SN54ALS646, SN54ALS648, SN54AS646

SN74ALS646A, SN74ALS648A, SN74AS646, SN74AS648

OCTAL BUS TRANSCEIVERS AND REGISTERS WITH 3-STATE OUTPUTS

SDAS039F – DECEMBER 1983 – REVISED JANUARY 1995

3

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

Function Tables

SN54ALS646, SN54AS646, SN74ALS646A, SN74AS646

INPUTS

DATA I/O

OPERATION OR FUNCTION

OE

DIR

CLKAB

CLKBA

SAB

SBA

A1– A8

B1– B8

OPERATION OR FUNCTION

X

X

↑

X

X

X

Input

Unspecified†

Store A, B unspecified†

X

XX

↑

X

X

Unspecified†

Input

Store B, A unspecified†

H

X

↑

↑

X

X

Input

Input

Store A and B data

H

X

H or L

H or L

X

X

Input disabled

Input disabled

Isolation, hold storage

L

L

X

X

X

L

Output

Input

Real-time B data to A bus

L

L

X

H or L

X

H

Output

Input

Stored B data to A bus

L

H

X

X

L

X

Input

Output

Real-time A data to B bus

L

H

H or L

X

H

X

Input

Output

Stored A data to B bus

† The data output functions can be enabled or disabled by various signals at OE and DIR. Data input functions are always enabled; i.e., data at

the bus terminals is stored on every low-to-high transition of the clock inputs.

SN54ALS648, SN74ALS648A, SN74AS648

INPUTS

DATA I/O

OPERATION OR FUNCTION

OE

DIR

CLKAB

CLKBA

SAB

SBA

A1– A8

B1– B8

OPERATION OR FUNCTION

X

X

↑

X

X

X

Input

Unspecified†

Store A, B unspecified†

X

XX

↑

X

X

Unspecified†

Input

Store B, A unspecified†

H

X

↑

↑

X

X

Input

Input

Store A and B data

H

X

H or L

H or L

X

X

Input disabled

Input disabled

Isolation, hold storage

L

L

X

X

X

L

Output

Input

Real-time B data to A bus

L

L

X

H or L

X

H

Output

Input

Stored B data to A bus

L

H

X

X

L

X

Input

Output

Real-time A data to B bus

L

H

H or L

X

H

X

Input

Output

Stored A data to B bus

† The data output functions can be enabled or disabled by various signals at OE and DIR. Data input functions are always enabled; i.e., data at

the bus terminals is stored on every low-to-high transition of the clock inputs.