测试文件里描述一个高电平为10ns，低电平为150ns的周期信号这样写可以吗？

      u1:  PROCESS
          variable time0 : TIME := 0 us;  
            BEGIN
              while time0<20us loop
               FS<='1';
               wait for 10ns;
               FS<='0';
               wait for 150ns;
               time0:=time0+160ns;
             end loop; 
            end process;