Unable to debug

The processor not responding at all is usually caused by one of those:

[list][*]bad clock (are you getting the clock from the right pin? If using a pll, are the frequencies correct, is the pll locked?)

[*]bad reset signal (the reset input on the SOPC component is active low, while most HDL designs use an active high signal)

[*]using a Nios CPU in evaluation mode without a license. In that case do not close the alert box saying that you are in Opencore evaluation (the one with the cancel button) or the CPU will stop answering[/list]