The Nios® II debugger may fail to connect and return the message below if the reset vector is to uninitialized memory:
Using cable "USB-BlasterII [1-1.1]", device 1, instance 0x00
Pausing target processor: not responding.
Resetting and trying again: FAILED
Leaving target processor paused
Examples of uninitialized memory include external memory interfaces and flash devices with random contents.
The Nios II processor begins execution from the reset vector. If a break instruction is executed before the debugger is connected and initialized, the processor may enter a state where it cannot execute a break instruction to pass execution to the debugger.
Ensure that when the Nios II processor exits the reset state, the memory at the reset vector is initialized.