ISE生成bit文件出错：Bitgen:342

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

右键generate programming file选择process properties，添加如下蓝色部分。