DS1244Y データシートの表示（PDF） - Dallas Semiconductor -> Maxim Integrated

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DS1244Y

256K NV SRAM with Phantom Clock

Dallas Semiconductor -> Maxim Integrated 

DS1244Y

DS1244Y

256K NV SRAM with Phantom Clock

FEATURES

• Real time clock keeps track of hundredths of seconds,

minutes, hours, days, date of the month, months, and

years

• 32K x 8 NV SRAM directly replaces volatile static

RAM or EEPROM

• Embedded lithium energy cell maintains calendar op-

eration and retains RAM data

• Watch function is transparent to RAM operation

• Month and year determine the number of days in each

month; volid up to 1200

• Standard 28–pin JEDEC pinout

• Full 10% operating range

• Operating temperature range 0°C to 70°C

• Accuracy is better than ±1 minute/month @ 25°C

• Over 10 years of data retention in the absence of

power

• Available in 120, 150 and 200 ns access time

ORDERING INFORMATION

DS1244Y–XXX

–120

–150

120 ns access

150 ns access

DS1244Y

200 ns access

PIN ASSIGNMENT

A14/RST 1

A12 2

A7 3

A6 4

A5 5

A4 6

A3 7

A2 8

A1 9

A0 10

DQ0 11

DQ1 12

DQ2 13

GND 14

28 VCC

27 WE

26 A13

25 A8

24 A9

23 A11

22 OE

21 A10

20 CE

19 DQ7

18 DQ6

17 DQ5

16 DQ4

15 DQ3

28–PIN ENCAPSULATED PACKAGE

740 MIL EXTENDED

PIN DESCRIPTION

Ao–A14

CE

GND

DQ0-DQ7

VCC

WE

OE

NC

RST

– Address Inputs

– Chip Enable

– Ground

– Data In/Data Out

– Power (+5V)

– Write Enable

– Output Enable

– No Connect

– Reset

DESCRIPTION

The DS1244Y 256K NV SRAM with Phantom Clock is a

fully static nonvolatile RAM (organized as 32,768 words

by 8 bits) with a built–in real time clock. The DS1244Y

has a self–contained lithium energy source and control

circuitry which constantly monitors VCC for an out–of–

tolerance condition. When such a condition occurs, the

lithium energy source is automatically switched on and

write protection is unconditionally enabled to prevent

garbled data in both the memory and real time clock.

The Phantom Clock provides timekeeping information

including hundredths of seconds, seconds, minutes,

hours, day, date, month, and year information. The date

at the end of the month is automatically adjusted for

months with less than 31 days, including correction for

leap years. The Phantom Clock operates in either

24–hour or 12–hour format with an AM/PM indicator.

ECopyright 1997 by Dallas Semiconductor Corporation.

All Rights Reserved. For important information regarding

patents and other intellectual property rights, please refer to

Dallas Semiconductor data books.

032697 1/12

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