TLF5370

February 1988

MM54HCT640MM74HCT640

Inverting Octal TRI-STATE

Transceiver

MM54HCT643MM74HCT643

True-Inverting Octal TRI-STATE Transceiver

General Description

These TRI-STATE bi-directional transceivers utilize advanced

silicon-gate CMOS technology and are intended for two-way

asynchronous communication between data buses They

have high drive current outputs which enable high speed

operation even when driving large bus capacitances These

circuits possess the low power consumption of CMOS cir-

cuitry yet have speeds comparable to low power Schottky

TTL circuits

All devices are TTL input compatible and can drive up to 15

LS-TTL loads and all inputs are protected from damage due

Both the MM54HCT640MM74HCT640 and the

MM54HCT643 MM74HCT643 have one active low enable

input (G) and a direction control (DIR) When the DIR input

is high data flows from the A inputs to the B outputs When

DIR is low data flows from B to A The MM54HCT640

MM74HCT640 transfers inverted data from one bus to the

other The MM54HCT643MM74HCT643 transfers inverted

data from the A bus to the B bus and non-inverted data from

the B bus to the A bus

MM54HCTMM74HCT devices are intended to interface be-

tween TTL and NMOS components and standard CMOS

devices These parts are also plug-in replacements for LS-

TTL devices and can be used to reduce power consumption

in existing designs

Features

Y

TTL input compatible

Y

Octal TRI-STATE outputs for mP bus applications

6 mA typical

Y

High speed 16 ns typical propagation delay

Y

Low power 80 mA maximum (74HCT)

Connection Diagram

Dual-In-Line Packages

TLF5370 – 1

Top View

Order Number MM54HCT640 or MM74HCT640

TLF5370 – 2

Top View

Order Number MM54HCT643 or MM74HCT643

Truth Table

Control

Operation

Inputs

G

DIR

640

643

LL

B data to A bus

B data to A bus

LH

A data to B bus

A data to B bus

H

X

Isolation

Isolation

TRI-STATE

is a registered trademark of National Semiconductor Corp

C1995 National Semiconductor Corporation

RRD-B30M105Printed in U S A