quartus ii unused pins的设置？
但是我发现还可以设为：As input tri-stated with bus-hold circuitry
不知道这二种有什么却别呢?什么时候必须选择第二种设置呢?
"As input tri-stated" can result in high current and device overheating if a dedicated input or I/O pin is completely floating on the board. The input buffer could oscillate. Refer to the .pin file produced by the Fitter to see how to connect each pin. The .pin file will tell you to connect pins that are not supposed to be left floating.
If your particular device allows it, it would be safer to set "Device and Pin Options --> Unused Pins --> Reserve all unused pins" to "As input tri-stated with bus-hold circuitry" or "As input tri-stated with weak pull-up resistor".
If you know you have a particular spare pin grounded on the board, the weak pull-up would of course use a little power. (Bus hold on a grounded pin is fine.) For specific pins you have grounded on the board, use the Assignment Editor to set "Reserve Pin" to "As output driving ground". You can use "Reserve all unused pins" for the rest of the spare pins instead of an Assignment Editor setting for each one.
受教了。
另外, As output driving ground 有时候会误接HIGH，这样就容易烧掉。
楼上的正解
还是不太明白呢……
能用中文解释吗?这样大家都好理解些。