ISE 报错 NCD was not produced 解决方法

错误原句如下

Pack:198 - NCD was not produced.  All logic was removed from the design.  This is usually due to having no input or output PAD connections in the design and no nets or symbols marked as 'SAVE'.  You can either add PADs or 'SAVE' attributes to the design, or run 'map -u' to disable logic trimming in the mapper.  For more information on trimming issues search the Xilinx Answers database for "ERROR:Pack:198" and read the Master Answer Record for MAP Trimming Issues.

这个报错是指该模块没有任何输入输出接口。

发生个这个错误的同时会伴随着大量其他ERROR，诸如：

ERROR:Xst:2035 - Port has illegal connections. This port is connected to an input buffer and other components.

或者：

ERROR:Xst:1706 - Unit : port of logic node has no source

正是这些error将我们的输入输出信号屏蔽掉了。

发生这种错误最可能的原因是使用了 initial语句，initial语句是不可综合的，仅供仿真使用。