers used to sto
re 128 bytes of user application data
when V
DD power is not present. They are not reset by a system or power reset, or when the
device wakes up from Standby mode.
The RTC clock sources can be:
• A
32.768 kHz external crystal (LSE)
• An external resonator or oscillator (LSE)
• The internal low-power RC oscillator (LSI, with typical frequency of 32 kHz)
• The high-speed external clock (HSE) divided by 32.
The RTC is functional in V
BAT
mode and in all low-power modes when it is clocked by the
LSE. When clocked by the LSI, the RTC is not functional in V
BAT
mode, but is functional in
all low-power modes.
All RTC events (Alarm, Wakeup Timer, Timestamp or Tamper) can generate an interrupt and
wakeu
p the device from the low-power modes.
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