Data Sheet

DS1307
2 of 12
OPERATION
The DS1307 operates as a slave device on the serial bus. Access is obtained by implementing a START
condition and providing a device identification code followed by a register address. Subsequent registers
can be accessed sequentially until a STOP condition is executed. When V
CC
falls below 1.25 x V
BAT
the
device terminates an access in progress and resets the device address counter. Inputs to the device will
not be recognized at this time to prevent erroneous data from being written to the device from an out of
tolerance system. When V
CC
falls below V
BAT
the device switches into a low-current battery backup
mode. Upon power-up, the device switches from battery to V
CC
when V
CC
is greater than V
BAT
+ 0.2V
and recognizes inputs when V
CC
is greater than 1.25 x V
BAT
. The block diagram in Figure 1 shows the
main elements of the serial RTC.
DS1307 BLOCK DIAGRAM Figure 1
TYPICAL OPERATING CIRCUIT