

                    Core name: Xilinx LogiCORE Fast Fourier Transform C model
                    Version: 8.0
                    Release Date: March 1, 2011


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This document contains the following sections: 

1. Introduction
2. New Features
3. Resolved Issues
4. Known Issues 
5. Technical Support
6. Other Information
7. Model Release History
8. Legal Disclaimer
 
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1. INTRODUCTION

For the most recent updates to the IP installation instructions for this core,
please go to:

   http://www.xilinx.com/ipcenter/coregen/ip_update_install_instructions.htm

 
For system requirements:

   http://www.xilinx.com/ipcenter/coregen/ip_update_system_requirements.htm 


This file contains release notes for the Xilinx LogiCORE IP Fast Fourier Transform v8.0 
C Model. For the latest core updates, see the product page at:
 
  http://www.xilinx.com/products/ipcenter/FFT.htm


2. NEW FEATURES  
 
   - None
 
3. RESOLVED ISSUES 
 
    - C model LSB mismatch for odd point sizes, streaming architecture
      - CR546238
      - CR576743
      - CR576806

4. KNOWN ISSUES 
   
   The following are known issues for v8.0 of this C model at time of release:

   - Slow model performance
     - The FFT bit accurate C model uses fixed point classes internally which make a number
       of malloc() and free() calls while the xfft_v8_0_bitacc_simulate() function is running.
       These kernel calls can impact the simulation speed of the model
     - CR471384

   - C model output incorrect for some 65536-point Pipelined, Streaming I/O FFTs with convergent rounding
     - When convergent rounding is used with a scaled or block floating point 64k Pipelined, Streaming I/O
       transform, some datasets can cause the final rounding operation performed by the model to produce
       values equal to +1.0, which cannot be represented by the IP core.  The IP core behaves correctly
       in these cases.
     - If the C model and IP core must match exactly in this case, using truncation rather than convergent
       rounding will yield the same results in both models.
     - CR476547

   The most recent information, including known issues, workarounds, and
   resolutions for this version is provided in the release notes Answer Record
   for the ISE 12.3 IP Update at 

   http://www.xilinx.com/support/documentation/user_guides/xtp025.pdf

5. TECHNICAL SUPPORT 

   To obtain technical support, create a WebCase at www.xilinx.com/support.
   Questions are routed to a team with expertise using this product.  
     
   Xilinx provides technical support for use of this product when used
   according to the guidelines described in the core documentation, and
   cannot guarantee timing, functionality, or support of this product for
   designs that do not follow specified guidelines.


6. OTHER INFORMATION
   
   Full documentation of the C model is provided in the document
   "xfft_bitacc_cmodel_ug459.pdf".


7. CORE RELEASE HISTORY 

Date        By            Version      Description
================================================================================
03/01/2011  Xilinx, Inc.  8.0          Bugfix for LSB mismatch in streaming architecture
09/21/2010  Xilinx, Inc.  8.0          C model for FFT v8.0
04/19/2010  Xilinx, Inc.  7.1          C model for FFT v7.1
06/24/2009  Xilinx, Inc.  7.0          C model for FFT v7.0
09/19/2008  Xilinx, Inc.  6.0          C model for FFT v6.0
10/10/2007  Xilinx, Inc.  5.0          First release of C model, for FFT v5.0
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8. Legal Disclaimer

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