Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

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The automatic echo mode allows bit-by-bit retransmission. When a bit is received on the URXD line, it is sent to 

the UTXD line. The transmitter operates normally, but has no effect on the UTXD line.
The local loopback mode allows the transmitted characters to be received. UTXD and URXD pins are not used 

and the output of the transmitter is internally connected to the input of the receiver. The URXD pin level has no 

effect and the UTXD line is held high, as in idle state. 
The remote loopback mode directly connects the URXD pin to the UTXD line. The transmitter and the receiver are 

disabled and have no effect. This mode allows a bit-by-bit retransmission.

Receiver

Transmitter

Disabled

RXD

TXD

Receiver

Transmitter

Disabled

RXD

TXD

V

DD

Disabled

Receiver

Transmitter

Disabled

RXD

TXD

Disabled

Automatic Echo

Local Loopback

Remote Loopback

V

DD