DS1644/DS1644P

2 of 13

PIN DESCRIPTION

PIN

PDIP

PowerCap

NAME

FUNCTION

1

32

A14

2

30

A12

3

25

A7

4

24

A6

5

23

A5

6

22

A4

7

21

A3

8

20

A2

9

19

A1

10

18

A0

Address Input

11

16

DQ0

12

15

DQ1

13

14

DQ2

Data Input/Output

14

17

GND

Ground

15

13

DQ3

16

12

DQ4

17

11

DQ5

18

10

DQ6

19

9

DQ7

Data Input/Output

20

8

CE

Active Low Chip-Enable Input

21

28

A10

Address Input

22

7

OE

Active Low Output-Enable Input

23

29

A11

24

27

A9

25

26

A8

26

31

A13

Address Input

27

6

WE

Active-Low Write-Enable Input

28

5

Power-Supply Input

-

4

RST

Active-Low Reset Output, Open Drain. Requires a pullup resistor for

proper operation.

-

1-3,33,34

NC

No Connection

-

X1, X2,

DESCRIPTION

The DS1644 is a 32k x 8 nonvolatile static RAM with a full function real time clock, which are both

accessible in a byte-wide format. The nonvolatile timekeeping RAM is functionally equivalent to any

JEDEC standard 32k x 8 SRAM. The device can also be easily substituted for ROM, EPROM and

EEPROM, providing read/write nonvolatility and the addition of the real time clock function. The real

time clock information resides in the eight uppermost RAM locations. The RTC registers contain year,

month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the day of the

month and leap year are made automatically. The RTC clock registers are double-buffered to avoid access

of incorrect data that can occur during clock update cycles. The double-buffered system also prevents

time loss as the timekeeping countdown continues unabated by access to time register data. The DS1644

tolerance condition. This feature prevents loss of data from unpredictable system operation brought on by