event是静态对象，通过"->"操作符触发，进程总是等待一个"@"操作符的事件被触发。"@"操作符是边沿敏感。

initial begin
  $display("@ %0t: 1 :before trigger",$time);
  ->e1;
  @e2;

   $display("@ %0t: 1 :after trigger",$time);
  end

initial begin
  $display("@ %0t: 2 :before trigger",$time);
  ->e2;
  @e1;
   
   $display("@ %0t: 2 :after trigger",$time);
  end

输出结果：

# @ 0: 1 :before trigger
# @ 0: 2 :before trigger
# @ 0: 1 :after trigger

原因：->e1是一个零脉冲，第二个线程会错过而被锁住

使用wait(.triggered());

initial begin
  $display("@ %0t: 1 :before trigger",$time);
  ->e1;
 wait(e2.triggered());
   $display("@ %0t: 1 :after trigger",$time);
  end

initial begin
  $display("@ %0t: 2 :before trigger",$time);
  ->e2;
 wait(e1.triggered());
   $display("@ %0t: 2 :after trigger",$time);
  end

结果：

# @ 0: 1 :before trigger
# @ 0: 2 :before trigger
# @ 0: 2 :after trigger
# @ 0: 1 :after trigger

原因：wait()是电平敏感

systemverilog中event使用方法