DS1677

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DS1677 ADDRESS MAP Figure 3

BIT7

BIT0

00

0

10 SECONDS

SECONDS

01

0

10 MINUTES

MINUTES

02

0

12

24

10 HR

A/P

10 HR

HOURS

03

0

0

0

0

0

DAY

04

0

0

10 DATE

DATE

05

0

0

0

10 MO.

MONTH

06

10 YEAR

YEAR

07

M

10 SEC ALARM

SECONDS ALARM

08

M

10 MIN ALARM

MINUTES ALARM

09

M

12

24

10 HR

A/P

10 HR

HOUR ALARM

0A

M

0

0

0

DAY ALARM

0B

CONTROL REGISTER

0C

STATUS REGISTER

0D

WATCHDOG REGISTER

0E

ADC REGISTER

0F

7F

RESERVED

CLOCK, CALENDAR AND ALARM

The time and calendar information is accessed by reading/writing the appropriate register bytes. Note

that some bits are set to zero. These bits will always read zero regardless of how they are written. Also

note that registers 0Fh to 7Fh are reserved. These registers will always read zero regardless of how they

are written. The contents of the time, calendar, and alarm registers are in the Binary–Coded Decimal

(BCD) format.

The DS1677 can 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 one being PM. In the 24–hour mode, bit 5 is the second 10–hour bit (20–23

hours).

The DS1677 also contains a time of day alarm. The alarm registers are located in registers 07h to 0Ah.

Bit 7 of each of the alarm registers are mask bits (see Table 1). When all of the mask bits are logic 0, an

alarm will occur 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 will be generated every day when mask bit of

the day alarm register is set to one. An alarm will be generated every hour when the day and hour alarm

mask bits are set to one. Similarly, an alarm will be generated every minute when the day, hour, and

minute alarm mask bits are set to one. When day, hour, minute, and seconds alarm mask bits are set to

one, an alarm will occur every second.