STM32F031X4 datasheet(19/106 Pages) STMICROELECTRONICS

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STM32F031x4 STM32F031x6

Functional overview

3.11.5

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 (HCLK or HCLK/8)

3.12

Real-time clock (RTC) and backup registers

The RTC and the five backup registers are supplied through a switch that takes power either

on VDD supply when present or through 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 at wake up from Standby mode.

The RTC is an independent BCD timer/counter. Its main features are the following:

•

calendar with subseconds, 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 day of the month

•

programmable alarm 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 the RTC 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

•

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

used to enhance the calendar precision

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

3.13

Inter-integrated circuit interface (I2C)

The I2C interface (I2C1) can operate in multimaster or slave modes. It can support Standard

mode (up to 100 kbit/s), Fast mode (up to 400 kbit/s) and Fast Mode Plus (up to 1 Mbit/s)

with 20 mA output drive.

It supports 7-bit and 10-bit addressing modes, multiple 7-bit slave addresses (two

addresses, one with configurable mask). It also includes programmable analog and digital

noise filters.

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