说明：  sdram控制器 这里考虑将SDRAM控制器结合目前项目开展来做相应的模块，而不做SDRAM通用控制器，这样也是考虑了FPGA的器件资源而采取的措施。同时编写的逻辑简单，没有多余的逻辑资源有利于提高控制器的速度，满足最后的设计要求。
(SDRAM controller here consider SDRAM controller current projects do the corresponding module, but not so common SDRAM controller, as well as consider the FPGA device resources and the measures taken. While the preparation of simple logic, the logic is no spare resources to improve the speed controller to meet the final design requirements.)