Datasheet

537
SAM9263 [DATASHEET]
Atmel-6249N-ATARM-SAM9263-Datasheet_14-Mar-16
33.6.5.3 IrDA Demodulator
The demodulator is based on the IrDA Receive filter comprised of an 8-bit down counter which is loaded with the
value programmed in US_IF. When a falling edge is detected on the RXD pin, the Filter Counter starts counting
down at the Master Clock (MCK) speed. If a rising edge is detected on the RXD pin, the counter stops and is
reloaded with US_IF. If no rising edge is detected when the counter reaches 0, the input of the receiver is driven
low during one bit time.
Figure 33-25 illustrates the operations of the IrDA demodulator.
Figure 33-25. IrDA Demodulator Operations
As the IrDA mode uses the same logic as the ISO7816, note that the FI_DI_RATIO field in US_FIDI must be set to
a value higher than 0 in order to assure IrDA communications operate correctly.
33.6.6 RS485 Mode
The USART features the RS485 mode to enable line driver control. While operating in RS485 mode, the USART
behaves as though in asynchronous or synchronous mode and configuration of all the parameters is possible. The
difference is that the RTS pin is driven high when the transmitter is operating. The behavior of the RTS pin is
controlled by the TXEMPTY bit. A typical connection of the USART to a RS485 bus is shown in Figure 33-26.
Figure 33-26. Typical Connection to a RS485 Bus
The USART is set in RS485 mode by programming the USART_MODE field in the Mode Register (US_MR) to the
value 0x1.
MCK
RXD
Receiver
Input
Pulse
Rejected
65432 6
1
65432 0
Pulse
Accepted
Counter
Value
USART
RTS
TXD
RXD
Differential
Bus