Nios Trace Format

[Altera_Forum]

is there a documentation for the Nios trace format? The handbook says it's in a compressed format, I'd like to know the format if it's not super secret information.

[Altera_Forum]

I'm asking about both off-chip and on-chip traces.

[Altera_Forum]

Hi! I'm also trying to look into it. Did you manage to find anything interesting?

[Altera_Forum]

I disassembled the monitor program java code and used the trace format decoder in there!

[Altera_Forum]

Aha! Which file is the java monitor program? 

 Mainly, I am hoping to get the trace from the off-chip pins (offchip_trace_clk, offchip_trace_data and trigout). From a look at SignalTap there doesn't seem to be much happening, which makes me think that perhaps the trace output needs to be 'enabled' (through the JTAG?) hence the trigout pin telling the logic to start recording.  If this is the case there are two issues I need to overcome: - how to enable the trace output - how to convert this output into address accesses  Any help on either of those would be much appreciated!

[Altera_Forum]

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).

[Altera_Forum]

Ah that makes a lot of sense! Indeed there are bursts of data on the off-chip trace, I just assumed it would be the direct memory access addresses instead of the compressed format you mention. Thanks for your help!