Rockwell Automation Logix5000 Controllers Tasks, Programs, and Routines Programming Manual - Manual (Page 41)

Manage event tasks Chapter 2
4. Change of state (COS)
If a digital device triggers the event, enable COS for only the point that triggers the event task.
•
Enable change of state for the type of transition that triggers the task, either Off → On, On → Off, or both.
• If you configure COS for both Off → On and On → Off, the point triggers an event task whenever the point turns on or off. Make sure
the duration of the input is longer than the scan time of the task. Otherwise an overlap could occur.
• Disable (clear) COS for the remaining points on the input module. If you configure multiple points on a module for COS, each point
could trigger the event task. This could cause an overlap.
5. Task priority
Configure the event task as the highest priority task.
If a periodic task has a higher priority, the event task may have to wait until the periodic task is done.
6. Motion planner The motion planner interrupts all other tasks, regardless of their priority.
•
The number of axes and coarse update period for the motion group effect how long and how often the motion planner executes.
• If the motion planner is executing when a task is triggered, the task waits until the motion planner is done.
• If the coarse update period occurs while a task is executing, the task pauses to let the motion planner execute.
7. Number of event tasks Limit the number of event tasks.
Each additional task reduces the processing time that is available for other tasks. This could cause an overlap.
8. Automatic Output
Processing
For an event task, you can typically disable automatic output processing (default). This reduces the elapsed time of the task.
9. IOT instruction
Use an IOT instruction for each output module that you reference in the event task.
The IOT instruction overrides the RPI for the module and immediately sends the data.
Rockwell Automation Publication 1756-PM005-EN-P - October 2014 41