What is the fastest way of accessing on-chip register contents?

The data you send across the link is not synchronous to the 10Gbps clock, so you must decouple it somehow right? One way of decoupling the data would be to packetize it. Each packet of data samples can be preceded by a header that contains; a timestamp (or packet ID code or incrementing count), a data rate (the thing you are trying to figure out now), and the number of samples to follow in the data payload. 
For example, lets say I have an Avalon-ST stream generating 16-bit samples at 100MHz clock rate, i.e., 200MB/s. I could capture a block of this data (using a FIFO or dual-port memory), prepend the header, send it over the link, and then generate a 16-bit 100MHz clock rate data stream on the other side of the link. So long as the Avalon-ST valid signal is used to indicate when samples are valid, the DSP logic on either side of the link should work correctly.

This is clear for me now, thanks Dave.

Regarding the communication between a host PC and modules of a design, beside using the Ethernet interface, if I use the bytestream service to send/receive byte-streams via the data mode of the JTAG-to-Avalon-ST bridge from/to an application running on the host PC, what is the maximum rate this service can provide?

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http://www.alterawiki.com/wiki/nios_ii_udp_offload_example

You can use it (and it's components) to get your bearings.

Basically, what you want to do is to create a new Qsys component with an Avalon-MM Master port and a state machine to execute the (various) reads to gather and/or compute the statistics you want to communicate to the host.

Then, take that data and encode it into the payload of a UDP packet.

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This is really what I am looking for to prepare for my next step. Thank you very much. If possible, when I start working on this, I would ask you for some further support.

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On the PC, you just need to write a simple socket utility to receive the UDP packets.

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How did you do this, I heard about this, it is simple but actually really new for me. If you can provide more details or references about this socket utility?

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Which route to go basically depends on whether you are a software person or a hardware/HDL person, and whether or not your hardware can support you.

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To be honest, I don't know if I am a software or hardware guy now. But I would say that I have some experience with Verilog, Altera tools like Qsys, System Console, TCL scripting, Signal Tap, Transceiver Toolkit and hardware verification.

Again, thank you very much

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Regarding the communication between a host PC and modules of a design, beside using the Ethernet interface, if I use the bytestream service to send/receive byte-streams via the data mode of the JTAG-to-Avalon-ST bridge from/to an application running on the host PC, what is the maximum rate this service can provide?

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The details are in the document I wrote and linked to.

The transport rate is limited by the 6MHz JTAG clock used on the USB-Blaster interface. When operating in byte-mode, it takes the equivalent of 10 6MHz clocks per byte

(there's 8 actual clocks and then a gap of a couple of clocks before the next byte), so about 600kB/s transfer rate. This is the data rate of master_read/write_memory for blocks of data, and its the data rate of the Avalon-ST interface - which the JTAG-to-Avalon-MM bridge is implemented using.

There's really no advantage in using the JTAG-to-Avalon-ST interface directly. The JTAG interface should only really be used for slow control/monitoring. For your application, you should be using the 10Gbps link to move your data and meta-data.

Cheers,

Dave

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The details are in the document I wrote and linked to.

There's really no advantage in using the JTAG-to-Avalon-ST interface directly. The JTAG interface should only really be used for slow control/monitoring. For your application, you should be using the 10Gbps link to move your data and meta-data.

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Thank you very much Dave. Your explanation really answers most of my wondering these days and gives me a clear direct for the next step to go.

Best,

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Thank you very much Dave.

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You're welcome.

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Your explanation really answers most of my wondering these days and gives me a clear direct for the next step to go.

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Its always best to start with a good plan! :)

Cheers,

Dave