Can not dowload the code into my Altera

Thanks for your reply.

I found the problem.For some reasons, the TMS, TDI, TDO and TCk pins were accidentally connected to four unused I/O pins besides being connected to the JTAG head. I cut the connections to the 4 I/O pins, it works.

Also, I noticed that in Settings, there is "Unused Pins" tab. I changed the setting of "Reserve all unused pins" from "As Output driving ground" to "As input tri-stated with weak pull-up resistor" and it works! I can download the code without cutting the connections mentioned above.

However, I found one of my output pin which was supposed to drve a LED does not work after changing the setting. Such pin is an output pin and it is not an "unused pin". I do not know why my setting change can affect it....

any idea?

Thank you!