Rockwell Automation 1769-L23E-QB1B_L23E-QBFC1B_L23-QBFC1B CompactLogix Packaged Controllers Quick Start and User Manual - Manual (Page 176)

176 Publication IASIMP-QS010B-EN-P - October 2009
Chapter 2 Network Communication
Modbus Support
To use Logix5000 controllers with the Modbus protocol, connect the
controllers through the serial port and execute specific ladder logic routines.
A sample controller project is available with RSLogix 5000 Enterprise
programming software by clicking Help and choosing Vendor Sample Projects.
Broadcast Messages Over a Serial Port
You can broadcast messages over a serial port connection from a master
controller to all of its slave controllers by using several communication
protocols. Those protocols are the following:
• DF1 Master
• DF1 Radio Modem
• DF1 Slave
Broadcasting over a serial port is achieved using the ‘message’ tag. Because
messages are sent to receiving controllers, only the ‘write’ type messages can
be used for broadcasting.
The broadcast feature can be set up by using ladder logic or structured text.
The broadcast feature can also be set by modifying the path value of a message
tag in the tag editor.
For this example, ladder logic programming software will be used.
Step 1: Set Broadcast - Controller Properties
First, set the System Protocol by following these steps.
1. In the Controller Organizer, right-click the controller and choose
Properties.