Datasheet

619
SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
32.7.9 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 disconnected or not and reconfigured
for loopback internally or externally.
32.7.9.1 Normal Mode
Normal mode connects the RXD pin on the receiver input and the transmitter output on the TXD pin.
Figure 32-55. Normal Mode Configuration
32.7.9.2 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 32-56. 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 32-56. Automatic Echo Mode Configuration
Table 32-16. Receiver Time-out Programming
LIN Specification Baud Rate Time-out period US_RTOR.TO
2.0
1 000 bit/s
4 s
4,000
2 400 bit/s 9,600
9 600 bit/s 38,400
19 200 bit/s 76,800
20 000 bit/s 80,000
1.3 – 25,000 t
bit
25,000
Receiver
Transmitter
RXD
TXD
Receiver
Transmitter
RXD
TXD