/* Example 9: by karttu, Dec 12 2004.
              Show the successive Factorial numbers when
              the user presses the rightmost push button.
 */

module esim9(CLK,PB_IN,SEG_OUT,DIGIT_OUT);
input CLK;
input PB_IN;
output [7:0] SEG_OUT;
output [3:0] DIGIT_OUT;

reg [15:0] next_n = 1;
reg [15:0] fact_n = 1;

wire PB_DEB; // State of the debounced push button.
reg pb_deb_prev = 0; // is saved here also.

debounced_button DBB(CLK,PB_IN,PB_DEB);

shw16dec DECDISPLAY(CLK,PB_DEB,fact_n,SEG_OUT,DIGIT_OUT);

always @(posedge CLK)
  begin
   if(PB_DEB && ~pb_deb_prev) // Only on @(posedge PB_DEB)
    begin // Do the thing.
     fact_n <= next_n * fact_n;
     next_n <= next_n + 1;
    end
   pb_deb_prev <= PB_DEB;
  end

endmodule