Light Curtain Muting

Briefing

A light curtain guards a hazardous machine zone. Under normal operation, any beam break (LIGHT_CURTAIN_OK = false) stops the machine and latches SAFETY_FAULT_LATCH. However, a legitimate material-handling conveyor must be able to pass product through the curtain without tripping the fault. This is called "muting" — a temporary, validated bypass. Valid muting requires MUTE_A to assert first, then MUTE_B within 2 seconds, with at least 50 ms gap between them. Simultaneous assertion, reversed order (B before A), or exceeding the 2 s window are all invalid — they latch SAFETY_FAULT_LATCH. RESET_PB clears a latched fault once all conditions are safe.

Objectives

• MACHINE_ENABLE is on while LIGHT_CURTAIN_OK is true and no fault is latched
• Beam break (LIGHT_CURTAIN_OK = false) without valid muting → latch SAFETY_FAULT_LATCH
• Valid mute: MUTE_A then MUTE_B, ≥50 ms apart, within 2 s — MUTE_LAMP asserts during the muted window
• MUTE_LAMP stays on as long as both mute sensors are active and the sequence was valid
• Invalid mute (simultaneous, reversed, or timeout) → latch SAFETY_FAULT_LATCH
• RESET_PB clears SAFETY_FAULT_LATCH only when LIGHT_CURTAIN_OK is true and no mute is active

I/O Table

Your program will be tested against:

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

1. #1Machine enables when curtain OK and started

   With LC clear and START_PB, MACHINE_ENABLE asserts and no fault

2. #2Beam break without muting latches SAFETY_FAULT_LATCH

   LC blocked with no valid mute → fault latches; releasing LC does not clear

3. #3Valid mute sequence allows curtain block without fault

   MUTE_A then MUTE_B within 2s, then LC blocked — no fault, MUTE_LAMP on

4. #4Simultaneous MUTE_A + MUTE_B latches fault

   Both mute sensors asserted at same time is an invalid mute — fault latches

5. #5MUTE_B before MUTE_A latches fault

   Reversed order is an invalid mute — SAFETY_FAULT_LATCH must latch