//******************************************************************************
//
//  Xilinx, Inc. 2002                 www.xilinx.com
//
//  XAPP 253 - Synthesizable DDR SDRAM Controller
//
//*******************************************************************************
//
//  File name :       ddr2_top
//
//  Description :     
//                    Main DDR SDRAM controller block. This includes the following
//                    features:
//                    - The main controller state machine that controlls the 
//                    initialization process upon power up, as well as the 
//                    read, write, and refresh commands. 
//                    - handles the data path during READ and WRITEs.
//                    - Generates control signals for other modules, including the
//                      data strobe(DQS) signal
//
//  Date - revision : 05/01/2002
//
//  Author :          Modified by Sailaja
//
//  Contact : e-mail  hotline@xilinx.com
//            phone   + 1 800 255 7778 
//
//  Disclaimer: LIMITED WARRANTY AND DISCLAMER. These designs are 
//              provided to you "as is". Xilinx and its licensors make and you 
//              receive no warranties or conditions, express, implied, 
//              statutory or otherwise, and Xilinx specifically disclaims any 
//              implied warranties of merchantability, non-infringement, or 
//              fitness for a particular purpose. Xilinx does not warrant that 
//              the functions contained in these designs will meet your 
//              requirements, or that the operation of these designs will be 
//              uninterrupted or error free, or that defects in the Designs 
//              will be corrected. Furthermore, Xilinx does not warrant or 
//              make any representations regarding use or the results of the 
//              use of the designs in terms of correctness, accuracy, 
//              reliability, or otherwise. 
//
//              LIMITATION OF LIABILITY. In no event will Xilinx or its 
//              licensors be liable for any loss of data, lost profits, cost 
//              or procurement of substitute goods or services, or for any 
//              special, incidental, consequential, or indirect damages 
//              arising from the use or operation of the designs or 
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//              of liability. This limitation will apply even if Xilinx 
//              has been advised of the possibility of such damage. This 
//              limitation shall apply not-withstanding the failure of the 
//              essential purpose of any limited remedies herein. 
//
//  Copyright