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FA-17896 / Time representation / Open access

RTC minute tens nibble is reversed or dropped · case 01

The decoded time state disagrees with the explicit regression oracle for minute.

Verified by executionVariant 1 · 15 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

RTC minute tens nibble is reversed or dropped.

THE FAILURE

RTC minute tens nibble is reversed or dropped.

Unsuccessful approach: The partial correction still substitutes (r['minute'] & 15) at the same fault site.

Case contract

Controlled RTC snapshot consists of packed BCD hour/minute/second bytes, an hour-mode flag, PM flag and oscillator-running flag. Decode BCD only if each nibble is decimal. In twelve-hour mode valid hours are 1..12; in twenty-four-hour mode 0..23 and PM is forbidden. A stopped oscillator invalidates the reading. Return valid and 24-hour components. Equal generation stamps before and after register reads are required for a coherent snapshot; previous_hour is stale diagnostic context and must not replace the current hour.

Why this case matters

Clock transfer and timestamp consumers require preserved coordinate, phase, validity and elapsed-time semantics.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
N = 1
observations = []
def solve(r):
    hour = (r['hour'] >> 4) * 10 + (r['hour'] & 15)
    minute = (r['minute'] & 15) * 10 + (r['minute'] >> 4)
    second = (r['second'] >> 4) * 10 + (r['second'] & 15)
    bcd = all(0 <= r[k] <= 255 and r[k] >> 4 <= 9 and r[k] & 15 <= 9 for k in ('hour','minute','second')) and r['generation_before'] == r['generation_after']
    hour_valid = 1 <= hour <= 12 if r['twelve'] else 0 <= hour <= 23
    minute_valid = 0 <= minute <= 59
    second_valid = 0 <= second <= 59
    mode_valid = r['twelve'] or not r['pm']
    converted_hour = hour % 12 + 12 * int(r['pm']) if r['twelve'] else hour
    valid = bcd and hour_valid and minute_valid and second_valid and mode_valid and r['running']
    return [valid,converted_hour,minute,second]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve({'hour': 18, 'minute': 52, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 0, 34, 56])
check('fixture 2', solve({'hour': 18, 'minute': 89, 'second': 89, 'twelve': True, 'pm': True, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 12, 59, 59])
check('fixture 3', solve({'hour': 35, 'minute': 0, 'second': 0, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 23, 0, 0])
check('fixture 4', solve({'hour': 0, 'minute': 0, 'second': 0, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 0, 0, 0])
check('fixture 5', solve({'hour': 0, 'minute': 0, 'second': 0, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 0, 0, 0])
check('fixture 6', solve({'hour': 19, 'minute': 0, 'second': 0, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 1, 0, 0])
check('fixture 7', solve({'hour': 16, 'minute': 96, 'second': 0, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 10, 60, 0])
check('fixture 8', solve({'hour': 16, 'minute': 0, 'second': 96, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 10, 0, 60])
check('fixture 9', solve({'hour': 26, 'minute': 0, 'second': 0, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 20, 0, 0])
check('fixture 10', solve({'hour': 1, 'minute': 0, 'second': 0, 'twelve': False, 'pm': True, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 1, 0, 0])
check('fixture 11', solve({'hour': 1, 'minute': 0, 'second': 0, 'twelve': True, 'pm': True, 'running': False, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 13, 0, 0])
check('fixture 12', solve({'hour': 1, 'minute': 0, 'second': 0, 'twelve': True, 'pm': True, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 13, 0, 0])
check('fixture 13', solve({'hour': 16, 'minute': 89, 'second': 88, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 10, 59, 58])
check('fixture 14', solve({'hour': 18, 'minute': 52, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 2}), [False, 0, 34, 56])
variant = [({'hour': 18, 'minute': 1, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 1, 56]), ({'hour': 18, 'minute': 2, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 2, 56]), ({'hour': 18, 'minute': 3, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 3, 56]), ({'hour': 18, 'minute': 4, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 4, 56]), ({'hour': 18, 'minute': 5, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 5, 56])]
check("variant capture", solve(variant[N-1][0]), variant[N-1][1])
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
fixture 1[True, 0, 43, 56][True, 0, 34, 56]Failed
fixture 2[False, 12, 95, 59][True, 12, 59, 59]Failed
fixture 3[True, 23, 0, 0][True, 23, 0, 0]Passed
fixture 4[True, 0, 0, 0][True, 0, 0, 0]Passed
fixture 5[False, 0, 0, 0][False, 0, 0, 0]Passed
fixture 6[False, 1, 0, 0][False, 1, 0, 0]Passed
fixture 7[True, 10, 6, 0][False, 10, 60, 0]Failed
fixture 8[False, 10, 0, 60][False, 10, 0, 60]Passed
fixture 9[False, 20, 0, 0][False, 20, 0, 0]Passed
fixture 10[False, 1, 0, 0][False, 1, 0, 0]Passed
fixture 11[False, 13, 0, 0][False, 13, 0, 0]Passed
fixture 12[True, 13, 0, 0][True, 13, 0, 0]Passed
fixture 13[False, 10, 95, 58][True, 10, 59, 58]Failed
fixture 14[False, 0, 43, 56][False, 0, 34, 56]Failed
variant capture[True, 0, 10, 56][True, 0, 1, 56]Failed

SHA-256 / 94f33f36ac950f3814a7cdb0ee2cfea2de266a5157349d94e4c4c65c432b5335

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
N = 1
observations = []
def solve(r):
    hour = (r['hour'] >> 4) * 10 + (r['hour'] & 15)
    minute = (r['minute'] & 15)
    second = (r['second'] >> 4) * 10 + (r['second'] & 15)
    bcd = all(0 <= r[k] <= 255 and r[k] >> 4 <= 9 and r[k] & 15 <= 9 for k in ('hour','minute','second')) and r['generation_before'] == r['generation_after']
    hour_valid = 1 <= hour <= 12 if r['twelve'] else 0 <= hour <= 23
    minute_valid = 0 <= minute <= 59
    second_valid = 0 <= second <= 59
    mode_valid = r['twelve'] or not r['pm']
    converted_hour = hour % 12 + 12 * int(r['pm']) if r['twelve'] else hour
    valid = bcd and hour_valid and minute_valid and second_valid and mode_valid and r['running']
    return [valid,converted_hour,minute,second]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve({'hour': 18, 'minute': 52, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 0, 34, 56])
check('fixture 2', solve({'hour': 18, 'minute': 89, 'second': 89, 'twelve': True, 'pm': True, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 12, 59, 59])
check('fixture 3', solve({'hour': 35, 'minute': 0, 'second': 0, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 23, 0, 0])
check('fixture 4', solve({'hour': 0, 'minute': 0, 'second': 0, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 0, 0, 0])
check('fixture 5', solve({'hour': 0, 'minute': 0, 'second': 0, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 0, 0, 0])
check('fixture 6', solve({'hour': 19, 'minute': 0, 'second': 0, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 1, 0, 0])
check('fixture 7', solve({'hour': 16, 'minute': 96, 'second': 0, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 10, 60, 0])
check('fixture 8', solve({'hour': 16, 'minute': 0, 'second': 96, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 10, 0, 60])
check('fixture 9', solve({'hour': 26, 'minute': 0, 'second': 0, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 20, 0, 0])
check('fixture 10', solve({'hour': 1, 'minute': 0, 'second': 0, 'twelve': False, 'pm': True, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 1, 0, 0])
check('fixture 11', solve({'hour': 1, 'minute': 0, 'second': 0, 'twelve': True, 'pm': True, 'running': False, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [False, 13, 0, 0])
check('fixture 12', solve({'hour': 1, 'minute': 0, 'second': 0, 'twelve': True, 'pm': True, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 13, 0, 0])
check('fixture 13', solve({'hour': 16, 'minute': 89, 'second': 88, 'twelve': False, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}), [True, 10, 59, 58])
check('fixture 14', solve({'hour': 18, 'minute': 52, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 2}), [False, 0, 34, 56])
variant = [({'hour': 18, 'minute': 1, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 1, 56]), ({'hour': 18, 'minute': 2, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 2, 56]), ({'hour': 18, 'minute': 3, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 3, 56]), ({'hour': 18, 'minute': 4, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 4, 56]), ({'hour': 18, 'minute': 5, 'second': 86, 'twelve': True, 'pm': False, 'running': True, 'previous_hour': 17, 'generation_before': 1, 'generation_after': 1}, [True, 0, 5, 56])]
check("variant capture", solve(variant[N-1][0]), variant[N-1][1])
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
fixture 1[True, 0, 4, 56][True, 0, 34, 56]Failed
fixture 2[True, 12, 9, 59][True, 12, 59, 59]Failed
fixture 3[True, 23, 0, 0][True, 23, 0, 0]Passed
fixture 4[True, 0, 0, 0][True, 0, 0, 0]Passed
fixture 5[False, 0, 0, 0][False, 0, 0, 0]Passed
fixture 6[False, 1, 0, 0][False, 1, 0, 0]Passed
fixture 7[True, 10, 0, 0][False, 10, 60, 0]Failed
fixture 8[False, 10, 0, 60][False, 10, 0, 60]Passed
fixture 9[False, 20, 0, 0][False, 20, 0, 0]Passed
fixture 10[False, 1, 0, 0][False, 1, 0, 0]Passed
fixture 11[False, 13, 0, 0][False, 13, 0, 0]Passed
fixture 12[True, 13, 0, 0][True, 13, 0, 0]Passed
fixture 13[True, 10, 9, 58][True, 10, 59, 58]Failed
fixture 14[False, 0, 4, 56][False, 0, 34, 56]Failed
variant capture[True, 0, 1, 56][True, 0, 1, 56]Passed

SHA-256 / 93b07e3e7ea3bb60209c2735cafd920d3b0353b44fe267fc149219a4df9397c3

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 15 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

Deterministic integer reference model with stipulated units and policies; not a complete clock, wire standard or platform implementation. 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 2026-09-29T14:39:52.470361+00:00.

Case digest / e7798ac854cedbc7b7a5349787c5d75495553c59409c616f9f8b31304d5ca465