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BQ3287A Datasheet(PDF) 1 Page - Texas Instruments |
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BQ3287A Datasheet(HTML) 1 Page - Texas Instruments |
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1 / 9 page  Features ® Direct clock/calendar replace- ment for IBM ® AT-compatible computers and other applications ® Functionally compatible with the DS1287/DS1287A and MC146818A ® 114 bytes of general nonvolatile storage ® Integral lithium cell and crystal ® 160 ns cycle time allows fast bus operation ® Selectable Intel or Motorola bus timing ® 14 bytes for clock/calendar and control ® BCD or binary format for clock and calendar data ® Time of day in seconds, minutes, and hours - 12- or 24-hour format - Optional daylight saving adjustment ® Calendar in day of the week, day of the month, months, and years with automatic leap-year adjust- ment ® Programmable square wave out- put ® Three individually maskable in- terrupt event flags: - Periodic rates from 122 µsto 500 ms - Time-of-day alarm once per second to once per day - End-of-clock update cycle ® Better than one minute per month clock accuracy General Description The CMOS bq3287/bq3287A is a low-power microprocessor periph- eral providing a time-of-day clock and 100-year calendar with alarm features and battery operation. Other features include three maskable interrupt sources, square- wave output, and 114 bytes of gen- eral non volatile storage. The bq3287A version is identical to the bq3287, with the addition of the RAM clear input. The bq3287 is a fully compatible real-time c loc k for IBM A T- compatible computers and other ap- plications. The bq3287 write- protects the clock, calendar, and storage registers during power fail- ure. The integral backup energy source then maintains data and op- erates the clock and calendar. As shipped from Benchmarq, the real time clock is turned off to maxi- mize battery capacity for in-system operation. The bq3287 is functionally equiva- lent to the bq3285, except that the battery (16, 20) and crystal (2, 3) pins are not accessible. These pins are connected internally to a coin cell and quartz crystal. The coin cell is sized to provide 10 years of data retention and clock operation in the absence of power. For a complete de- scription of features, operating con- ditions, electrical characteristics, bus timing, and pin descriptions, see the bq3285 data sheet. 1 Pin Names AD0–AD7 Multiplexed address/data input/output MOT Bus type select input CS Chip select input AS Address strobe input DS Data strobe input R/W Read/write input INT Interrupt request output 1 PN328701.eps 24-Pin DIP Module 2 3 4 5 6 7 8 24 23 22 21 20 19 18 17 9 10 16 15 11 12 14 13 VCC SQW NC NC INT RST DS NC R/W AS CS MOT NC NC AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7 VSS NC/RCL Sept. 1996 D RST Reset input SQW Square wave output NC No connect RCL RAM clear input (bq3287A only) VCC +5V supply VSS Ground Pin Connections bq3287/bq3287A Real-Time Clock (RTC) Module Not Recommended For New Designs |
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