DS1557 查看數據表（PDF） - Dallas Semiconductor -> Maxim Integrated

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DS1557

4MEG NV Y2KC Timekeeping RAM

Dallas Semiconductor -> Maxim Integrated 

PRELIMINARY

DS1557

4MEG NV Y2KC Timekeeping RAM

www.dalsemi.com

FEATURES

Integrated NV SRAM, real time clock, crystal,

power-fail control circuit and lithium energy

source

Clock registers are accessed identically to the

static RAM; these registers are resident in the

16 top RAM locations

Century byte register; i.e., Y2K complaint

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%

VCC power supply tolerance

Lithium energy source is electrically

disconnected to retain freshness until power is

applied for the first time

ORDERING INFORMATION

DS1557P-XXX

(5-Volt)

-70 70 ns access

-100 100 ns access

*DS1557WP-XXX (3.3 Volt)

-120 120 ns access

-150 150 ns access

*DS9034PCX (PowerCap) Required:

must be ordered seperately

PIN ASSIGNMENT

IRQ/FT 1

34

A18

A15 2

A16 3

RST 4

VCC

WE

5

6

OE 7

CE

DQ7

8

9

33

A17

32

A14

31

A13

30

A12

29

A11

28

A10

27

A9

26

A8

DQ6 10

25

A7

DQ5 11

DQ4 12

24

A6

23

A5

DQ3 13

22

A4

DQ2

DQ1

DQ0

14

21

15

16

X1 GND VBAT X2

20

19

A3

A2

A1

GND 17

18

A0

34-Pin POWERCAP MODULE BOARD

(USES DS9034PCX POWERCAP)

PIN DESCRIPTION

A0-A14

- Address Input

DQ0-DQ7

- Data Input/Outputs

IRQ \FT

- Interrupt, Frequency Test

Output (Open Drain)

RST

- Power-On Reset Output

(Open Drain)

CE

- Chip Enable

OE

- Output Enable

WE

VCC

GND

NC

X1, X2

VBAT

- Write Enable

- Power Supply Input

- Ground

- No Connection

- Crystal Connection

- Battery Connection

DESCRIPTION

The DS1557 is a full function, year 2000-compliant (Y2KC), real-time clock/calendar (RTC) with a RTC

alarm, watchdog timer, power-on reset, battery monitor, and 512k x 8 non-volatile static RAM. User

access to all registers within the DS1557 is accomplished with a bytewide interface as shown in Figure 1.

The RTC Registers contain century, year, month, date, day, hours, minutes, and seconds data in 24-hour

BCD format. Corrections for day of month and leap year are made automatically.

1of 19

012700

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