DS12885 Maxim, DS12885 Datasheet - Page 17

• Manufacturer Part Number: DS12885
• Description: The DS12885, DS12887, and DS12C887 real-time clocks (RTCs) are designed to be direct replacements for the DS1285 and DS1287
• Manufacturer: Maxim

Bit 7: Interrupt Request Flag (IRQF). This bit is set to
1 when any of the following are true:
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.
MSB
MSB
Bit 7: Valid RAM and Time (VRT). This bit indicates
the condition of the battery connected to the V
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
BIT 7
BIT 7
IRQF
PF = PIE = 1
AF = AIE = 1
UF = UIE = 1
VRT
BIT 6
BIT 6
PF
0
BIT 5
BIT 5
AF
0
____________________________________________________________________
BAT
BIT 4
BIT 4
UF
0
pin.
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.
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 3
BIT 3
0
0
Real-Time Clocks
BIT 2
BIT 2
0
0
Control Register C
BIT 1
Control Register D
BIT 1
0
0
BIT 0
BIT 0
0
0
LSB
LSB
17