Rockwell Automation 1770 DH,DHII,DH485 CABLE - Manual (Page 101)

DHĆ485 Overview
Chapter 7
7-2
DH-485 uses token-passing protocol to allow nodes on the network to transmit
messages over the cables. With token-passing protocol, only the node
possessing the token can transmit messages. As long as a node possesses the
token, it is the master.
When a node has sent all of its messages or used all of its token-hold time, it
passes the token to the node with the next highest address. Token passing
continues in this manner until the token is passed to the node with the lowest
address. When the node with the lowest address is finished with the token, the
cycle begins again.
In this chapter we provided you with a general overview of the DH-485 cable
system. You are now ready to plan your network. Refer to Chapter 8.
Important: Chapter 8 provides important specifications, guidelines and
precautions that you need to know before you construct your DH-485 network.
Be sure to read Chapter 8 before beginning any construction of your
cable system.
How Nodes Communicate
on DHĆ485