AT32UC3C1512C Automotive Atmel Corporation, AT32UC3C1512C Automotive Datasheet - Page 593

• Manufacturer Part Number: AT32UC3C1512C Automotive
• Manufacturer: Atmel Corporation

25.6.6
9166C–AVR-08/11
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 25-35. Typical Connection to a RS485 Bus
The USART is set in RS485 mode by programming the MODE field in the Mode Register (MR)
to the value 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 com-
pletion.
when the timeguard is enabled.
Figure 25-36. Example of RTS Drive with Timeguard
Figure 25-36
Baud Rate
TXEMPTY
TXRDY
Clock
Write
THR
TXD
RTS
gives an example of the RTS waveform during a character transmission
USART
Start
Bit
RXD
TXD
RTS
D0
D1
D2
D3
D4
D5
D6
Figure
D7
Parity
Bit
25-35.
Stop
Bit
Differential
Bus
TG = 4
AT32UC3C
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