sdram core in EDK

Hello all:

I am sorry for troubling you for something this trivial, but I am new to
EDK.
I have instanced a generic sdram controller for a MicroBlaze on a Spartan 3.
The problem is that the refresh is not functioning. The memory buss is
totally
quiescent except when reads or writes are occurring. I am sure there is some
initialization command or signal I am overlooking.

Thanks,

Fayette