up_count_500.v

用vierilog语言描写的电子时钟源码

module up_count_500(clk,reset,cout);

input clk,reset;

output cout;

reg [8:0] q;
reg cout;

always @(posedge clk or negedge reset)
      begin
            if (!reset)
                 begin 
                     q<=0;
                     cout<=0;
                 end
            else 
                 if (q==499)
                       begin
                            q<=0;
                            cout<=~cout;
                       end
                 else
                       begin
                            q<=q+1;
                            cout<=0;
                       end
       end
endmodule