BQ3285P

实时时钟 Real-Time Clock

General Description

The CMOS bq3285 is a low-power microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and battery operation. Other features in clude three maskable interrupt sources, square wave output, and 114 bytes of general nonvolatile storage.

The bq3285 write-protects the clock, calendar, and storage registers during power failure. A backup battery then maintains data and operates the clock and calendar.

The bq3285 is a fully compatible real-time clock for IBM AT compatible computers and other applications. The only external components are a 32.768kHz crystal and a backup battery

Features

➤ Direct clock/calendar replacement for IBM® AT-compatible computers and other applications

➤ Functionally compatible with the DS1285

   - Closely matches MC146818A pin configuration

➤ 114 bytes of general nonvolatile storage

➤ 160ns cycle time allows fast bus operation

➤ Selectable Intel or Motorola bus timing

➤ Less than 0.5µA load under battery operation

➤ 14 bytes for clock/calendar and control

➤ BCD or binary format for clock and calendar data

➤ Calendar in day of the week, day of the month, months, and years, with automatic leap-year adjustment

➤ Time of day in seconds, minutes, and hours

   - 12- or 24-hour format

   - Optional daylight saving adjustment

➤ Programmable square wave output

➤ Three individually maskable in terrupt event flags:

   - Periodic rates from 122µs to 500ms

   - Time-of-day alarm once per second to once per day

   - End-of-clock update cycle

➤ 24-pin plastic DIP or SOIC