Features

Direct clock/calendar replacement

for IBM® AT-compatible

computers and other applications

Functionally compatible with the

DS1285

- Closely matches MC146818A

pin configuration

2.7–3.6V operation (bq3285L);

4.5–5.5V operation (bq3285E)

242 bytes of general nonvolatile

storage

32.768kHz output for power management

System wake-up capability—

alarm interrupt output active in

battery-backup mode

Less than 0.5mA load under battery

operation

Selectable Intel or Motorola bus

timing

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 interrupt

event flags:

- Periodic rates from 122ms to

500ms

- Time-of-day alarm once per

second to once per day

- End-of-clock update cycle

24-pin plastic DIP, SOIC, or

SSOP

General Description

The CMOS bq3285E/L is a lowpower

microprocessor peripheral

providing a time-of-day clock and

100-year calendar with alarm features

and battery operation. The

bq3285L supports 3V systems.

Other bq3285E/L features include

three maskable interrupt sources,

square-wave output, and 242 bytes

of general nonvolatile storage.

A 32.768kHz output is available for

sustaining power-management activities.

Wake-up capability is provided

by an alarm interrupt, which

is active in battery-backup mode.

The bq3285E/L write-protects the

clock, calendar, and storage registers

during power failure. A backup

battery then maintains data and operates

the clock and calendar.

The bq3285E/L 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.