STM32L021D4 datasheet(31/114 Pages) STMICROELECTRONICS

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STM32L021x4

Functional overview

3.16.2

Universal synchronous/asynchronous receiver transmitter (USART)

The USART interface (USART2) is able to communicate at speeds of up to 4 Mbit/s.

It provides hardware management of the CTS, RTS and RS485 driver enable (DE) signals,

multiprocessor communication mode and single-wire half-duplex communication mode.

USART2 also supports Smartcard communication (ISO 7816, T=0 protocol) and IrDA SIR

ENDEC.

USART2 interface can be served by the DMA controller.

Table 9 for the supported modes and features of USART interface.

3.16.3

Low-power universal asynchronous receiver transmitter (LPUART)

The devices embed one Low-power UART. The LPUART supports asynchronous serial

communication with minimum power consumption. It supports half duplex single wire

communication and modem operations (CTS/RTS). It allows multiprocessor

communication.

The LPUART has a clock domain independent from the CPU clock, and can wake up the

system from Stop mode, using baudrates up to 46 Kbaud. The Wakeup events from Stop

mode are programmable and can be:

•

Start bit detection

•

Or any received data frame

•

Or a specific programmed data frame

Only a 32.768 kHz clock (LSE) is needed to allow LPUART communication up to 9600

baud. Therefore, even in Stop mode, the LPUART can wait for an incoming frame while

having an extremely low energy consumption. Higher speed clock can be used to reach

higher baudrates.

LPUART interface can be served by the DMA controller.

Table 9. USART implementation

USART modes/features(1)

1. X = supported.

USART2

Hardware flow control for modem

Continuous communication using DMA

Multiprocessor communication

Synchronous mode

Smartcard mode

Single-wire half-duplex communication

IrDA SIR ENDEC block

LIN mode

Dual clock domain and wakeup from Stop mode

Receiver timeout interrupt

Modbus communication

Auto baud rate detection (4 modes)

Driver Enable

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