STM32U535NET6QTR datasheet(73/278 Pages) STMICROELECTRONICS

73 / 278 page

DS14217 Rev 1

73/278

STM32U535xx

Functional overview

When TrustZone is disabled, only one SysTick timer is available. This timer (secure or

non-secure) is dedicated to real-time operating systems, but can also be used as a standard

down counter. It features:

•

A 24-bit down counter

•

Autoreload capability

•

Maskable system interrupt generation when the counter reaches 0

•

Programmable clock source.

3.37

Real-time clock (RTC), tamper and backup registers

3.37.1

Real-time clock (RTC)

The RTC supports the following features:

•

Calendar with subsecond, seconds, minutes, hours (12 or 24 format), weekday, date,

month, year, in BCD (binary-coded decimal) format

•

Binary mode with 32-bit free-running counter

•

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 that 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 wake-up timer (WUT) for periodic events with programmable

resolution and period

•

TrustZone support:

–

RTC fully securable

–

Alarm A, alarm B, wake-up timer and timestamp individual secure or nonsecure

configuration

–

Alarm A, alarm B, wake-up timer and timestamp individual privileged protection

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 one of the following:

•

32.768 kHz external crystal (LSE)

•

external resonator or oscillator (LSE)

•

internal low-power RC oscillator (LSI, with typical frequency of 32 kHz)

•

high-speed external clock (HSE), divided by a prescaler in the RCC.

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 except Shutdown mode.

STM32U535NET6QTR Datasheet(PDF) 73 Page - STMicroelectronics

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