Rockwell Automation 1770 DH,DHII,DH485 CABLE - Manual (Page 65)

Constructing a Data Highway or
Data Highway Plus Cable System
Chapter 3
3-33
After your DH or DH+ network has been operating for some time, you may find
it necessary to add or remove nodes from the network. This section explains
how to modify a network constructed with droplines and station connectors to
accommodate these changes.
In this section we explain how to:
add a node to DH and DH+
remove a node from DH and DH+
Important: This section only describes the changes that must be made to the
cable system when you reconfigure the nodes. You may need to make
programming changes at some or all of the nodes so that the nodes can
communicate properly after they have been reconfigured. Refer to your
interface user’s manual for information on how to make programming changes.
Add a Node to DH and DH+
To add a node to a DH and DH+ network, follow these steps:
1. Obtain enough connectors and twinaxial cable to construct the additional
dropline and trunkline segments necessary for the new node.
2. Attach the electrical connector to the dropline as explained in the section
‘‘Attach an Electrical Connector to the Dropline” earlier in this chapter.
3. Install the station connector as explained earlier in this chapter in the
section ‘‘Install the 1770-SC Station Connector” or ‘‘Install the 1770-XG
Connector Kit.”
ATTENTION: The next step will stop all network communication.
Individual nodes can continue to perform their independent
functions, but disconnecting all nodes may result in the loss of
transmitted messages and the activation of REMOTE/LOCAL
FAULT indicators by the node interface modules.
4. At each node on the network, disconnect the electrical connector from the
interface module on the node.
5. Connect the new dropline and trunkline segments to the existing network.
Important: If you add the new trunkline segment to either the first or last
connectors on the network, you must move the terminating resistor to the new
termination point on the trunkline.
6. Reconnect all droplines to the node interface modules.
Reconfigure a Network
Constructed with Droplines
and Station Connectors
(If Necessary)