Datasheet

DocID027107 Rev 6 33/202
STM32F446xC/E Functional overview
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3.21.4 Independent watchdog
The independent watchdog is based on a 12-bit downcounter and 8-bit prescaler. It is
clocked from an independent 32 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.
3.21.5 Window watchdog
The 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 main clock. It has an early warning interrupt capability and the counter can be frozen in
debug mode.
3.21.6 SysTick timer
This timer is dedicated to real-time operating systems, but could also be used as a standard
downcounter. It features:
• A 24-bit downcounter
• Autoreload capability
• Maskable system interrupt generation when the counter reaches 0
• Programmable clock source.
3.22 Inter-integrated circuit interface (I
2
C)
Four I²C bus interfaces can operate in multimaster and slave modes. Three I²C can support
the standard (up to 100 KHz) and fast (up to 400 KHz) modes.
One I²C can support the standard (up to 100 KHz), fast (up to 400 KHz) and fast mode plus
(up to 1MHz) modes.
They (all I²C) support the 7/10-bit addressing mode and the 7-bit dual addressing mode (as
slave).
A hardware CRC generation/verification is embedded.
They can be served by DMA and they support SMBus 2.0/PMBus.
The devices also include programmable analog and digital noise filters (see Table 7).
Table 7. Comparison of I2C analog and digital filters
- Analog filter Digital filter
Pulse width of
suppressed spikes
≥ 50 ns
Programmable length from 1 to 15
I2C peripheral clocks
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