Information

Functional overview STM32F20xxx
32/178 DocID15818 Rev 11
3.20.4 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.
The counter can be frozen in debug mode.
3.20.5 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.
3.20.6 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
3.21 Inter-integrated circuit interface (I²C)
Up to three I
2
C bus interfaces can operate in multimaster and slave modes. They can
support the Standard- and Fast-modes. They 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.
3.22 Universal synchronous/asynchronous receiver transmitters
(UARTs/USARTs)
The STM32F20x devices embed four universal synchronous/asynchronous receiver
transmitters (USART1, USART2, USART3 and USART6) and two universal asynchronous
receiver transmitters (UART4 and UART5).
These six interfaces provide asynchronous communication, IrDA SIR ENDEC support,
multiprocessor communication mode, single-wire half-duplex communication mode and
have LIN Master/Slave capability. The USART1 and USART6 interfaces are able to
communicate at speeds of up to 7.5 Mbit/s. The other available interfaces communicate at
up to 3.75 Mbit/s.
USART1, USART2, USART3 and USART6 also provide hardware management of the CTS
and RTS signals, Smart Card mode (ISO 7816 compliant) and SPI-like communication
capability. All interfaces can be served by the DMA controller.