DS1644L-120 View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated
Part Name
Description
Manufacturer
DS1644L-120 Datasheet PDF : 11 Pages
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DS1644LPM
DS1644L TRUTH TABLE Table 1
VCC
CE
OE
WE
VIH
X
X
X
X
X
5 VOLTS ± 10% VIL
X
VIL
VIL
VIL
VIH
VIL
VIH
VIH
<4.5 VOLTS
>VBAT
X
X
X
<VBAT
X
X
X
MODE
DESELECT
DESELECT
WRITE
READ
READ
DESELECT
DESELECT
DQ
HIGH–Z
HIGH–Z
DATA IN
DATA OUT
HIGH–Z
HIGH–Z
HIGH–Z
POWER
STANDBY
STANDBY
ACTIVE
ACTIVE
ACTIVE
CMOS STANDBY
DATA RETENTION
MODE
SETTING THE CLOCK
The eighth bit of the control register is the write bit. Set-
ting the write bit to a one, like the read bit, halts updates
to the DS1644L registers. The user can then load them
with the correct day, date and time data in 24 hour BCD
format. Resetting the write bit to a zero then transfers
those values to the actual clock counters and allows
normal operation to resume.
STOPPING AND STARTING THE CLOCK
OSCILLATOR
The clock oscillator may be stopped at any time. To in-
crease the shelf life, the oscillator can be turned off to
minimize current drain from the battery. The OSC bit is
the MSB for the seconds registers. Setting it to a one
stops the oscillator.
FREQUENCY TEST BIT
Bit 6 of the day byte is the frequency test bit. When the
frequency test bit is set to logic “1” and the oscillator is
running, the LSB of the seconds register will toggle at
512 Hz. When the seconds register is being read, the
DQ0 line will toggle at the 512 Hz frequency as long as
conditions for access remain valid (i.e., CE low, OE low,
and address for seconds register remain valid and
stable).
CLOCK ACCURACY
The DS1644L is guaranteed to keep time accuracy to
within ±1 minute per month at 25°C. The clock is cali-
brated at the factory by Dallas Semiconductor using
special calibration nonvolatile tuning elements. The
DS1644L does not require additional calibration, and
temperature deviations will have a negligible effect in
most applications. For this reason, methods of field
clock calibration are not available and not necessary.
Attempts to calibrate the clock that may be used with
similar device types (MK48T08 family) will not have any
effect even though the DS1644L appears to accept cal-
ibration data.
041697 3/11
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