SAM3SD8B Atmel Corporation, SAM3SD8B Datasheet - Page 739

• Manufacturer Part Number: SAM3SD8B
• Manufacturer: Atmel Corporation

32.7.8.7
32.7.9
32.7.9.1
Figure 32-40. Normal Mode Configuration
32.7.9.2
Figure 32-41. Automatic Echo Mode Configuration
32.7.9.3
11090A–ATARM–10-Feb-12
11090A–ATARM–10-Feb-12
Test Modes
Normal Mode
Automatic Echo Mode
Local Loopback Mode
Receiver Timeout
reception but only a low level. However, this low level must be present on the slave select line
(NSS) at least 1 Tbit before the first serial clock cycle corresponding to the MSB bit.
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).
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
Receiver
Receiver
32-42. The TXD and RXD pins are not used. The RXD pin has no effect on
Figure
32-41. Programming the transmitter has no effect on
RXD
TXD
RXD
TXD
SAM3S8/SD8
SAM3S8/SD8
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