DS12B887 Dallas Semiconductor, DS12B887 Datasheet - Page 3

• Manufacturer Part Number: DS12B887
• Description: Real Time Clock
• Manufacturer: Dallas Semiconductor

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SIGNAL DESCRIPTIONS
GND, V
pins. V
within normal limits, the device is fully accessible and
data can be written and read. When V
volts typical, reads and writes are inhibited. However,
the timekeeping function continues unaffected by the
lower input voltage. As V
the RAM and timekeeper are switched over to an inter-
nal lithium energy source. The timekeeping function
maintains an accuracy of 1 minute per month at 25
regardless of the voltage input on the V
PERIODIC INTERRUPT RATE AND SQUARE WAVE OUTPUT FREQUENCY Table 1
RS3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
CC
CC
SELECT BITS REGISTER A
is the +5 volt input. When 5 volts are applied
- DC power is provided to the device on these
RS2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
CC
RS1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
falls below 3 volts typical,
RS0
CC
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
CC
is below 4.25
pin.
o
INTERRUPT RATE
C
t
t
1.953125 ms
PI
PI
976.5625 s
3.90625 ms
3.90625 ms
122.070 s
244.141 s
488.281 s
7.8125 ms
15.625 ms
7.8125 ms
31.25 ms
62.5 ms
125 ms
250 ms
500 ms
PERIODIC
PERIODIC
None
SQW (Square Wave Output) - The SQW pin can output
a signal from one of 13 taps provided by the 15 internal
divider stages of the Real Time Clock. The frequency of
the SQW pin can be changed by programming Register
A as shown in Table 1. The SQW signal can be turned
on and off using the SQWE bit in Register B. The SQW
signal is not available when V
typical.
SQW OUTPUT
SQW OUTPUT
FREQUENCY
CC
8.192 kHz
4.096 kHz
2.048 kHz
1.024 kHz
is less than 4.25 volts
256 Hz
128 Hz
512 Hz
256 Hz
128 Hz
64 Hz
32 Hz
16 Hz
None
8 Hz
4 Hz
2 Hz
080895 3/16
DS12B887