Document
DS14285/DS14287 Real-Time Clock with NV RAM Control Control
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FEATURES
Direct Replacement for IBM AT Computer Clock/Calendar Functionally Compatible with the DS1285/DS1287 Available as Chip (DS14285, DS14285S, or DS14285Q) or Stand-Alone Module with Embedded Lithium Battery and Crystal (DS14287) Automatic Backup Supply and Write www.DataSheet4U.com Protection to Make External SRAM Nonvolatile Counts Seconds, Minutes, Hours, Days, Day of the Week, Date, Month, and Year with Leap Year Compensation Valid Up to 2100 Binary or BCD Representation of Time, Calendar, and Alarm 12- or 24-Hour Clock with AM and PM in 12-Hour Mode Daylight Saving Time Option Multiplex Bus for Pin Efficiency Interfaced with Software as 128 RAM Locations 14 Bytes of Clock and Control Registers 114 Bytes of General Purpose RAM Programmable Square-Wave Output Signal Bus-Compatible Interrupt Signals (IRQ) Three Interrupts are Separately SoftwareMaskable and Testable Time-of-Day Alarm Once/Second to Once/Day Periodic Rates from 122µs to 500ms End of Clock Update Cycle Optional Industrial Temperature Version Available: DS14285 DIP, SO, and PLCC
PIN CONFIGURATIONS
TOP VIEW VCCO X1 X2 AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7 GND 1 2 3 4 5 6 7 8 9 10 11 12 24 23 22 21 20 19 18 17 16 15 14 13 VCC SQW CEO CEI VBAT IRQ RESET DS GND R/W AS CS
DIP/SO
X2 X1 MOT VCCO VCC SQW CE0 AD0 AD1 AD2 AD3 AD4 AD5 N.C.
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 3 2 1 28 27 26 25 24
DS14285
DS14285
23 22 21 20 19
CEI VBAT IRQ RESET DS GND R/W
AD6 N.C. AD7 GND CS AS N.C.
PLCC
VCCO N.C. N.C. AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7 GND
24 1 23 2 3 DS14287 22 21 4 20 5 19 6 18 7 17 8 16 9 15 10 14 11 13 12
VCC SQW CEO CEI N.C. IRQ RESET DS N.C. R/W AS CS
Encapsulated Package
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REV: 112105
DS14285/DS14287
ORDERING INFORMATION
PART DS14285 DS14285+ DS14285N DS14285N+ DS14285Q DS14285Q+ DS14285QN DS14285QN+ DS14285S DS14285S+ DS14285SN DS14285SN+ DS14285SN/T&R www.DataSheet4U.com DS14285SN+T&R DS14285S/T&R DS14285S+T&R DS14287 DS14287+ TEMP RANGE 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C VOLTAGE (V) 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 PIN-PACKAGE 24 DIP (0.600″) 24 DIP (0.600″) 24 DIP (0.600″) 24 DIP (0.600″) 28 PLCC 28 PLCC 28 PLCC 28 PLCC 24 SO (0.300″) 24 SO (0.300″) 24 SO (0.300″) 24 SO (0.300″) 24 SO (0.300″)/Tape & Reel 24 SO (0.300″)/Tape & Reel 24 SO (0.300″)/Tape & Reel 24 SO (0.300″)/Tape & Reel 24 EDIP (0.740″) 24 EDIP (0.740″) TOP MARK* DS14285 DS14285 DS14285N DS14285N DS14285Q DS14285Q DS14285QN DS14285QN DS14285S DS14285S DS14285SN DS14285SN DS14285SN DS14285SN DS14285S DS14285S DS14287 DS14287
+ Denotes a lead-free/RoHS-compliant device. * A “+” anywhere on the top mark denotes a lead-free/RoHS-compliant device. An “N” denotes an industrial temperature grade device.
PIN DESCRIPTION
AD0-AD7 NC MOT
CS
AS R/ W DS
RESET
IRQ
SQW VCC GND VCCO
CEI CEO
X1, X2 VBAT
- Multiplexed Address/Data Bus - No Connection - Bus Type Select (DS14285Q only) - Chip Select - Address Strobe - Read/Write Input - Data Strobe - Reset Input - Interrupt Request Output - Square Wave Output - +5V Supply - Ground - RAM Power Supply Output - RAM Chip Enable In - RAM Chip Enable Out - 32.768 kHz Crystal Connections - +3V Battery Input
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DS14285/DS14287
DETAILED 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 VBAT 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 (CL) 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 VCC output sourced from its internal battery.
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For the DS14287 the internal lithium cell is electrically isolated from the clock and memory when shipped from the factory. This isolation is removed a.