74F157ASC 查看數據表（PDF） - Fairchild Semiconductor
零件编号
产品描述 (功能)
生产厂家
74F157ASC Datasheet PDF : 6 Pages
| |||
Unit Loading/Fan Out
Pin Names
Description
I0a–I0d
I1a–I1d
E
S
Za–Zd
Source 0 Data Inputs
Source 1 Data Inputs
Enable Input (Active LOW)
Select Input
Outputs
U.L.
HIGH/LOW
1.0/1.0
1.0/1.0
1.0/1.0
1.0/1.0
50/33.3
Input IIH/IIL
Output IOH/IOL
20 µA/−0.6 mA
20 µA/−0.6 mA
20 µA/−0.6 mA
20 µA/−0.6 mA
−1 mA/20 mA
Truth Table
Inputs
E
S
I0
H
X
X
L
H
X
L
H
X
L
L
L
L
L
H
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Functional Description
Output
The F157A is a quad 2-input multiplexer. It selects four bits
of data from two sources under the control of a common
I1
Z
Select input (S). The Enable input (E) is active LOW. When
E is HIGH, all of the outputs (Z) are forced LOW regardless
X
L
of all other inputs. The F157A is the logic implementation of
a 4-pole, 2-position switch where the position of the switch
L
L
is determined by the logic levels supplied to the Select
H
H
input. The logic equations for the outputs are shown below:
X
L
Zn = E • (I1nS + I0n S)
A common use of the F157A is the moving of data from two
X
H
groups of registers to four common output busses. The
particular 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 F157A can generate any four of
the 16 different functions of two variables with one variable
common. This is useful for implementing highly irregular
logic.
Logic Diagram
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
www.fairchildsemi.com
2
Share Link: 