DS1307 Maxim, DS1307 Datasheet - Page 9

• Manufacturer Part Number: DS1307
• Description: The DS1307 serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM
• Manufacturer: Maxim

CONTROL REGISTER
The DS1307 control register is used to control the operation of the SQW/OUT pin.
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.
BIT 7
OUT
RS1
X
X
0
0
1
1
BIT 6
0
RS0
X
X
0
1
0
1
BIT 5
0
SQW/OUT OUTPUT
SQWE
BIT 4
32.768kHz
4.096kHz
8.192kHz
1Hz
9 of 14
0
1
BIT 3
0
DS1307 64 x 8, Serial, I
BIT 2
SQWE
0
1
1
1
1
0
0
BIT 1
RS1
2
C Real-Time Clock
OUT
X
X
X
X
0
1
BIT 0
RS0