Motorola MC74F251D, MC54F251J Datasheet
4-117
FAST AND LS TTL DATA
8-INPUT MULTIPLEXER
WITH 3-STATE OUTPUTS
The MC54/74F251 is a high-speed 8-input digital multiplexer. It provides,
in one package, the ability to select one bit of data from up to eight sources.
It can be used as a universal function generator to generate any logic function
of four variables. Both assertion and negation outputs are provided.
• Multifunctional Capacity
• On-Chip Select Logic Decoding
• Inverting and Noninverting 3-State Outputs
FUNCTIONAL DESCRIPTION
This device is a logical implementation of a single-pole, 8-position switch
with the switch position controlled by the state of three Select inputs, S0, S1,
S2. Both assertion and negation outputs are provided. The Output Enable input (OE
) is active LOW. When it is activated, the logic function provided at the
output is:
Z = OE
• (I0 • S0 • S1 • S2 + I1 • S0 • S1 • S2 +
I2 • S
0
• S1 • S2 + I3 • S0 • S1 • S2 +
I4 • S
0
• S1 • S2 + I5 • S0 • S1 • S2 +
I6 • S
0
• S1 • S2 + I7 • S0 • S1 • S2 +
When the Output Enable is HIGH, both outputs are in the high impedance
(high Z) state. This feature allows multiplexer expansion by tying the outputs
of up to 128 devices together. When the outputs of the 3-state devices are tied
together, all but one device must be in the high impedance state to avoid high
currents that would exceed the maximum ratings. The Output Enable signals
should be designed to ensure there is no overlap in the active LOW portion
of the enable voltages.
CONNECTION DIAGRAM
1516 14 13 12 11 10
21 3 4 5 6 7
V
CC
9
8
I
4
GND
I
5I6I7S0S1S2
I3I
2I1I0
Z Z
OE
FAST SCHOTTKY TTL
8-INPUT MULTIPLEXER
WITH 3-STATE OUTPUTS
MC54/74F251
J SUFFIX
CERAMIC
CASE 620-09
N SUFFIX
PLASTIC
CASE 648-08
16
1
16
1
ORDERING INFORMATION
MC54FXXXJ Ceramic
MC74FXXXN Plastic
MC74FXXXD SOIC
16
1
D SUFFIX
SOIC
CASE 751B-03
LOGIC SYMBOL
9 11
6
5
7
4
3
2
1
15
14
13
I
3
I
2
I
0
S
2
I
6
I
5
I
4
I
1
OE
VCC = PIN 16
GND = PIN 8
10
12
I
7
S1S
0
4-118
FAST AND LS TTL DATA
MC54/74F251
FUNCTION TABLE
Inputs Outputs
OE S
2
S
1
S
0
Z Z
H X X X Z Z
L L L L I
0
I
0
L L L H I
1
I
1
L L H L I
2
I
2
L L H H I
3
I
3
L H L L I
4
I
4
L H L H I
5
I
5
L H H L I
6
I
6
L H H H I
7
I
7
H = HIGH Voltage Level
L = LOW Voltage Level
X = Don’t Care
Z = High Impedance
LOGIC DIAGRAM
I
0
I
1
I
2
I
3
I
4
I
5
I
6
I
7
S
2
S
1
S
0
OE
Z Z
GUARANTEED OPERATING RANGES
Symbol Parameter Min Typ Max Unit
V
CC
Supply Voltage 54, 74 4.5 5.0 5.5 V
T
A
Operating Ambient Temperature Range 54 -55 25 125 °C
74 0 25 70
I
OH
Output Current — High 54, 74 –3.0 mA
I
OL
Output Current — Low 54, 74 24 mA
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