Invalid instruction exception?

We are running some code on a NIOS2/CycloneII platform.

Somehow the code is telling the processor to execute some instructions that is outside the code segment. Not sure yet if this is a hardware or software issue.

I can break into the debugger and examine registers, but the ra register (return address?) is 0xFFFFFFFF.

Is there anyway to set a breakpoint if the pc is outside a certain range?

Is there a way to break into the debugger when an invalid instruction is executed?