182 Rockwell Automation Publication 1766-UM001O-EN-P - September 2021
Appendix E Connect to Networks via RS-232/RS-485 Interface
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…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 Data
Highway Plus™ (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.
Use a 1763-NC01 Series A or later cable to connect a MicroLogix 1400 controller to a
DH-485 network.
You can connect a MicroLogix 1400 controller to your DH-485 network directly without
using a RS-232 to RS-485 converter and optical isolator, such as the AIC+, catalog
number 1761-NET-AIC, as shown in Figure 72 on page 183
, because Channel 0 has
isolation and RS-485 built-in.
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