STM32H7B3AI datasheet(29/238 Pages) STMICROELECTRONICS

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3.34.6

Window watchdog

The window watchdog is based on a 7-bit downcounter that can be set as free-running. It can be used as a

watchdog to reset the device when a problem occurs. It is clocked from the main clock. It has an early warning

interrupt capability and the counter can be frozen in debug mode.

3.34.7

SysTick timer

This timer is dedicated to real-time operating systems, but could also be used as a standard downcounter. It

features:

•

A 24-bit downcounter

•

Autoreload capability

•

Maskable system interrupt generation when the counter reaches 0

•

Programmable clock source.

3.35

Real-time clock (RTC)

The RTC is an independent BCD timer/counter. It supports the following features:

•

Calendar 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.

•

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 VBAT mode.

•

17-bit auto-reload wakeup timer (WUT) for periodic events with programmable resolution and period.

The RTC is supplied through a switch that takes power either from the VDD supply when present or from the VBAT

pin.

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 VBAT 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 VBAT mode, but is functional in all low-power modes.

All RTC events (Alarm, Wakeup Timer, Timestamp or Tamper) can generate an interrupt and wakeup the device

from the low-power modes.

3.36

Tamper and backup registers (TAMP)

The TAMP main features are the following:

•

32 backup registers:

–

The backup registers (TAMP_BKPxR) are implemented in the RTC domain that remains powered-on

by VBAT when the VDD power is switched off.

•

Three external tamper detection events

–

Each external event can be configured to be active or passive

–

External passive tampers with configurable filter and internal pull-up

•

Seven internal tamper events

•

Any tamper detection can generate an RTC timestamp event

•

Any tamper detection can erase the RTC backup registers, the backup SRAM and the memory regions

protected by the on-the-fly decryption engine (OTFDEC)

STM32H7B3xI

Real-time clock (RTC)

DS13139 - Rev 8

page 29/238

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