Datasheet

DocID022691 Rev 4 23/131
STM32F37xxx Functional overview
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3.17.3 Independent watchdog (IWDG)
The independent watchdog is based on a 12-bit downcounter and 8-bit prescaler. 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.
3.17.4 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 APB1 clock (PCLK1) derived from the main clock. It has an early warning
interrupt capability and the counter can be frozen in debug mode.
3.17.5 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
3.18 Real-time clock (RTC) and backup registers
The RTC and the backup registers are supplied through a switch that takes power either
from V
DD
supply when present or through the V
BAT
pin. The backup registers are thirty two
32-bit registers used to store 128 bytes of user application data.
They are not reset by a system or power reset, and they are not reset when the device
wakes up from the Standby mode.