参照艾米电子的程序进行改写的

//date : 2014,5,4 


module for_beep (
                              clock ,
                              reset ,
                              out_beep 
                              );
input  clock ,reset ;
output  reg out_beep ; 

reg [2:0]    state ; 
reg [3:0]     clk1 ; 
reg [12:0]   cnt0 ;         
reg [24:0]   delay_cnt1;                      
                              
parameter   du  =  4775 ,
                    re  =  4255 ,
                    mi =  3790 ,
                    fa =   3580 ,
                    so =  3185 ,
                    la  =  2840 ,
                    xi  =  2530 ,
                    do1 =  2385 ; 
                    
always @ (posedge clock  or negedge reset )
        begin 
                if (!reset )
                        begin
                                clk1              <=    4'd0 ; 
                                state            <=    3'd0 ; 
                                cnt0             <=  13'd0 ;
                                delay_cnt1  <=  24'd0 ; 
                                out_beep     <=   1'd0 ; 
                        end 
                else  if(clk1 == 4'd8)
                        begin 
                                case (state)
                                        3'd0    :    begin 
                                                                delay_cnt1  <= delay_cnt1 + 24'd1;
                                                                if(delay_cnt1 == 25'h1ff_ffff)
                                                                                state          <=  3'd1 ;

                                                                if(cnt0 != du)
                                                                            cnt0 <= cnt0 + 13'd1 ; 
                                                                else 
                                                                        begin 
                                                                            cnt0 <= 13'd0 ; 
                                                                            out_beep <= ~out_beep ;
                                                                        end 
                                                        end 
                                        3'd1    :    begin 
                                                                delay_cnt1  <= delay_cnt1 + 24'd1;
                                                                if(delay_cnt1 == 25'h1ff_ffff)
                                                                                state          <=  3'd2 ;

                                                                if(cnt0 != re)
                                                                            cnt0 <= cnt0 + 13'd1 ; 
                                                                else 
                                                                        begin 
                                                                            cnt0 <= 13'd0 ; 
                                                                            out_beep <= ~out_beep ;
                                                                        end 
                                                        end 
                                        3'd2    :    begin 
                                                                delay_cnt1  <= delay_cnt1 + 24'd1;
                                                                if(delay_cnt1 == 25'h1ff_ffff)
                                                                                state          <=  3'd3 ;

                                                                if(cnt0 != mi)
                                                                            cnt0 <= cnt0 + 13'd1 ; 
                                                                else 
                                                                        begin 
                                                                            cnt0 <= 13'd0 ; 
                                                                            out_beep <= ~out_beep ;
                                                                        end 
                                                        end 
                                        3'd3    :    begin 
                                                                delay_cnt1  <= delay_cnt1 + 24'd1;
                                                                if(delay_cnt1 == 25'h1ff_ffff)
                                                                                state          <=  3'd4 ;

                                                                if(cnt0 != fa)
                                                                            cnt0 <= cnt0 + 13'd1 ; 
                                                                else 
                                                                        begin 
                                                                            cnt0 <= 13'd0 ; 
                                                                            out_beep <= ~out_beep ;
                                                                        end 
                                                        end 
                                        3'd4    :    begin 
                                                                delay_cnt1  <= delay_cnt1 + 24'd1;
                                                                if(delay_cnt1 == 25'h1ff_ffff)
                                                                                state          <=  3'd5 ;

                                                                if(cnt0 != so)
                                                                            cnt0 <= cnt0 + 13'd1 ; 
                                                                else 
                                                                        begin 
                                                                            cnt0 <= 13'd0 ; 
                                                                            out_beep <= ~out_beep ;
                                                                        end 
                                                        end 
                                        3'd5    :    begin 
                                                                delay_cnt1  <= delay_cnt1 + 24'd1;
                                                                if(delay_cnt1 == 25'h1ff_ffff)
                                                                                state          <=  3'd6 ;

                                                                if(cnt0 != la)
                                                                            cnt0 <= cnt0 + 13'd1 ; 
                                                                else 
                                                                        begin 
                                                                            cnt0 <= 13'd0 ; 
                                                                            out_beep <= ~out_beep ;
                                                                        end 
                                                        end 
                                        3'd6    :    begin 
                                                                delay_cnt1  <= delay_cnt1 + 24'd1;
                                                                if(delay_cnt1 == 25'h1ff_ffff)
                                                                                state          <=  3'd7 ;

                                                                if(cnt0 != xi)
                                                                            cnt0 <= cnt0 + 13'd1 ; 
                                                                else 
                                                                        begin 
                                                                            cnt0 <= 13'd0 ; 
                                                                            out_beep <= ~out_beep ;
                                                                        end 
                                                        end 
                                        3'd7    :    begin 
                                                                delay_cnt1  <= delay_cnt1 + 24'd1;
                                                                if(delay_cnt1 == 25'h1ff_ffff)
                                                                                state          <=  3'd0 ;

                                                                if(cnt0 != do1)
                                                                            cnt0 <= cnt0 + 13'd1 ; 
                                                                else 
                                                                        begin 
                                                                            cnt0 <= 13'd0 ; 
                                                                            out_beep <= ~out_beep ;
                                                                        end 
                                                        end 
                                                        
                                endcase 
                        end 
                 else  if(clk1 < 4'd9 )  clk1 <= clk1 + 4'd1 ; 
                 else                           clk1 <= 4'd0  ;
        end 
                              
                              
                              
                              
endmodule