STM32U375CE datasheet(41/222 Pages) STMICROELECTRONICS

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3.30.8

SysTick timer

The Cortex®-M33 with TrustZone® embeds two SysTick timers.

When TrustZone® is activated, two SysTick timers are available:

•

SysTick, secure instance

•

SysTick, nonsecure instance

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

3.31

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 autoreload 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 privilege 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.

All RTC events (alarm, wake-up timer, timestamp) can generate an interrupt and wake-up the device from the low-

power modes.

3.32

Tamper and backup registers (TAMP)

The antitamper detection circuit is used to protect sensitive data from external attacks. Thirty-two 32-bit backup

registers are retained in all low-power modes and also in VBAT mode. The backup registers, as well as other

secrets in the device, are protected by this antitamper detection circuit with five tamper pins and nine internal

tampers. The external tamper pins can be configured for edge detection, or level detection with or without filtering.

TAMP main features:

•

A tamper detection can optionally erase the backup registers, SRAM2, cache, and cryptographic

peripherals. The device resources protected by tamper are named "device secrets". The list of device

secrets is configurable by software.

STM32U375xx

Functional overview

DS14861 - Rev 2

page 41/222

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