请问各位高手：  
   
  问题一：     事件SetRTS（OnOff:   Boolean）有什么用：  
  帮助中这样写：  
  Enables   or   diables   RTS   signal.  
  procedure   SetRTS(OnOff:   Boolean);  
   
  Description  
  Use   SetRTS   function   to   enable   or   disable   RTS   (request-to-send)   signal.   OnOff   parameter   can   be   one   of   the   following   values:  
   
  Value Meaning  
  True Sets   RTS   signal  
  False Clears   RTS   signal  
   
  Note  
  If   FlowControl.ControlRTS   property   is   set   to   rtsHandshake,   it   is   an   error   for   the   application   to   call   SetRTS   function   and   EComPort   exception   is   raised.  
   
  问题二，串口通讯中的流控制又是怎么回事：  
  帮助中这样写：  
  Sets   common   flow   control   type.  
   
  type   TFlowControl   =   (fcHardware,   fcSoftware,   fcNone,   fcCustom);  
  property   FlowControl:   TFlowControl;  
   
  Description  
  Set   FlowControl   property   to   set   one   of   common   flow   control   types   (e.g.   hardware,   software).   FlowControl   property   is   virtual   property,   so   its   value   depends   on   the   following   properties:   ControlRTS,   OutCTSFlow,   XonXoffIn   and   XonXoffOut.  
   
  Note  
  Setting   FlowControl   property   usually   changes   other   properties   of   TComFlowControl   class.   Also   setting   other   properties   of   TComFlowControl   class   changes   FlowControl   property.  
  谢谢各位  
   
  最后，我最近在编写串口程序，自感基础知识不够，有没有参考书推荐一下。