Datasheet

812
SAM9G15 [DATASHEET]
11052D–ATARM–31-Oct-12
Figure 39-56.Local Loopback Mode Configuration
39.7.9.4 Remote Loopback Mode
Remote loopback mode directly connects the RXD pin to the TXD pin, as shown in Figure 39-57. The transmitter and the
receiver are disabled and have no effect. This mode allows bit-by-bit retransmission.
Figure 39-57.Remote Loopback Mode Configuration
39.7.10 Write Protection Registers
To prevent any single software error that may corrupt USART behavior, certain address spaces can be write-protected
by setting the WPEN bit in the USART Write Protect Mode Register (US_WPMR).
If a write access to the protected registers is detected, then the WPVS flag in the USART Write Protect Status Register
(US_WPSR) is set and the WPVSRC field indicates in which register the write access has been attempted.
The WPVS flag is automatically reset by reading the USART Write Protect Mode Register (US_WPMR) with the
appropriate access key, WPKEY.
The protected registers are:
z “USART Mode Register”
z “USART Baud Rate Generator Register”
z “USART Receiver Time-out Register”
z “USART Transmitter Timeguard Register”
z “USART FI DI RATIO Register”
z “USART IrDA FILTER Register”
z “USART Manchester Configuration Register”
Receiver
Transmitter
RXD
TXD
1
Receiver
Transmitter
RXD
TXD
1