Rockwell Automation 1769-L23E-QB1B_L23E-QBFC1B_L23-QBFC1B CompactLogix Packaged Controllers Quick Start and User Manual - Manual (Page 183)

Publication IASIMP-QS010B-EN-P - October 2009 183
Network Communication Chapter 2
7. From the Communication tab, select the Broadcast Radio button and
the Channel from the pull-down menu, then choose OK.
ATTENTION
When using structured text, broadcast over a serial port is set
by typing MSG(aMsg) and right-clicking on aMSG to display the
Message Configuration dialog box.