EEPW论坛

如题，编译的工程是用MIG生成的DDR2控制器，自己为了测试添加了几个模块，写了一个顶层文件，并且根据自己的板子调整了UCF文件，在综合的时候出现了下面的问题，百思不得其解。求哪位能知道这是为什么嘛？要怎么改正呢？

ERROR:LIT:600 - IOBUFDS symbol
   "XLXI_1/u_ddr2_top_0/u_mem_if_top/u_phy_top/u_phy_io/gen_dqs[0].u_iob_dqs/gen_dqs_iob_ddr2.u_iobuf_dqs" (output
   signal=XLXI_1/u_ddr2_top_0/u_mem_if_top/u_phy_top/u_phy_io/gen_dqs[0].u_iob_d
   qs/dqs_ibuf) does not have IOSTANDARD specified. Map is unable to generate a
   default IOSTANDARD for IOBUFDS, one has to be explicitly provided.
Errors found during logical drc.

Design Summary
--------------
Number of errors   :   1
Number of warnings :   0

Process "Map" failed
Preparing to edit top.ucf...