Datasheet DS1307 (Maxim) - 9

DS1307 64 x 8, Serial, I2C Real-Time Clock
CONTROL REGISTER
The DS1307 control register is used to control the operation of the SQW/OUT pin.
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
OUT 0 0 SQWE 0 0 RS1 RS0
Bit 7: Output Control (OUT).
This bit controls the output level of the SQW/OUT pin when the square-wave output is disabled. If SQWE = 0, the logic level on the SQW/OUT pin is 1 if OUT = 1 and is 0 if OUT = 0. On initial application of power to the device, this bit is typically set to a 0.
Bit 4: Square-Wave Enable (SQWE).
This bit, when set to logic 1, enables the oscillator output. The frequency of the square-wave output depends upon the value of the RS0 and RS1 bits. With the square-wave output set to 1Hz, the clock registers update on the falling edge of the square wave. On initial application of power to the device, this bit is typically set to a 0.
Bits 1 and 0: Rate Select (RS[1:0]).
These bits control the frequency of the square-wave output when the square- wave output has been enabled. The following table lists the square-wave frequencies that can be selected with the RS bits. On initial application of power to the device, these bits are typically set to a 1.
RS1 RS0 SQW/OUT OUTPUT SQWE OUT
0 0 1Hz 1 X 0 1 4.096kHz 1 X 1 0 8.192kHz 1 X 1 1 32.768kHz 1 X X X 0 0 0 X X 1 0 1 9 of 14 Document Outline TYPICAL OPERATING CIRCUIT PIN CONFIGURATIONS ORDERING INFORMATION ABSOLUTE MAXIMUM RATINGS RECOMMENDED DC OPERATING CONDITIONS (TA = 0 C to +70 C, TA = -40 C to +85 C.) (Notes 1, 2) DC ELECTRICAL CHARACTERISTICS (VCC = 4.5V to 5.5V; TA = 0 C to +70 C, TA = -40 C to +85 C.) (Notes 1, 2) DC ELECTRICAL CHARACTERISTICS (VCC = 0V, VBAT = 3.0V; TA = 0 C to +70 C, TA = -40 C to +85 C.) (Notes 1, 2) AC ELECTRICAL CHARACTERISTICS (VCC = 4.5V to 5.5V; TA = 0 C to +70 C, TA = -40 C to +85 C.) CAPACITANCE (TA = +25 C) 64 x 8, Serial, I2C Real-Time Clock SYMBOL TIMING DIAGRAM CLOCK ACCURACY RTC AND RAM ADDRESS MAP CLOCK AND CALENDAR CONTROL REGISTER I2C DATA BUS RS1