AT32UC3L064-D3HES ATMEL [ATMEL Corporation], AT32UC3L064-D3HES Datasheet - Page 405

• Manufacturer Part Number: AT32UC3L064-D3HES
• Manufacturer: ATMEL [ATMEL Corporation]

20.6.11
20.6.11.1
20.6.11.2
20.6.11.3
32099D–06/2010
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.
Figure 20-35. Normal Mode Configuration
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.
Figure 20-36. Automatic Echo Mode Configuration
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 20-37. Local Loopback Mode Configuration
Figure
20-37. The TXD and RXD pins are not used. The RXD pin has no effect on
Transmitter
Transmitter
Transmitter
Receiver
Receiver
Receiver
Figure
20-36. Programming the transmitter has no effect on
1
AT32UC3L016/32/64
RXD
TXD
RXD
TXD
RXD
TXD
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