¿Dónde debo incluir la creación de instancias en el módulo superior (contador)

Estoy haciendo un módulo de contador en la placa Basys-2. Esta es mi instanciación del circuito de desmontaje

 debouncing U0(
.clock(clock),
.reset(reset),
.button(button),
.out(out)
 );

Pero estoy recibiendo un error en Xilinx 14.7 como

ADVERTENCIA: Xst: 646 - La señal se asigna pero nunca se usa. Esta señal desconectada se recortará durante el proceso de optimización. ADVERTENCIA: Xst: 1290 - El bloque jerárquico está desconectado en el bloque.    Será eliminado del diseño.

Si es que tengo que incluir esta creación de instancias en el módulo contador, ¿dónde debería y por qué recibo este error?

Counter Circuit
module button_binary(
input clock,
input reset,
input button,
output led,
output led2,
output led3,
output led4,
output led5,
output led6,
output led7,
output led8
);

reg [7:0]count;

  always @ (posedge clock or posedge reset)
  begin
 if (reset)
    count <= 0;
else if (button)
    count <= count + 1;
end

assign led = count[0];
assign led2 = count[1];
assign led3 = count[2];
assign led4 = count[3];
assign led5 = count[4];
assign led6 = count[5];
assign led7 = count[6];
assign led8 = count[7];
endmodule 

// Módulo de debouncing

module debouncing(
input clock,
input reset,
input button,
output reg out
);

localparam N = 19;        //for a 10ms tick
reg [N-1:0]count;
wire tick; 

//the counter that will generate the tick.

always @ (posedge clock or posedge reset)
 begin
    if(reset)
        count <= 0;
    else
        count <= count + 1;        
 end

 assign tick = &count;        //AND every bit of count with itself. Tick will only go high when all 19 bits of count are 1, i.e. after 10ms

 // now for the debouncing FSM

 localparam[2:0]                     //defining the various states to be used
            zero = 3'b000, 
            high1 = 3'b001,
            high2 = 3'b010,
            high3 = 3'b011,
            one = 3'b100,
            low1 = 3'b101,
            low2 = 3'b110,
            low3 = 3'b111;

reg [2:0]state_reg;
reg [2:0]state_next;

always @ (posedge clock or posedge reset)      
 begin
    if (reset)
        state_reg <= zero;
    else
        state_reg <= state_next;
end


always @ (*)
 begin
    state_next <= state_reg;  // to make the current state the default state
    out <= 1'b0;                    // default output low

    case(state_reg)
        zero:
            if (button)                    //if button is detected go to next state high1
                state_next <= high1;
        high1:
            if (~button)                //while here if button goes back to zero then input is not yet stable and go back to state zero
                state_next <= zero;
            else if (tick)                //but if button remains high even after 10 ms, go to next state high2.
                state_next <= high2;
        high2:
            if (~button)                //while here if button goes back to zero then input is not yet stable and go back to state zero
                state_next <= zero;
            else if (tick)                //else if after 20ms (10ms + 10ms) button is still high go to high3
                state_next <= high3;
        high3:
            if (~button)                //while here if button goes back to zero then input is not yet stable and go back to state zero
                state_next <= zero;
            else if (tick)                //and finally even after 30 ms input stays high then it is stable enough to be considered a valid input, go to state one
                state_next <= one;

        one:                                //debouncing eliminated make output high, now here I'll check for bouncing when button is released
            begin
                out <= 1'b1;
                    if (~button)        //if button appears to be released go to next state low1
                        state_next <=  low1;
            end
        low1:
            if (button)                //while here if button goes back to high then input is not yet stable and go back to state one
                state_next <= one;
            else if (tick)            //else if after 10ms it is still high go to next state low2
                state_next <= low2;
        low2:
            if (button)                //while here if button goes back to high then input is not yet stable and go back to state one
                state_next <= one;
            else if (tick)            //else if after 20ms it is still high go to next state low3
                state_next <= low3;
        low3:
            if (button)                //while here if button goes back to high then input is not yet stable and go back to state one
                state_next <= one;
            else if (tick)            //after 30 ms if button is low it has actually been released and bouncing eliminated, go back to zero state to wait for next input.
                state_next <= zero;
        default state_next <= zero;

    endcase
  end
endmodule