Fault 05 — Scan-Order Race

Briefing

An interlock occasionally trips for no apparent reason. Under normal running it recovers immediately, but the downstream safety relay catches the momentary drop and latches a fault. Use slow-scan step mode to watch the scan execute rung-by-rung and identify the ordering problem.

Objectives

• Use slow-scan step mode to walk through the ladder one scan at a time
• Identify which rung reads a tag before another rung writes it
• Reorder the rungs to eliminate the one-scan lag
• Verify INTERLOCK_OK stays stable with the corrected rung order

I/O Table

Your program will be tested against:

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

1. #1INTERLOCK_OK stable when ENABLE_CMD goes true

   On the same scan that ENABLE_CMD transitions, INTERLOCK_OK should go true without a glitch

2. #2Both outputs go false when ENABLE_CMD goes false

   Disabling command removes both valve and interlock