Kintex7 Aurora生成bit文件出错

最近在做一个关于光纤的项目，使用了Kintex 7的Xilinx Aurora IP核，ISE 14.7，但是他的例程在生成Bit文件时候报错，
ERROR:Bitgen:342 - This design contains pins which have locations (LOC) that are
   not user-assigned or I/O Standards (IOSTANDARD) that are not user-assigned.
   This may cause I/O contention or incompatibility with the board power or
   connectivity affecting performance, signal integrity or in extreme cases
   cause damage to the device or the components to which it is connected.  To
   prevent this error, it is highly suggested to specify all pin locations and
   I/O standards to avoid potential contention or conflicts and allow proper
   bitstream creation.  To demote this error to a warning and allow bitstream
   creation with unspecified I/O location or standards, you may apply the
   following bitgen switch: -g UnconstrainedPins:Allow

请问有谁遇到过这个问题吗?该怎么解决呢?谢谢！
补充：Xilinx官网查的好像是Kintex7对电平的要求比较严格，所以不能用默认电平，必须亲自设置电平。他默认的是LVCMOS18，我就在PlanAhead里面挨个点选了LVCMOS18（去掉了default），可以生成bit文件了。但是我是根据默认是什么电平就设置了什么电平，我应该在哪找他真实正确的电平设置?Kintex 7用户手册里面没找到说哪个引脚用什么电平之类的说明啊。对电平约束这块真是一点不懂，如果有什么好的科普资料也请分享一下谢谢