DS1337

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CLOCK ACCURACY

The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match

between the capacitive load of the oscillator circuit and the capacitive load for which the crystal was

trimmed. Crystal frequency drift caused by temperature shifts creates additional error. External circuit

noise coupled into the oscillator circuit can result in the clock running fast. Refer to Application Note 58:

Crystal Considerations with Dallas Real-Time Clocks for detailed information.

ADDRESS MAP

The address map for the registers of the DS1337 is shown in Table 1. During a multibyte access, when

the address pointer reaches the end of the register space (0Fh) it wraps around to location 00h. On a 2-

wire START, STOP, or address pointer incrementing to location 00h, the current time is transferred to a

second set of registers. The time information is read from these secondary registers, while the clock may

continue to run. This eliminates the need to re-read the registers in case of an update of the main registers

during a read.

Table 1. Timekeeper Registers

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 Minutes

Minutes

Minutes

00-59

AM/PM

02H

0

12/24

10hr

10hr

Hour

Hours

1-12

+AM/PM

00-23

03H

0

0

0

0

0

Day

Day

1-7

04H

0

0

10 Date

Date

Date

00-31

05H

Century

0

0

10 Mo

Month

Month/

Century

01-12 +

Century

06H

10 Year

Year

Year

00-99

07H

A1M1

10 Seconds

Seconds

Alarm 1

Seconds

00-59

08H

A1M2

10 Minutes

Minutes

Alarm 1

Minutes

00-59

AM/PM

09H

A1M3

12/24

10hr

10hr

Hour

Alarm 1

Hours

1-12 +

AM/PM

00-23

0AH

A1M4

DY/DT

10 DATE

Day

Date

Alarm 1

Day

Alarm 1

Date

1-7

1-31

0BH

A2M2

10 Minutes

Minutes

Alarm 2

Minutes

00-59

AM/PM

0CH

A2M3

12/24

10hr

10hr

Hour

Alarm 2

Hours

1-12 +

AM/PM

00-23

0DH

A2M4

DY/DT

10 Date

Day

Date

Alarm 2

Day

Alarm 2

Date

1-7

1-31

0EH

EOSC

0

0

RS2

RS1

INTCN

A2IE

A1IE

Control

0FH

OSF

0

0

0

0

0

A2F

A1F

Status