I got my papilio pro board a couple of weeks ago, I'm an experience programmer but I'm new to FPGA, I've read a couple of books on VHDL, and for the most part I understand the basics, I spent the last couple of days implementing an SDRAM controller. I did finally get it working, but it became really apparent my understanding of when to use OBUF's, BUFG's etc etc, was at best an educated guess. Is there a good discussion on when and why to use the SelectIO resources, I've read the Xilinx piece, but while I think I understand what they are, I have no intuition on when or why to use them. Thanks