Dear AP KANNAN
I use the EC-2 adapter.
If you intend to build your own adapter you have to make your own software witch is not to much complicated but time consuming.
As for a scheme of a JTAG adapter using PC parallel interface please take a look at:

http://toolbox.xilinx.com/docsan/2_.../fig26.htm

There are also many other solutions on the web.
However, the software is specific and I doubt you will find it on the web.
Using the PC’s parallel port raises some reliability problems for the motherboard so I think is safety to use a serial port as EC-2 does.

As Michael Karas advised you, use the DLL lib and the EC-2 dongle; I think is the cheaper and easiest solution.
The DLL is accompanying the application note AN017 on the Cygnal site.


Regards,
Cristian