Datasheet

913
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
Figure 38-36. Typical Connection to a RS485 Bus
The USART is set in RS485 mode by writing the value 0x1 to the USART_MODE field in US_MR.
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. Figure 38-37 gives an example
of the RTS waveform during a character transmission when the timeguard is enabled.
Figure 38-37. Example of RTS Drive with Timeguard
USART
RTS
TXD
RXD
Differential
Bus
D0 D1 D2 D3 D4 D5 D6 D7
TXD
Start
Bit
Parity
Bit
Stop
Bit
Baud Rate
Clock
TG = 4
Write
US_THR
TXRDY
TXEMPTY
RTS
1