1.问题的提出:spartan6中不允许时钟信号直接连到IO口上面? 2.解决办法: ODDR2的使用 ODDR2Primitive: Double Data Rate Output D Flip-Flop with Optional Data Alignment, Clock Enable and Programmable Synchronous or Asynchronous Set/Reset The ODDR2 is an output double data rate (DDR) re