Datasheet

Bit 7: Interrupt Request Flag (IRQF). This bit is set to

1 when any of the following are true:

PF = PIE = 1 WF = WIE = 1

AF = AIE = 1 KF = KSE = 1

UF = UIE = 1 RF = RIE = 1

Any time the IRQF bit is 1, the IRQ pin is driven low.

Flag bits PF, AF, and UF are cleared after reading

Bit 6: Periodic Interrupt Flag (PF). This is a read-only

bit that is set to 1 when an edge is detected on the

selected tap of the divider chain. The RS3–RS0 bits

establish the periodic rate. PF is set to 1 independent

of the state of the PIE bit. When both PF and PIE are 1s,

the IRQ signal is active and sets the IRQF bit. Reading

Bit 5: Alarm Interrupt Flag (AF). A 1 in this bit indicates

that the current time has matched the alarm time. If the

AIE bit is also 1, the IRQ pin goes low and a 1 appears in

the IRQF bit. Reading Register C clears this bit.

Bit 4: Update-Ended Interrupt Flag (UF). This bit is

set after each update cycle. When the UIE bit is set to

1, the 1 in UF causes the IRQF bit to be 1, which

asserts IRQ. Reading Register C clears this bit.

Bits 3 to 0: Unused. These unused bits always read 0

and cannot be written.

DS17285/DS17287/DS17485/DS17487/DS17885/DS17887

Real-Time Clocks

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BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

IRQF PF AF UF 0000

MSB LSB

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

VRT0000000

MSB LSB

Bit 7: Valid RAM and Time (VRT). This bit indicates

the condition of the battery connected to the V

BAT

and

BAUX

pin. If either supply is above the internal voltage

threshold, VRT

TRIP

, the bit will be high. This bit is not

writeable and should always be a 1 when read. If a 0 is

ever present, an exhausted internal lithium energy

source is indicated and both the contents of the RTC

data and RAM data are questionable.

Bits 6 to 0: Unused. These bits cannot be written and,

when read, always read 0.