at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 533

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

33.6.7
33.6.7.1
Figure 33-28. Normal Mode Configuration
33.6.7.2
Figure 33-29. Automatic Echo Mode Configuration
33.6.7.3
Figure 33-30. Local Loopback Mode Configuration
6249D–ATARM–20-Dec-07
Test Modes
Normal Mode
Automatic Echo Mode
Local Loopback Mode
The USART can be programmed to operate in three different test modes. The internal loopback
capability allows on-board diagnostics. In the loopback mode the USART interface pins are dis-
connected or not and reconfigured for loopback internally or externally.
Normal mode connects the RXD pin on the receiver input and the transmitter output on the TXD
pin.
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
the TXD pin. The RXD pin is still connected to the receiver input, thus the receiver remains
active.
Local loopback mode connects the output of the transmitter directly to the input of the receiver,
as shown in
the receiver and the TXD pin is continuously driven high, as in idle state.
Figure
Transmitter
Transmitter
Transmitter
Receiver
Receiver
Receiver
33-30. The TXD and RXD pins are not used. The RXD pin has no effect on
Figure
1
33-29. Programming the transmitter has no effect on
AT91SAM9263 Preliminary
RXD
TXD
RXD
TXD
RXD
TXD
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