When FPGA Express v1.2 is used as a module generator, the XNF generated by FPGA Express incorrectly contains EXT records when the "Do not insert I/O" option is selected. These EXT records must be replaced with SIG records if the XNF from FPGA Express is used as a module in a larger design.
This problem has been fixed in FGPA Express 2.0.
A script (ext2sig.pl) in Perl was wrote which can covert the EXT records of a XNF file into SIG records. Perl for Windows 95 or Perl for Windows NT will be required to run this script.
Perl is a public domain software tool which can be found on the Web. A search via the search engine of your choice can list many sites which provide Perl for Windows 95 and/or NT. One such site is:
Take the file ext2sig.pl and place it in the same directory as the XNF file you want to change. To use the script, type the following at the DOS prompt:
perl ext2sig.pl <xnffilename>.xnf
where <xnffilename> is the name of the XNF. ext2sig will create a copy of your original file with the extension .org. A file of the same name as the input file to ext2sig will be created.
For example, let's say you have a file called module.xnf generated by FPGA Express. Copy module.xnf and ext2sig.pl into the same directory. In the directory that contains module.xnf and ext2sig.pl, type at the DOS prompt:
perl ext2sig module.xnf
After running this command, you will have a file called module.xnf and another file called module.xnf.org. module.xnf has all EXT records converted to SIG records. module.xnf.org is your original file.