DS1643/DS1643P

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BLOCK DIAGRAM DS1643 Figure 1

DS1643 TRUTH TABLE Table 1

CE

CE2

OE

WE

MODE

DQ

POWER

X

X

X

DESELECT

HIGH Z

STANDBY

X

X

DESELECT

HIGH Z

STANDBY

WRITE

DATA IN

ACTIVE

READ

DATA OUT

ACTIVE

5 VOLTS

± 10%

READ

HIGH Z

ACTIVE

<4.5 VOLTS

XXXX

DESELECT

HIGH Z

CMOS STANDBY

XXXX

DESELECT

HIGH Z

DATA RETENTION

MODE

SETTING THE CLOCK

The 8-bit of the control register is the write bit. Setting the write bit to a 1, like the read bit, halts updates

to the DS1643 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 0 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 increase the shelf life, the oscillator can be turned off

a 1 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

CLOCK ACCURACY (DIP MODULE)

The DS1643 is guaranteed to keep time accuracy to within

±1 minute per month at 25°C.

CLOCK ACCURACY (POWERCAP MODULE)

The DS1643P and DS9034PCX are each individually tested for accuracy. Once mounted together, the

module is guaranteed to keep time accuracy to within

±1.53 minutes per month (35 ppm) at 25°C.