AT91SAM7S32-AI ATMEL [ATMEL Corporation], AT91SAM7S32-AI Datasheet - Page 290

• Manufacturer Part Number: AT91SAM7S32-AI
• Description: AT91 ARM Thumb-based Microcontrollers
• Manufacturer: ATMEL [ATMEL Corporation]

Test Modes
Normal Mode
Automatic Echo Mode
Local Loopback Mode
Remote Loopback
Mode
290
AT91SAM7S32 Preliminary
The USART can be programmed to operate in three different test modes. The internal loop-
back capability allows on-board diagnostics. In the loopback mode the USART interface pins
are disconnected 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 126. 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 Figure 127. 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 127. Automatic Echo Mode Configuration
Local loopback mode connects the output of the transmitter directly to the input of the receiver,
as shown in Figure 128. The TXD and RXD pins are not used. The RXD pin has no effect on
the receiver and the TXD pin is continuously driven high, as in idle state.
Figure 128. Local Loopback Mode Configuration
Remote loopback mode directly connects the RXD pin to the TXD pin, as shown in Figure 129.
The transmitter and the receiver are disabled and have no effect. This mode allows bit-by-bit
retransmission.
Transmitter
Transmitter
Transmitter
Receiver
Receiver
Receiver
1
RXD
TXD
RXD
TXD
RXD
TXD
6071A–ATARM–28-Oct-04