Atmel Evaluation Kit AT91SAM9G25-EK AT91SAM9G25-EK Data Sheet
Product codes
AT91SAM9G25-EK
839
SAM9G25 [DATASHEET]
11032D–ATARM–10-Mar-2014
Figure 39-34.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.
value higher than 0 in order to assure IrDA communications operate correctly.
39.7.6 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
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 39-35.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.
0x1.
The RTS pin is at a level inverse to the TXEMPTY bit. Significantly, the RTS pin remains high when a timeguard is
programmed so that the line can remain driven after the last character completion.
programmed so that the line can remain driven after the last character completion.
gives an example of the
RTS waveform during a character transmission when the timeguard is enabled.
MCK
RXD
Receiver
Input
Pulse
Rejected
6
5
4
3
2
6
1
6
5
4
3
2
0
Pulse
Accepted
Counter
Value
USART
RTS
TXD
RXD
Differential
Bus