Datasheet

627
6120F–ATARM–03-Oct-06
AT91SAM7X512/256/128 Preliminary
41.2.7.4 TWI: Possible Receive Holding Register Corruption
When loading the TWI_RHR, the transfer direction is ignored. The last data byte received in the
TWI_RHR is corrupted at the end of the first subsequent transmit data byte. Neither RXRDY nor
OVERRUN status bits are set if this occurs.
Problem Fix/Workaround
The user must be sure that received data is read before transmitting any new data.
41.2.7.5 TWI: Software Reset
when a software reset is performed during a frame and when TWCK is low, it is impossible to ini-
tiate a new transfer in READ or WRITE mode.
Problem Fix/Workaround
None.
41.2.8 Universal Synchronous Asynchronous Receiver Transmitter (USART)
41.2.8.1 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.
41.2.8.2 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.
41.2.8.3 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.