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74F153
Unit Loading/Fan Out
Truth Table
H = HIGH Voltage Level
L = LOW
X = Immaterial
Functional Description
The F153 is a d ua l 4- in pu t mu ltiplexer. It can se l ect t wo b i t s
of data from up to four so urces under the control of the
common Select inputs (S
0
, S1). The two 4-input multiplexer
circuits have individual active LOW Enables (E
a
, Eb) which
can be used to strobe the outputs independently. When the
Enables (E
a
, Eb) are HIGH, the corresponding outputs (Za,
Z
b
) are forced LOW. The F153 is the logic impleme ntation
of a 2-pole, 4-position switch, where the position of the
switch is determined by the logic levels s upplied to the two
Select inputs. The logic e quations for the outputs are as
follows:
Z
a
= Ea•(I0a•S1•S0 + I1a•S1•S0 +
I
2a•S1•S0
+ I3a•S1•S0)
Z
b
= Eb•(I0b•S1•S0 + I1b•S1•S0 +
I
2b•S1•S0
+ I3b•S1•S0)
The F153 can be used to mo ve da ta fr om a gro up of registers to a common output bus. The particular reg ister from
which the data came would be det ermined by the state of
the Select inputs. A less obvious appl ication is as a function generator. The F153 can generate two functions of
three variables. This is useful for implementing highly irregular random logic.
Logic Diagram
Please note that this diagram is provided o nly f or t he understanding of lo gic operations and should not be used to estimate propagation delays.
Pin Names Description
U.L.
Input I
IH/IIL
HIGH/LOW
Output I
OH/IOL
I0a–I
3a
Side A Data Inputs 1.0/1.0 20 µA/−0.6 mA
I
0b–I3b
Side B Data Inputs 1.0/1.0 20 µA/−0.6 mA
S
0
, S
1
Common Select Inputs 1.0/1.0 20 µA/−0.6 mA
E
a
Side A Enable Input (Active LOW) 1.0/1.0 20 µA/−0.6 mA
E
b
Side B Enable Input (Active LOW) 1.0/1.0 20 µA/−0.6 mA
Z
a
Side A Output 50/33.3 −1 mA/20 mA
Z
b
Side B Output 50/33.3 −1 mA/20 mA
Select Inputs Inputs (a or b) Output
S
0
S1E I0I1I2I
3
Z
X X HXXXX L
L L LLXXX L
L L LHXXX H
H L LXLXX L
HLLXHXXH
LHLXXLXL
LHLXXHXH
H H LXXXL L
H H LXXXH H