Rockwell Automation Logix5000 Controllers Tasks, Programs, and Routines Programming Manual - Manual (Page 65)

Manage event tasks Chapter 2
Example – EVENT Instruction trigger
A controller uses multiple programs except for a common shut down procedure.
Each program uses a program-scoped tag named Shut_Down_Line that turns on if
the program detects a condition that requires a shut down.
Event Task Properties
Let an event trigger this task.
Let an EVENT instruction trigger the task.
No tag is required.
Interrupt all other tasks.
Ladder Diagram in Program_A
If Shut_Down_Line = on (conditions require a shut down) then
run the Shut_Down task one time.
Rockwell Automation Publication 1756-PM005-EN-P - October 2014 65