Industrial Engineer · phase 3 of 16 · noun

Periodic Task

Task scheduled to run at a configured time interval.

The Explain card

Plain English: A periodic task runs on a fixed schedule, every so many milliseconds, whatever else is going on. The controller interrupts lower priority work to keep the period.
Example: A flow totalizer that integrates a rate every 100 milliseconds lives in a 100 millisecond periodic task. The math is right because the interval is exactly what the code assumes.
Why it matters: Fixed rate logic, PID loops and anything that counts time by counting executions belong here. A period set shorter than the task's own execution time overlaps itself and faults the controller.
Hook: Runs on the clock, and only on the clock.

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

The PLC executes the Periodic Task every 10 ms to read the encoder and update the conveyor speed command.

Why these words

periodic Greek periodikos, recurring, through Latin periodicus modifies task by identifying its timing pattern
task Old North French tasque, duty or imposed work names the unit of controller work

Where it came from

Origin: Greek periodikos through Latin periodicus, combined with Middle English task from Old North French tasque
Entered the language: 20th century
What changed: Periodic developed from describing cycles or circuits to describing regular recurrence, while task broadened from assigned labor to a unit of computer execution.

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What it sits beside

Same subject

Same shape

controller task types

task timing properties

Phase 3: PLC Program Organization and Execution

How the logic is arranged and how the scan actually runs it, which is the difference between code that works and code that works every time.