DS1685/DS1687 3V/5V Real-Time Clocks

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“don’t care” codes in all three time alarm bytes create an interrupt every second. The three time-alarm bytes can be

used with the date alarm as described in the Wake-Up/Kickstart section. The century counter is discussed later in

this text.

All registers can be directly written or read except for the following:

Table 2A. Time, Calendar, and Alarm Data Modes—BCD Mode (DM = 0)

ADDRESS

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

FUNCTION

RANGE

00H

0

10 Seconds

Seconds

Seconds

00-59

01H

0

10 Seconds

Seconds

Seconds

Alarm

00-59

02H

0

10 Minutes

Minutes

Minutes

00-59

03H

0

10 Minutes

Minutes

Minutes

Alarm

00-59

04H

AM/PM

0

0

10 Hour

Hours

Hours

1-12

+AM/PM

00-23

0

10 Hour

05H

AM/PM

0

0

10 Hour

Hours

Hours

Alarm

1-12

+AM/PM

00-23

0

10 Hr

06H

0

0

0

0

0

Day

Day

01-07

07H

0

0

10 Date

Date

Date

01-31

08H

0

0

0

10 Month

Month

Month

01-12

09H

10 Year

Year

Year

00-99

0AH

UIP

DV2

DV1

DV0

RS3

RS2

RS1

RS0

Control

0BH

SET

PIE

AIE

UIE

SQWE

DM

24/12

DSE

Control

0CH

IRQF

PF

AF

UF

0

0

0

0

Control

0DH

VRT

0

0

0

0

0

0

0

Control

48H

Century

Bank 1

Century

00-99

49H

10 Date

Date

Bank 1

Date Alarm

01-31

X = Read/Write Bit.

Note 1: Unless otherwise specified, the state of the registers is not defined when power is first applied.

Note 2: Except for the seconds register, 0 bits in the time and date registers can be written to a 1, but may be modified when the clock updates.

0 bits should always be written to 0 except for alarm mask bits.