© 2001 Fairchild Semiconductor Corporation

DS009174

www.fairchildsemi.com

October 1986

Revised June 2001

DM74ALS652

Octal 3-STATE Bus Transceiver and Register

General Description

This device incorporates an octal transceiver and an octal

D-type register configured to enable transmission of data

from bus to bus or internal register to bus.

This bus transceiver features totem-pole 3-STATE outputs

designed specifically for driving highly-capacitive or rela-

tively low-impedance loads. The high-impedance state and

increased high level logic drive provide this device with the

capability of being connected directly to and driving the bus

lines in a bus organized system without need for interface

or pull-up components. They are particularly attractive for

implementing buffer registers, I/O ports, bidirectional bus

drivers, and working registers.

The registers in the DM74ALS652 are edge-triggered

D-type flip-flops. On the positive transition of the clock

(CAB or CBA), the input data is stored into the appropriate

register. The CAB input controls the transfer of data into

the A register and the CBA input controls the B register.

The SAB and SBA control pins are provided to select

whether real-time data or stored data is transferred. A LOW

input level selects real-time data and a HIGH level selects

stored data. The select controls have a “make before

break” configuration to eliminate a glitch which would nor-

mally occur in a typical multiplexer during the transition

between stored and real-time data.

The enable (GAB and GBA) control pins provide four

modes of operation: real-time data transfer from bus A to

B, real-time data transfer from bus B to A, real-time bus A

and/or B data transfer to internal storage, or internal stored

data transfer to bus A and/or B.

Features

s Switching specifications at 50 pF

s Switching specifications guaranteed over full tempera-

s Advanced oxide-isolated, ion-implanted Schottky TTL

process

s 3-STATE buffer-type outputs drive bus lines directly

s Independent registers and enables for A and B buses

s Multiplexed real-time and stored data

Ordering Code:

Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.

Connection Diagram

Order Number

Package Number

Package Description

DM74ALS652WM

M24B

24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide

DM74ALS652NT

N24C

24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide