SAM7S256_14 Datasheet, PDF (751/775 Pages) ATMEL Corporation – ARM-based Flash MCU

40.25.6 Universal Synchronous Asynchronous Receiver Transmitter (USART)
40.25.6.1 USART: DCD is active High instead of Low
The DCD signal is active at High level in the USART Modem Mode.
DCD should be active at Low level.
Problem Fix/Workaround
Add an inverter.
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
751