Revised March 2000
Octal 3-STATE Bus Transceiver and Register
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 regis-
ter. 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.
s Switching specifications at 50 pF
s Switching specifications guaranteed over full tempera-
ture and VCC range
s Advanced oxide-isolated, ion-implanted Schottky TTL
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
Order Number Package Number Package Description
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-100, 0.300 Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
© 2000 Fairchild Semiconductor Corporation DS009174