Rockwell Automation 1766-Lxxxx MicroLogix 1400 Programmable Controllers User Manual - Manual (Page 232)

192 Rockwell Automation Publication 1766-UM001H-EN-P - May 2014
Appendix E Connecting to Networks via RS-232/RS-485 Interface
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 controllers is 1...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 19,200.
This is the default baud rate for a MicroLogix 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
maximum node address of your controllers. It should be set to the highest node
address being used.
MicroLogix Remote Packet Support
MicroLogix controllers can respond and initiate with communications (or
commands) that do not originate on the local DH-485 network. This is useful in
installations where communication is needed between DH-485 and DH+
networks.
The example below shows how to send messages from a device on the DH+
network to a MicroLogix controller on the DH-485 network. This method uses
an SLC 5/04 processor as the bridge connection.
When using this method (as shown in the illustration below):
• PLC-5 devices can send read and write commands to MicroLogix
controllers.
• MicroLogix controllers can respond to MSG instructions received.
• The MicroLogix controllers can initiate MSG instructions to devices on
the DH+ network.
• PC can send read and write commands to MicroLogix controllers.
• PC can do remote programming of MicroLogix controllers.
IMPORTANT All devices should be set to the same maximum node address.