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DS14285/DS14287

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ORDERING INFORMATION

DS14285 RTC Chip; 24-pin DIP

DS14285N RTC Chip; 24-pin DIP; Industrial Temp Range

DS14285S RTC Chip; 24-pin SOIC

DS14285SN RTC Chip; 24-pin SOIC; Industrial Temp Range

DS14285Q RTC Chip; 28-pin PLCC

DS14285QN RTC Chip; 28-pin PLCC; Industrial Temp Range

DS14287 RTC Module; 24-pin DIP

PIN DESCRIPTION

AD0-AD7 - Multiplexed Address/Data Bus

NC - No Connection

MOT - Bus Type Select (DS14285Q only)

CS - Chip Select

AS - Address Strobe

R/ W - Read/Write Input

DS - Data Strobe

RESET - Reset Input

IRQ - Interrupt Request Output

SQW - Square Wave Output

- +5V Supply

GND - Ground

CCO

- RAM Power Supply Output

CEI - RAM Chip Enable In

CEO - RAM Chip Enable Out

X1, X2 - 32.768 kHz Crystal Connections

BAT

- +3V Battery Input

DESCRIPTION

The DS14285/DS14287 Real Time Clock with NVRAM Control provides the industry standard DS1287

clock function with the additional feature of providing nonvolatile control for an external SRAM.

Functions include a nonvolatile time-of-day clock, alarm, 100-year calendar, programmable interrupt,

square wave generator, and 114 bytes of nonvolatile static RAM. For the DS14287 a lithium energy

source, quartz crystal, and write protection circuitry are contained within a 24-pin dual in-line package.

The DS14285 requires an external quartz crystal connected to the X1 and X2 pins as well as an external

energy source connected to the V

BAT

pin. A standard 32.768 kHz quartz crystal can be directly connected

to the DS14285 via pins 1 and 2 (X1, X2). The crystal selected for use should have a specified load

capacitance (C

) of 6 pF. For more information on crystal selection and crystal layout considerations,

please consult Application Note 58, “Crystal Considerations with Dallas Real-time Clocks.”

The DS14285/DS14287 uses its backup energy source and battery-backup controller to make a standard

CMOS static RAM nonvolatile during power-fail conditions. During power fail, the DS14285/DS14287

automatically write-protects the external SRAM and provides a V

output sourced from its internal

battery.

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