RocketIO over cable

vt2001cpe,

http://www.xilinx.com/products/design_resources/conn_central/grouping/aurora.htm

details the Aurora protocol, which should be lightweight enough that it
does not burden your data transfers.

You need something to: keep track of connection state, bond more than
one MGT together (to get more bandwidth), deal with errors, organize
data into frames, perform flow control, encode/decode in 8b/10b or
84b/66b, etc.

Using the MGT all by itself is starting from scratch, and you will
eventually have to decide how to deal with all of the items I mentioned
above.

Thus, the reason why we created Aurora, and offer it license free, with
supported IP.

Enjoy,

Austin

vt2001cpe wrote:
> Perhaps I did not phrase my question correctly. Assume a hypothetical
> system where raw captured data from an ADC is streamed from one box to
> another. The two boxes are connected via some sort of RocketIO link
> over copper. Ideally, I would like to transmit just the raw samples,
> but it seems some sort of overhead will be required to keep the link
> established and aligned. In the event that bit errors occur, and a
> comma character is falsly detected by the receiver, what happens? For
> example, will the receiver try to realign and continue pumping out
> data, now misaligned by the false comma, until the real comma is
> detected? Or will the receiver raise an error flag, but not try and
> realign. I am more interested in maintaining the throughput, and less
> concerned that data is "correct". That having been said, I would like
> to have correct data, but I do not think I can afford the overhead of
> error correction.
> 
> Any insight or suggestions?
> --Dennis
> 
> Ed McGettigan wrote:
>> vt2001cpe wrote:
>>> Thank you everyone for your quick and informative responses! In the
>>> event of a large number of bit errors, is it possible for a comma
>>> character to be incorrectly introduced? What would the effect be? Will
>>> the CRC fail and put the state machine into an error state, or will
>>> data continue to transmit, unaware?
>> It is possible to generate more than a single bit error in the same
>> 8b10b word, but with a well designed link this is very unlikely to
>> occur.  In any case your transmitter is completely unaware that an
>> error actually occurred and will happily continue transmitting. It's
>> your receiver logic needs to be able to handle any errors that happen.
>>
>> The worst case that could happen is that the error generates a comma
>> character that is out of alignment with the previous alignment.  This
>> would cause a constant stream of errors until a correct comma character
>> is received and the link realigns to the correct 8b10b word. All of
>> this is fairly standard stuff and has been around for decades in
>> many different protocols.
>>
>> Since it doesn't look like you have a particular protocol in mind. I
>> would suggest that you take a look at the light weight Aurora protocol
>> http://www.xilinx.com/aurora  Even if you decide to not use it, you
>> should be able to learn a lot from it.
>>
>> Ed McGettigan
>> --
>> Xilinx Inc.
>