用nios 8.0时在debug..时出现Select a JTAG cable. If none are available, you must install one first.但是JTAG cable为灰色不能选~~~然后就有The specified JTAG device (in the Target Connection tab) is invalid. Use the Run|Run... or Run|Debug... menus to check your launch settings and try again.请高手帮忙~~万分感谢~~