DS1339A Datasheet, PDF (13/19 Pages) Maxim Integrated Products – Low-Current, I2C, Serial Real-Time Clock

DS1339A
Low-Current, I²C, Serial Real-Time Clock
Status Register (0Fh)
The control register controls the operation of the SQW/INT pin and provides oscillator status.
Bit #
Name
POR
BIT 7
OSF
1
BIT 6
0
0
BIT 5
0
0
BIT 4
0
0
BIT 3
0
0
BIT 2
0
0
BIT 1
A2F
0
BIT 0
A1F
0
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.
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