STM32L031C6 datasheet(30/118 Pages) STMICROELECTRONICS

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Functional overview

STM32L031x4/6

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DocID027063 Rev 4

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

I2C bus

One I2C interface (I2C1) can operate in multimaster or slave modes. The I2C 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 I2C 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 11 for the supported modes and features of I2C interface.

Table 10. 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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