Connecting RS422 Devices
To use the serial interface in the RS422 mode you have to connect
the pins of the devices as shown in the illustration below.
For proper operation of the serial interface (UART) you have to pay
attention to line termination and grounding.
Objective
In RS422 mode, line termination is essential, especially for faster data
transfer rates and long cables. Because RS422 allows only one
transmitter on the bus, the termination resistor (120 Ω) must be
placed at the end of the cable near the last receiver between RXD and
RXD.
Line termination
R R
R R
DS1103 (RS422 mode)
R
T
TXD
T = Transmitter
R = Receiver
RXD
T
TXD
RXD
R
120 Ω
120 Ω
TXD
RXD
TXD
RXD
s
Serial Interface
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DS1103 Hardware Installation and Configuration November 2014
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