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+19 votes

Consider the following combinational function block involving four Boolean variables $x,\:y,\:a,\:b$ where $x,\:a,\:b$ are inputs and $y$ is the output.

f(x, a, b, y)
    if(x is 1) y = a;
    else y = b;

Which one of the following digital logic blocks is the most suitable for implementing this function?

  1. Full adder
  2. Priority encoder
  3. Multiplexor
  4. Flip-flop
asked in Digital Logic by Veteran (97.7k points)
retagged by | 1.6k views

3 Answers

+23 votes
Best answer

$\text{If} \qquad X=1 \qquad Y=a;$
$\text{else}\quad (X=0)\qquad Y = b;$

$\text{Input}: (a,b,X)\qquad\qquad \text{Output}: Y$

$Y = \bar X b + Xa.$

Correct Answer: $C$

answered by Loyal (8.3k points)
edited by
Why can't it be flip flop? Please explain
Flip is one bit storage device. It will store one bit.We dont have any selection logic in flip flop as in MUX


Can we implement it using priority encoder ???

2 X 1 Priority encoder

Input (No use)        X  Output (Y)
$\phi$       1  a
$\phi$       0     b 


Same doubt.

@jatin khachane 1

1. x,a,b are the inputs.

2. y is output.

a,b will be given to Encoder but how will you check if condition?

+16 votes
2X1 multiplexer
answered by Active (3.7k points)
+3 votes
lovely question x1=a x0=b MULTIPLEXER
answered by Active (3.1k points)

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