Datasheet

555
11011B–ATARM–21-Feb-12
SAM3N
555
11011B–ATARM–21-Feb-12
SAM3N
30.7.7.7 Receiver Timeout
Because the receiver baudrate clock is active only during data transfers in SPI Mode, a receiver
timeout is impossible in this mode, whatever the Time-out value is (field TO) in the Time-out
Register (US_RTOR).
30.7.8 Test Modes
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.
30.7.8.1 Normal Mode
Normal mode connects the RXD pin on the receiver input and the transmitter output on the TXD
pin.
Figure 30-30. Normal Mode Configuration
30.7.8.2 Automatic Echo Mode
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 30-31. 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 30-31. Automatic Echo Mode Configuration
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DATA 0
DATA N
RXRDY
USART3
LIN CONTROLLER
APB bus
READ BUFFER
NACT = SUBSCRIBE
DATA 0
DATA N
TXRDY
USART3
LIN CONTROLLER
APB bus
WRITE BUFFER
(Peripheral) DMA
Controller
(Peripheral) DMA
Controller
Receiver
Transmitter
RXD
TXD
Receiver
Transmitter
RXD
TXD