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Universal synchronous/asynchronous receiver transmitter (USART/UART) RM0367

784/1043 RM0367 Rev 7

detection range (bit duration not between 16 and 65536 clock periods (oversampling by 16)

and not between 8 and 65536 clock periods (oversampling by 8)).

The RXNE interrupt will signal the end of the operation.

At any later time, the auto baud rate detection may be relaunched by resetting the ABRF

flag (by writing a 0).

Note: If the USART is disabled (UE=0) during an auto baud rate operation, the BRR value may be

corrupted.

29.5.7 Multiprocessor communication using USART

In multiprocessor communication, the following bits are to be kept cleared:

• LINEN bit in the USART_CR2 register,

• HDSEL, IREN and SCEN bits in the USART_CR3 register.

It is possible to perform multiprocessor communication with the USART (with several

USARTs connected in a network). For instance one of the USARTs can be the master, its TX

output connected to the RX inputs of the other USARTs. The others are slaves, their

respective TX outputs are logically ANDed together and connected to the RX input of the

master.

In multiprocessor configurations it is often desirable that only the intended message

recipient should actively receive the full message contents, thus reducing redundant USART

service overhead for all non addressed receivers.

The non addressed devices may be placed in mute mode by means of the muting function.

In order to use the mute mode feature, the MME bit must be set in the USART_CR1

In mute mode:

• None of the reception status bits can be set.

• All the receive interrupts are inhibited.

• The RWU bit in USART_ISR register is set to 1. RWU can be controlled automatically

by hardware or by software, through the MMRQ bit in the USART_RQR register, under

certain conditions.

The USART can enter or exit from mute mode using one of two methods, depending on the

WAKE bit in the USART_CR1 register:

• Idle Line detection if the WAKE bit is reset,

• Address Mark detection if the WAKE bit is set.

ST STM32L0x3 User Manual

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