/* Example 14: by karttu, Jan 2 2005.
               Show permutations '43210' - '01234',
               the four rightmost in 7-segment display,
               and the leftmost's binary expansion
               in the three rightmost leds.
               Permutation changes with each successive
               pressing of the rightmost push button.
 */

module esim14(CLK,PB_IN,SEG_OUT,DIGIT_OUT,LED_OUT);
input CLK;
input PB_IN;
output [7:0] SEG_OUT;
output [3:0] DIGIT_OUT;
output [2:0] LED_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);

parameter w = 2;

reg [w:0] d [3:0];

wire [w:0] d_sig [3:0];

`define DIG0 {1'b0,d[0]}
`define DIG1 {1'b0,d[1]}
`define DIG2 {1'b0,d[2]}
`define DIG3 {1'b0,d[3]}

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);
fex4perm FEX4PERM(f0,f1,f2,f3,d_sig[0],d_sig[1],d_sig[2],d_sig[3],LED_OUT);

integer i;

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);

   for(i=0; i<=3; i=i+1) d[i] <= d_sig[i];

  end

endmodule