at91rm3400 ATMEL Corporation, at91rm3400 Datasheet - Page 287

• Manufacturer Part Number: at91rm3400
• Description: Atmel Advanced At91 Arm Microcontroller
• Manufacturer: ATMEL Corporation

Disable Successive
Receive NACK
Protocol T = 1
IrDA Mode
1790A–ATARM–11/03
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.
The ITERATION bit in US_CSR can be cleared by writing the Control Register with the RSIT
bit at 1.
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.
When operating in ISO7816 protocol T = 1, the transmission is similar to an asynchronous for-
mat 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 USART features an IrDA mode supplying half-duplex point-to-point wireless communica-
tion. It embeds the modulator and demodulator which allows a glueless connection to the
infrared transceivers, as shown in Figure 111. The modulator and demodulator are compliant
with the IrDA specification version 1.1 and support data transfer speeds ranging from 2,4 Kbps
to 115,2 Kbps.
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 demodula-
tor 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 111. Connection to IrDA Transceivers
The receiver and the transmitter must be enabled or disabled according to the direction of the
transmission to be managed.
Transmitter
Receiver
USART
Demodulator
Modulator
RXD
TXD
RX
TX
AT91RM3400
Transceivers
IrDA
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