Datasheet

Status Register (0Fh)
ThecontrolregistercontrolstheoperationoftheSQW/INT pin and provides oscillator status.
Bit 7: Oscillator Stop Flag (OSF). A logic 1 in this bit indicates that the oscillator has stopped or was stopped for some
time period and can be used to judge the validity of the clock and calendar data. This bit is edge triggered, and is set to
logic 1 when the internal circuitry senses the oscillator has transitioned from a normal run state to a stopped condition.
ThefollowingareexamplesofconditionsthatmaycausetheOSFbittobeset:
The first time power is applied.
 ThevoltagepresentonV
CC
andV
BAT
are insufficient to support oscillation.
The EOSC bit is set to 1, disabling the oscillator.
 Externalinfluencesonthecrystal(i.e.,noise,leakage,etc.).
Thisbitremainsatlogic1untilwrittentologic0.Thisbitcanonlybewrittentologic0.AttemptingtowriteOSFtologic
1 leaves the value unchanged.
Bit 1: Alarm 2 Flag (A2F).
Alogic1intheAlarm2FlagbitindicatesthatthetimematchedtheAlarm2registers.Ifthe
A2IEbitisalogic1andtheINTCNbitissettoalogic1,theSQW/INTpinisalsoasserted.A2Fisclearedwhenwritten
tologic0.Thisbitcanonlybewrittentologic0.Attemptingtowritetologic1leavesthevalueunchanged.
Bit 0: Alarm 1 Flag (A1F).Alogic1intheAlarm1FlagbitindicatesthatthetimematchedtheAlarm1registers.Ifthe
A1IEbitisalogic1andtheINTCNbitissettoalogic1,theSQW/INTpinisalsoasserted.A1Fisclearedwhenwritten
tologic0.Thisbitcanonlybewrittentologic0.Attemptingtowritetologic1leavesthevalueunchanged.
Bit # BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
Name OSF 0 0 0 0 0 A2F A1F
POR 1 0 0 0 0 0 0 0
DS1339B Low-Current, I
2
C, Serial Real-Time Clock
For High-ESR Crystals
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