Problem with FPGA and SRAM

I have a problem with my FPGA board.MY board mainly contains EP1C6T144I7N(FPGA),

IS61LV12816L (external sram ) and EPCS16. Application program can run in SRAM

successfully online .If I download the sof file and the elf file into EPCS16 and turn on the power again,the application program can't run successfully in external sram . If the application program dosen't run in external sram but in on-chip ram of FPGA,the application program can run successfully after I download the sof file and the elf file into EPCS16.What should I pay attention to when use SRAM? Could anyone do me a favor?