2X1 Multiplexer

 

Boolean Equation

Y = I0 if {S = 0}

Y = I1 if {S = 1}

Truth Table

Dataflow Modeling

module mux_21(I0,I1,S,Y);

    input I0,I1,S;

    output Y;

    assign Y = (S)?I1:I0;

endmodule

Behavioral Modeling

module mux_21(I0,I1,S,Y);

    input I0,I1,S;

    output Y;

    reg Y;

    always@(I0 or I1 or S)

    begin

        if(S == 1'b1)

            Y = I1;

        else

            Y = I0;

      end

endmodule

Case Statement

module mux_21(I0,I1,S,Y);

    input I0,I1,S;

    output Y;

    reg Y;

    always@(I0 or I1 or S)

    begin

        case(S)

            1'b1 : Y = I1;

            1'b0 : Y = I0;

         endcase

    end

endmodule

Testbench

module mux_21_tb;

    reg t_I0,t_I1,t_S;

    wire t_Y;

    mux_21 mux_21_tb(.I0(t_I0),.I1(t_I1),.S(t_S),.Y(t_Y));

    initial

        begin

             t_I0 = 1'b0;

             t_I1 = 1'b0;

             t_S = 1'b0;

         end

      always #10 t_s = ~t_s;

      always #20 t_I0 = ~t_I0;

      always #40 t_I1 = ~t_I1;

      always@(t_I0 or t_I1 or t_S)

      begin

          $monitor("%t,t_S=%d,t_I0=%d,t_I1=%d,t_Y=%d",$time,t_S,t_I0,t_I1,t_Y);

      end

endmodule