Design of Serial Multiplier Based on FPGA Verilog

Serial multiplier:
Disadvantage: longer time consumption
Advantage: less resource consumption

module    mult(	
	input    clk, 
	input    [7:0]x, 
	input    [7:0]y, 
	
	output   reg[15:0]result
	);

  parameter s0 = 0, s1 = 1, s2 = 2;

  reg [2:0] count = 0;
  reg [1:0] state = 0;
  reg [15:0] P, T;
  reg [7:0] y_reg;

  always@(posedge clk ) begin
      case (state)
          s0: begin
              count <= 0;
              P <= 0;
              y_reg <= y;
              T <= {
   
   {8{1'b0}}, x};//把X的高八位填充为0
              state <= s1;
          end
          s1: begin
              if(count == 3'b111)
                  state <= s2;
              else begin
                  if(y_reg[0] == 1'b1)
                      P <= P + T;
                  else
                      P <= P;
                  y_reg <= y_reg >> 1;
                  T <= T << 1;
                  count <= count + 1;
                  state <= s1;
              end
          end
          s2: begin
              result <= P;
              state <= s0;
          end
          default: ;
      endcase
  end
endmodule

Simulation: (It can be seen that the delay between output and input is large)