Semiconductor Components Industries, LLC, 2001
October, 2001 Rev. 7
1
Publication Order Number:
SN74LS194A/D
SN74LS194A
4-Bit Bidirectional
Universal Shift Register
The SN74LS194A is a High Speed 4-Bit Bidirectional Universal
Shift Register. As a high speed multifunctional sequential building
block, it is useful in a wide variety of applications. It may be used in
serial-serial, shift left, shift right, serial-parallel, parallel-serial, and
parallel-parallel data register transfers. The LS194A is similar in
operation to the LS195A Universal Shift Register, with added features
of shift left without external connections and hold (do nothing) modes
of operation. It utilizes the Schottky diode clamped process to achieve
high speeds and is fully compatible with all ON Semiconductor TTL
families.
Typical Shift Frequency of 36 MHz
Asynchronous Master Reset
Hold (Do Nothing) Mode
Fully Synchronous Serial or Parallel Data Transfers
Input Clamp Diodes Limit High Speed Termination Effects
GUARANTEED OPERATING RANGES
Symbol
Parameter
Min
Typ
Max
Unit
VCC
Supply Voltage
4.75
5.0
5.25
V
TA
Operating Ambient
Temperature Range
0
25
70
C
IOH
Output Current High
0.4
mA
IOL
Output Current Low
8.0
mA
LOW
POWER
SCHOTTKY
SOIC
D SUFFIX
CASE 751B
PLASTIC
N SUFFIX
CASE 648
16
1
16
1
Device
Package
Shipping
ORDERING INFORMATION
SN74LS194AN
16 Pin DIP
2000 Units/Box
SN74LS194AD
SOIC16
38 Units/Rail
SN74LS194ADR2
SOIC16
2500/Tape & Reel
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SN74LS194A
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2
CONNECTION DIAGRAM DIP (TOP VIEW)
Mode Control Inputs
Parallel Data Inputs
Serial (Shift Right) Data Input
Serial (Shift Left) Data Input
Clock (Active HIGH Going Edge) Input
Master Reset (Active LOW) Input
Parallel Outputs
S0, S1
P0 - P3
DSR
DSL
CP
MR
Q0 - Q3
0.5 U.L.
0.5 U.L.
0.5 U.L.
0.5 U.L.
0.5 U.L.
0.5 U.L.
10 U.L.
0.25 U.L.
0.25 U.L.
0.25 U.L.
0.25 U.L.
0.25 U.L.
0.25 U.L.
5 U.L.
NOTES:
a) 1 TTL Unit Load (U.L.) = 40 mA HIGH/1.6 mA LOW.
HIGH
LOW
(Note a)
LOADING
PIN NAMES
14
13
12
11
10
9
1
2
3
4
5
6
7
16
15
8
VCC
MR
Q0
Q1
Q2
Q3
S1
CP
S0
DSR P0
P1
P2
P3
DSL GND
SN74LS194A
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3
LOGIC DIAGRAM
VCC = PIN 16
GND = PIN 8
= PIN NUMBERS
S1
S0
DSR
DSL
CP
MR
Q0
Q1
Q2
Q3
P0
P1
P2
P3
14
1
2
6
7
3
4
5
9
11
12
10
13
15
S
Q0
CP
R
CLEAR
S
Q1
CP
R
CLEAR
S
Q2
CP
R
CLEAR
S
Q3
CP
R
CLEAR
FUNCTIONAL DESCRIPTION
The Logic Diagram and Truth Table indicate the
functional
characteristics of the LS194A 4-Bit Bidirectional
Shift Register. The LS194A is similar in operation to the
ON Semiconductor LS195A Universal Shift Register when
used in serial or parallel data register transfers. Some of the
common features of the two devices are described below:
All data and mode control inputs are edge-triggered,
responding only to the LOW to HIGH transition of the Clock
(CP). The only timing restriction, therefore, is that the mode
control and selected data inputs must be stable one set-up
time prior to the positive transition of the clock pulse.
The register is fully synchronous, with all operations
taking place in less than 15 ns (typical) making the device
especially useful for implementing very high speed CPUs,
or the memory buffer registers.
The four parallel data inputs (P0, P1, P2, P3) are D-type
inputs. When both S0 and S1 are HIGH, the data appearing
on P0, P1, P2, and P3 inputs is transferred to the Q0, Q1, Q2,
and Q3 outputs respectively following the next LOW to
HIGH transition of the clock.
The asynchronous Master Reset (MR), when LOW,
overrides all other input conditions and forces the Q outputs
LOW.
Special logic features of the LS194A design which
increase the range of application are described below:
Two mode control inputs (S0, S1) determine the
synchronous
operation of the device. As shown in the Mode
Selection Table, data can be entered and shifted from left to
right (shift right, Q0 ! Q1, etc.) or right to left (shift left, Q3
! Q2, etc.), or parallel data can be entered loading all four
bits of the register simultaneously. When both S0 and S1,are
LOW, the existing data is retained in a "do nothing" mode
without restricting the HIGH to LOW clock transition.
D-type serial data inputs (DSR, DSL) are provided on both
the first and last stages to allow multistage shift right or shift
left data transfers without interfering with parallel load
operation.
SN74LS194A
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4
MODE SELECT -- TRUTH TABLE
OPERATING MODE
INPUTS
OUTPUTS
OPERATING MODE
MR
S1
S0
DSR
DSL
Pn
Q0
Q1
Q2
Q3
Reset
L
X
X
X
X
X
L
L
L
L
Hold
H
I
I
X
X
X
q0
q1
q2
q3
Shift Left
H
h
I
X
I
X
q1
q2
q3
L
H
h
I
X
h
X
q1
q2
q3
H
Shift Right
H
I
h
I
X
X
L
q0
q1
q2
H
I
h
h
X
X
H
q0
q1
q2
Parallel Load
H
h
h
X
X
Pn
P0
P1
P2
P3
L = LOW Voltage Level
H = HIGH Voltage Level
X = Don't Care
I = LOW voltage level one set-up time prior to the LOW to HIGH clock transition
h = HIGH voltage level one set-up time prior to the LOW to HIGH clock transition
pn (qn) = Lower case letters indicate the state of the referenced input (or output) one set-up time prior to the LOW to HIGH clock transition.
DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE
(unless otherwise specified)
Limits
Symbol
Parameter
Min
Typ
Max
Unit
Test Conditions
VIH
Input HIGH Voltage
2.0
V
Guaranteed Input HIGH Voltage for
All Inputs
VIL
Input LOW Voltage
0.8
V
Guaranteed Input LOW Voltage for
All Inputs
VIK
Input Clamp Diode Voltage
0.65
1.5
V
VCC = MIN, IIN = 18 mA
VOH
Output HIGH Voltage
2.7
3.5
V
VCC = MIN, IOH = MAX, VIN = VIH
or VIL per Truth Table
VOL
Output LOW Voltage
0.25
0.4
V
IOL = 4.0 mA
VCC = VCC MIN,
VIN VIL or VIH
VOL
Output LOW Voltage
0.35
0.5
V
IOL = 8.0 mA
VIN = VIL or VIH
per Truth Table
IIH
Input HIGH Current
20
A
VCC = MAX, VIN = 2.7 V
IIH
Input HIGH Current
0.1
mA
VCC = MAX, VIN = 7.0 V
IIL
Input LOW Current
0.4
mA
VCC = MAX, VIN = 0.4 V
IOS
Short Circuit Current (Note 1)
20
100
mA
VCC = MAX
ICC
Power Supply Current
23
mA
VCC = MAX
Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.
AC CHARACTERISTICS
(TA = 25
C)
Limits
Symbol
Parameter
Min
Typ
Max
Unit
Test Conditions
fMAX
Maximum Clock Frequency
25
36
MHz
tPLH
tPHL
Propagation Delay,
Clock to Output
14
17
22
26
ns
VCC = 5.0 V
CL = 15 pF
tPHL
Propagation Delay,
MR to Output
19
30
ns
CL = 15 pF
SN74LS194A
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5
AC SETUP REQUIREMENTS
(TA = 25
C)
Limits
Symbol
Parameter
Min
Typ
Max
Unit
Test Conditions
tW
Clock or MR Pulse Width
20
ns
ts
Mode Control Setup Time
30
ns
ts
Data Setup Time
20
ns
VCC = 5.0 V
th
Hold time, Any Input
0
ns
CC
trec
Recovery Time
25
ns
DEFINITIONS OF TERMS
SETUP TIME(ts) --is defined as the minimum time
required for the correct logic level to be present at the logic
input prior to the clock transition from LOW to HIGH in
order to be recognized and transferred to the outputs.
HOLD TIME (th) -- is defined as the minimum time
following the clock transition from LOW to HIGH that the
logic level must be maintained at the input in order to ensure
continued recognition. A negative HOLD TIME indicates
that the correct logic level may be released prior to the clock
transition from LOW to HIGH and still be recognized.
RECOVERY TIME (trec) -- is defined as the minimum time
required between the end of the reset pulse and the clock
transition from LOW to HIGH in order to recognize and
transfer HIGH Data to the Q outputs.
AC WAVEFORMS
The shaded areas indicate when the input is permitted to change for predictable output performance.
Figure 1. Clock to Output Delays Clock Pulse
Width and fmax
Figure 2. Master Reset Pulse Width, Master Reset
to Output Delay and Master Reset to Clock
Recovery Time
1.3 V
1.3 V
OTHER CONDITIONS: S1 = L, MR = H, S0 = H
OTHER CONDITIONS: S0, S1 = H
OTHER CONDITIONS:
PO = P1 = P2 = P3 = H
OTHER CONDITIONS: MR = H
OTHER CONDITIONS:
*DSR SET UP TIME AFFECTS Q0 ONLY
OTHER CONDITIONS:
DSL SET UP TIME AFFECTS Q3 ONLY
OTHER CONDITIONS: MR = H
S0
S1
DSR DSL
P0 P1 P2 P3
CLOCK
OUTPUT*
(--- IS SHIFT LEFT)
CLOCK
CLOCK
CLOCK
OUTPUT
OUTPUT
S0 S1
ts(H)
th(L) = 0
th(H) = 0
th(H) = 0
ts(H)
th(L) = 0
ts(L)
th = 0
th = 0
(STABLE TIME)
tPHL
tPLH
1/fmax
tW
ts(L)
MR
tW
trec
tPHL
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
1.3 V
ts
ts
Figure 3. Setup (ts) and Hold (th) Time for Serial Data
(DSR, DSL) and Parallel Data (P0, P1, P2, P3)
Figure 4. Setup (ts) and Hold (th) Time for S Input
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