Rockwell-automation Logix5000 Controllers Tasks, Programs, and Routine Bedienungsanleitung PDF herunterladen (Seite 12)

Chapter 1 Manage tasks

The number of priority levels depends on the controller.

This Logix5000 controller Has this many priority levels

CompactLogix 15

ControlLogix 15

DriveLogix 15

FlexLogix 15

SoftLogix5800 3

To assign a priority to a task, use the following guidelines.

If you want Then Notes

This task to interrupt

another task

Assign a priority number that is less than the

priority number of the other task.

•

A higher priority task interrupts all

lower priority tasks.

• A higher priority task can interrupt a

lower priority task multiple times.

Another task to interrupt

this task

Assign a priority number that is greater than the

priority number of the other task.

This task to share controller

time with another task

Assign the same priority number to both tasks. The controller switches back and forth

between each task and runs each task

for 1 ms.

Additional considerations

As you estimate the execution interrupts for a task, consider the following.

Consideration Description

Motion planner The motion planner interrupts all user tasks, regardless of their priority.

•

The number of axes and coarse update period for the motion group affect how long and how

often the motion planner runs.

• If the motion planner is running when a task is triggered, the task waits until the motion

planner is done.

• If the coarse update period occurs while a task is running, the task pauses to let the motion

planner run.

I/O task

CompactLogix, FlexLogix, and DriveLogix controllers use a dedicated periodic task to process I/O

data. This I/O task:

• Does not show up in the Tasks folder of the controller.

• Does not count toward the task limits for the controller.

• Operates at priority 6.

• Runs at the fastest RPI you have scheduled for the system.

• Runs for as long as it takes to scan the configured I/O modules.

As you assign priorities to your tasks, consider the I/O task.

If you want a task to Then assign one of these priorities

Interrupt or delay I/O processing 1…5

Share controller time with I/O processing 6

Let I/O processing interrupt or delay the task 7…15

12 Rockwell Automation Publication 1756-PM005-EN-P - October 2014

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