Lenze E94AxPExxxx - Manual (Page 71)

Lenze · 9400 Servo PLC· Reference manual · DMS 4.0 EN · 11/2013 · TD05/06
71
4 PLC functionality
4.8 Appendix
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Example of pre-emptive multitasking
In the following example, three interval-controlled user tasks share the available 350 μs of
computing time per millisecond.
• The respective task cycle will not be used completely by the tasks so that a small amount of
calculating time remains after the lower-priority task 3.
• In the grey areas, processing in the respective task is frozen since either a higher-priority task,
the system part, or the basic motion control functions are being processed.
[4-5] Example "pre-emptive multitasking"

Tip!
The example in illustration
[4-5] shows that, e.g. for task 3 with the lowest priority, not the
total 1400 μs calculating time (4 task cycles * 350 μs per millisecond) is available but only
the part of the time that remains after processing the higher-priority task 1 and task 2.
 Task 1  Task 2  Task 3  Free calculating time
8VHU3/& 8VHU3/& 8VHU3/& 8VHU3/&
PV PV PV PV PV
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User task Priority Task interval
 Task 1 1 1 ms
 Task 2 2 2 ms
 Task 3 3 4 ms