FPGA nios 系统timestamp问题

在FPGA上搭建nios系统，在上面实现hello world应用，总是出现如下错误：

Reading System ID at address 0x00000808: 

    ID value does not match: read 0xFFFFFFFF; expected 0x5E5B656D

    Timestamp value does not match: image on board is older than expected

    Read timestamp  7:59:59 1970/01/01; expected  9:48:46 2011/02/23

The software you are downloading may not run on the system which is currently

configured into the device.  Please download the correct SOF or recompile.

一般出现上述错误原因为在FPGA板上烧的sof文件和nios ide软件工程文件不匹配，但自己反复编译多次仍出现上述错误。最后解决方法如下：

在quartus II 工程setting中，点击device and pin option。出现对话框中在unused选项卡中将reversed all unused pins 设为 as input tri-stated。重新编译，烧入FPGA板。再在nios ide中运行helloworld即可。