DS1307/1308

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DESCRIPTION

The DS1307 Serial Real Time Clock is a low power, full BCD clock/calendar plus 56 bytes of

nonvolatile SRAM.

Address and data are transferred serially via a 2-wire bi-directional bus.

The

clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the

month date is automatically adjusted for months with less than 31 days, including corrections for leap

year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The DS1307

has a built-in power sense circuit which detects power failures and automatically switches to the battery

supply.

The DS1308 incorporates the DS1307 chip with a 32.768 kHz crystal in a surface mountable, 36-pin ball

grid array package (BGA). The close proximity of the embedded crystal to the high impedance crystal

input pins on the DS1307 minimizes capacitive loading and noise injection problems associated with

many other oscillator designs. The total area required for installation is less than that of one United States

dime: thus, minimizing PCB space required.

OPERATION

The DS1307/1308 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

device will not be recognized at this time to prevent erroneous data from being written to the device from

the main elements of the Serial Real Time Clock.

DS1307/DS1308 BLOCK DIAGRAM Figure 1