M74HC651

M74HC652

October 1993

HC652 OCTAL BUS TRANSCEIVER/REGISTER (3-STATE)

HC651 OCTAL BUS TRANSCEIVER/REGISTER (3-STATE, INV.)

B1R

(Plastic Package)

ORDER CODES :

M74HCXXXM1R

M74HCXXXB1R

M1R

(Micro Package)

INPUT AND OUTPUT EQUIVALENT CIRCUIT

PIN CONNECTIONS (top view)

.

HIGH SPEED

.

LOW POWER DISSIPATION

.

HIGH NOISE IMMUNITY

.

OUTPUT DRIVE CAPABILITY

15 LSTTL LOADS

.

SYMMETRICAL OUTPUT IMPEDANCE

.

BALANCED PROPAGATION DELAYS

.

WIDE OPERATING VOLTAGE RANGE

.

PIN AND FUNCTION COMPATIBLE

WITH 54/74LS651/652

DESCRIPTION

M74HC651/652 are high speed CMOS OCTAL

BUS TRANSCEIVERS AND REGISTERS (3-

STATE), fabricated in silicon gate C

ogy. They have the same high speed performance

of LSTTL combined with true CMOS low power con-

sumption. These devices consist of bus transceiver

circuits, D-type flip-flops, and control circuitry ar-

ranged for multiplexed transmission of data directly

from the input bus or from the internal storage reg-

isters. Enable GAB and GBA are provided to control

the transceiver functions.

Select AB and Select BA control pins are provided

to select whether real-time or stored data is trans-

fered. A low input level selects real-time data, and

a high selects stored data.

Data on the A or B bus, or both, can be stored in the

internal D flip-flops by low-to-high transitions at the

appropriate clock pins (CLOCK AB or CLOCK BA)

regardless of the select or enable control pins. When

select AB and select BA are in the real-time transfer

mode, it is also possible to store data without using

the internal D-type flip-flops by simultaneously en-

abling GAB and GBA. In this configuration each out-

put reinforces its input. Thus, when all other data

sources to the two sets of bus lines are at high im-

pedance, each set of bus lines will remain at its last

state. All inputs are equipped with protection circuits

against static discharge and transient excess volt-

age.

GAB, GAB, CAB,

A, B

SAB, SBA, CBA

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