Datasheet

DocID027973 Rev 5 29/119
STM32L011x3/4 Functional overview
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3.14.4 Independent watchdog (IWDG)
The independent watchdog is based on a 12-bit downcounter and 8-bit prescaler. It is
clocked from an independent 37 kHz internal RC and, as it operates independently of 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.
3.14.5 Window watchdog (WWDG)
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.
3.15 Communication interfaces
3.15.1 I
2
C bus
One I
2
C interface (I2C1) can operate in multimaster or slave modes. The I
2
C interface can
support Standard mode (Sm, up to 100 kbit/s), Fast mode (Fm, up to 400 kbit/s) and Fast
Mode Plus (Fm+, up to 1 Mbit/s) with 20 mA output drive on some I/Os.
The I
2
C interface supports 7-bit and 10-bit addressing modes, multiple 7-bit slave
addresses (2 addresses, 1 with configurable mask). They also include programmable
analog and digital noise filters.
In addition, I2C1 provides hardware support for SMBus 2.0 and PMBus 1.1: ARP capability,
Host notify protocol, hardware CRC (PEC) generation/verification, timeouts verifications and
ALERT protocol management. I2C1 also has a clock domain independent from the CPU
clock, allowing the I2C1 to wake up the MCU from Stop mode on address match.
The I2C interface can be served by the DMA controller.
Refer to Table 9 for the supported modes and features of I2C interface.
Table 8. 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
Benefits Available in Stop mode
1. Extra filtering capability vs.
standard requirements.
2. Stable length
Drawbacks
Variations depending on
temperature, voltage, process
Wakeup from Stop on address
match is not available when digital
filter is enabled.
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