Rainbow Electronics DS1643P - Manual (Page 3)

DS1643/DS1643P
3 of 14
BLOCK DIAGRAM DS1643 Figure 1
DS1643 TRUTH TABLE Table 1
V
CC CE
CE2
OE WE
MODE DQ POWER
V
IH
X X X DESELECT HIGH Z STANDBY
X V
IL
X X DESELECT HIGH Z STANDBY
V
IL
V
IH
X V
IL
WRITE DATA IN ACTIVE
V
IL
V
IH
V
IL
V
IH
READ DATA OUT ACTIVE
5 VOLTS
±
10%
V
IL
V
IH
V
IH
V
IH
READ HIGH Z ACTIVE
<4.5 VOLTS
>V
BAT
X X X X DESELECT HIGH Z CMOS STANDBY
BAT
X X X X 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
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.
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, CE2 high, and address for seconds register remain valid and stable).
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.