FPGA 中的警告：Warning: Some pins have incomplete I/O assignments （Missing drive strength and slew rate）

最近在FPGA程序全综合时碰到了个奇怪的问题：

Warning: Some pins have incomplete I/O assignments. Refer to the I/O Assignment Warnings report for details

查看了compilation report-> I/O Assignment Warnings 提示是 输出管脚“ Missing drive strength and slew rate”。记得用过CycloneII芯片就不会出现这种警告，google了下，是因为后续高级的芯片的 drive strength 和 slew rate 都是可编程的。如果不指定的话，quartus会给出默认值并给出警告。消除警告的办法是在pin planner 分配管脚时同时制定这两个值。设置方法如下：

In the pin planner in the pin list there's a column called Current Strength.
If it doesn't show up there, right-click your mouse in the pin list and select customize columns.... You can add the currenth strenght column and select the desired drive strength.

网址：http://www.alteraforum.com/forum/showthread.php?t=24347