Datasheet

616
42023E–SAM–07/2013
ATSAM4L8/L4/L2
Figure 24-53. ASK Modulator Output
Figure 24-54. FSK Modulator Output
24.6.17 Test Modes
The internal loopback feature enables on-board diagnostics, and allows the USART to operate
in three different test modes, with reconfigured pin functionality, as shown below.
24.6.17.1 Normal Mode
During normal operation, a receiver RXD pin is connected to a transmitter TXD pin.
Figure 24-55. Normal Mode Configuration
24.6.17.2 Automatic Echo Mode
Automatic echo mode allows bit-by-bit retransmission. When a bit is received on the RXD pin, it
is also sent to the TXD pin, as shown in Figure 24-56. Transmitter configuration has no effect.
Manchester
encoded
data
default polarity
unipolar output
Txd
ASK Modulator
Output
Uptstream Frequency F0
NRZ stream
10 0 1
Manchester
encoded
data
default polarity
unipolar output
Txd
FSK Modulator
Output
Uptstream Frequencies
[F0, F0+offset]
NRZ stream
10 0 1
Receiver
Transmitter
RXD
TXD