Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 438)

Appendix D
Understanding the Communication Protocols
D–12
Important DH-485 Network Planning Considerations
Carefully plan your network configuration before installing any hardware.
Listed below are some of the factors that can affect system performance:
•
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 will be installed.
When the communication cable is installed, you need to know how many
devices are to be connected during installation and how many devices will be
added in the future. The following sections help you understand and plan the
network.
Number of Devices and Length of Communication Cable
You must install an AIC+ Advanced Interface Converter, catalog number
1761-NET-AIC, for each node on the network. If you plan to add nodes
later, provide additional advanced interface converters during the initial
installation to avoid recabling after the network is in operation.
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 on the network.