DS1307/1308

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CONTROL REGISTER

The DS1307/DS1308 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

X

X

SQWE

X

X

RS1

RS0

OUT (Output control): 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.

SQWE (Square Wave Enable): This bit, when set to a logic 1, will enable the oscillator output. The

frequency of the square wave output depends upon the value of the RS0 and RS1 bits.

RS (Rate Select): These bits control the frequency of the square wave output when the square wave

output has been enabled. Table 1 lists the square wave frequencies that can be selected with the RS bits.

SQUAREWAVE OUTPUT FREQUENCY Table 1

RS1

RS0

SQW OUTPUT

FREQUENCY

00

1 Hz

0

1

4.096 kHz

1

0

8.192 kHz

1

1

32.768 kHz

2-WIRE SERIAL DATA BUS

The DS1307 supports a bi-directional 2-wire bus and data transmission protocol. A device that sends

data onto the bus is defined as a transmitter and a device receiving data as a receiver. The device that

controls the message is called a master. The devices that are controlled by the master are referred to as

slaves. The bus must be controlled by a master device which generates the serial clock (SCL), controls

the bus access, and generates the START and STOP conditions. The DS1307/DS1308 operates as a slave

on the 2-wire bus. A typical bus configuration using this 2-wire protocol is show in Figure 4.

TYPICAL 2-WIRE BUS CONFIGURATION Figure 4