Warning: xx pins must meet Altera requirements for 3.3-, 3.0-, and 2.5-V interfaces. For more information, refer to AN 447: Interfacing Cyclone IV E Devices with 3.3/3.0/2.5-V LVTTL/LVCMOS I/O Systems
问题描述：
Cyclone IV EP4CE6E22C8N
Quartus II编译
每次编译完，都有个warning：
Warning: xx pins must meet Altera requirements for 3.3-, 3.0-, and 2.5-V interfaces. For more information, refer to AN 447: Interfacing Cyclone IV E Devices with 3.3/3.0/2.5-V LVTTL/LVCMOS I/O Systems
处理办法：
这个warning是Quartus II用来提醒用户的，没法消除，告诉用户要注意引脚而已。
参考资料：
