Lenze E94AxPExxxx - Manual (Page 70)

4 PLC functionality
4.8 Appendix
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Lenze · 9400 Servo PLC· Reference manual · DMS 4.0 EN · 11/2013 · TD05/06
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4.8.3 User task
9 user tasks can be created. User tasks can be event-controlled, time-controlled or unsolicited. Only
one unsolicited task can be created. The user tasks can interrupt themselves in the form of pre-
emptive multitasking and thus make optimum use of the available computing time.

Tip!
The tasks are created and configured in the »PLC Designer« via the task configuration that
is located as an object in the Object Organizer in the Resources tab.
Priorities
Each task is assigned to a priority (1: highest ..... 9: lowest). The hierarchy determines the
distribution of the available calculating time to the tasks.
• One priority cannot be assigned for several tasks.
• The task with the highest priority must be a cyclic task.
• The unsolicited task must always have the lowest priority.
Distribution of the calculating time
Max. 350 μs of calculating time per millisecond are available for the task with the highest priority,
see illustration [4-4] . The calculating time not required remains for the lower-level tasks which
share this calculating time according to their priority.
• If the processing time in a task with higher priority takes longer, the free calculating time in the
lower-priority tasks is automatically reduced.
• In »PLC Designer«, an interval time of 1 ms, 2 ms, 4 ms or 8 ms must be set for the task with the
highest priority. After this interval time, the task is followed by processing of the basic motor
control functions.

Note!
The »9400 ServoPLC« only ensures data consistency of the task images for the user task
with the highest priority. For all other tasks, the user is responsible for consistency.
 Data consistency ( 73)
Pre-emptive multi-tasking may cause the task images to start with a delay or being
interrupted by tasks with a higher priority.  Example of pre-emptive multitasking
( 71)