FA-17930 / Time representation / Member archive

RTC mode validation ignores forbidden PM bit or rejects valid PM · case 05

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

Member previewVariant 5 · 3 implementations · 15 checks per implementation

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.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
fixture 10	`[true, 1, 0, 0]`	`[false, 1, 0, 0]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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