Nios Trace Format

I think the off-chip trace was running by default, double check that, and make sure you get enough samples, it sends out bursty data.

In a nutshell, the trace format is compressed, meaning that only the outcome of branches and interrupts are sent out with some checkpointing data. So you need the binary file running on Nios to find out what addresses are actually being executed. Take a look at Lauterbach's trace32, I think they have an OK documentation about how off-chip tracing works (Nios conforms to Lauterbach's format I think which is called Nexus something, I can't recall the actual name).