DS1646 View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated
Part Name
Description
Manufacturer
DS1646 Datasheet PDF : 12 Pages
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DS1646/DS1646P
TRUTH TABLE DS1646 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
X
X
X
>VBAT
<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 DS1646 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 1 stops
the oscillator.
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 (DIP MODULE)
The DS1646 is guaranteed to keep time accuracy to
within ±1 minute per month at 25°C.
CLOCK ACCURACY (POWERCAP MODULE)
The DS1646P and DS9034PCX are each individually
tested for accuracy. Once mounted together, the mod-
ule is guaranteed to keep time accuracy to within ±1.53
minutes per month (35 ppm) at 25°C.
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
031698 3/12
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