NOVUS RS422 Basics - Manual (Page 5)

RS485 & RS422 Basics
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The common terminal must be connected to the corresponding terminals of all network devices, to ensure the same
potential in all devices. If a common wire is not connected to all devices, all must be properly grounded according to the
manufacturer recommendation. This demand results in using a third wire that, although not being part of the
communication process, is essential to ensure the electrical integrity of the network devices.
The need to install termination resistors depends on the total length of the communication bus and the communication
speed (baud rate).
RS485 FULL-DUPLEX (4 WIRES)
In this mode two pairs of wires are used. Data from the RS485 converter to the networked devices are transmitted
through one pair, and the other pair carries data from the devices to the RS485 converter. Multiple devices are
connected as shown in the next figure.
The common terminal must be connected to the corresponding terminals of all network devices, to ensure the same
potential in all devices. If a common wire is not connected to all devices, all must be properly grounded according to the
manufacturer recommendation. This demand results in using a fifth wire that, although not being part of the
communication process, is essential to ensure the electrical integrity of the network devices.
The need to install termination resistors depends on the total length of the communication bus and the communication
speed (baud rate).
RS422
Full-Duplex RS485 specification supersedes RS422. The same connection instructions shown for Full-Duplex RS485
apply for RS422 connection.