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Altera_Forum
Honored Contributor
13 years agoAvalon 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 Zubair2 Replies
- Altera_Forum
Honored 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
Honored 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