module PWM(clk,addr,wr_n,wrdata,reset,pwm1,pwm2,pwm3,pwm4);input clk,wr_n,reset;                       input [1:0]addr; input [15:0]wrdata;  output pwm1,pwm2,pwm3,pwm4;                           /*                      reg [15:0]duty; reg [15:0]period; reg [15:0]counter; *///testreg[15:0] counter=16'h0000,duty=16'h0003,period=16'h0007;//testreg start=1;reg out;reg direct=0;reg pwm1,pwm2,pwm3,pwm4;//testinitialbegin    #20 direct=1;    #18 direct=0;#4 start=1;end//testalways @(posedge clk or negedge reset)begin    if (reset == 1'b0)    begin     			duty[15:0] <= 16'h0007;			{direct,start} <= 2'b00;			period[15:0] <= 16'h000f;    end     else    begin         if (wr_n == 1'b0)       begin                     if (addr[1:0] == 2'b00) 		    begin			   {direct,start} <= wrdata[1:0];			   period[15:0] <= period[15:0];			   duty[15:0] <= duty[15:0];		    end          else if (addr[1:0] == 2'b01) 		    begin			   start <= start;			   direct <= direct;			   period[15:0] <= wrdata[15:0];			   duty[15:0] <= duty[15:0];		    end		              else if (addr[1:0] == 2'b10) 		    begin			   duty[15:0] <= wrdata[15:0];			   start <= start;			   direct <= direct;			   period[15:0] <= period[15:0];		    end		    		    else		    begin			   duty[15:0] <= duty[15:0];			   start <= start;			   direct <= direct;			   period[15:0] <= period[15:0];		    end	           end	    else	    begin		   duty[15:0] <= duty[15:0];		   start <= start;		   direct <= direct;		   period[15:0] <= period[15:0];	    end   end   endalways @(posedge clk)begin        if ((wr_n == 1'b0) && (addr[1:0] == 2'b11))     begin       counter[15:0] <= wrdata[15:0];    end    else if (start == 1'b1)    begin        if (counter[15:0] < period[15:0]) counter[15:0] <= counter[15:0] + 16'b1;        else counter[15:0] <= 16'b0;    end    else counter[15:0] <= counter[15:0];        if (start == 1'b1)    begin       if (counter[15:0] <= duty[15:0]) out <= 1'b1;       else out <= 1'b0;   end   else out <= 1'b0;endalways @(out or start or direct)begin    if (start == 1'b0)    begin        pwm1 = 1'b0;        pwm2 = 1'b0;        pwm3 = 1'b0;        pwm4 = 1'b0;    end    else if (direct == 1'b0)     begin        pwm1 = 1'b1;        pwm2 = 1'b0;        pwm3 = out;        pwm4 = 1'b0;    end    else    begin        pwm1 = 1'b0;        pwm2 = 1'b1;        pwm3 = 1'b0;        pwm4 = out;    endendendmodule