Quartus CPLD未使用引脚处理
未使用的引脚可以设置成输出,三态输入,弱上拉输入等。Quartus 8.0默认设置成输出低电平(As output driving ground)。
引脚设置方法:
【Assignments】->【Setting】->【Device】->【Device and Pin Options】->【Unuse Pins】
As input tri-stated:三态输入(高阻输入)
三态输入很安全,不会因外部电路接错导致烧坏IC,但是三态输入通常会增加系统耗电(若引脚未与外部电路相连,是悬空的)。
As input tri-stated with bus-hold circuitry:三态输入总线保持
As input tri-stated with weak pull-up resistor:弱上拉输入
As output driving an unspecified signal:输出高阻
As output driving ground:输出低电平
这个有可能导致IC自身非常烫