8-INPUT PRIORITY ENCODERS
WITH 3-STATE OUTPUTS
The SN54 / 74LS348 and the SN54 / 74LS848 are eight input priority encod-
ers which provide the 8-line to 3-line function.
The outputs (A0 – A2) and inputs (0 – 7) are active low. The active low input
which has the highest priority (input 7 has the highest) is represented on the
outputs (output A0 is the lowest bit). An example would be if inputs 1, 2 and 4
were low, then a binary 4 would be represented on the outputs.
The GS (Group Signal) output is active low when any of the inputs are low. It
serves to indicate when any of the inputs are active.
A0, A1 and A2 are three-state outputs. This allows for up to 64 line expan-
sion without the need for special external circuitry.
A logical one on the Enable Input (EI) forces A0, A1 ared A2 to the disabled
state and outputs GS and EO to the high state. A high on all data inputs (0 – 7)
together with a low on the EI input disables outputs A0, A1, and A2 and forces
output GS to the high state and output EO to the low state.
Use of the EI input in conjunction with the EO output provides for the capa-
bility of having priority encoding of n input signals.
The LS848 has special internal circuitry providing for a greatly reduced neg-
ative going glitch on the GS (Group Signal) output and on a reduced tendency
for the A0, A1 and A2 outputs to become momentarily enabled. Both of these
occurrences happen when the EI input goes from a logical one to a logical zero
and all data inputs (0 – 7) are held at logical ones. The internal glitch reduction
circuitry does add an additional fan-in of one on all data inputs (compared to
that of the LS348).
OUTPUTS
VCC
16
EO
15
EO
4
5
1
4
2
5
6
3
6
INPUTS
7
4
7
EI
5
EI
A2
6
A2
GS
14
GS
3
13
3
INPUTS
2
12
2
1
11
1
0
10
0
A0
A1
8
GND
OUTPUT
A0
9
SN54/74LS348
SN54/74LS848
8-INPUT PRIORITY ENCODERS
WITH 3-STATE OUTPUTS
LOW POWER SCHOTTKY
J SUFFIX
CERAMIC
CASE 620-09
16
1
16
1
N SUFFIX
PLASTIC
CASE 648-08
16
1
D SUFFIX
SOIC
CASE 751B-03
ORDERING INFORMATION
SN54LSXXXJ
SN74LSXXXN
SN74LSXXXD
Ceramic
Plastic
SOIC
7
A1
OUTPUTS
FUNCTION TABLE
INPUTS
EI
H
L
L
L
L
L
L
L
L
L
0
X
H
X
X
X
X
X
X
X
L
1
X
H
X
X
X
X
X
X
L
H
2
X
H
X
X
X
X
X
L
H
H
3
X
H
X
X
X
X
L
H
H
H
4
X
H
X
X
X
L
H
H
H
H
5
X
H
X
X
L
H
H
H
H
H
6
X
H
X
L
H
H
H
H
H
H
7
X
H
L
H
H
H
H
H
H
H
A2
Z
Z
L
L
L
L
H
H
H
H
OUTPUTS
A1
Z
Z
L
L
H
H
L
L
H
H
A0
Z
Z
L
H
L
H
L
H
L
H
GS
H
H
L
L
L
L
L
L
L
L
EO
H
L
H
H
H
H
H
H
H
H
H = HIGH Logic Level
L = LOW Logic Level
X = Irrelevant
Z = High Impedance State
FAST AND LS TTL DATA
5-499
SN54/74LS348
•
SN54/74LS848
BLOCK DIAGRAMS
(5)
EI
(10)
EI
0
(5)
(10)
(15)
EO
(14)
GS
0
G13
G29
(15)
EO
(14)
GS
G1
″
1
(11)
(11)
1
G2
′
′
G9
G31
G30
G14
(12)
(9)
A0
3
(13)
3
(1)
(1)
4
(2)
(7)
A1
(2)
5
(3)
6
(3)
(4)
7
6
(6)
A2
(4)
7
G24
G8
G7
G6
(13)
(12)
2
G3
(9)
A0
G18
2
G15
′
G4
′
′
′
′
′
′
G16
G17
4
G5
G10
G19
(7)
A1
G23
5
G11
′
′
G20
G21
G22
G12
G25
G26
G27
G28
(6)
A2
SN54 / 74LS348
SN54 / 74LS848
GUARANTEED OPERATING RANGES
Symbol
VCC
TA
IOH
IOH
IOL
IOL
Supply Voltage
Operating Ambient Temperature Range
Output Current — High
Output Current — High
Output Current — Low
Output Current — Low
EO, GS
A0, A1, A2
A0, A1, A2
EO, GS
A0, A1, A2
A0, A1, A2
Parameter
54
74
54
74
54, 74
54
74
54
74
54
74
Min
4.5
4.75
– 55
0
Typ
5.0
5.0
25
25
Max
5.5
5.25
125
70
– 0.4
– 1.0
– 2.6
4.0
8.0
12
24
Unit
V
°C
mA
mA
mA
mA
FAST AND LS TTL DATA
5-500
SN54/74LS348
•
SN54/74LS848
DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE
(unless otherwise specified)
Limits
Symbol
VIH
VIL
VIK
Parameter
Input HIGH Voltage
54
Input LOW Voltage
74
Input Clamp Diode Voltage
Output HIGH Voltage
A0, A1, A2
VOH
EO, GS
EO, GS
VOL
Output LOW Voltage
EO, GS
Output LOW Voltage
A0, A1, A2
Output Off Current HIGH
Output Off Current LOW
Input HIGH Current
Input 0, EI — LS348
Input 0 — LS848
Other — LS348
Other — LS848
IIH
Input HIGH Current
Input 0, EI — LS348
Input 0 — LS848
Other — LS348
Other — LS848
Input LOW Current
Input 0, EI — LS348
IIL
Input 0 — LS848
Other — LS348
Other — LS848
Short Circuit Current (Note 1)
EO, GS
A0, A1, A2
Power Supply Current
Total, Output HIGH
ICC
Total, Output LOW
13
25
– 20
– 30
12
54, 74
54
74
54, 74
74
54, 74
74
2.4
2.5
2.7
– 0.65
3.1
3.5
3.5
0.25
0.35
0.25
0.35
0.4
0.5
0.4
0.5
20
–20
20
40
40
60
0.1
0.2
0.2
0.3
– 0.4
– 0.8
– 0.8
– 1.2
– 120
– 130
23
mA
VCC = MAX, Inputs 7, EI = GND
All Others Open
0.8
– 1.5
V
V
V
V
V
V
V
V
µA
µA
µA
µA
µA
µA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
VCC = MAX
All Inputs and Outputs Open
VCC = MAX, VIN = 0.4 V
VCC = MAX, VIN = 7.0 V
VCC = MAX, VIN = 2.7 V
IOL = 4.0 mA
IOL = 8.0 mA
IOL = 12 mA
IOL = 24 mA
VCC = VCC MIN,
VIN = VIL or VIH
per Truth Table
VCC = VCC MIN,
VIN = VIL or VIH
per Truth Table
Min
2.0
0.7
V
Typ
Max
Unit
V
Test Conditions
Guaranteed Input HIGH Voltage for
All Inputs
Guaranteed Input LOW Voltage for
All Inputs
VCC = MIN, IIN = – 18 mA
VCC = MIN, IOH = MAX, VIN = VIH
or VIL per Truth Table
VOL
IOZH
IOZL
VCC = MAX, VOUT = 2.7 V
VCC = MAX, VOUT = 0.4 V
IOS
VCC = MAX
Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.
FAST AND LS TTL DATA
5-501
SN54/74LS348
•
SN54/74LS848
AC CHARACTERISTICS
(VCC = 5.0 V, TA = 25°C)
From
(Input)
1 thru 7
To
(Output)
A0, A1 or A2
output
Out-of-Phase
1 thru 7
A0, A1 or A2
output
EI
A0, A1 or A2
24
Out-of-Phase
0 thru 7
E0
output
In-Phase
0 thru 7
GS
output
In-Phase
EI
GS
output
In-Phase
EI
EO
output
EI
A0, A1 or A2
23
35
23
35
25
18
40
27
30
18
45
27
ns
CL = 5.0 pF
RL = 667
Ω
14
17
36
21
14
17
36
21
ns
9.0
11
21
17
9.0
11
21
17
ns
26
38
40
55
26
38
40
55
ns
CL = 15 pF
RL = 2.0
Ω
11
41
18
24
11
41
18
ns
23
25
35
39
23
25
35
39
ns
20
23
30
35
20
23
30
35
ns
CL = 45 pF
RL = 667
Ω
LS348
Limits
Waveform
In-Phase
Min
Typ
11
Max
17
Min
LS848
Limits
Typ
12
Max
18
ns
Unit
Test Conditions
Symbol
tPLH
tPHL
tPLH
tPHL
tPZH
tPZL
tPLH
tPHL
tPLH
tPHL
tPLH
tPHL
tPLH
tPHL
tPHZ
tPLZ
FAST AND LS TTL DATA
5-502
-A-
Case 751B-03 D Suffix
16-Pin Plastic
SO-16
NOTES:
1.
DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2.
3.
CONTROLLING DIMENSION: MILLIMETER.
DIMENSION A AND B DO NOT INCLUDE MOLD
PROTRUSION.
4.
MAXIMUM MOLD PROTRUSION 0.15 (0.006)
PER SIDE.
5.
751B 01 IS OBSOLETE, NEW STANDARD
751B 03.
16
9
-B-
1
8
P
8 PL
0.25 (0.010)
M
B
M
R X 45°
G
-T-
D
16 PL
0.25 (0.010)
M
C
SEATING
PLANE
K
T
B
S
M
F
J
A
S
DIM
A
B
C
D
F
G
J
K
M
P
R
MILLIMETERS
MIN
MAX
9.80
3.80
1.35
0.35
0.40
10.00
4.00
1.75
0.49
1.25
INCHES
MIN
MAX
0.386
0.150
0.054
0.014
0.016
0.393
0.157
0.068
0.019
0.049
1.27 BSC
0.19
0.10
0
0.25
0.25
7
0.050 BSC
0.008
0.004
0
0.009
0.009
7
°
°
°
°
5.80
0.25
6.20
0.50
0.229
0.010
0.244
0.019
Case 648-08 N Suffix
16-Pin Plastic
-A-
16
9
NOTES:
1.
DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2.
3.
CONTROLLING DIMENSION: INCH.
DIMENSION L" TO CENTER OF LEADS WHEN
FORMED PARALLEL.
4.
DIMENSION B" DOES NOT INCLUDE MOLD
FLASH.
5.
6.
ROUNDED CORNERS OPTIONAL.
648 01 THRU 07 OBSOLETE, NEW STANDARD
648 08.
B
1
8
F
S
C
-T-
K
SEATING
PLANE
L
H
G
D
16 PL
0.25 (0.010)
M
J
M
T
A
M
DIM
A
B
C
D
F
G
H
J
K
L
M
S
MILLIMETERS
MIN
MAX
18.80
6.35
3.69
0.39
1.02
19.55
6.85
4.44
0.53
1.77
INCHES
MIN
MAX
0.740
0.250
0.145
0.015
0.040
0.770
0.270
0.175
0.021
0.070
2.54 BSC
1.27 BSC
0.21
2.80
7.50
0
0.38
3.30
7.74
10
0.100 BSC
0.050 BSC
0.008
0.110
0.295
0
0.015
0.130
0.305
10
°
°
°
°
0.51
1.01
0.020
0.040
-A-
16
9
Case 620-09 J Suffix
16-Pin Ceramic Dual In-Line
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
-B-
1
8
3. DIMENSION L TO CENTER OF LEAD WHEN
FORMED PARALLEL.
4. DIM F MAY NARROW TO 0.76 (0.030) WHERE
THE LEAD ENTERS THE CERAMIC BODY.
C
L
5. 620 01 THRU 08 OBSOLETE, NEW STANDARD
620 09.
-T-
SEATING
PLANE
K
E
F
D
16 PL
0.25 (0.010)
M
N
G
T
A
S
M
J
16 PL
0.25 (0.010)
M
T
B
S
DIM
A
B
C
D
E
F
G
J
K
L
M
N
MILLIMETERS
MIN
MAX
19.05
6.10
19.55
7.36
4.19
0.39
0.53
INCHES
MIN
MAX
0.750
0.240
0.770
0.290
0.165
0.015
0.021
1.27 BSC
1.40
1.77
0.050 BSC
0.055
0.070
2.54 BSC
0.23
0.27
5.08
7.62 BSC
0
0.100 BSC
0.009
0.011
0.200
0.300 BSC
0
°
15
°
°
15
°
0.39
0.88
0.015
0.035
FAST AND LS TTL DATA
5-503
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