Rockwell-automation Logix5000 Controllers Tasks, Programs, and Routine Bedienungsanleitung PDF herunterladen (Seite 13)

Manage tasks Chapter 1

System overhead System overhead is the time that the controller spends on unscheduled communication.

• Unscheduled communication is any communication that you do not configure through the

I/O configuration folder of the project, such as Message (MSG) instructions and

communication with HMIs or workstations.

• System overhead interrupts only the continuous task.

• The system overhead time slice specifies the percentage of time (excluding the time for

periodic or event tasks) that the controller devotes to unscheduled communication.

• The controller performs unscheduled communication for up to 1 ms at a time and then

resumes the continuous task.

Continuous task You do not assign a priority to the continuous task. It always runs at the lowest priority. All

other tasks interrupt the continuous task.

Example

The following example shows the execution of a project with three user tasks.

Task Priority Period Execution time Duration

Motion planner N/A 8 ms (base update

rate)

1 ms 1 ms

Event task 1 1 N/A 1 ms 1…2 ms

Periodic task 1 2 12 ms 2 ms 2…4 ms

I/O task—n/a to ControlLogix and

SoftLogix controllers. See

Additional

Considerations on page 12.

7 5 ms (fastest RPI) 1 ms 1…5 ms

System overhead N/A Time slice = 20% 1 ms 1…6 ms

Continuous task N/A N/A 20 ms 48 ms

Rockwell Automation Publication 1756-PM005-EN-P - October 2014 13

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 72 73

Keine Kommentare

Rockwell-automation Logix5000 Controllers Tasks, Programs, and Routine Bedienungsanleitung Seite 13