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Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device

FEATURES

 Integrated NV SRAM, Real-Time Clock

(RTC), Crystal, Power-Fail Control Circuit,

and Lithium Energy Source

 Clock Registers are Accessed Identically to

the Static RAM; These Registers Reside in

the 16 Top RAM Locations

 Century Byte Register (i.e., Y2K Compliant)

 Totally Nonvolatile with Over 10 Years of

Operation in the Absence of Power

 Precision Power-On Reset

 Programmable Watchdog Timer and RTC

Alarm

 BCD-Coded Year, Month, Date, Day, Hours,

Minutes, and seconds with Automatic Leap-

Year Compensation Valid Up to the Year

2100

 Battery Voltage-Level Indicator Flag

 Power-Fail Write Protection Allows for

10%

 Lithium Energy Source is Electrically

Disconnected to Retain Freshness Until

Power is Applied for the First Time

 Also Available in Industrial Temperature

Range: -40°C to +85°C

PIN CONFIGURATIONS

DS1556

1M, Nonvolatile, Y2K-Compliant

Timekeeping RAM

www.maxim-ic.com

RST

A15

IRQ/FT

WE

A13

A8

A9

A11

OE

A10

CE

DQ7

DQ5

DQ6

DQ4

DQ3

13

1

2

3

4

5

6

7

8

9

10

11

12

14

31

A14

A7

A5

A4

A3

A2

A1

A0

DQ1

DQ0

32

30

29

28

27

26

25

24

23

22

21

19

20

A16

A12

A6

DQ2

GND

15

16

18

17

Encapsulated DIP

Maxim

DS1556

TOP VIEW

IRQ/FT

1

2

3

A15

A16

RST

OE

CE

DQ7

DQ6

DQ5

DQ4

DQ3

DQ2

DQ1

DQ0

GND

4

5

6

7

8

9

10

11

12

13

14

15

16

17

N.C.

A14

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

A13

A12

A11

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

34

N.C.

X1

GND

X2

PowerCap Module Board

(Uses DS9034PCX PowerCap)

WE

Maxim

DS1556

19-5500; Rev 9/10