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FA-91891 / PLC ladder logic scan cycles / Open access

TOF timing bit reports an expired timer as timing · case 01

TT is true on false-rung scans after the off-delay has already finished, and at power-up.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

TT is computed from the rung state only and ignores whether the delay is still in progress.

THE FAILURE

TT is computed from the rung state only and ignores whether the delay is still in progress.

Unsuccessful approach: Using DN alone reports timing while the rung is still true.

Case contract

Off-delay timer (TOF) evaluated once per scan; scans is a list of [rung_in, elapsed_ms]. At power-up the timer is expired (ACC = preset, DN false). A true rung clears ACC and sets DN. After the rung drops, ACC accumulates each later false scan's elapsed time (the true-to-false scan itself is not credited), clamped at preset, and DN clears when ACC >= preset. TT is DN and not rung_in. Return [DN, TT, ACC] per scan.

Why this case matters

Ladder programs are executed as repeated scans; each defect here changes what a rung, timer, counter or data-table instruction reports on a particular scan, which is how commissioning and field faults are actually observed.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(preset, scans):
    acc = preset
    dn = False
    prev = False
    out = []
    for rung_in, dt in scans:
        rung_in = bool(rung_in)
        if rung_in:
            acc = 0
            dn = True
        elif dn:
            if not prev:
                acc = min(preset, acc + dt)
            if acc >= preset:
                dn = False
        tt = not rung_in
        prev = rung_in
        out.append([dn, tt, acc])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: scenario 1',
   [60, [[False, 70], [True, 10], [True, 70], [True, 10], [False, 70], [False, 10], [True, 10], [False, 30]]],
   [[False, False, 60],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 10],
    [True, False, 0],
    [True, True, 0]]],
  ['regression: scenario 2',
   [60, [[False, 30], [True, 50], [True, 20], [True, 30], [True, 70], [False, 50], [False, 50], [False, 70]]],
   [[False, False, 60],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 50],
    [False, False, 60]]],
  ['regression: scenario 3',
   [40,
    [[True, 70],
     [True, 0],
     [False, 50],
     [True, 30],
     [False, 0],
     [False, 50],
     [False, 30],
     [False, 50],
     [False, 10],
     [True, 20]]],
   [[True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, True, 0],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40],
    [True, False, 0]]],
  ['regression: scenario 4',
   [100,
    [[False, 30],
     [False, 70],
     [True, 30],
     [False, 30],
     [False, 20],
     [False, 50],
     [False, 70],
     [True, 50],
     [True, 50],
     [False, 20],
     [False, 50]]],
   [[False, False, 100],
    [False, False, 100],
    [True, False, 0],
    [True, True, 0],
    [True, True, 20],
    [True, True, 70],
    [False, False, 100],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 50]]]],
 [['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: scenario 1',
   [0, [[False, 30], [True, 20], [True, 30], [False, 50], [True, 0], [True, 50], [True, 50]]],
   [[False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0]]],
  ['regression: scenario 2',
   [0, [[False, 10], [True, 0], [True, 70], [False, 0], [True, 70], [False, 20], [False, 10]]],
   [[False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0]]],
  ['regression: scenario 3',
   [150,
    [[False, 50],
     [False, 10],
     [False, 0],
     [False, 50],
     [True, 50],
     [False, 70],
     [False, 10],
     [True, 70],
     [False, 50],
     [False, 70],
     [False, 20],
     [True, 50],
     [False, 0],
     [True, 30]]],
   [[False, False, 150],
    [False, False, 150],
    [False, False, 150],
    [False, False, 150],
    [True, False, 0],
    [True, True, 0],
    [True, True, 10],
    [True, False, 0],
    [True, True, 0],
    [True, True, 70],
    [True, True, 90],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0]]],
  ['regression: scenario 4',
   [60,
    [[False, 0],
     [False, 10],
     [True, 20],
     [False, 20],
     [False, 0],
     [False, 0],
     [True, 50],
     [True, 20],
     [True, 10],
     [True, 0],
     [True, 10],
     [False, 20],
     [False, 70]]],
   [[False, False, 60],
    [False, False, 60],
    [True, False, 0],
    [True, True, 0],
    [True, True, 0],
    [True, True, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [False, False, 60]]]],
 [['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: scenario 1',
   [0,
    [[False, 50],
     [True, 10],
     [False, 0],
     [True, 20],
     [False, 70],
     [False, 50],
     [True, 70],
     [False, 10],
     [False, 10],
     [False, 20],
     [True, 70]]],
   [[False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0]]],
  ['regression: scenario 2',
   [0,
    [[False, 30],
     [True, 50],
     [False, 50],
     [True, 0],
     [True, 10],
     [True, 10],
     [False, 10],
     [False, 50],
     [False, 10]]],
   [[False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0]]],
  ['regression: scenario 3',
   [0,
    [[False, 10],
     [False, 10],
     [False, 70],
     [False, 30],
     [True, 50],
     [False, 10],
     [False, 0],
     [True, 20],
     [False, 70],
     [True, 10],
     [False, 70],
     [True, 20],
     [False, 70],
     [True, 0]]],
   [[False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0]]],
  ['regression: scenario 4',
   [0,
    [[False, 30],
     [True, 0],
     [False, 70],
     [False, 0],
     [True, 20],
     [False, 50],
     [False, 0],
     [False, 10],
     [False, 20],
     [False, 50],
     [False, 50]]],
   [[False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0]]]],
 [['regression: scenario 1',
   [40, [[True, 70], [True, 20], [True, 20], [False, 30], [False, 30], [False, 0], [False, 70], [False, 20]]],
   [[True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 30],
    [True, True, 30],
    [False, False, 40],
    [False, False, 40]]],
  ['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: scenario 2',
   [100,
    [[False, 30],
     [False, 20],
     [True, 20],
     [True, 10],
     [True, 70],
     [False, 20],
     [False, 10],
     [True, 20],
     [False, 0],
     [True, 0],
     [True, 0]]],
   [[False, False, 100],
    [False, False, 100],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 10],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, False, 0]]],
  ['regression: scenario 3',
   [60, [[False, 70], [True, 30], [True, 0], [True, 50], [True, 30], [True, 70], [True, 0]]],
   [[False, False, 60],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0]]],
  ['regression: scenario 4',
   [150, [[True, 10], [False, 30], [True, 70], [False, 10], [False, 50], [True, 70], [True, 50]]],
   [[True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 50],
    [True, False, 0],
    [True, False, 0]]]],
 [['regression: scenario 2',
   [40,
    [[False, 70],
     [True, 70],
     [False, 50],
     [True, 70],
     [False, 10],
     [False, 30],
     [True, 0],
     [True, 50],
     [False, 0],
     [False, 30]]],
   [[False, False, 40],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 30],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 30]]],
  ['regression: scenario 1',
   [40,
    [[True, 70], [True, 20], [False, 50], [False, 20], [False, 50], [False, 50], [False, 50], [False, 0]]],
   [[True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 20],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40]]],
  ['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: scenario 3',
   [0,
    [[False, 50],
     [False, 50],
     [False, 20],
     [False, 20],
     [True, 10],
     [True, 50],
     [True, 20],
     [False, 70],
     [False, 30],
     [False, 10],
     [True, 10],
     [True, 70],
     [True, 10],
     [False, 50]]],
   [[False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0]]],
  ['regression: scenario 4',
   [40,
    [[False, 50],
     [True, 10],
     [False, 20],
     [False, 20],
     [True, 70],
     [False, 10],
     [True, 10],
     [False, 50],
     [False, 70],
     [False, 30],
     [False, 20],
     [False, 0]]],
   [[False, False, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 20],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, True, 0],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40]]]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: power-up with false rung[[False, True, 60], [False, True, 60], [False, True, 60], [True, False, 0]][[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]Failed
regression: re-energized mid delay[[True, False, 0], [True, True, 0], [True, True, 40], [True, False, 0], [True, True, 0], [True, True, 40], [True, True, 80]][[True, False, 0], [True, True, 0], [True, True, 40], [True, False, 0], [True, True, 0], [True, True, 40], [True, True, 80]]Passed
regression: zero preset drop[[True, False, 0], [False, True, 0], [False, True, 0]][[True, False, 0], [False, False, 0], [False, False, 0]]Failed
regression: exact expiry[[True, False, 0], [True, True, 0], [True, True, 30], [False, True, 60], [False, True, 60]][[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]Failed
regression: scenario 1[[False, True, 60], [True, False, 0], [True, False, 0], [True, False, 0], [True, True, 0], [True, True, 10], [True, False, 0], [True, True, 0]][[False, False, 60], [True, False, 0], [True, False, 0], [True, False, 0], [True, True, 0], [True, True, 10], [True, False, 0], [True, True, 0]]Failed
regression: scenario 2[[False, True, 60], [True, False, 0], [True, False, 0], [True, False, 0], [True, False, 0], [True, True, 0], [True, True, 50], [False, True, 60]][[False, False, 60], [True, False, 0], [True, False, 0], [True, False, 0], [True, False, 0], [True, True, 0], [True, True, 50], [False, False, 60]]Failed
regression: scenario 3[[True, False, 0], [True, False, 0], [True, True, 0], [True, False, 0], [True, True, 0], [False, True, 40], [False, True, 40], [False, True, 40], [False, True, 40], [True, False, 0]][[True, False, 0], [True, False, 0], [True, True, 0], [True, False, 0], [True, True, 0], [False, False, 40], [False, False, 40], [False, False, 40], [False, False, 40], [True, False, 0]]Failed
regression: scenario 4[[False, True, 100], [False, True, 100], [True, False, 0], [True, True, 0], [True, True, 20], [True, True, 70], [False, True, 100], [True, False, 0], [True, False, 0], [True, True, 0], [True, True, 50]][[False, False, 100], [False, False, 100], [True, False, 0], [True, True, 0], [True, True, 20], [True, True, 70], [False, False, 100], [True, False, 0], [True, False, 0], [True, True, 0], [True, True, 50]]Failed

SHA-256 / b6d562ccf36a9d18d38dca3080c28cf84b3d8183139432ab080e2536cea32f47

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(preset, scans):
    acc = preset
    dn = False
    prev = False
    out = []
    for rung_in, dt in scans:
        rung_in = bool(rung_in)
        if rung_in:
            acc = 0
            dn = True
        elif dn:
            if not prev:
                acc = min(preset, acc + dt)
            if acc >= preset:
                dn = False
        tt = dn
        prev = rung_in
        out.append([dn, tt, acc])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: scenario 1',
   [60, [[False, 70], [True, 10], [True, 70], [True, 10], [False, 70], [False, 10], [True, 10], [False, 30]]],
   [[False, False, 60],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 10],
    [True, False, 0],
    [True, True, 0]]],
  ['regression: scenario 2',
   [60, [[False, 30], [True, 50], [True, 20], [True, 30], [True, 70], [False, 50], [False, 50], [False, 70]]],
   [[False, False, 60],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 50],
    [False, False, 60]]],
  ['regression: scenario 3',
   [40,
    [[True, 70],
     [True, 0],
     [False, 50],
     [True, 30],
     [False, 0],
     [False, 50],
     [False, 30],
     [False, 50],
     [False, 10],
     [True, 20]]],
   [[True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, True, 0],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40],
    [True, False, 0]]],
  ['regression: scenario 4',
   [100,
    [[False, 30],
     [False, 70],
     [True, 30],
     [False, 30],
     [False, 20],
     [False, 50],
     [False, 70],
     [True, 50],
     [True, 50],
     [False, 20],
     [False, 50]]],
   [[False, False, 100],
    [False, False, 100],
    [True, False, 0],
    [True, True, 0],
    [True, True, 20],
    [True, True, 70],
    [False, False, 100],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 50]]]],
 [['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: scenario 1',
   [0, [[False, 30], [True, 20], [True, 30], [False, 50], [True, 0], [True, 50], [True, 50]]],
   [[False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0]]],
  ['regression: scenario 2',
   [0, [[False, 10], [True, 0], [True, 70], [False, 0], [True, 70], [False, 20], [False, 10]]],
   [[False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0]]],
  ['regression: scenario 3',
   [150,
    [[False, 50],
     [False, 10],
     [False, 0],
     [False, 50],
     [True, 50],
     [False, 70],
     [False, 10],
     [True, 70],
     [False, 50],
     [False, 70],
     [False, 20],
     [True, 50],
     [False, 0],
     [True, 30]]],
   [[False, False, 150],
    [False, False, 150],
    [False, False, 150],
    [False, False, 150],
    [True, False, 0],
    [True, True, 0],
    [True, True, 10],
    [True, False, 0],
    [True, True, 0],
    [True, True, 70],
    [True, True, 90],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0]]],
  ['regression: scenario 4',
   [60,
    [[False, 0],
     [False, 10],
     [True, 20],
     [False, 20],
     [False, 0],
     [False, 0],
     [True, 50],
     [True, 20],
     [True, 10],
     [True, 0],
     [True, 10],
     [False, 20],
     [False, 70]]],
   [[False, False, 60],
    [False, False, 60],
    [True, False, 0],
    [True, True, 0],
    [True, True, 0],
    [True, True, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [False, False, 60]]]],
 [['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: scenario 1',
   [0,
    [[False, 50],
     [True, 10],
     [False, 0],
     [True, 20],
     [False, 70],
     [False, 50],
     [True, 70],
     [False, 10],
     [False, 10],
     [False, 20],
     [True, 70]]],
   [[False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0]]],
  ['regression: scenario 2',
   [0,
    [[False, 30],
     [True, 50],
     [False, 50],
     [True, 0],
     [True, 10],
     [True, 10],
     [False, 10],
     [False, 50],
     [False, 10]]],
   [[False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0]]],
  ['regression: scenario 3',
   [0,
    [[False, 10],
     [False, 10],
     [False, 70],
     [False, 30],
     [True, 50],
     [False, 10],
     [False, 0],
     [True, 20],
     [False, 70],
     [True, 10],
     [False, 70],
     [True, 20],
     [False, 70],
     [True, 0]]],
   [[False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [True, False, 0]]],
  ['regression: scenario 4',
   [0,
    [[False, 30],
     [True, 0],
     [False, 70],
     [False, 0],
     [True, 20],
     [False, 50],
     [False, 0],
     [False, 10],
     [False, 20],
     [False, 50],
     [False, 50]]],
   [[False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0]]]],
 [['regression: scenario 1',
   [40, [[True, 70], [True, 20], [True, 20], [False, 30], [False, 30], [False, 0], [False, 70], [False, 20]]],
   [[True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 30],
    [True, True, 30],
    [False, False, 40],
    [False, False, 40]]],
  ['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: scenario 2',
   [100,
    [[False, 30],
     [False, 20],
     [True, 20],
     [True, 10],
     [True, 70],
     [False, 20],
     [False, 10],
     [True, 20],
     [False, 0],
     [True, 0],
     [True, 0]]],
   [[False, False, 100],
    [False, False, 100],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 10],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, False, 0]]],
  ['regression: scenario 3',
   [60, [[False, 70], [True, 30], [True, 0], [True, 50], [True, 30], [True, 70], [True, 0]]],
   [[False, False, 60],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0]]],
  ['regression: scenario 4',
   [150, [[True, 10], [False, 30], [True, 70], [False, 10], [False, 50], [True, 70], [True, 50]]],
   [[True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 50],
    [True, False, 0],
    [True, False, 0]]]],
 [['regression: scenario 2',
   [40,
    [[False, 70],
     [True, 70],
     [False, 50],
     [True, 70],
     [False, 10],
     [False, 30],
     [True, 0],
     [True, 50],
     [False, 0],
     [False, 30]]],
   [[False, False, 40],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 30],
    [True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 30]]],
  ['regression: scenario 1',
   [40,
    [[True, 70], [True, 20], [False, 50], [False, 20], [False, 50], [False, 50], [False, 50], [False, 0]]],
   [[True, False, 0],
    [True, False, 0],
    [True, True, 0],
    [True, True, 20],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40]]],
  ['regression: power-up with false rung',
   [60, [[False, 20], [False, 20], [False, 20], [True, 10]]],
   [[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]],
  ['regression: re-energized mid delay',
   [100, [[True, 10], [False, 40], [False, 40], [True, 40], [False, 40], [False, 40], [False, 40]]],
   [[True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 40],
    [True, True, 80]]],
  ['regression: zero preset drop',
   [0, [[True, 10], [False, 10], [False, 10]]],
   [[True, False, 0], [False, False, 0], [False, False, 0]]],
  ['regression: exact expiry',
   [60, [[True, 10], [False, 30], [False, 30], [False, 30], [False, 30]]],
   [[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]],
  ['regression: scenario 3',
   [0,
    [[False, 50],
     [False, 50],
     [False, 20],
     [False, 20],
     [True, 10],
     [True, 50],
     [True, 20],
     [False, 70],
     [False, 30],
     [False, 10],
     [True, 10],
     [True, 70],
     [True, 10],
     [False, 50]]],
   [[False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0],
    [False, False, 0],
    [False, False, 0],
    [True, False, 0],
    [True, False, 0],
    [True, False, 0],
    [False, False, 0]]],
  ['regression: scenario 4',
   [40,
    [[False, 50],
     [True, 10],
     [False, 20],
     [False, 20],
     [True, 70],
     [False, 10],
     [True, 10],
     [False, 50],
     [False, 70],
     [False, 30],
     [False, 20],
     [False, 0]]],
   [[False, False, 40],
    [True, False, 0],
    [True, True, 0],
    [True, True, 20],
    [True, False, 0],
    [True, True, 0],
    [True, False, 0],
    [True, True, 0],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40],
    [False, False, 40]]]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: power-up with false rung[[False, False, 60], [False, False, 60], [False, False, 60], [True, True, 0]][[False, False, 60], [False, False, 60], [False, False, 60], [True, False, 0]]Failed
regression: re-energized mid delay[[True, True, 0], [True, True, 0], [True, True, 40], [True, True, 0], [True, True, 0], [True, True, 40], [True, True, 80]][[True, False, 0], [True, True, 0], [True, True, 40], [True, False, 0], [True, True, 0], [True, True, 40], [True, True, 80]]Failed
regression: zero preset drop[[True, True, 0], [False, False, 0], [False, False, 0]][[True, False, 0], [False, False, 0], [False, False, 0]]Failed
regression: exact expiry[[True, True, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]][[True, False, 0], [True, True, 0], [True, True, 30], [False, False, 60], [False, False, 60]]Failed
regression: scenario 1[[False, False, 60], [True, True, 0], [True, True, 0], [True, True, 0], [True, True, 0], [True, True, 10], [True, True, 0], [True, True, 0]][[False, False, 60], [True, False, 0], [True, False, 0], [True, False, 0], [True, True, 0], [True, True, 10], [True, False, 0], [True, True, 0]]Failed
regression: scenario 2[[False, False, 60], [True, True, 0], [True, True, 0], [True, True, 0], [True, True, 0], [True, True, 0], [True, True, 50], [False, False, 60]][[False, False, 60], [True, False, 0], [True, False, 0], [True, False, 0], [True, False, 0], [True, True, 0], [True, True, 50], [False, False, 60]]Failed
regression: scenario 3[[True, True, 0], [True, True, 0], [True, True, 0], [True, True, 0], [True, True, 0], [False, False, 40], [False, False, 40], [False, False, 40], [False, False, 40], [True, True, 0]][[True, False, 0], [True, False, 0], [True, True, 0], [True, False, 0], [True, True, 0], [False, False, 40], [False, False, 40], [False, False, 40], [False, False, 40], [True, False, 0]]Failed
regression: scenario 4[[False, False, 100], [False, False, 100], [True, True, 0], [True, True, 0], [True, True, 20], [True, True, 70], [False, False, 100], [True, True, 0], [True, True, 0], [True, True, 0], [True, True, 50]][[False, False, 100], [False, False, 100], [True, False, 0], [True, True, 0], [True, True, 20], [True, True, 70], [False, False, 100], [True, False, 0], [True, False, 0], [True, True, 0], [True, True, 50]]Failed

SHA-256 / 6fbff6398dcb81950dc0cfb997a1af8ec404f8446099e5a305cd252e4afbb17b

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic bounded teaching model of one PLC instruction or rung pattern evaluated scan by scan. The stated contract is a stipulated toy convention, not a claim of conformance to any vendor controller or IEC 61131-3 runtime. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:51:40.385637+00:00.

Case digest / 7eebc8b0a6461d234fe8c1966a1b19726a891e8d23fe41f5748bbbd960a65720