74F158ASC National Semiconductor, 74F158ASC Datasheet - Page 2

• Manufacturer Part Number: 74F158ASC
• Description: Quad 2-Input Multiplexer
• Manufacturer: National Semiconductor

Unit Loading Fan Out
Functional Description
The ’F158A quad 2-input multiplexer selects four bits of
data from two sources under the control of a common Se-
lect input (S) and presents the data in inverted form at the
four outputs The Enable input (E) is active LOW When E is
HIGH all of the outputs (Z) are forced HIGH regardless of
all other inputs The ’F158A is the logic implementation of a
4-pole 2-position switch where the position of the switch is
determined by the logic levels supplied to the Select input
A common use of the ’F158A is the moving of data from two
groups of registers to four common output busses The par-
ticular register from which the data comes is determined by
the state of the Select input A less obvious use is as a
function generator The ’F158A can generate four functions
of two variables with one variable common This is useful for
implementing gating functions
Logic Diagram
Pin Names
I
I
E
S
Z
0a
1a
a
–Z
–I
–I
0d
1d
d
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays
Source 0 Data Inputs
Source 1 Data Inputs
Enable Input (Active LOW)
Select Input
Inverted Outputs
Description
HIGH LOW
50 33 3
1 0 1 0
1 0 1 0
1 0 1 0
1 0 1 0
U L
54F 74F
2
20 A
20 A
20 A
20 A
Output I
b
Input I
1 mA 20 mA
Truth Table
b
b
b
b
IH
OH
0 6 mA
0 6 mA
0 6 mA
0 6 mA
H
L
X
Z
n
I
e
e
IL
e
I
e
OL
E
H
L
L
L
L
LOW Voltage Level
Immaterial
HIGH Voltage Level
E
c
(I
1n
S
X
H
H
L
L
Inputs
S
a
I
0n
I
H
X
L
X
X
0
S)
I
X
X
X
H
L
1
Outputs
H
H
H
Z
L
L
TL F 9484– 4