Go look on Xilinx's or Altera's web site. Go look on the FPGAs4Fun website, there are a lot of example designs using various features of various boards galore.
Why should I (or anyone else) have to produce an example design for you!?
lol. I did not ask for an example design. I only asked for example of a situation where we need to use it. Anyway, I am going to look at these websites to determine the answer to this question.