SAM7S256_14 Datasheet, PDF (605/775 Pages) ATMEL Corporation – ARM-based Flash MCU

None.
40.4.8.2 TWI: Software Reset
when a software reset is performed during a frame and when TWCK is low, it is impossible to initiate a new transfer
in READ or WRITE mode.
Problem Fix/Workaround
None.
40.4.8.3 TWI: Disabling Does not Operate Correctly
Any transfer in progress is immediately frozen if the Control Register (TWI_CR) is written with the bit MSDIS at 1.
Furthermore, the status bits TXCOMP and TXRDY in the Status Register (TWI_SR) are not reset.
Problem Fix/Workaround
The user must wait for the end of transfer before disabling the TWI. In addition, the interrupts must be disabled
before disabling the TWI.
40.4.8.4 TWI: NACK Status Bit Lost
During a master frame, if TWI_SR is read between the Non Acknowledge condition detection and the TXCOMP bit
rising in the TWI_SR, the NACK bit is not set.
Problem Fix/Workaround
The user must wait for the TXCOMP status bit by interrupt and must not read the TWI_SR as long as transmission
is not completed.
TXCOMP and NACK fields are set simultaneously and the NACK field is reset after the read of the TWI_SR.
40.4.8.5 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 cor-
rupted 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.
40.4.9 Universal Synchronous Asynchronous Receiver Transmitter (USART)
40.4.9.1 USART: CTS in Hardware Handshaking
When Hardware Handshaking is used and if CTS goes high near the end of the start bit, a character can be lost.
CTS must not go high during a time slot occurring between 2 Master Clock periods before and 16 Master Clock
periods after the rising edge of the start bit.
Problem Fix/Workaround
None.
40.4.9.2 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 con-
tent 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.
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
605