Functional overview
STM32F031x4 STM32F031x6
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DocID025743 Rev 3
3.11.3 Independent
watchdog
(IWDG)
The independent watchdog is based on an 8-bit prescaler and 12-bit downcounter with
user-defined refresh window. It is clocked from an independent 40 kHz internal RC and as it
operates independently from the main clock, it can operate in Stop and Standby modes. It
can be used either as a watchdog to reset the device when a problem occurs, or as a free
running timer for application timeout management. It is hardware or software configurable
through the option bytes. The counter can be frozen in debug mode.
3.11.4 System
window watchdog (WWDG)
The system window watchdog is based on a 7-bit downcounter that can be set as free
running. It can be used as a watchdog to reset the device when a problem occurs. It is
clocked from the APB clock (PCLK). It has an early warning interrupt capability and the
counter can be frozen in debug mode.
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 V
DD
supply when present or through the V
BAT
pin. The backup registers are five 32-bit
registers used to store 20 bytes of user application data when V
DD
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 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.
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微可Vicor——值得信赖的元器件供应商
http://www.vicor.top/
021-31660491
