Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 436)

Appendix D
Understanding the Communication Protocols
D–10
DH-485 Configuration Parameters
When the system mode driver is DH-485 Master, the following parameters
can be changed:
Parameter Description Default
Baud Rate Toggles between the communication rate of 9600 and 19200. 19200
Node Address
This is the node address of the processor on the DH-485 network. The
valid range is 1–31.
1
Max Node
Address
This is the maximum node address of an active processor. (fixed at 31)
Set the node addresses of the devices on the network to low, sequential
numbers for best network performance. Then, set the maximum node
address to the value of the last node.
31
Token Hold
Factor Determines the number of transactions allowed to make each DH-485
token rotation. (fixed at 1)
1
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 begins 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.
Important: You cannot connect the Hand-Held Programmer,
1761-HHP-B30, to the AIC+.