Biasing And Termination; Rs-485 Configuration; 4-Wire Configuration; 2-Wire Configuration - PowerLogic EGX200 Instruction Bulletin

Chapter 4—Installation and Wiring
Wiring Connections

Biasing and Termination

RS-485 Configuration

On RS-485 daisy chains, correct biasing is required to ensure reliable communication
with field devices. The EGX200's dip switches for each RS-485 port provide flexibility
in configuring the correct biasing. Figure 4–10 shows the biasing and termination label,
as well as the typical dip switch settings for both 4-wire and 2-wire configurations.
In addition, the RS-485 daisy chain should be terminated to ensure reliable
communication. The last device on the daisy chain usually needs a terminator (part
number MCT-485 or MCTAS-485). Please refer to the instruction bulletin for the last
device on the daisy chain to determine whether a terminator is required. If one is
required, contact your local sales representative.

4-Wire Configuration

For RS-485, 4-wire configuration, the biasing and termination dip switches should be
ON (switches 1, 2, 3, 4 for COM 2 and switches 7, 8, 9, and 10 for COM 1 — switches
5 and 6 are not used). The EGX200 is shipped with all dip switches in the ON position
(default). Therefore, you do not need to change the dip switches unless a different
termination or biasing is required.

2-Wire Configuration

For RS-485 2-wire communication, the biasing dip switches for Rx+ and Rx- should be
ON. The termination dip switches for either Rx or Tx should be OFF. Therefore, either
switch 7 or switch 8 should be OFF for COM 1, and either switch 1 or switch 2 should
be OFF for COM 2.
Figure 4–10: Biasing and Termination
26
Dip switch settings
COM 2
1 2 3 4 5
4-Wire
COM 2
1 2 3 4 5
2-Wire
= ON
© 2001 Schneider Electric All Rights Reserved
63230-314-200/A2
8/2001
COM 1
6 7 8 9 10
COM 1
6 7 8 9 10
= OFF