This is a known issue with the way in which NetGen is writing out the netlist.
This issue is fixed in ISE 8.1i Service Pack 2.
There is a patch available for ISE 8.1i Service Pack 1 for this issue:
http://www.xilinx.com/txpatches/pub/swhelp/ise8_updates/cr218903.tar.gzThe instructions on using the patch is below:
Date: 9th January 2006
File Name: cr218903.tar.gz
Description: Patch for CR218903. NetGen does not buffer the input to the X_IDELAY primitive.
Platform: All
Applicable Software version: ISE 8.1i Service Pack 1
Installation/Use:
Extract the archived file as shown below:
PC :
Use any unzip utility to unarchive this file.
Once the file is unarchived, the following directory should be visible:
virtex4
Set an environment variable called MYXILINX to point to this directory.
For example, if the directory is in the "C:\cr218903" folder, the environment variable would be set as follows
> set MYXILINX=C:\cr218903
Setting MYXILINX will override the XILINX variable when using the data files.
Unix / Linux:
Type the following:
>gunzip cr218903.tar.gz
>tar -xvf cr218903.tar
Once the file is unarchived, the following directory should be visible:
virtex4
Set an environment variable called MYXILINX to point to this directory.
For example, if the two directories are in the "/home/duthv/CR218903"
folder, then the environment variable would be set as follows:
> setenv MYXILINX /home/duthv/CR218903
Setting MYXILINX will override the XILINX variable when using the data files.
Testing:
Once the files are extracted and the MYXILINX environment variable is set, please retry NetGen and the HDL file should be generated accurately.
If it does not work, verify that the MYXILINX variable does point to the directory where the "virtex4" directory resides.
This can be done by typing the following:
PC :
echo %MYXILINX% in a command prompt window
Unix / Linux :
echo $MYXILINX in a terminal/xterm window.