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Altera_Forum's avatar
Altera_Forum
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13 years ago

Avalon data bus between two fpgas

Hi,

I need a little advice/direction regarding connecting two fpgas via a bus.

HW setup

Stratix III (DE3) Stratix V

8 x LVDS Tx pairs ---------------------> 8 x LVDS Rx pairs

Any other I/O requirement for signaling is flexible. But for data, the DE3->Stratix V is limited at these 8 LVDS pairs.

The bus has to be capable of running at around 10g in total. i.e. around 1.2-1.4Gbps per LVDS pair.

Data is mainly from the DE3 to the Stratix V.

Ideally I would like to have seamless Avalon interfaces on both sides.

Can a dual-clock Avalon ST Fifo span across to the other FPGA via the AltLVDS megafunction?

e.g.

On the Stratix III (DE3)

I configure the Dual Clock Fifo

I use the SGDMA(scatter gather) to take data and Stream it out to a Dual Clock Fifo using Avalon ST.

I export the signals of the output side of the Dual Clock Fifo.

I connect the signals to the alt-lvds Tx megafunction.

The valid signal of the FIFO will act as the LVDS Clock for the transfer.

On the Stratix V side.

I receive the data via the alt-lvds Rx megafunction.

I put it in another Dual Clock FIFO and another SGDMA to read the data.

Can all this achieve around 10G..

Comments and suggestions (or complete alternate methods) welcome.

Regards

Zubair

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    Try it and see.

    Since the ALTLVDS interface will be serializing and deserializing data, you will also need a frame clock. If your data can accommodate some 'extra' symbols, then you can convert the Avalon-ST start-of-packet, end-of-packet, etc, wires into symbols in the data stream. This is how the JTAG-to-Avalon-ST interface works - read the following for details

    http://www.ovro.caltech.edu/~dwh/correlator/pdf/altera_jtag_to_avalon_analysis.pdf

    http://www.ovro.caltech.edu/~dwh/correlator/pdf/altera_jtag_to_avalon_analysis.zip

    This might give you a few ideas.

    Cheers,

    Dave
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    Yes. I will need a frame clock as well. I think I missed it out and its available in the hardware layout as well. Will double check.

    Also, I checked the Avalon ST spec. It has a valid signal. This should be usable to generate the frame clock using the Alt-lvds megafunction itself.

    Thank-you. Seems there are no obvious mistakes.. I guess I'll go ahead and play.

    Cheers

    Zubair