nios interface with fifo

If it's a simple fifo then put a fifo outside, create a custom interface to the fifo (uses the avalon bus), bypass cache if you are using NIOS II/f, and read like you do from any other register. I've never taken a look at the IP that's posted in the forum, but if it sounds easy enough to use then try it, otherwise the solution I rambled off should do the trick too.