Datasheet

633
6120F–ATARM–03-Oct-06
AT91SAM7X512/256/128 Preliminary
41.3.8 Universal Synchronous Asynchronous Receiver Transmitter (USART)
41.3.8.1 USART: CTS in Hardware Handshaking
When Hardware Handshaking is used and if CTS goes low close to the end of the starting bit, a
character can be lost.
Problem Fix/Workaround
CTS must not go low during a time slot occurring between 2 Master Clock periods before the
starting bit and 16 Master Clock periods after the rising edge of the starting bit.
41.3.8.2 USART: Hardware Handshaking – Two Characters Sent
If CTS switches from 0 to 1 during the TX of a character and if the holding register (US_THR) is
not empty, the content of US_THR will also be transmitted.
Problem Fix/Workaround
Don't use the PDC in transmit mode and do not fill US_THR before TXEMPTY is set at 1.
41.3.8.3 USART: XOFF Character Bad Behavior
The XOFF character is sent only when the receive buffer is detected full. While the XOFF is
being sent, the remote transmitter is still transmitting. As only one Holding register is available in
the receiver, characters will be lost in reception. This makes the software handshaking function-
ality ineffective.
Problem Fix/Workaround
None.