STM32F334X4 datasheet(25/115 Pages) STMICROELECTRONICS

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STM32F334x4 STM32F334x6 STM32F334x8

Functional overview

3.14.7

SysTick timer

This timer is dedicated to real-time operating systems, but could 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

3.15

Real-time clock (RTC) and backup registers

The RTC and the 5 backup registers are supplied through a switch that takes power from

either the VDD supply when present or the VBAT pin. The backup registers are five 32-bit

registers used to store 20 bytes of user application data when VDD 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 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.

•

Reference clock detection: a more precise second source clock (50 or 60 Hz) can be

used to enhance the calendar precision.

•

Automatic correction for 28, 29 (leap year), 30, and 31 days of the month.

•

Two programmable alarms with wake up from Stop and Standby mode capability.

•

On-the-fly correction from 1 to 32767 RTC clock pulses. This can be used to

synchronize it with a master clock.

•

Digital calibration circuit with 1 ppm resolution, to compensate for quartz crystal

inaccuracy.

•

Two anti-tamper detection pins with programmable filter. The MCU can be woken up

from Stop and Standby modes on tamper event detection.

•

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. The MCU can be

woken up from Stop and Standby modes on timestamp event detection.

•

17-bit Auto-reload counter for periodic interrupt with wakeup from STOP/STANDBY

capability.

The RTC clock sources can be:

•

A 32.768 kHz external crystal

•

A resonator or oscillator

•

The internal low-power RC oscillator (typical frequency of 40 kHz)

•

The high-speed external clock divided by 32.

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