DDR SDRAM is a high speed and largecapacity memory,but because of the need of synchronous clock and the characteristic that it is controlled by control command,there must be a controller between the system and DDR SDRAM.

• DDR SDRAM是一种大容量,高速度的同步动态存储器,但是由于其对同步性的要求以及需要由控制字来控制的特点使得他与系统之间必须有一个接口来实现时钟同步和对DDR SDRAM进行控制。