A1F and A2F ignore a written 1, so the status write-back now writes the flag not being cleared as 1: an alarm firing between the read and the write was cleared with the other. BBSQW gates the alarm interrupt on battery as well as the square wave (19-5170 rev. 4), so arming an alarm no longer clears it. Both register computations are consteval-tested. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>