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ATSAM4S-XPLD
714
SAM4S [DATASHEET]
11100E–ATARM–24-Jul-13
Transmit Character Repetition
When the USART is transmitting a character and gets a NACK, it can automatically repeat the character before moving
on to the next one. Repetition is enabled by writing the MAX_ITERATION field in the Mode Register (US_MR) at a value
higher than 0. Each character can be transmitted up to eight times; the first transmission plus seven repetitions.
on to the next one. Repetition is enabled by writing the MAX_ITERATION field in the Mode Register (US_MR) at a value
higher than 0. Each character can be transmitted up to eight times; the first transmission plus seven repetitions.
If MAX_ITERATION does not equal zero, the USART repeats the character as many times as the value loaded in
MAX_ITERATION.
MAX_ITERATION.
When the USART repetition number reaches MAX_ITERATION, the ITERATION bit is set in the Channel Status Register
(US_CSR). If the repetition of the character is acknowledged by the receiver, the repetitions are stopped and the iteration
counter is cleared.
(US_CSR). If the repetition of the character is acknowledged by the receiver, the repetitions are stopped and the iteration
counter is cleared.
The ITERATION bit in US_CSR can be cleared by writing the Control Register with the RSIT bit to 1.
Disable Successive Receive NACK
The receiver can limit the number of successive NACKs sent back to the remote transmitter. This is programmed by
setting the bit DSNACK in the Mode Register (US_MR). The maximum number of NACK transmitted is programmed in
the MAX_ITERATION field. As soon as MAX_ITERATION is reached, the character is considered as correct, an
acknowledge is sent on the line and the ITERATION bit in the Channel Status Register is set.
setting the bit DSNACK in the Mode Register (US_MR). The maximum number of NACK transmitted is programmed in
the MAX_ITERATION field. As soon as MAX_ITERATION is reached, the character is considered as correct, an
acknowledge is sent on the line and the ITERATION bit in the Channel Status Register is set.
35.7.4.3 Protocol T = 1
When operating in ISO7816 protocol T = 1, the transmission is similar to an asynchronous format with only one stop bit.
The parity is generated when transmitting and checked when receiving. Parity error detection sets the PARE bit in the
Channel Status Register (US_CSR).
The parity is generated when transmitting and checked when receiving. Parity error detection sets the PARE bit in the
Channel Status Register (US_CSR).
35.7.5 IrDA Mode
The USART features an IrDA mode supplying half-duplex point-to-point wireless communication. It embeds the
modulator and demodulator which allows a glueless connection to the infrared transceivers, as shown in
modulator and demodulator which allows a glueless connection to the infrared transceivers, as shown in
.
The modulator and demodulator are compliant with the IrDA specification version 1.1 and support data transfer speeds
ranging from 2.4 Kb/s to 115.2 Kb/s.
ranging from 2.4 Kb/s to 115.2 Kb/s.
The USART IrDA mode is enabled by setting the USART_MODE field in the Mode Register (US_MR) to the value 0x8.
The IrDA Filter Register (US_IF) allows configuring the demodulator filter. The USART transmitter and receiver operate
in a normal asynchronous mode and all parameters are accessible. Note that the modulator and the demodulator are
activated.
The IrDA Filter Register (US_IF) allows configuring the demodulator filter. The USART transmitter and receiver operate
in a normal asynchronous mode and all parameters are accessible. Note that the modulator and the demodulator are
activated.
Figure 35-33.Connection to IrDA Transceivers
The receiver and the transmitter must be enabled or disabled according to the direction of the transmission to be
managed.
managed.
To receive IrDA signals, the following needs to be done:
Disable TX and Enable RX
IrDA
Transceivers
RXD
RX
TXD
TX
USART
Demodulator
Modulator
Receiver
Transmitter