Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 341)

Reference
Understanding the Communication Protocols
D–13
DH-485 Network Initialization
Network initialization begins when a period of inactivity exceeding the time of a
link dead timeout is detected by an initiator on the network. When the time for a
link dead timeout is exceeded, usually the initiator with the lowest address claims
the token. When an initiator has the token it will begin to build the network. The
network requires at least one initiator to initialize it.
Building a network begins when the initiator that claimed the token tries to pass the
token to the successor node. If the attempt to pass the token fails, or if the initiator
has no established successor (for example, when it powers up), it begins a linear
search for a successor starting with the node above it in the addressing.
When the initiator finds another active initiator, it passes the token to that node,
which repeats the process until the token is passed all the way around the network to
the first node. At this point, the network is in a state of normal operation.
Devices that use the DH-485 Network
In addition to the Series C or later MicroLogix 1000 discrete controllers and all
MicroLogix 1000 analog controllers, the devices shown in the following table also
support the DH-485 network.
Note You cannot connect the Hand-Held Programmer, 1761-HHP-B30, to the AIC+.