在使用vivado做兩位十進位制數倒計時動態顯示時，出現以下錯誤。

提示錯誤：

[DRC NSTD-1] Unspecified I/O Standard: 4 out of 34 logical ports use I/O standard (IOSTANDARD) value 'DEFAULT', instead of a user assigned specific value. 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 correct this violation, specify all I/O standards. This design will fail to generate a bitstream unless all logical ports have a user specified I/O standard value defined. To allow bitstream creation with unspecified I/O standard values (not recommended), use this command: set_property SEVERITY {Warning} [get_drc_checks NSTD-1].  NOTE: When using the Vivado Runs infrastructure (e.g. launch_runs Tcl command), add this command to a .tcl file and add that file as a pre-hook for write_bitstream step for the implementation run. Problem ports: seg_cs[4], seg_cs[3], sm_duan[0], and sm_duan_ge[0].

檢查XDC檔案： 

解決：將約束檔案的後面註釋文字去掉，應該是不允許在XDC後加註釋吧。