Dallas Maxim DS12885, Manual

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DS12885/DS12887/DS12887A/DS12C887/DS12C887A
Real-Time Clock
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Bit 7: Interrupt Request Flag (IRQF). This bit is set to
1 when any of the following are true:
PF = PIE = 1
AF = AIE = 1
UF = UIE = 1
Any time the IRQF bit is 1, the
IRQ
pin is driven low.
This bit can be cleared by reading Register C or with a
RESET
.
Bit 6: Periodic Interrupt Flag (PF).
This bit is read-
only and is set to 1 when an edge is detected on the
selected tap of the divider chain. The RS3 through RS0
bits establish the periodic rate. PF is set to 1 indepen-
dent of the state of the PIE bit. When both PF and PIE
are 1s, the
IRQ
signal is active and sets the IRQF bit.
This bit can be cleared by reading Register C or with a
RESET
.
Bit 5: Alarm Interrupt Flag (AF). A 1 in the AF bit indi-
cates 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. This bit can be cleared by
reading Register C or with a
RESET
.
Bit 5: 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 a 1, which
asserts the
IRQ
pin. This bit can be cleared by reading
Register C or with a
RESET
.
Bits 3 to 0: Unused. These bits are unused in Register
C. These bits always read 0 and cannot be written.
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
IRQF PF AF UF 0 0 0 0
Control Register C
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
VRT 0 0 0 0 0 0 0
Control Register D
Bit 7: Valid RAM and Time (VRT). This bit indicates
the condition of the battery connected to the V
BAT
pin.
This bit is not writeable and should always be 1 when
read. If a 0 is ever present, an exhausted internal lithi-
um energy source is indicated and both the contents of
the RTC data and RAM data are questionable. This bit
is unaffected by
RESET
.
Bits 6 to 0: Unused. The remaining bits of Register D
are not usable. They cannot be written and they always
read 0.
MSB LSB
MSB LSB