Philips Semiconductors

Product specification

74ALS646/74ALS646-1

74ALS648/74ALS648-1

Transceiver/register

1991 Feb 08

4

BUS MANAGEMENT FUNCTIONS

The following examples demonstrate the four fundamental

bus-management functions that can be performed with the

74ALS646/646-1 and 74ALS648/648-1.

The select pins determine whether data is stored or transferred

through the device in real time.

The DIR determines which bus will receive data when the OE pin is

Low.

REAL TIME BUS TRANSFER

BUS B TO BUS A

REAL TIME BUS TRANSFER

BUS A TO BUS B

STORAGE FROM

A, B, OR A AND B

TRANSFER STORED DATA

TO A AND/OR B

OE DIR CPAB CPBA SAB SBA

LL

X

X

X

L

BUS A

BUS A

BUS A

BUS A

BUS B

BUS B

BUS B

BUS B

OE DIR CPAB CPBA SAB SBA

LH

X

X

L

X

OE DIR CPAB CPBA SAB SBA

XX

↑

XX

X

XX

X

↑

XX

HX

↑↑

XX

OE DIR CPAB CPBA SAB SBA

L

L

X

H or L

X

H

L

H

H or L

X

H

X

SF00392