/* Example 12: by karttu, Jan 2 2005.
               Show numbers 0 - 120 in factorial expansion,
               as '0000' - '4321'.
               One with each successive
               pressing of the rightmost push button.
               (show the previous word after the user
                presses the leftmost button).
 */

module esim12b(CLK,PB_IN,SEG_OUT,DIGIT_OUT);
input CLK;
input PB_IN;
output [7:0] SEG_OUT;
output [3:0] DIGIT_OUT;

// Binary coded registers for the digits of the factorial expansion:

reg f0 = 0;
reg [1:0] f1 = 0;
reg [1:0] f2 = 0;
reg [2:0] f3 = 0;

wire inc_f0;
wire [1:0] inc_f1;
wire [1:0] inc_f2;
wire [2:0] inc_f3;

wire PB_INC; // State of the debounced push button for incrementing.
reg pb_inc_prev = 0; // is saved here also.

wire inc_it = (PB_INC && ~pb_inc_prev);

debounced_button DBB0(CLK,PB_IN,PB_INC);

`define DIG0 {3'b000,f0}
`define DIG1 {2'b00,f1}
`define DIG2 {2'b00,f2}
`define DIG3 {1'b0,f3}

show4hex DIGDISPLAY(CLK,`DIG0,`DIG1,`DIG2,`DIG3,SEG_OUT,DIGIT_OUT);

inc4fexb INC4FEX(f0,f1,f2,f3,inc_f0,inc_f1,inc_f2,inc_f3);


always @(posedge CLK)
  begin
   pb_inc_prev <= PB_INC;

   f0 <= (inc_it ? inc_f0 : f0);
   f1 <= (inc_it ? inc_f1 : f1);
   f2 <= (inc_it ? inc_f2 : f2);
   f3 <= (inc_it ? inc_f3 : f3);

  end

endmodule