Verilog 2

=================================================================
//OG.v
module OG(input q1, q2, q3, output o);
    assign o = (q3);
endmodule
=================================================================
//NSG.v
module NSG(input x, q1, q2, q3, output d1, d2, d3);
    assign d3 = (x & q2 & q1);
    assign d2 = (x & q2 & q1) | ((~x) & q2 & (~q1));
    assign d1 = (q2 & (~q1)) | (x & (~q1));
endmodule
=================================================================
//FF.v
module FF(input d, clk, r, output reg q);
    always @(posedge clk, negedge r)
        begin
            if(clk)
                q <= d;
            else if(!r)
                q <= r;
        end
endmodule
=================================================================
//FSM.v
`include "OG.v"
`include "NSG.v"
`include "FF.v"
module FSM(input x, clk, r, output o);
    wire q1, q2, q3, d1, d2, d3, o;
    NSG next(x, q1, q2, q3, d1, d2, d3);
    FF ff1(d1, clik, r, q1);
    FF ff2(d2, clik, r, q2);
    FF ff3(d3, clik, r, q3);
    OG out(q1, q2, q3, o);
endmodule
=================================================================
//main.v
`include "FSM.v"
module main;
    reg x, clk, r;
    wire o;

    initial
        begin
            clk= 1;
            r = 0;
            x =   0;
            #1;
            r = 1;
        end

    initial
        begin
            $monitor(" x=%x t=%3d o=%x ", x, $time, o);
        end
    initial
        repeat( 16 )
        begin
            #1 clk = ~clk;
        end
    initial
        //1011011010110100
        begin
            #2
            #1 x = 1;
            #1 x = 0;
            #1 x = 1;
            #1 x = 1;
            #1 x = 0;
            #1 x = 1;
            #1 x = 1;
            #1 x = 0;
            #1 x = 1;
            #1 x = 0;
            #1 x = 1;
            #1 x = 1;
            #1 x = 0;
            #1 x = 1;
            #1 x = 0;
            #1 x = 0;

        end

endmodule
=================================================================
Output
x=0 t=1 o=0
x=0 t=2 o=0
x=1 t=4 o=0
x=0 t=6 o=0
x=1 t=8 o=0
x=1 t=10 o=0
x=0 t=12 o=0
x=1 t=14 o=1
x=1 t=16 o=0
x=0 t=18 o=0
x=1 t=20 o=1
x=0 t=22 o=0
x=1 t=24 o=0
x=1 t=26 o=0
x=0 t=28 o=1
x=1 t=30 o=0
x=0 t=32 o=0
x=0 t=34 o=0