DM74AS651 • DM74AS652 Octal Bus Transceiver and Register
October 1986
Revised July 2003
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 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-
ture and V
CC
range
s
Advanced oxide-isolated, ion-implanted Schottky TTL
process
s
3-STATE buffer-type outputs drive bus lines directly
s
Guaranteed performance over industrial temperature
range (
−
40
°
C to
+
85
°
C) in 64-grade products
Ordering Code:
Order Number
DM74AS651WM
DM74AS651NT
DM74AS652WM
DM74AS652NT
Package Number
M24B
N24C
M24B
N24C
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-001, 0.300" Wide
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide
24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
© 2003 Fairchild Semiconductor Corporation
DS006325
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DM74AS651 • DM74AS652
Connection Diagram
Function Table
INPUTS
GAB GBA CAB
CBA
SAB
SBA
DATA I/O (Note 1)
A1
THRU
A8
L
L
L
L
H
H
H
X
H
H
H
L
L
H
H
L
H
H
H or L H or L
X
X
X
X
L
H
H
X
X
(Note
2)
X
X
X
X
L
Output
X
X
H or L
H or L
X
X
H
X
Input
X
H
X
X
Output
Input
Input
Output
Output
Input
B1
THRU
B8
Input
Isolation
Store A and B Data
Real Time B Data to A
Bus
Stored B Data to A Bus
Real Time A Data to B
Bus
Stored A Data to B Bus
Stored A Data to B Bus
Isolation
Store A and B Data
Real Time B Data to A
Bus
Stored B Data to A Bus
Real Time A Data to B
Bus
Stored A Data to B Bus
Stored A Data to B Bus
Store A, Hold B
Store A in both registers
OPERATION OR FUNCTION
DM74AS651
DM74AS652
↑
X
↑
X
Input
H or L H or L
& Stored B Data to A Bus & Stored B Data to A Bus
↑
↑
H or L
Unspecified Store A, Hold B
(Note 1)
Output
Store A in both registers
↑
L
L
X
L
H or L
↑
↑
X
X
(Note
2)
Unspecified
(Note 1)
Output
Input
Input
Hold A, Store B
Store B in both registers
Hold A, Store B
Store B in both registers
↑
H
=
HIGH Level
L
=
LOW Level
X
=
Irrelevant
↑ =
LOW-to-HIGH Transition
Note 1:
The data output functions may be enabled or disabled by various signals at the GAB and GBA inputs. Data input functions are always enabled,
i.e., data at the bus pins will be stored on every LOW-to-HIGH transition on the clock inputs.
Note 2:
If the select control is LOW, the clocks can occur simultaneously. If the select control is HIGH, the clocks must be staggered in order to load both
registers.
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DM74AS651 • DM74AS652
Absolute Maximum Ratings
(Note 3)
Supply Voltage
Input Voltage
Control Inputs
I/O Ports
Operating Free Air Temperature Range
Storage Temperature Range
Typical
θ
JA
N Package
M Package
41.1
°
C/W
81.5
°
C/W
7V
5.5V
0
°
C to
+
70
°
C
7V
−
65
°
C to
+
150
°
C
Note 3:
The “Absolute Maximum Ratings” are those values beyond which
the safety of the device cannot be guaranteed. The device should not be
operated at these limits. The parametric values defined in the Electrical
Characteristics tables are not guaranteed at the absolute maximum ratings.
The “Recommended Operating Conditions” table will define the conditions
for actual device operation.
Recommended Operating Conditions
Symbol
V
CC
V
IH
V
IL
I
OH
I
OL
f
CLK
t
WCLK
t
SU
t
H
T
A
Supply Voltage
HIGH Level Input Voltage
LOW Level Input Voltage
HIGH Level Output Current
LOW Level Output Current
Clock Frequency
Width of Enable Pulse
Data Setup Time
Data Hold Time
Operating Free Air Temperature
HIGH
LOW
0
5
6
6
0
0
70
Parameter
Min
4.5
2
0.8
Nom
5
Max
5.5
Units
V
V
V
mA
mA
MHz
ns
ns
ns
−
15
48
90
°
C
Electrical Characteristics
over recommended operating free air temperature range. All typical values are measured at V
CC
=
5V, T
A
=
25°C.
Symbol
V
IK
V
OH
Parameter
Input Clamp Voltage
HIGH Level
Output Voltage
V
CC
=
4.5V to 5.5V
V
OL
I
I
I
IH
I
IL
I
O
I
CC
LOW Level Output Voltage
Input Current at
Max Input Voltage
HIGH Level
Input Current
LOW Level
Input Current
Output Drive Current
Supply Current
V
CC
=
5.5V,
V
IH
=
2.7V
V
CC
=
5.5V,
V
IL
=
0.4V
V
CC
=
5.5V, V
O
=
2.25V
V
CC
=
5.5V
DM74AS651
Outputs HIGH
Outputs LOW
Outputs Disabled
Outputs HIGH
DM74AS652
Outputs LOW
Outputs Disabled
V
CC
=
4.5V, I
OL
=
Max
V
CC
=
5.5V
V
I
=
7V
V
I
=
5.5V
Control Inputs
A or B Ports
Control Inputs
A or B Ports
Control Inputs
A or B Ports
−30
110
120
130
120
130
130
V
CC
=
4.5V
Conditions
V
CC
=
4.5V, I
I
= −18
mA
I
OH
=
Max
I
OH
= −3
mA
I
OH
= −2
mA
2
2.4
V
CC
−
2
0.35
0.5
0.1
0.1
20
70
−0.5
−0.75
−112
185
195
195
195
211
211
mA
V
mA
µA
mA
mA
3.2
V
Min
Typ
Max
−1.2
Units
V
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