Specifications

Chapter 2 - System Configuration RS-422 And RS-485 Applications Ebook
Page 24 of 137 Manual Documentation Number: <DocNumber>
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RS-422 Point-to-Point Connections
The most common use for RS-422 devices is in point-to-point serial
links where other interface standards such as RS-232 do not provide
adequate distance or speed. If the link is simplex (single direction of
data flow) a RS-422 system requires a pair of wires for TDA(-) and
TDB(+) and a ground.
Figure 14: RS-422 Point-to-Point Connection
For duplex communication a separate driver and receiver must be used
at both ends. Each direction requires twisted pair for communications
but one signal ground can be used for both.
Figure 15: RS-422 Four-Wire Full Duplex Connection
If RS-422 is being used to extend the distance or speed of an interface
such as RS-232, which may implement several handshake lines,
additional driver/receiver combinations are needed, as well as a
dedicated pair of wires for each signal.