Subversion Repositories fht

// Code for Fast Hadamhard Transforms

// Developed by Kaushal D. Buch

// March, 2007.

module fht ( clk, reset, data_i , data_o );

input clk,reset ;

input [7:0] data_i ;

output [7:0] data_o ;

wire clk,reset ;

wire [7:0] data_i,comp ;

reg [7:0] data_o ;

reg [7:0] data_d,a,b,data_od,a_d,b_d,comp_d,temp_d,temp ;

reg [1:0] cnt ;

reg data_valid ;

always@(posedge clk or negedge reset)

begin

  if(!reset)

  begin

    data_d  <= 'b0 ;

    comp_d  <= 'b0 ;

    temp_d  <= 'b0 ;

  end

  else

  begin

    data_d  <= data_i ;

    comp_d  <= comp ;

    temp_d  <= temp ;

  end

end

always@(posedge clk or negedge reset)

begin

  if(!reset)

  begin

    cnt     <= 'b0 ;

  end

  else if(cnt < 2'b11)

  begin

    cnt     <= cnt + 'b1 ;

  end

  else

  begin

    cnt     <= 'b0 ;

  end

end

always@(cnt or data_d or a or b or temp_d)

begin

  case(cnt)

  2'b00 : begin

            temp  =  data_d  ;

            data_valid = 'b0 ;

          end

  2'b01 : begin

            temp  =  comp_d  ;

            data_valid = 'b0 ;

          end

  2'b10 : begin

            temp  =  comp_d  ;

            data_valid = 'b1 ;

          end

  default : begin

            temp = temp_d    ;

            data_valid = 'b0 ;

            end

  endcase

end

assign comp = {temp[6] - temp[7], temp[4] - temp[5], temp[2] - temp[3],

  temp[0] - temp[1], temp[6] + temp[7], temp[4] + temp[5], temp[2]

  + temp[3], temp[0] + temp[1]} ;

always@(posedge clk or negedge reset)

begin

  if(!reset)

  begin

    data_o  <= 'b0 ;

  end

  else if(data_valid)

  begin

    data_o  <= temp ;

  end

end

endmodule