Prioritize periodic and event tasks, Use caution in the number of tasks that you use – Rockwell Automation Logix5000 Controllers Tasks, Programs, and Routines Programming Manual User Manual
Page 11
Manage tasks Chapter 1
For this example situation
Use this type of task
In a production line, if any of the programs detect an unsafe condition the entire line
must shut down. The shutdown procedure is the same regardless of the unsafe
condition.
Event task
The number of tasks supported depends on the controller.
This controller
Supports this number of
tasks
Notes
ControlLogix
1756-L71
1756-L72
1756-L73
1756-L74
1756-L75
GuardLogix
1756-L71S
1756-L72S
1756-L73S
SoftLogix5800
1756-L7SP
32
32
32
Only one task can be
continuous.
CompactLogix
1769-L2x
1769-L31
1769-L32x
1769-L35x
1768-L43
1768-L45
1769-L16x
1769-L18x
1769-L24x
1769-L27x
1769-L30x
1769-L33x
1769-L36x
3
4
6
8
16
32
Use caution in the number of tasks that you use
Typically, each task takes controller time away from the other tasks. If you have
too many tasks, then:
•
The continuous task may take too long to complete.
•
Other tasks may overlap. If a task is interrupted too frequently or too long,
it may not finish running before it is triggered again.
Although a project can contain multiple tasks, the controller runs only one task at
a time. If a periodic or event task is triggered while another task is running, the
priority of each task indicates what the controller should do.
Prioritize periodic and
event tasks
Rockwell Automation Publication 1756-PM005-EN-P - October 2014
11