These octal bus transceivers are designed for asynchronous two-way communication between data buses. The
control-function implementation allows for maximum flexibility in timing.
These devices allow data transmission from the A bus to the B bus or from the B bus to the A bus, depending
upon the logic levels at the output-enable (OEAB and OEBA
) inputs.
The output-enable inputs disable the device so that the buses are effectively isolated. The dual-enable
configuration gives the transceivers the capability to store data by simultaneously enabling OEAB and OEBA
Each output reinforces its input in this transceiver configuration. When both OEAB and OEBA
are enabled and
all other data sources to the two sets of bus lines are in the high-impedance state, both sets of bus lines (16 total)
remain at their last states. The 8-bit codes appearing on the two sets of buses are identical for the
SN74ALS621A, SN74ALS623A, and SN74AS623 or complementary for the SN74ALS620A.
.
The -1 versions of the SN74ALS620A and SN74ALS621A are identical to the standard versions, except that
the recommended maximum I
is increased to 48 mA in the -1 versions.
OL
The SN74ALS620A, SN74ALS621A, SN74ALS623A, and SN74AS623 are characterized for operation from
0°C to 70°C.
FUNCTION TABLE
INPUTS
OEBA
OEABSN74ALS620A
LLB data to A busB data to A bus
HHA data to B busA data to B bus
HLIsolationIsolation
LH
B data to A bus,
A
data to B bus
OPERATION
SN74ALS621A
SN74ALS623A
SN74AS623
B data to A bus,
A data to B bus
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Copyright 1995, Texas Instruments Incorporated
1
SN74ALS620A, SN74ALS621A, SN74ALS623A, SN74AS623
OCTAL BUS TRANSCEIVERS
SDAS226A – DECEMBER 1982 – REVISED JANUAR Y 1995
logic symbols
†
SN74ALS620A
OEBA
OEAB
A1
A2
A3
A4
A5
A6
A7
A8
19
1
2
3
4
5
6
7
8
9
EN1
EN2
1
18
B1
2
17
16
15
14
13
12
11
B2
B3
B4
B5
B6
B7
B8
SN74ALS621A
A1
A2
A3
A4
A5
A6
A7
A8
19
1
2
3
4
5
6
7
8
9
OEBA
OEAB
†
These symbols are in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
EN1
EN2
1
OEBA
OEAB
18
B1
2
17
16
15
14
13
12
11
B2
B3
B4
B5
B6
B7
B8
A1
A2
A3
A4
A5
A6
A7
A8
19
1
2
3
4
5
6
7
8
9
SN74ALS623A, SN74AS623
EN1
EN2
1
2
18
17
16
15
14
13
12
11
B1
B2
B3
B4
B5
B6
B7
B8
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
logic diagrams (positive logic)
SN74ALS620ASN74ALS621A
OEBA
19
SN74ALS620A, SN74ALS621A, SN74ALS623A, SN74AS623
OCTAL BUS TRANSCEIVERS
SDAS226A – DECEMBER 1982 – REVISED JANUARY 1995
OEBA
19
OEAB
A1
1
2
To Seven Other Transceivers
OEBA
OEAB
A1
18
B1
SN74ALS623A, SN74AS623
19
1
OEAB
A1
1
2
To Seven Other Transceivers
182
B1
18
B1
To Seven Other Transceivers
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions.
PLZ
FROM
(INPUT)
TO
(OUTPUT)
R1 = 500 Ω
R2 = 500 Ω,
TA = MIN to MAX
,
SN74AS623
MINMAX
19
18
19
18.5
211
210
17.5
111.5
211.5
211
17
19
UNIT
†
8
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
From Output
Under Test
(see Note A)
SN74ALS620A, SN74ALS621A, SN74ALS623A, SN74AS623
OCTAL BUS TRANSCEIVERS
SDAS226A – DECEMBER 1982 – REVISED JANUARY 1995
PARAMETER MEASUREMENT INFORMATION
SERIES 54ALS/74ALS AND 54AS/74AS DEVICES
7 V
V
CC
S1
R
L
Test
Point
C
L
R
L
From Output
Under Test
C
(see Note A)
Test
Point
L
From Output
Under Test
(see Note A)
R1
C
L
RL = R1 = R2
Test
Point
R2
LOAD CIRCUIT FOR
BI-STATE
TOTEM-POLE OUTPUTS
Timing
Input
t
su
Data
Input
VOLTAGE WAVEFORMS
SETUP AND HOLD TIMES
Output
Control
(low-level
enabling)
Waveform 1
S1 Closed
(see Note B)
Waveform 2
S1 Open
(see Note B)
t
PZL
t
PZH
ENABLE AND DISABLE TIMES, 3-STATE OUTPUTS
VOLTAGE WAVEFORMS
1.3 V
t
PHZ
1.3 V
1.3 V
t
h
1.3 V1.3 V
1.3 V1.3 V
FOR OPEN-COLLECTOR OUTPUTS
t
PLZ
LOAD CIRCUIT
3.5 V
0.3 V
3.5 V
0.3 V
3.5 V
0.3 V
[
3.5 V
V
OL
0.3 V
V
OH
0.3 V
[
0 V
High-Level
Pulse
Low-Level
Pulse
In-Phase
Out-of-Phase
(see Note C)
FOR 3-STATE OUTPUTS
1.3 V1.3 V
1.3 V1.3 V
VOLTAGE WAVEFORMS
PULSE DURATIONS
Input
Output
Output
t
PLH
t
PHL
1.3 V1.3 V
VOLTAGE WAVEFORMS
PROPAGATION DELAY TIMES
LOAD CIRCUIT
t
w
1.3 V1.3 V
1.3 V1.3 V
t
PHL
t
PLH
3.5 V
0.3 V
3.5 V
0.3 V
3.5 V
0.3 V
V
V
V
V
OH
OL
OH
OL
NOTES: A. CL includes probe and jig capacitance.
B. Waveform 1 is for an output with internal conditions such that the output is low except when disabled by the output control.
Waveform 2 is for an output with internal conditions such that the output is high except when disabled by the output control.
C. When measuring propagation delay items of 3-state outputs, switch S1 is open.
D. All input pulses have the following characteristics: PRR ≤ 1 MHz, tr = tf = 2 ns, duty cycle = 50%.
E. The outputs are measured one at a time with one transition per measurement.
Figure 1. Load Circuits and Voltage Waveforms
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
9
IMPORTANT NOTICE
T exas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue
any product or service without notice, and advise customers to obtain the latest version of relevant information
to verify, before placing orders, that information being relied on is current and complete. All products are sold
subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those
pertaining to warranty, patent infringement, and limitation of liability.
TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty . Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.
CERT AIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF
DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL
APPLICATIONS”). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, AUTHORIZED, OR
WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT DEVICES OR SYSTEMS OR OTHER
CRITICAL APPLICA TIONS. INCLUSION OF TI PRODUCTS IN SUCH APPLICATIONS IS UNDERST OOD TO
BE FULLY AT THE CUSTOMER’S RISK.
In order to minimize risks associated with the customer’s applications, adequate design and operating
safeguards must be provided by the customer to minimize inherent or procedural hazards.
TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent
that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other
intellectual property right of TI covering or relating to any combination, machine, or process in which such
semiconductor products or services might be or are used. TI’s publication of information regarding any third
party’s products or services does not constitute TI’s approval, warranty or endorsement thereof.
Copyright 1998, Texas Instruments Incorporated
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