DS1306

5 of 20

CLOCK, CALENDAR, AND ALARM

The time and calendar information is obtained by reading the appropriate register bytes. The real time

clock registers are illustrated in Figure 3. The time, calendar, and alarm are set or initialized by writing

the appropriate register bytes. Note that some bits are set to 0. These bits will always read 0 regardless

of how they are written. Also note that registers 12h to 1Fh (read) and registers 92h to 9Fh are reserved.

These registers will always read 0 regardless of how they are written. The contents of the time, calendar,

and alarm registers are in the Binary-Coded Decimal (BCD) format.

RTC REGISTERS Figure 3

RTC REGISTERS DS1306

HEX ADDRESS

READ

WRITE

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

RANGE

00H

80H

0

10 SEC

SEC

00-59

01H

81H

0

10 MIN

MIN

00-59

10

01-12 + P/A

02H

82H

0

12/2

4

P/A

10 HR

HOURS

00-23

03H

83H

0

0

0

0

0

DAY

01-07

04H

84H

0

0

10 DATE

DATE

1-31

05H

85H

0

0

10 MONTH

MONTH

01-12

06H

86H

10 YEAR

YEAR

00-99

Alarm 0

07H

87H

M

10 SEC ALARM

SEC ALARM

00-59

08H

88H

M

10 MIN ALARM

MIN ALARM

00-59

10

01-12 + P/A

09H

89H

M

12/2

4

P/A

10 HR

HOUR ALARM

00-23

0AH

8AH

M

0

0

0

0

DAY ALARM

01-07

Alarm 1

0BH

8BH

M

10 SEC ALARM

SEC ALARM

00-59

0CH

8CH

M

10 MIN ALARM

MIN ALARM

00-59

10

01-12 + P/A

0DH

8DH

M

12/2

4

P/A

10 HR

HOUR ALARM

00-23

0EH

8EH

M

0

0

0

0

DAY ALARM

01-07

0FH

8FH

CONTROL REGISTER

10H

90H

STATUS REGISTER

11H

91H

TRICKLE CHARGER REGISTER

12-1FH

92-9FH

RESERVED

NOTE:

Range for alarm registers does not include mask’m’ bits.