Suppose we want to design a synchronous circuit that processes a string of 0’s…

GATE · 2021 · CS · Set 2 · Computer Science & IT

Suppose we want to design a synchronous circuit that processes a string of 0’s and 1’s. Given a string, it produces another string by replacing the first 1 in any subsequence of consecutive 1’s by a 0. Consider the following example.

Input sequence : 00100011000011100 Output sequence : 00000001000001100

A Mealy MachineMealy \ Machine is a state machine where both the next state and the output are functions of the present state and the current input. The above mentioned circuit can be designed as a two-state Mealy machine. The states in the Mealy machine can be represented using Boolean values 0 and 1. We denote the current state, the next state, the next incoming bit, and the output bit of the Mealy machine by the variables s, t, bs, \ t, \ b and yy respectively. Assume the initial state of the Mealy MachineMealy \ Machine is 0.

What are the Boolean expressions corresponding to tt and yy in terms of ss and bb?

  1. A.

    t=s+by=sb\begin{array}{l} t=s+b \\ y=sb \end{array} \\

  2. B.

    t=by=sb\begin{array}{l} t=b \\ y=sb \end{array} \\

  3. C.

    t=by=sb‾\begin{array}{l} t=b \\ y=s \overline{b} \end{array} \\

  4. D.

    t=s+by=sb‾\begin{array}{l} t=s+b \\ y=s \overline{b} \end{array}

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