WEBVTT

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Ground Truth, for engineers.

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Inside the logic.

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The program came from a
MicroLogix 1200 backup:

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three ladder files, fifty-five
rungs, and not a single comment.

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It is small and fully determined:

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two trip latches, one sixty-second
timer, and seven one-shots.

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This is the extracted ladder itself,
executing, with live power flow.

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The cause and effect matrix is live too:

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each row lights while its cause
is true, and cites its rungs.

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Two findings, with their rungs.

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First, the stop drops the pump
permissive, but nothing latches it,

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so the release re-permits the pump.

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Second, the reset is level-sensitive.

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With the button held, a
trip latch cannot hold:

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it drops out the moment its cause clears.

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In proposed corrections mode, the proposed
structured-text program runs against the

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same plant, with the corrections built in.

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Here the stop is hardwired
through a safety relay,

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and the reset acts only on its rising edge.

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After an E-stop, the pumps stay
off until two deliberate resets:

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the safety relay, then the controller.

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No auto-restart.

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Verification is on the page:

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five hundred forty thousand word checks
against an independent simulator with zero

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mismatches, and all
seventy-eight test cases pass.

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With the corrections removed, the proposed
listing matches the original ladder,

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scan for scan.

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Every statement traced to a ladder
rung, and every rung executed.