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ATSAM4S-XPLD
677
SAM4S [DATASHEET]
11100E–ATARM–24-Jul-13
34.5.5 Test Modes
The UART supports three test modes. These modes of operation are programmed by using the field CHMODE (Channel
Mode) in the mode register (UART_MR).
Mode) in the mode register (UART_MR).
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.
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.
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.
disabled and have no effect. This mode allows a bit-by-bit retransmission.
Figure 34-11.Test Modes
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