Rockwell Automation 1769-L23E-QB1B_L23E-QBFC1B_L23-QBFC1B CompactLogix Packaged Controllers Quick Start and User Manual - Manual (Page 171)

Publication IASIMP-QS010B-EN-P - October 2009 171
Network Communication Chapter 2
If you are configuring a 1769-L23-QBFC1B controller, click the system
protocol tab that corresponds to the serial port you configured in
step 2
(for example, CH0-System Protocol).
6. From the Protocol pull-down menu, choose a DF1 protocol.
7. Specify DF1 settings according to your system.
1769-L23E
1769-L23