Pro
12 min

Fault 06 — Timer Not Resetting

fault-injectiontimerreset
Fault 06 — Timer Not Resetting scenario preview

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Briefing

A cyclic process runs once but never repeats. The first cycle completes correctly, but subsequent start commands have no effect. The timer output stays permanently true after the first completion.

Objectives

  • Use the Variables tab to watch T_CYCLE.ET across multiple cycle starts
  • Identify why the timer's elapsed time never resets to 0
  • Find and fix the missing reset logic for the timer enable
  • Verify the cycle repeats correctly after your fix

Hints

  • Switch to the Variables tab and monitor T_CYCLE.ET
  • A TON timer only resets when its IN input goes false — what drives IN?
  • Add a rung to reset CYCLE_ACTIVE when CYCLE_COMPLETE fires

I/O Table

Inputs

START_CMD

Cycle start command

BOOL · %I0.0

Outputs

CYCLE_COMPLETE

Cycle-complete output pulse

BOOL · %Q0.0

RUNNING_LAMP

Cycle-running indicator

BOOL · %Q0.1

Your program will be tested against:

All test cases run automatically when you submit. Assertions are hidden until you pass.

  1. #1First cycle completes after start

    START_CMD → RUNNING_LAMP ON → after 500ms CYCLE_COMPLETE pulses

  2. #2Cycle can be restarted after completion

    After the first cycle, a second START_CMD restarts the cycle

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