180 Rockwell Automation Publication 1766-UM001O-EN-P - September 2021
Appendix E Connect to Networks via RS-232/RS-485 Interface
Important DH-485 Network Planning Considerations
Carefully plan your network configuration before installing any hardware.
Some of the factors that can affect system performance are:
• amount of electrical noise, temperature, and humidity in the network
environment.
• number of devices on the network.
• connection and grounding quality in installation.
• amount of communication traffic on the network.
• type of process being controlled.
• network configuration.
The major hardware and software issues you need to resolve before installing a
network are discussed in the following sections.
Hardware Considerations
You need to decide the length of the communication cable, where you route it,
and how to protect it from the environment where it is installed.
When the communication cable is installed, you need to know how many
devices are to be connected during installation and how many devices are
added in the future. The following sections help you understand and plan the
network.
Number of Devices and Length of Communication Cable
The maximum length of the communication cable is 1219 m (4000 ft). This is
the total cable distance from the first node to the last node in a segment.
However, two segments can be used to extend the DH-485 network to 2438 m
(8000 ft.). For additional information on connections using the AIC+, see
Advanced Interface Converter DeviceNet Interface User Manual, publication
1761-IN002
.
Planning Cable Routes
Follow these guidelines to help protect the communication cable from
electrical interference:
• Keep the communication cable at least 1.52 m (5 ft.) from any electric
motors, transformers, rectifiers, generators, arc welders, induction
furnaces, or sources of microwave radiation.
• If you must run the cable across power feed lines, run the cable at right
angles to the lines.
• If you do not run the cable through a contiguous metallic wireway or
conduit, keep the communication cable at least 0.15 m (6 in.) from AC
1784-PCMK PCMCIA IM
PCMCIA slot in
computer
Provides DH-485 using RSLinx. 1784-UM519
2711-K5A2, 2711-B5A2,
2711-K5A5, 2711-B5A5,
2711-K5A1, 2711-B5A1,
2711-K9A2, 2711-T9A2,
2711-K9A5, 2711-T9A5,
2711-K9A1, 2711-T9A1
PanelView 550 and
PanelView 900
Operator Terminals
Panel Mount Provides electronic operator interface for SLC 500 processors. 2711-UM014
Table 21 - Devices that Support DH-45 Network (Continued)
Catalog Number Description Installation Function Publication
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