Rockwell Automation 1762-Lxxxx MicroLogix 1200 Programmable Controllers - Manual (Page 138)

Publication 1762-UM001G-EN-P - March 2011
E-8 Connect to Networks via RS-232 Interface
– Install the conduit so that it meets all applicable codes and
environmental specifications.
For more information on planning cable routes, see Industrial Automation
Wiring and Grounding Guidelines, publication Number 1770-4.1.
Software Considerations
Software considerations include the configuration of the network and the
parameters that can be set to the specific requirements of the network. The
following are major configuration factors that have a significant effect on
network performance:
• number of nodes on the network
• addresses of those nodes
• baud rate
The following sections explain network considerations and describe ways to
select parameters for optimum network performance (speed). See your
programming software’s user manual for more information.
Number of Nodes
The number of nodes on the network directly affects the data transfer time
between nodes. Unnecessary nodes (such as a second programming terminal
that is not being used) slow the data transfer rate. The maximum number of
nodes on the network is 32.
Setting Node Addresses
The best network performance occurs when node addresses are assigned in
sequential order. Initiators, such as personal computers, should be assigned
the lowest numbered addresses to minimize the time required to initialize the
network. The valid range for the MicroLogix 1200 controllers is 1 to 31
(controllers cannot be node 0). The default setting is 1. The node address is
stored in the controller Communications Status file (CS0:5/0 to CS0:5/7).
Setting Controller Baud Rate
The best network performance occurs at the highest baud rate, which is 19200.
This is the default baud rate for a MicroLogix 1200 device on the DH-485
network. All devices must be at the same baud rate. This rate is stored in the
controller Communications Status file (CS0:5/8 to CS0:5/15).
Setting Maximum Node Address
Once you have an established network set up and are confident that you will
not be adding more devices, you may enhance performance by adjusting the