`timescale 10ns/1nsmodule Signal_detect (                     //inputs                     DIN,        // serial data                     CLK,        // system clock                     RESET,      // system reset                     //outputs                       Signal_A,   // detect A                     Signal_B,   // detect B                     Signal_C,   // detect C                     BIT_EN_temp // detect A or B or C                     );input  DIN,CLK,RESET;output Signal_A,Signal_B,Signal_C,BIT_EN_temp;reg Signal_A,Signal_B,Signal_C;//reg A_BIT_EN,B_BIT_EN,C_BIT_EN; // "BIT_EN" signalassign BIT_EN_temp = Signal_A|Signal_B|Signal_C;//A_BIT_EN|B_BIT_EN|C_BIT_EN;parameter A=2'b00,  // state A          B=2'b01,  // state B          C=2'b10;  // state Creg[1:0] state;reg[4:0] count_temp;  // count the num of H levelreg[4:0] count;       // save the value of "count_temp"// ouput detected Signal & BIT_EN flagalways @(posedge CLK)begin  Signal_A<= 1'b0; Signal_B<= 1'b0; Signal_C<= 1'b0; // A_BIT_EN <= 1'b0; B_BIT_EN <= 1'b0; C_BIT_EN <= 1'b0;  if (count_temp ==5'd1 && state ==A)    begin    Signal_A <=1'b1; //   A_BIT_EN <=1'b1;    end  else if ( (count_temp ==5'd14 || count_temp == 5'd30) && state ==B) // 13,30    begin       Signal_B <=1'b1;  //  B_BIT_EN <=1'b1;    end    else if (count_temp ==5'd1 && state ==C)    begin    Signal_C <= 1'b1; //   C_BIT_EN <= 1'b1;    end  else    begin    Signal_A<= 1'b0; Signal_B<= 1'b0; Signal_C<= 1'b0; //   A_BIT_EN <= 1'b0; B_BIT_EN <= 1'b0; C_BIT_EN <= 1'b0;       endend    //end/////////////   count  ////////////////////always @(negedge DIN or posedge CLK)begin  if (!DIN)    begin      count  <= 5'b0;       count  <= count_temp;      count_temp <= 5'b0;      end    else  // posedge of clk    begin      if (count_temp >= 5'd31)        count_temp<=31;      else         count_temp <= count_temp +1;        end        // next B signal  if (state == A && count_temp == 5'd12)       count <= count_temp;     if (state == C && count_temp == 5'd20)      count <= count_temp;     //end//////////// state Transform  /////////////begin C: count       next//            11         C//            19         A//            27,35,>35  BC/BA/BB //end//begin A: count       next//            11         A//            19,27,>27  BC/BA/BB //begin B: count       next//            19         C//            27         A//            >27        B   //endalways @(negedge RESET or count or state ) begin  if (!RESET)    begin      state = B; count = 5'd0; count_temp =5'd31;      end    else    begin      case (state)          B:begin              if (count == 5'd19 || count == 5'd31)                state = C;              else if (count == 5'd27)                state = A;     //              else state = B;              end                    A:begin              if (count == 5'd11)                state = A;              else if (count > 5'd11) // ==========================                state = B;              else state =A;            end                    C:begin              if (count == 5'd11)                state = C;              else if (count == 5'd19)                state = A;              else if (count > 5'd19)                state =B;              else state =C;            end                    default:state = B;      endcase        end // end of elseend // end of always blockendmodule