SDRAM with FrontPanel USB


I am working with SDRAM and I am wondering how would you make a driver that communicates through USB, because the SDRAM write or read cycle takes few clk cycles (example ACTIVE,NOP, READ, NOP, PRECHARGE) and ok_readFromPipeOut() works instantly. Also the SDRAM works on clk1 of FPGA and USB has ti_clk.
I thank you for an answer in advance.