FAILURE MAP
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FA-91906 / PLC ladder logic scan cycles / Open access

RES clears the RTO accumulator but leaves DN latched · case 01

After a reset the done bit stays on while ACC reads zero.

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

ROOT CAUSE

The reset instruction only writes the accumulator.

THE FAILURE

The reset instruction only writes the accumulator.

Unsuccessful approach: Clearing DN only when the rung is disabled leaves DN latched for a reset issued while enabled.

Case contract

Retentive timer (RTO) on rung 1 and its reset (RES) on a later rung, evaluated per scan; scans is a list of [enable, reset, elapsed_ms]. An enabled scan whose previous scan was also enabled adds the elapsed time (clamped at preset); DN sets when ACC >= preset while enabled. A disabled rung retains ACC and DN. Because RES is a later rung, a reset in a scan clears ACC and DN after the RTO has run; the enable edge memory is not touched by RES. Return [DN, 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 = 0
    dn = False
    prev = False
    out = []
    for en, res, dt in scans:
        en = bool(en)
        if en:
            if prev:
                acc = min(preset, acc + dt)
            if acc >= preset:
                dn = True
        prev = en
        if res:
            acc = 0
        out.append([dn, acc])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['regression: scenario 3',
   [100,
    [[False, False, 50],
     [False, False, 20],
     [True, False, 50],
     [True, False, 10],
     [True, False, 20],
     [True, False, 20],
     [True, False, 50],
     [True, False, 50],
     [True, True, 10],
     [True, False, 50]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 10],
    [False, 30],
    [False, 50],
    [True, 100],
    [True, 100],
    [False, 0],
    [False, 50]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['control: scenario 1',
   [100,
    [[False, False, 10],
     [False, False, 50],
     [False, False, 40],
     [True, True, 20],
     [False, False, 40],
     [True, False, 40],
     [True, False, 20],
     [False, False, 40]]],
   [[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 20], [False, 20]]],
  ['control: scenario 2',
   [50,
    [[False, False, 30],
     [False, False, 30],
     [True, False, 50],
     [False, False, 50],
     [False, False, 10],
     [True, False, 30],
     [False, False, 50],
     [True, False, 30],
     [True, False, 40]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 40]]],
  ['control: scenario 4',
   [100,
    [[True, False, 20],
     [True, False, 10],
     [False, False, 20],
     [True, False, 30],
     [False, False, 20],
     [False, False, 30]]],
   [[False, 0], [False, 10], [False, 10], [False, 10], [False, 10], [False, 10]]]],
 [['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['regression: scenario 2',
   [0,
    [[True, False, 10],
     [False, False, 30],
     [True, False, 20],
     [True, False, 30],
     [True, False, 50],
     [True, False, 50],
     [True, True, 20],
     [True, False, 20],
     [False, False, 40]]],
   [[True, 0], [True, 0], [True, 0], [True, 0], [True, 0], [True, 0], [False, 0], [True, 0], [True, 0]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['control: scenario 1',
   [80,
    [[False, False, 10],
     [True, False, 30],
     [True, False, 10],
     [True, True, 40],
     [True, False, 50],
     [False, False, 40],
     [False, False, 50],
     [False, False, 40]]],
   [[False, 0], [False, 0], [False, 10], [False, 0], [False, 50], [False, 50], [False, 50], [False, 50]]],
  ['regression: scenario 3',
   [50,
    [[True, True, 10],
     [True, False, 20],
     [True, False, 10],
     [True, False, 20],
     [True, False, 40],
     [True, False, 50],
     [True, False, 30],
     [False, False, 20],
     [True, False, 40],
     [False, True, 20]]],
   [[False, 0],
    [False, 20],
    [False, 30],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [False, 0]]],
  ['regression: scenario 4',
   [80,
    [[False, False, 20],
     [False, False, 40],
     [True, False, 50],
     [True, False, 40],
     [True, True, 40],
     [False, False, 10],
     [True, False, 10],
     [True, False, 30],
     [True, False, 50],
     [True, False, 40],
     [False, True, 30]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 40],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 30],
    [True, 80],
    [True, 80],
    [False, 0]]]],
 [['regression: scenario 1',
   [0,
    [[False, False, 40],
     [False, True, 30],
     [True, False, 10],
     [True, False, 30],
     [True, False, 20],
     [False, True, 30],
     [True, False, 40],
     [True, False, 30],
     [True, False, 30],
     [False, False, 20],
     [False, False, 10],
     [True, False, 30],
     [True, False, 50],
     [False, False, 10]]],
   [[False, 0],
    [False, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [False, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0]]],
  ['regression: scenario 13',
   [0,
    [[True, False, 10],
     [True, False, 40],
     [False, False, 10],
     [True, False, 30],
     [False, False, 20],
     [True, False, 20],
     [False, False, 20],
     [True, False, 30],
     [True, True, 10],
     [True, False, 50]]],
   [[True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [False, 0],
    [True, 0]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['regression: scenario 2',
   [50,
    [[True, False, 10],
     [True, False, 20],
     [True, False, 50],
     [True, False, 20],
     [True, False, 20],
     [False, False, 50],
     [False, False, 40],
     [False, True, 10],
     [False, False, 10]]],
   [[False, 0],
    [False, 20],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [False, 0],
    [False, 0]]],
  ['control: scenario 3',
   [150,
    [[True, False, 50],
     [True, False, 30],
     [False, False, 50],
     [False, False, 40],
     [False, False, 50],
     [False, False, 20]]],
   [[False, 0], [False, 30], [False, 30], [False, 30], [False, 30], [False, 30]]]],
 [['regression: scenario 4',
   [50,
    [[False, False, 30],
     [True, False, 10],
     [False, False, 40],
     [False, False, 40],
     [True, False, 50],
     [True, False, 40],
     [True, False, 50],
     [True, True, 10],
     [False, False, 10],
     [False, False, 20],
     [False, True, 40],
     [True, False, 30]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 40],
    [True, 50],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0]]],
  ['regression: scenario 15',
   [0,
    [[True, True, 20],
     [True, False, 10],
     [True, True, 30],
     [False, False, 30],
     [False, True, 30],
     [False, False, 30],
     [False, False, 40]]],
   [[False, 0], [True, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['regression: scenario 1',
   [0,
    [[False, False, 50],
     [False, False, 20],
     [False, False, 30],
     [True, True, 40],
     [False, True, 10],
     [True, False, 10],
     [False, False, 30]]],
   [[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [True, 0], [True, 0]]],
  ['control: scenario 2',
   [100,
    [[True, False, 20],
     [True, False, 30],
     [True, False, 10],
     [True, True, 10],
     [True, False, 10],
     [True, False, 20],
     [False, False, 50],
     [False, True, 40],
     [False, False, 30],
     [False, False, 40],
     [True, False, 10],
     [True, False, 50]]],
   [[False, 0],
    [False, 30],
    [False, 40],
    [False, 0],
    [False, 10],
    [False, 30],
    [False, 30],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 50]]]],
 [['regression: scenario 7',
   [80,
    [[False, False, 10],
     [False, False, 40],
     [False, False, 30],
     [True, False, 40],
     [True, False, 10],
     [True, False, 50],
     [True, True, 20],
     [True, False, 20],
     [True, False, 30],
     [True, False, 20],
     [True, False, 20],
     [False, False, 40]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 10],
    [False, 60],
    [False, 0],
    [False, 20],
    [False, 50],
    [False, 70],
    [True, 80],
    [True, 80]]],
  ['regression: scenario 14',
   [80,
    [[True, True, 20],
     [True, False, 40],
     [False, False, 40],
     [True, False, 20],
     [True, False, 20],
     [True, False, 30],
     [False, False, 50],
     [True, True, 20],
     [True, False, 10],
     [False, True, 10]]],
   [[False, 0],
    [False, 40],
    [False, 40],
    [False, 40],
    [False, 60],
    [True, 80],
    [True, 80],
    [False, 0],
    [False, 10],
    [False, 0]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['regression: scenario 1',
   [0,
    [[True, False, 30],
     [True, False, 10],
     [True, False, 10],
     [True, False, 40],
     [False, False, 30],
     [False, False, 50],
     [False, True, 40],
     [True, False, 10],
     [True, False, 30],
     [True, False, 50],
     [False, False, 20],
     [False, False, 30],
     [False, False, 40],
     [False, False, 50]]],
   [[True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [False, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0]]],
  ['control: scenario 2',
   [50,
    [[True, True, 50],
     [False, False, 10],
     [True, False, 50],
     [False, True, 50],
     [False, False, 20],
     [True, False, 20]]],
   [[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0]]]]]
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: reset done timer while enabled[[False, 0], [True, 50], [True, 50], [True, 0], [True, 25], [True, 50]][[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]Failed
regression: scenario 3[[False, 0], [False, 0], [False, 0], [False, 10], [False, 30], [False, 50], [True, 100], [True, 100], [True, 0], [True, 50]][[False, 0], [False, 0], [False, 0], [False, 10], [False, 30], [False, 50], [True, 100], [True, 100], [False, 0], [False, 50]]Failed
control: interrupted timing retained[[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]][[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]Passed
control: reset while enabled[[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]][[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]Passed
regression: reset done timer while disabled[[False, 0], [True, 50], [True, 50], [True, 0], [True, 0]][[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]Failed
control: scenario 1[[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 20], [False, 20]][[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 20], [False, 20]]Passed
control: scenario 2[[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 40]][[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 40]]Passed
control: scenario 4[[False, 0], [False, 10], [False, 10], [False, 10], [False, 10], [False, 10]][[False, 0], [False, 10], [False, 10], [False, 10], [False, 10], [False, 10]]Passed

SHA-256 / f4882ffc415b6c8ab7d1f8600255a0ca710935c87dc98f88db46b67d055a0b95

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(preset, scans):
    acc = 0
    dn = False
    prev = False
    out = []
    for en, res, dt in scans:
        en = bool(en)
        if en:
            if prev:
                acc = min(preset, acc + dt)
            if acc >= preset:
                dn = True
        prev = en
        if res:
            acc = 0
            if not en:
                dn = False
        out.append([dn, acc])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['regression: scenario 3',
   [100,
    [[False, False, 50],
     [False, False, 20],
     [True, False, 50],
     [True, False, 10],
     [True, False, 20],
     [True, False, 20],
     [True, False, 50],
     [True, False, 50],
     [True, True, 10],
     [True, False, 50]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 10],
    [False, 30],
    [False, 50],
    [True, 100],
    [True, 100],
    [False, 0],
    [False, 50]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['control: scenario 1',
   [100,
    [[False, False, 10],
     [False, False, 50],
     [False, False, 40],
     [True, True, 20],
     [False, False, 40],
     [True, False, 40],
     [True, False, 20],
     [False, False, 40]]],
   [[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 20], [False, 20]]],
  ['control: scenario 2',
   [50,
    [[False, False, 30],
     [False, False, 30],
     [True, False, 50],
     [False, False, 50],
     [False, False, 10],
     [True, False, 30],
     [False, False, 50],
     [True, False, 30],
     [True, False, 40]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 40]]],
  ['control: scenario 4',
   [100,
    [[True, False, 20],
     [True, False, 10],
     [False, False, 20],
     [True, False, 30],
     [False, False, 20],
     [False, False, 30]]],
   [[False, 0], [False, 10], [False, 10], [False, 10], [False, 10], [False, 10]]]],
 [['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['regression: scenario 2',
   [0,
    [[True, False, 10],
     [False, False, 30],
     [True, False, 20],
     [True, False, 30],
     [True, False, 50],
     [True, False, 50],
     [True, True, 20],
     [True, False, 20],
     [False, False, 40]]],
   [[True, 0], [True, 0], [True, 0], [True, 0], [True, 0], [True, 0], [False, 0], [True, 0], [True, 0]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['control: scenario 1',
   [80,
    [[False, False, 10],
     [True, False, 30],
     [True, False, 10],
     [True, True, 40],
     [True, False, 50],
     [False, False, 40],
     [False, False, 50],
     [False, False, 40]]],
   [[False, 0], [False, 0], [False, 10], [False, 0], [False, 50], [False, 50], [False, 50], [False, 50]]],
  ['regression: scenario 3',
   [50,
    [[True, True, 10],
     [True, False, 20],
     [True, False, 10],
     [True, False, 20],
     [True, False, 40],
     [True, False, 50],
     [True, False, 30],
     [False, False, 20],
     [True, False, 40],
     [False, True, 20]]],
   [[False, 0],
    [False, 20],
    [False, 30],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [False, 0]]],
  ['regression: scenario 4',
   [80,
    [[False, False, 20],
     [False, False, 40],
     [True, False, 50],
     [True, False, 40],
     [True, True, 40],
     [False, False, 10],
     [True, False, 10],
     [True, False, 30],
     [True, False, 50],
     [True, False, 40],
     [False, True, 30]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 40],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 30],
    [True, 80],
    [True, 80],
    [False, 0]]]],
 [['regression: scenario 1',
   [0,
    [[False, False, 40],
     [False, True, 30],
     [True, False, 10],
     [True, False, 30],
     [True, False, 20],
     [False, True, 30],
     [True, False, 40],
     [True, False, 30],
     [True, False, 30],
     [False, False, 20],
     [False, False, 10],
     [True, False, 30],
     [True, False, 50],
     [False, False, 10]]],
   [[False, 0],
    [False, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [False, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0]]],
  ['regression: scenario 13',
   [0,
    [[True, False, 10],
     [True, False, 40],
     [False, False, 10],
     [True, False, 30],
     [False, False, 20],
     [True, False, 20],
     [False, False, 20],
     [True, False, 30],
     [True, True, 10],
     [True, False, 50]]],
   [[True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [False, 0],
    [True, 0]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['regression: scenario 2',
   [50,
    [[True, False, 10],
     [True, False, 20],
     [True, False, 50],
     [True, False, 20],
     [True, False, 20],
     [False, False, 50],
     [False, False, 40],
     [False, True, 10],
     [False, False, 10]]],
   [[False, 0],
    [False, 20],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [True, 50],
    [False, 0],
    [False, 0]]],
  ['control: scenario 3',
   [150,
    [[True, False, 50],
     [True, False, 30],
     [False, False, 50],
     [False, False, 40],
     [False, False, 50],
     [False, False, 20]]],
   [[False, 0], [False, 30], [False, 30], [False, 30], [False, 30], [False, 30]]]],
 [['regression: scenario 4',
   [50,
    [[False, False, 30],
     [True, False, 10],
     [False, False, 40],
     [False, False, 40],
     [True, False, 50],
     [True, False, 40],
     [True, False, 50],
     [True, True, 10],
     [False, False, 10],
     [False, False, 20],
     [False, True, 40],
     [True, False, 30]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 40],
    [True, 50],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0]]],
  ['regression: scenario 15',
   [0,
    [[True, True, 20],
     [True, False, 10],
     [True, True, 30],
     [False, False, 30],
     [False, True, 30],
     [False, False, 30],
     [False, False, 40]]],
   [[False, 0], [True, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['regression: scenario 1',
   [0,
    [[False, False, 50],
     [False, False, 20],
     [False, False, 30],
     [True, True, 40],
     [False, True, 10],
     [True, False, 10],
     [False, False, 30]]],
   [[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [True, 0], [True, 0]]],
  ['control: scenario 2',
   [100,
    [[True, False, 20],
     [True, False, 30],
     [True, False, 10],
     [True, True, 10],
     [True, False, 10],
     [True, False, 20],
     [False, False, 50],
     [False, True, 40],
     [False, False, 30],
     [False, False, 40],
     [True, False, 10],
     [True, False, 50]]],
   [[False, 0],
    [False, 30],
    [False, 40],
    [False, 0],
    [False, 10],
    [False, 30],
    [False, 30],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 50]]]],
 [['regression: scenario 7',
   [80,
    [[False, False, 10],
     [False, False, 40],
     [False, False, 30],
     [True, False, 40],
     [True, False, 10],
     [True, False, 50],
     [True, True, 20],
     [True, False, 20],
     [True, False, 30],
     [True, False, 20],
     [True, False, 20],
     [False, False, 40]]],
   [[False, 0],
    [False, 0],
    [False, 0],
    [False, 0],
    [False, 10],
    [False, 60],
    [False, 0],
    [False, 20],
    [False, 50],
    [False, 70],
    [True, 80],
    [True, 80]]],
  ['regression: scenario 14',
   [80,
    [[True, True, 20],
     [True, False, 40],
     [False, False, 40],
     [True, False, 20],
     [True, False, 20],
     [True, False, 30],
     [False, False, 50],
     [True, True, 20],
     [True, False, 10],
     [False, True, 10]]],
   [[False, 0],
    [False, 40],
    [False, 40],
    [False, 40],
    [False, 60],
    [True, 80],
    [True, 80],
    [False, 0],
    [False, 10],
    [False, 0]]],
  ['control: interrupted timing retained',
   [100,
    [[True, False, 30],
     [True, False, 40],
     [False, False, 40],
     [True, False, 40],
     [True, False, 40],
     [True, False, 40]]],
   [[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]],
  ['control: reset while enabled',
   [100, [[True, False, 30], [True, False, 60], [True, True, 30], [True, False, 30], [True, False, 30]]],
   [[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]],
  ['regression: reset done timer while enabled',
   [50,
    [[True, False, 30],
     [True, False, 60],
     [True, False, 10],
     [True, True, 10],
     [True, False, 25],
     [True, False, 25]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]],
  ['regression: reset done timer while disabled',
   [50, [[True, False, 30], [True, False, 60], [False, False, 10], [False, True, 10], [False, False, 10]]],
   [[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]],
  ['regression: scenario 1',
   [0,
    [[True, False, 30],
     [True, False, 10],
     [True, False, 10],
     [True, False, 40],
     [False, False, 30],
     [False, False, 50],
     [False, True, 40],
     [True, False, 10],
     [True, False, 30],
     [True, False, 50],
     [False, False, 20],
     [False, False, 30],
     [False, False, 40],
     [False, False, 50]]],
   [[True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [False, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0],
    [True, 0]]],
  ['control: scenario 2',
   [50,
    [[True, True, 50],
     [False, False, 10],
     [True, False, 50],
     [False, True, 50],
     [False, False, 20],
     [True, False, 20]]],
   [[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0]]]]]
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: reset done timer while enabled[[False, 0], [True, 50], [True, 50], [True, 0], [True, 25], [True, 50]][[False, 0], [True, 50], [True, 50], [False, 0], [False, 25], [True, 50]]Failed
regression: scenario 3[[False, 0], [False, 0], [False, 0], [False, 10], [False, 30], [False, 50], [True, 100], [True, 100], [True, 0], [True, 50]][[False, 0], [False, 0], [False, 0], [False, 10], [False, 30], [False, 50], [True, 100], [True, 100], [False, 0], [False, 50]]Failed
control: interrupted timing retained[[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]][[False, 0], [False, 40], [False, 40], [False, 40], [False, 80], [True, 100]]Passed
control: reset while enabled[[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]][[False, 0], [False, 60], [False, 0], [False, 30], [False, 60]]Passed
regression: reset done timer while disabled[[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]][[False, 0], [True, 50], [True, 50], [False, 0], [False, 0]]Passed
control: scenario 1[[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 20], [False, 20]][[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 20], [False, 20]]Passed
control: scenario 2[[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 40]][[False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 0], [False, 40]]Passed
control: scenario 4[[False, 0], [False, 10], [False, 10], [False, 10], [False, 10], [False, 10]][[False, 0], [False, 10], [False, 10], [False, 10], [False, 10], [False, 10]]Passed

SHA-256 / 95cd79d5d8ea29bea479a93674bff95873b204af1a2899316c75528ff60d23da

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 2026-09-29T14:51:40.485418+00:00.

Case digest / 408e2f5f30300723a2b3b1409fc2a1a7585f7c3afe3da9e1c60393551625a36b