STM32F050C4 datasheet(20/97 Pages) STMICROELECTRONICS

20 / 97 page

Functional overview

STM32F050xx

20/97

Doc ID 023683 Rev 1

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 5 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 when the device wakes up from Standby

mode.

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

●

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

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

●

Automatically 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 it with a master clock.

●

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

inaccuracy.

●

2 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

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.

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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