DS1306

6 of 21

Figure 2. RTC REGISTERS AND ADDRESS MAP

HEX ADDRESS

READ

WRITE

Bit

7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

RANGE

00H

80H

0

10 SEC

SEC

00–59

01H

81H

0

10 MIN

MIN

00–59

P

12

A

01–12 + P/A

02H

82H

0

24

10

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

07H

87H

M

10-SEC ALARM 0

SEC ALARM 0

00–59

08H

88H

M

10-MIN ALARM 0

MIN ALARM 0

00–59

P

12

A

01–12 + P/A

09H

89H

M

24

10

10-HR

HOUR ALARM 0

00–23

0AH

8AH

M

0

0

0

0

DAY ALARM 0

01–07

0BH

8BH

M

10 SEC ALARM 1

SEC ALARM 1

00–59

0CH

8CH

M

10 MIN ALARM 1

MIN ALARM 1

00–59

P

12

A

01–12 + P/A

0DH

8DH

M

24

10

10-HR

HOUR ALARM 1

00–23

0EH

8EH

M

0

0

0

0

DAY ALARM 1

01–07

—

0FH

8FH

CONTROL REGISTER

—

10H

90H

STATUS REGISTER

—

11H

91H

TRICKLE CHARGER REGISTER

—

12–1FH

92–9FH

RESERVED

—

20–7FH

A0–

FFH

96-BYTES USER RAM

—

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

The DS1306 can be run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the

12- or 24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is

the AM/PM bit with logic high being PM. In the 24-hour mode, bit 5 is the second 10-hour bit (20 to 23

hours).

The DS1306 contains two time-of-day alarms. Time-of-day alarm 0 can be set by writing to registers 87h

to 8Ah. Time-of-day Alarm 1 can be set by writing to registers 8 Bh to 8 Eh. Bit 7 of each of the time-of-

day alarm registers are mask bits (Table 1). When all of the mask bits are logic 0, a time-of-day alarm

only occurs once per week when the values stored in timekeeping registers 00h to 03h match the values

stored in the time-of-day alarm registers. An alarm is generated every day when bit 7 of the day alarm

register is set to a logic 1. An alarm is generated every hour when bit 7 of the day and hour alarm

registers is set to a logic 1. Similarly, an alarm is generated every minute when bit 7 of the day, hour, and