© 2003 Fairchild Semiconductor Corporation DS006325 www.fairchildsemi.com
October 1986
Revised July 2003
DM74AS651 • DM74AS652 Octal Bus Transceiver and Register
DM74AS651 • DM74AS652
Octal Bus Transceiver and Register
General Description
These devices incorporate an octal transceiver and an
octal D-type register configured to enable transmission of
data from bus to bus or internal register to bus. The
DM74AS651 offers 64-Industrial grade product guarantee-
ing performance from
−40°C to +85°C.
These bus transceivers feature totem-pole 3-STATE out-
puts designed specifically for driving highly-capacitive or
relatively low-impedance loads. The high-impedance state
and increased high-logic-level drive provide these devices
with the capability of being connected directly to and driv-
ing 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, bidi-
rectional bus drivers, and working registers.
The registers in the DM74AS651 and DM74AS652 are
edge-triggered D-type flip-flops. On the positive transition
of the clock (CAB or CBA), the input data is stored.
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 G
BA) 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
■ Switching specifications at 50 pF
■ Switching specifications guaranteed over full tempera-
ture and V
CC
range
■ Advanced oxide-isolated, ion-implanted Schottky TTL
process
■ 3-STATE buffer-type outputs drive bus lines directly
■ Guaranteed performance over industrial temperature
range (
−40°C to +85°C) in 64-grade products
Ordering Code:
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Order Number Package Number Package Description
DM74AS651WM M24B 24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide
DM74AS651NT N24C 24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
DM74AS652WM M24B 24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide
DM74AS652NT N24C 24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
