在ISE中调试程序，综合过后，会出现下面的错误，求大神指导怎么解决啊?

浮生素问

ERROR:MapLib:978 - LUT3 symbol
   "u_DDR3/u_memc_ui_top_std/u_ui_top/ui_wr_data0/app_wdf_data_ns1<0>1" (output
   signal=u_DDR3/u_memc_ui_top_std/u_ui_top/ui_wr_data0/app_wdf_data_ns1<0>) has
   an equation that uses input pin I2, which no longer has a connected signal.
   Please ensure that all the pins used in the equation for this LUT have
   signals that are not trimmed (see Section 5 of the Map Report File for
   details on which signals were trimmed).