module imult_ord_radix_4(prod,ready,multiplicand,multiplier,start,clk);

   input [15:0]  multiplicand, multiplier;
   input         start, clk;
   output        prod;
   output        ready;

   reg [32:0]    product;
   wire [31:0]   prod = product[31:0];

   reg [4:0]     bit;
   wire          ready = !bit;

   reg [17:0]    pp;

   initial bit = 0;

   wire [17:0]   multiplicand_X_1 = {1'b0,multiplicand};
   wire [17:0]   multiplicand_X_2 = {multiplicand,1'b0};
   wire [17:0]   multiplicand_X_3 = multiplicand_X_2 + multiplicand_X_1;

   always @( posedge clk )

     if( ready && start ) begin

        bit     = 8;
        product = { 16'd0, multiplier };

     end else if( bit ) begin

        case ( {product[1:0]} )
          2'd0: pp = {2'b0, product[31:16] };
          2'd1: pp = {2'b0, product[31:16] } + multiplicand_X_1;
          2'd2: pp = {2'b0, product[31:16] } + multiplicand_X_2;
          2'd3: pp = {2'b0, product[31:16] } + multiplicand_X_3;
        endcase

        product = { pp, product[15:2] };
        bit     = bit - 1;

     end

endmodule


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