cnt10de.v

交通灯。1）当乡村公路无车时

module cnt10de(clk,lod,a,q,cout);
input clk,lod;
input[3:0] a;
output[3:0] q;
output cout;
reg[3:0] q;
reg cout;
always @ (posedge clk or negedge lod)
     begin
      if(~lod)begin q=a;cout=1;end
          else if (q>0) begin q=q-1;
             if (q==0)cout=0;
                else cout=1;
                 end
          else if(q==0) begin q=9;cout=1;end
      end 
endmodule