Glossary · Automation fundamentals, platforms and components
Multitasking
Also known as: Multiple tasks
German: Multitasking
In computing and PLCs, multitasking is the ability to manage several tasks concurrently, with a scheduler deciding which task runs when, based on priorities, cycles or events. IEC 61131-3 lets programs be assigned to tasks with intervals or triggering events and priorities.
- Automation components
In one sentence
Multitasking manages several tasks at once, with a scheduler running them by priority, cycle or event; IEC 61131-3 uses such tasks.
Example
A PLC runs a fast 2 ms task for axis control, a 20 ms task for machine logic and a free-running background task for diagnostics.
How it applies
- Engineering: Assigning time-critical code to high-priority cyclic tasks and the rest to slower tasks keeps response times low. Data shared between tasks needs consistent access, since a higher-priority task can interrupt a lower one mid-operation.
- Commissioning: Task load and overruns are checked; an overloaded task can cause watchdog errors.
- Documentation: Software documentation should list tasks, their priorities, intervals and assigned programs. This helps maintenance staff understand timing-related faults.
- Maintenance: Moving code between tasks changes timing and data consistency, so such changes need testing like any functional change.
Multitasking vs. parallel processing
On a single core, multitasking switches between tasks; only one runs at any moment. On Multi-core architecture hardware, tasks can truly run in parallel. Both need rules for shared data.