FAILURE MAP
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FA-92106 / PLC ladder logic scan cycles / Open access

Sequencer advances and writes on a scan that is also resetting · case 01

A reset coinciding with a step pulse outputs the next step pattern while the position reads 0.

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

ROOT CAUSE

The advance is processed before the reset in the same scan.

THE FAILURE

The advance is processed before the reset in the same scan.

Unsuccessful approach: Skipping the edge-memory update on a reset scan makes a held enable advance right after the reset.

Case contract

Sequencer output (SQO). words is the sequencer file whose element 0 is the home step; position starts at 0. On each rising edge of enable the position advances; past the last element it wraps to 1 (not 0). Each advance writes dest = (dest AND NOT mask) OR (word AND mask) in 16 bits. A reset input returns position to 0 without writing dest and has priority over a coincident advance; the enable edge memory is always updated. steps is a list of [enable, reset]; return [position, dest] 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(words, mask, start_dest, steps):
    pos = 0
    dest = start_dest
    prev = False
    length = len(words) - 1
    out = []
    for en, res in steps:
        en = bool(en)
        if en and not prev:
            pos += 1
            if pos > length:
                pos = 1
            dest = (dest & ~mask & 0xFFFF) | (words[pos] & mask)
        if res:
            pos = 0
        prev = en
        out.append([pos, dest])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['regression: scenario 6',
   [[29507, 12756, 63003, 15441, 3378],
    61440,
    54790,
    [[False, False],
     [False, False],
     [True, True],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False]]],
   [[0, 54790],
    [0, 54790],
    [0, 54790],
    [0, 54790],
    [0, 54790],
    [0, 54790],
    [1, 13830],
    [1, 13830],
    [1, 13830],
    [2, 62982]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: scenario 1',
   [[26918, 50611, 8879, 59828],
    65535,
    52597,
    [[False, False],
     [False, False],
     [False, False],
     [True, True],
     [False, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False]]],
   [[0, 52597],
    [0, 52597],
    [0, 52597],
    [0, 52597],
    [0, 52597],
    [0, 52597],
    [0, 52597],
    [1, 50611],
    [1, 50611],
    [1, 50611]]],
  ['regression: scenario 2',
   [[42968, 29173, 43546],
    255,
    5794,
    [[True, False],
     [False, False],
     [False, False],
     [False, False],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [False, False]]],
   [[1, 5877],
    [1, 5877],
    [1, 5877],
    [1, 5877],
    [2, 5658],
    [2, 5658],
    [2, 5658],
    [2, 5658],
    [0, 5658],
    [0, 5658]]],
  ['control: scenario 3',
   [[16785, 47110, 21847, 45361],
    61440,
    41889,
    [[True, False],
     [True, False],
     [True, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False]]],
   [[1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985]]]],
 [['regression: scenario 8',
   [[65487, 45479, 8754],
    61440,
    1982,
    [[False, False],
     [True, False],
     [True, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False],
     [True, True],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [True, False]]],
   [[0, 1982],
    [1, 47038],
    [1, 47038],
    [1, 47038],
    [1, 47038],
    [1, 47038],
    [2, 10174],
    [0, 10174],
    [0, 10174],
    [0, 10174],
    [0, 10174],
    [0, 10174],
    [0, 10174]]],
  ['regression: scenario 31',
   [[26490, 1121, 33414, 24311],
    65535,
    26582,
    [[True, True],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [False, True],
     [False, False],
     [False, False],
     [True, True],
     [True, False],
     [True, False],
     [True, False],
     [True, False],
     [True, False]]],
   [[0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['control: scenario 1',
   [[8488, 43469, 38296, 4034],
    255,
    44563,
    [[False, False],
     [True, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False]]],
   [[0, 44563],
    [1, 44749],
    [1, 44749],
    [1, 44749],
    [1, 44749],
    [2, 44696],
    [2, 44696],
    [3, 44738],
    [3, 44738],
    [1, 44749],
    [1, 44749],
    [2, 44696]]],
  ['control: scenario 2',
   [[43079, 20640, 23622, 26553],
    255,
    15109,
    [[False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [False, True]]],
   [[0, 15109],
    [0, 15109],
    [1, 15264],
    [1, 15264],
    [1, 15264],
    [1, 15264],
    [2, 15174],
    [2, 15174],
    [2, 15174],
    [2, 15174],
    [3, 15289],
    [0, 15289]]]],
 [['regression: scenario 5',
   [[8300, 19450, 62969],
    255,
    8070,
    [[True, True],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False]]],
   [[0, 8070],
    [0, 8070],
    [0, 8070],
    [1, 8186],
    [1, 8186],
    [1, 8186],
    [1, 8186],
    [2, 8185],
    [2, 8185],
    [2, 8185],
    [2, 8185],
    [2, 8185],
    [1, 8186],
    [1, 8186]]],
  ['regression: scenario 20',
   [[27683, 27069, 29983],
    255,
    29648,
    [[False, False],
     [True, False],
     [False, True],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [False, True]]],
   [[0, 29648],
    [1, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['control: scenario 1',
   [[38610, 2229],
    65535,
    14704,
    [[False, False],
     [False, False],
     [False, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, True],
     [False, False]]],
   [[0, 14704], [0, 14704], [0, 14704], [0, 14704], [0, 14704], [1, 2229], [1, 2229], [0, 2229], [0, 2229]]],
  ['regression: scenario 2',
   [[36741, 30504],
    65535,
    26589,
    [[True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [True, False],
     [False, False]]],
   [[1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [0, 30504],
    [0, 30504],
    [0, 30504]]]],
 [['regression: scenario 23',
   [[17706, 2201, 35072],
    3855,
    50743,
    [[True, True], [True, False], [False, False], [False, True], [True, False], [False, False]]],
   [[0, 50743], [0, 50743], [0, 50743], [0, 50743], [1, 51257], [1, 51257]]],
  ['regression: scenario 37',
   [[46144, 38157],
    61440,
    18798,
    [[False, True], [False, False], [False, False], [False, False], [True, True], [True, False]]],
   [[0, 18798], [0, 18798], [0, 18798], [0, 18798], [0, 18798], [0, 18798]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['control: scenario 1',
   [[61786, 58708],
    255,
    45362,
    [[False, False],
     [False, False],
     [False, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False]]],
   [[0, 45362], [0, 45362], [0, 45362], [1, 45396], [1, 45396], [1, 45396], [1, 45396]]],
  ['control: scenario 2',
   [[57902, 51779],
    61440,
    26811,
    [[True, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False]]],
   [[1, 51387], [1, 51387], [1, 51387], [1, 51387], [1, 51387], [1, 51387], [1, 51387], [1, 51387]]]],
 [['regression: scenario 10',
   [[42427, 61110, 22519, 20082, 65253],
    65535,
    32195,
    [[True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [False, False],
     [False, False],
     [False, False]]],
   [[1, 61110],
    [1, 61110],
    [2, 22519],
    [2, 22519],
    [3, 20082],
    [3, 20082],
    [3, 20082],
    [3, 20082],
    [3, 20082],
    [0, 20082],
    [0, 20082],
    [0, 20082],
    [0, 20082]]],
  ['regression: scenario 19',
   [[7514, 21129, 31492],
    61440,
    5749,
    [[True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [True, False],
     [False, True],
     [True, False],
     [False, False]]],
   [[1, 22133],
    [1, 22133],
    [1, 22133],
    [1, 22133],
    [2, 30325],
    [2, 30325],
    [2, 30325],
    [0, 30325],
    [1, 22133],
    [1, 22133]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['control: scenario 1',
   [[39974, 26951],
    3855,
    4546,
    [[False, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, True]]],
   [[0, 4546],
    [0, 4546],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [0, 6599]]],
  ['regression: scenario 2',
   [[43067, 57880, 6921, 33106, 51712],
    255,
    13830,
    [[True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, True],
     [True, True],
     [False, False],
     [True, False],
     [False, False]]],
   [[1, 13848],
    [1, 13848],
    [1, 13848],
    [2, 13833],
    [2, 13833],
    [2, 13833],
    [3, 13906],
    [3, 13906],
    [0, 13906],
    [0, 13906],
    [0, 13906],
    [1, 13848],
    [1, 13848]]]]]
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 with advance[[0, 170], [0, 426], [0, 426], [1, 426]][[0, 170], [0, 170], [0, 170], [1, 426]]Failed
regression: scenario 6[[0, 54790], [0, 54790], [0, 13830], [0, 13830], [0, 13830], [0, 13830], [1, 13830], [1, 13830], [1, 13830], [2, 62982]][[0, 54790], [0, 54790], [0, 54790], [0, 54790], [0, 54790], [0, 54790], [1, 13830], [1, 13830], [1, 13830], [2, 62982]]Failed
control: wrap past last step[[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]][[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]Passed
control: two element file[[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]][[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]Passed
control: reset while enabled[[1, 65523], [0, 65523], [0, 65523], [1, 65523]][[1, 65523], [0, 65523], [0, 65523], [1, 65523]]Passed
regression: scenario 1[[0, 52597], [0, 52597], [0, 52597], [0, 50611], [0, 50611], [0, 50611], [0, 50611], [1, 50611], [1, 50611], [1, 50611]][[0, 52597], [0, 52597], [0, 52597], [0, 52597], [0, 52597], [0, 52597], [0, 52597], [1, 50611], [1, 50611], [1, 50611]]Failed
regression: scenario 2[[1, 5877], [1, 5877], [1, 5877], [1, 5877], [2, 5658], [2, 5658], [2, 5658], [2, 5658], [0, 5877], [0, 5877]][[1, 5877], [1, 5877], [1, 5877], [1, 5877], [2, 5658], [2, 5658], [2, 5658], [2, 5658], [0, 5658], [0, 5658]]Failed
control: scenario 3[[1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985]][[1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985]]Passed

SHA-256 / f158f02663c880bd14b4cc6b0fad3d9a98567da7fba5ef3bbd7b5b1743724b3f

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(words, mask, start_dest, steps):
    pos = 0
    dest = start_dest
    prev = False
    length = len(words) - 1
    out = []
    for en, res in steps:
        en = bool(en)
        if res:
            pos = 0
        elif en and not prev:
            pos += 1
            if pos > length:
                pos = 1
            dest = (dest & ~mask & 0xFFFF) | (words[pos] & mask)
        prev = en if not res else prev
        out.append([pos, dest])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['regression: scenario 6',
   [[29507, 12756, 63003, 15441, 3378],
    61440,
    54790,
    [[False, False],
     [False, False],
     [True, True],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False]]],
   [[0, 54790],
    [0, 54790],
    [0, 54790],
    [0, 54790],
    [0, 54790],
    [0, 54790],
    [1, 13830],
    [1, 13830],
    [1, 13830],
    [2, 62982]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: scenario 1',
   [[26918, 50611, 8879, 59828],
    65535,
    52597,
    [[False, False],
     [False, False],
     [False, False],
     [True, True],
     [False, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False]]],
   [[0, 52597],
    [0, 52597],
    [0, 52597],
    [0, 52597],
    [0, 52597],
    [0, 52597],
    [0, 52597],
    [1, 50611],
    [1, 50611],
    [1, 50611]]],
  ['regression: scenario 2',
   [[42968, 29173, 43546],
    255,
    5794,
    [[True, False],
     [False, False],
     [False, False],
     [False, False],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [False, False]]],
   [[1, 5877],
    [1, 5877],
    [1, 5877],
    [1, 5877],
    [2, 5658],
    [2, 5658],
    [2, 5658],
    [2, 5658],
    [0, 5658],
    [0, 5658]]],
  ['control: scenario 3',
   [[16785, 47110, 21847, 45361],
    61440,
    41889,
    [[True, False],
     [True, False],
     [True, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False]]],
   [[1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985]]]],
 [['regression: scenario 8',
   [[65487, 45479, 8754],
    61440,
    1982,
    [[False, False],
     [True, False],
     [True, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False],
     [True, True],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [True, False]]],
   [[0, 1982],
    [1, 47038],
    [1, 47038],
    [1, 47038],
    [1, 47038],
    [1, 47038],
    [2, 10174],
    [0, 10174],
    [0, 10174],
    [0, 10174],
    [0, 10174],
    [0, 10174],
    [0, 10174]]],
  ['regression: scenario 31',
   [[26490, 1121, 33414, 24311],
    65535,
    26582,
    [[True, True],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [False, True],
     [False, False],
     [False, False],
     [True, True],
     [True, False],
     [True, False],
     [True, False],
     [True, False],
     [True, False]]],
   [[0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582],
    [0, 26582]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['control: scenario 1',
   [[8488, 43469, 38296, 4034],
    255,
    44563,
    [[False, False],
     [True, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False]]],
   [[0, 44563],
    [1, 44749],
    [1, 44749],
    [1, 44749],
    [1, 44749],
    [2, 44696],
    [2, 44696],
    [3, 44738],
    [3, 44738],
    [1, 44749],
    [1, 44749],
    [2, 44696]]],
  ['control: scenario 2',
   [[43079, 20640, 23622, 26553],
    255,
    15109,
    [[False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [False, True]]],
   [[0, 15109],
    [0, 15109],
    [1, 15264],
    [1, 15264],
    [1, 15264],
    [1, 15264],
    [2, 15174],
    [2, 15174],
    [2, 15174],
    [2, 15174],
    [3, 15289],
    [0, 15289]]]],
 [['regression: scenario 5',
   [[8300, 19450, 62969],
    255,
    8070,
    [[True, True],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False]]],
   [[0, 8070],
    [0, 8070],
    [0, 8070],
    [1, 8186],
    [1, 8186],
    [1, 8186],
    [1, 8186],
    [2, 8185],
    [2, 8185],
    [2, 8185],
    [2, 8185],
    [2, 8185],
    [1, 8186],
    [1, 8186]]],
  ['regression: scenario 20',
   [[27683, 27069, 29983],
    255,
    29648,
    [[False, False],
     [True, False],
     [False, True],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [False, True]]],
   [[0, 29648],
    [1, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629],
    [0, 29629]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['control: scenario 1',
   [[38610, 2229],
    65535,
    14704,
    [[False, False],
     [False, False],
     [False, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, True],
     [False, False]]],
   [[0, 14704], [0, 14704], [0, 14704], [0, 14704], [0, 14704], [1, 2229], [1, 2229], [0, 2229], [0, 2229]]],
  ['regression: scenario 2',
   [[36741, 30504],
    65535,
    26589,
    [[True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [True, False],
     [False, False]]],
   [[1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [1, 30504],
    [0, 30504],
    [0, 30504],
    [0, 30504]]]],
 [['regression: scenario 23',
   [[17706, 2201, 35072],
    3855,
    50743,
    [[True, True], [True, False], [False, False], [False, True], [True, False], [False, False]]],
   [[0, 50743], [0, 50743], [0, 50743], [0, 50743], [1, 51257], [1, 51257]]],
  ['regression: scenario 37',
   [[46144, 38157],
    61440,
    18798,
    [[False, True], [False, False], [False, False], [False, False], [True, True], [True, False]]],
   [[0, 18798], [0, 18798], [0, 18798], [0, 18798], [0, 18798], [0, 18798]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['control: scenario 1',
   [[61786, 58708],
    255,
    45362,
    [[False, False],
     [False, False],
     [False, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False]]],
   [[0, 45362], [0, 45362], [0, 45362], [1, 45396], [1, 45396], [1, 45396], [1, 45396]]],
  ['control: scenario 2',
   [[57902, 51779],
    61440,
    26811,
    [[True, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False]]],
   [[1, 51387], [1, 51387], [1, 51387], [1, 51387], [1, 51387], [1, 51387], [1, 51387], [1, 51387]]]],
 [['regression: scenario 10',
   [[42427, 61110, 22519, 20082, 65253],
    65535,
    32195,
    [[True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [False, False],
     [True, True],
     [False, False],
     [False, False],
     [False, False]]],
   [[1, 61110],
    [1, 61110],
    [2, 22519],
    [2, 22519],
    [3, 20082],
    [3, 20082],
    [3, 20082],
    [3, 20082],
    [3, 20082],
    [0, 20082],
    [0, 20082],
    [0, 20082],
    [0, 20082]]],
  ['regression: scenario 19',
   [[7514, 21129, 31492],
    61440,
    5749,
    [[True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [True, False],
     [False, True],
     [True, False],
     [False, False]]],
   [[1, 22133],
    [1, 22133],
    [1, 22133],
    [1, 22133],
    [2, 30325],
    [2, 30325],
    [2, 30325],
    [0, 30325],
    [1, 22133],
    [1, 22133]]],
  ['control: wrap past last step',
   [[0, 17, 34],
    255,
    43776,
    [[True, False], [False, False], [True, False], [False, False], [True, False], [True, False]]],
   [[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]],
  ['control: two element file',
   [[5, 9], 65535, 0, [[True, False], [False, False], [True, False], [False, False], [True, False]]],
   [[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]],
  ['control: reset while enabled',
   [[0, 3, 12], 15, 65520, [[True, False], [True, True], [False, False], [True, False]]],
   [[1, 65523], [0, 65523], [0, 65523], [1, 65523]]],
  ['regression: reset with advance',
   [[0, 256, 512], 65280, 170, [[False, False], [True, True], [False, False], [True, False]]],
   [[0, 170], [0, 170], [0, 170], [1, 426]]],
  ['control: scenario 1',
   [[39974, 26951],
    3855,
    4546,
    [[False, False],
     [False, False],
     [True, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, True]]],
   [[0, 4546],
    [0, 4546],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [1, 6599],
    [0, 6599]]],
  ['regression: scenario 2',
   [[43067, 57880, 6921, 33106, 51712],
    255,
    13830,
    [[True, False],
     [False, False],
     [False, False],
     [True, False],
     [True, False],
     [False, False],
     [True, False],
     [False, False],
     [True, True],
     [True, True],
     [False, False],
     [True, False],
     [False, False]]],
   [[1, 13848],
    [1, 13848],
    [1, 13848],
    [2, 13833],
    [2, 13833],
    [2, 13833],
    [3, 13906],
    [3, 13906],
    [0, 13906],
    [0, 13906],
    [0, 13906],
    [1, 13848],
    [1, 13848]]]]]
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 with advance[[0, 170], [0, 170], [0, 170], [1, 426]][[0, 170], [0, 170], [0, 170], [1, 426]]Passed
regression: scenario 6[[0, 54790], [0, 54790], [0, 54790], [1, 13830], [1, 13830], [1, 13830], [2, 62982], [2, 62982], [2, 62982], [3, 13830]][[0, 54790], [0, 54790], [0, 54790], [0, 54790], [0, 54790], [0, 54790], [1, 13830], [1, 13830], [1, 13830], [2, 62982]]Failed
control: wrap past last step[[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]][[1, 43793], [1, 43793], [2, 43810], [2, 43810], [1, 43793], [1, 43793]]Passed
control: two element file[[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]][[1, 9], [1, 9], [1, 9], [1, 9], [1, 9]]Passed
control: reset while enabled[[1, 65523], [0, 65523], [0, 65523], [1, 65523]][[1, 65523], [0, 65523], [0, 65523], [1, 65523]]Passed
regression: scenario 1[[0, 52597], [0, 52597], [0, 52597], [0, 52597], [0, 52597], [0, 52597], [0, 52597], [1, 50611], [1, 50611], [1, 50611]][[0, 52597], [0, 52597], [0, 52597], [0, 52597], [0, 52597], [0, 52597], [0, 52597], [1, 50611], [1, 50611], [1, 50611]]Passed
regression: scenario 2[[1, 5877], [1, 5877], [1, 5877], [1, 5877], [2, 5658], [2, 5658], [2, 5658], [2, 5658], [0, 5658], [0, 5658]][[1, 5877], [1, 5877], [1, 5877], [1, 5877], [2, 5658], [2, 5658], [2, 5658], [2, 5658], [0, 5658], [0, 5658]]Passed
control: scenario 3[[1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985]][[1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985], [1, 45985]]Passed

SHA-256 / 7281f3b7a1828ede71afdd4679fc2d08a8cc61a04701c0518c9db569708c2d73

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 2026-09-29T14:51:42.513818+00:00.

Case digest / 773aafd4651aa7fa5d1a9f564d5a847cc267fd04239b3c1977791ad998060452