MM54HCT640 MM74HCT640 Inverting Octal TRI-STATE Transceiver
MM54HCT643 MM74HCT643 True-Inverting Octal TRI-STATE Transceiver
February 1988
MM54HCT640 MM74HCT640
Inverting Octal TRI-STATE Transceiver
MM54HCT643 MM74HCT643
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
to static discharge by diodes to V
CC
and ground
Both the MM54HCT640 MM74HCT640 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 MM54HCT643 MM74HCT643 transfers inverted
data from the A bus to the B bus and non-inverted data from
the B bus to the A bus
MM54HCT MM74HCT 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
Y
Y
Y
TTL input compatible
Octal TRI-STATE outputs for
mP
bus applications
6 mA typical
High speed 16 ns typical propagation delay
Low power 80
mA
maximum (74HCT)
Connection Diagram
Dual-In-Line Packages
TL F 5370 鈥?1
TL F 5370 鈥?2
Top View
Order Number MM54HCT640 or MM74HCT640
Top View
Order Number MM54HCT643 or MM74HCT643
Truth Table
Control
Inputs
G
L
L
H
DIR
L
H
X
640
B data to A bus
A data to B bus
Isolation
Operation
643
B data to A bus
A data to B bus
Isolation
H
e
high level L
e
low level X
e
irrelevant
TRI-STATE is a registered trademark of National Semiconductor Corp
C
1995 National Semiconductor Corporation
TL F 5370
RRD-B30M105 Printed in U S A
1
2
3
4
