[DRC NSTD-1] Unspecified I/O Standard: 2 out of 25 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: NAND_RE_N_0, and NAND_RE_N_c_0.

这是一个 Vivado 工具的警告信息，意思是有部分逻辑端口的输入/输出标准没有指定具体的类型，可能会导致电路板电源或连接性的问题，从而影响性能、信号完整性甚至可能对设备或其连接的组件造成损坏。为了解决这个问题，需要指定所有的输入/输出标准。如果不想指定，则可以使用提供的命令来允许生成位流文件，但这并不推荐。需要注意的是，当使用 Vivado 运行基础设施时（如 launch_runs Tcl 命令），需要将该命令添加到 .tcl 文件中，并将该文件作为实现运行的 write_bitstream 步骤的前钩子。在这个问题中，NAND_RE_N_0 和 NAND_RE_N_c_0 是存在问题的端口。