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28 votes
28 votes

In the following truth table, $V = 1$ if and only if the input is valid.

$$\begin{array}{cc}
\textbf{Inputs}&\textbf{Outputs}\\ 
\begin{array}{|c|c|c|c|} \hline
{D_0}&D_1&D_2&D_3 \\ \hline
0&0&0&0 \\ \hline
1&0&0&0 \\ \hline
\text{x}&1&0&0 \\ \hline
\text{x}&\text{x}&1&0 \\ \hline
\text{x}&\text{x}&\text{x}&1 \\ \hline
\end{array}&
\begin{array}{|c|c|c|} \hline
X_0&X_1&V \\ \hline
\text{x}&\text{x}&0\\ \hline
0&0&1\\ \hline
0&1&1\\ \hline
1&0&1\\ \hline
1&1&1\\ \hline
\end{array} \\
\end{array}$$

What function does the truth table represent?

  1. Priority encoder    
  2. Decoder    
  3. Multiplexer    
  4. Demultiplexer
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3 Answers

Best answer
30 votes
30 votes

Answer is A.

For $2^n \text{ inputs we are having } n \text{ outputs. Here n=2. }$ 

http://en.wikipedia.org/wiki/Priority_encoder

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19 votes
19 votes

....

4 votes
4 votes
Here it is a priority encoder as input bits are $2^n$  and output bits are n

also priority is defined as D3 >D2>D1>D0

i.e. when $D3$ =1 output is $0 1$ we don’t care about others, as others have less priority than $D3$

similarly for other if $D3$ =0 $D2$=1 output is $10$ we don’t care about others and so on
Answer:

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