at91rm3400 ATMEL Corporation, at91rm3400 Datasheet - Page 292

• Manufacturer Part Number: at91rm3400
• Description: Atmel Advanced At91 Arm Microcontroller
• Manufacturer: ATMEL Corporation

Automatic Echo
Local Loopback
Remote Loopback
292
AT91RM3400
Automatic echo mode allows bit-by-bit retransmission. When a bit is received on the RXD pin,
it is sent to the TXD pin, as shown in Figure 117. Programming the transmitter has no effect on
the TXD pin. The RXD pin is still connected to the receiver input, thus the receiver remains
active.
Figure 117. Automatic Echo
The local loopback mode connects the output of the transmitter directly to the input of the
receiver, as shown in Figure 118. The TXD and RXD pins are not used. The RXD pin has no
effect on the receiver and the TXD pin is continuously driven high, as in idle state.
Figure 118. Local Loopback
Remote loopback mode directly connects the RXD pin to the TXD pin, as shown in Figure 119.
The transmitter and the receiver are disabled and have no effect. This mode allows bit-by-bit
retransmission.
Figure 119. Remote Loopback
Transmitter
Transmitter
Transmitter
Receiver
Receiver
Receiver
1
1
RXD
TXD
RXD
TXD
RXD
TXD
1790A–ATARM–11/03