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Rockwell Automation Publication 1789-UM002K-EN-P - January 2015
Chapter 2
What is the SoftLogix System?
Determining Programs
Each program contains program tags, a main executable routine, other routines,
and an optional fault routine. Each task can schedule as many as 100 programs
(including equipment phases).
The scheduled programs within a task execute to completion from first to last.
Programs that are not attached to any task appear as unscheduled programs.
You must specify (schedule) a program within a task before the controller can
scan the program.
Table 2 - Task Execution Order for Application with Periodic Tasks and Continuous Task
Task
Priority Level
Task Type
Actual Execution Time
Worst Case
Execution Time
1
1
20 ms periodic task
2 ms
2 ms
2
2
10 ms periodic task
4 ms
6 ms
N/A
None (lowest)
Continuous task
25 ms
35 ms
N/A
None
Dwell time
10 ms
14 ms
Task 1
Task 2
Continuous
Task
Dwell
Time
Task
Description
A
The highest priority task interrupts all lower priority tasks.
B
A lower priority task can be interrupted multiple times by a higher priority task.
C
The continuous task runs at the lowest priority and is interrupted by all other tasks.
D
The dwell time starts when the continuous task completes. The dwell time does not affect periodic tasks.
Periodic tasks execute as scheduled, regardless of the dwell time.
E
The continuous tasks restart, when the dwell time completes, unless a higher priority task is running.
