Setting the clock, Stopping and starting the clock oscillator, Frequency test bit – Rainbow Electronics DS1647P User Manual
Page 3
DS1647/DS1647P
3 of 11
BLOCK DIAGRAM DS1647 Figure 1
TRUTH TABLE DS1647 Table 1
V
CC
CE
OE
WE
MODE
DQ
POWER
V
IH
X
X
DESELECT
HIGH-Z
STANDBY
X
X
X
DESELECT
HIGH-Z
STANDBY
V
IL
X
V
IL
WRITE
DATA IN
ACTIVE
V
IL
V
IL
V
IH
READ
DATA OUT
ACTIVE
5V
± 10%
V
IL
V
IH
V
IH
READ
HIGH-Z
ACTIVE
<4.5V >V
BAT
X
X
X
DESELECT
HIGH-Z
CMOS STANDBY
BAT X X X DESELECT HIGH-Z DATA RETENTION MODE SETTING THE CLOCK The MSB Bit, B7, of the control register is the write bit. Setting the write bit to a 1, like the read bit halts 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 OSC bit is the MSB for the second’s 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 CE low, OE low, and address for seconds register remain valid and stable).
updates to the DS1647 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.
to minimize current drain from the battery. The
oscillator is running, the LSB of the second’s 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.,