Rockwell Automation Logix5000 Controllers Add-on Instructions Programming Manual - Manual (Page 52)

Chapter 2 Defining Add-On Instructions
3. Click New for Prescan routine.
4. On the New Scan Mode Routine dialog box, from the Type list, select the
type of programming language; Ladder Diagram, Function Block, or
Structured Text.
5. In the Description box, type the Prescan behavior.
6. Click OK to create the routine and return to the Scan Modes tab.
7. Define if the prescan routine executes (or not) by checking or clearing
Execute Prescan routine after the logic routine is prescanned check box.
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The Prescan routine can now be edited like any other routine.
Rockwell Automation Publication 1756-PM010F-EN-P - October 2014