SRAM pin assignement problem

I would like to generate a system with sram, in oder to write something inside and to read it.

I have to face many pin assignement problem. Indeed, i've added IDT71V416 SRAM in SOPC builder and generated my system.

Then i've do the compliation. During the pin assignement, there are less pins in the DE2 board that the numbers of pin that it ask to assign.

Indeed there are 18 pins for the adress of Sram and 16 pins for data on DE2 Board.

And the programm ask me to assign 19 pin for dram adress and 32 pin for dram bidirectionnel data.

And there are about 5 pins that i don't understand what to do with, it's : be_n_to_the_sram[0],be_n_to_the_sram[1],be_n_to_the_sram[2],be_n_to_the_sram[3],be_n_to_the_sram[4]

Can someone help me ?

thx