TLF6681

May 1991

MM58174A

Microprocessor-Compatible Real-Time Clock

General Description

The MM58174A is a low-threshold metal-gate CMOS circuit

that functions as a real-time clock and calendar in bus-ori-

ented microprocessor systems The device includes an in-

terrupt timer which may be programmed to one of three

times Timekeeping is maintained down to 22V to allow low

power standby battery operation The timebase is generat-

ed from a 32768 Hz crystal-controlled oscillator

Features

Y

Microprocessor compatible

Y

Tenths of seconds seconds tens of seconds minutes

tens of minutes

day of week

days

tens of days

months tens of months independent registers

Y

Automatic leap year calculation

Y

Internal pull-ups to safeguard data

Y

Protection for read during data changing

Y

Independent interrupt system with open drain output

Y

TTL compatible

Y

Low power standby operation (22V 10 mA)

Y

Low cost internally biased oscillator

Y

Low cost 16-pin dual-in-line package

Y

Available for commercial and military temperature

ranges

Applications

Y

Point-of-sale terminals

Y

Word processors

Y

Teller terminals

Y

Event recorders

Y

Microprocessor-controlled instrumentation

Y

Microprocessor time clock

Y

TVVCR reprogramming

Y

Intelligent telephone

Block Diagram

TLF6681 – 1

FIGURE 1

TRI-STATE

is a registered trademark of National Semiconductor Corporation

C1995 National Semiconductor Corporation

RRD-B30M105Printed in U S A