Rockwell Automation 1770 DH,DHII,DH485 CABLE - Manual (Page 86)

Planning a DH II Cable System
Chapter 5
5-10
You must install a tap for each node on the network.
In addition, if you plan to add nodes at a later date, you should install taps for
these additional nodes when you install the initial cable system. This will help
avoid the disruption of recabling after the network is in operation.
The I/O raceway layout of a system is reflective of where the different types of
I/O modules are placed in an I/O chassis. Therefore, you should determine I/O
module placement prior to any layout and routing of wires. However, when
planning your I/O module placement, segregate the modules based upon the
conductor categories published for each I/O module so that you can follow these
guidelines. These guidelines coincide with the guidelines for “the installation of
electrical equipment to minimize electrical noise inputs to controllers from
external sources” in IEEE standard 518-1982.
Categorize Conductors
Segregate all wires and cables into the three categories shown in
Table 5.C. Refer to the publication for each I/O module for the conductor
category classification of each I/O line.
Selecting the Number of
Taps
I/O Raceway Layout
Considerations