Cyclone II On-chip RAM megafunction

Thank you for the reply. Let me elaborate it a little clearer. The Altera FFT megafunction does not allow the user to customize how the on-chip RAM is used. In other words, I don't know which chunk of RAM will be used by the FFT core when it is being instantiated. I need to use the on-chip RAM to store some data for future computation. So, my worry is that the RAM used by FFT core may be overlapping with the memory I used to store the data. My data may be overwritten by the FFT core during the computation if this is the case. So, I would like to get some hints on how the FFT core allocate Memory and how we can avoid such Memory conflict in the design.