OC - Booth M.

module booth_modificat
#( parameter OPERAND_BITS = 8,
parameter RESULT_BITS = 16)
(

input clk,
input rst,
input [OPERAND_BITS - 1 : 0] a,
input [OPERAND_BITS - 1 : 0] b,
input start,
output[RESULT_BITS - 1 : 0] result,
output reg ovr
);

reg f;
reg [OPERAND_BITS-1 : 0] A;
reg [OPERAND_BITS : 0] Q;
reg Q_1;
reg [OPERAND_BITS-1 : 0] M;
reg [2:0] count;

reg [3:0] state;

localparam [3:0] s0=4'd0, s1=4'd1, s2=4'd2, s3=4'd3, s4=4'd4, s5=4'd5, s6=4'd6, s7=4'd7, s8=4'd8, s9=4'd9;

// sequential process

always
@(posedge clk, posedge rst)

begin

if (rst)

begin

state <= s0;
A <= 0;
Q <= 0;
M <= 0;
Q_1 <= 0;
count <= 0;

end

else

begin
   case(state)
       s0: begin
            if(start)
              state <= s1;
          end
       s1:
          begin
              A <= 0;
              count <= 0;
              f <= 0;
              ovr <= 0;
              M <= a;
              Q <= b[7:0];
              Q_1 <= b[0];
              state <= s2;
          end
       s2:
          begin
              if(Q == 9'd0)
                state <= s9;
              else if(M == 8'd0)
                state <= s3;
              else
                state <= s4;
          end
       s3:
          begin
              Q <= 0;
              Q_1 <= 0;
              state <= s9;
          end
       s4:
          begin
              if(f == 1'b0)
               begin
                 if({Q[0],Q[1]} == 2'b01)
                    begin
                        A <= A + M;
                        ovr <= 1'b1;
                    end
                else if({Q[0],Q[1]} == 2'b11)
                    begin
                        A <= A - M;
                        ovr <= 1'b1;
                        f <= 1'b1;
                    end
               end
               else
               begin
                   if({Q[0],Q[1]} == 2'b00)
                      begin
                          A <= A + M;
                          ovr <= 1'b1;
                          f <= 1'b0;
                      end
                   else if({Q[0],Q[1]} == 2'b10)
                      begin
                          A <= A - M;
                          ovr <= 1'b1;
                      end
               end
               if(count == 2'd7)
                  state <= s9;
               else
                  state <= s8;
          end

       s8:
          begin
              A[7] <= (A[7] && M[7] && !ovr) || (f && !M[7]) || (f && M[7] && ovr);
              //{A[7:1], Q} <= {A, Q[6:0], Q_1};
              //{Q, A[7:1]} <= {Q[6:0], Q_1, A};
              //A[7]={{A[7],M[7]},~(ovr)} + {{f,~(M[7])},ovr};
              {A[6:0],Q}={A,Q[8:1]};
              count <= count + 1'b1;
              state <= s4;
          end
       s9:
          begin
             Q[1] <= 0;
          end
   endcase

end
end

assign result = {A, Q, Q_1};

endmodule