KCU105 board 16G SFP+ links

[stmallios]

Dear experts, I would like to establish a 16G (14.025Gb/s data rate) SFP+ links using the GTY transceivers provided by the KCU105 evaluation board. I am a little confused regarding the specification required to establish the link. From what I understand the sfp+ modules provided with the board support a maximum line rate of 10G, so I need to buy new modules. I am between those two http://www.mouser.ch/Search/ProductDetail.aspx?R=FTLF8529P4BCVvirtualkey58360000virtualkey508FTLF8529P4BCV http://www.digikey.fr/products/fr?keywords=AFBR-57F5PZ but i see that for 16G links I need to comply with the following specification ftp://ftp.seagate.com/sff/SFF-8081.PDF. This describes everything you need for a 16G SFP+ fiber channel link. But for the plug and cage of the sfp+ module I need the SFF-8432 specification. The board SFF+ specification is SFF-8431. My question is are the two modules above compatible with the board, and is it possible to establish the 16G link? Thank you very much and sorry for the long massage!!

[allanherriman]

Both the SFP modules you mention are suited to 16G Fibrechannel.

The SFP+ modules will fit in the SFP+ cage on the KCU105.

The GTH transceivers on the FPGA (which I think has an FF package, -2 speedgrade) are rated to work at 16.375Gb/s, and will handle 14.025Gb/s just fine.

(BTW, "16GFC" is actually 14.025Gb/s on the line.)

Things I haven't checked:

• Whether the PCB is good for 14.025Gb/s
• Whether the right reference clock frequencies are available
• Whether there is an IP core that will make it all work.

Allan

[stmallios]

Thanks for the answer and the help. So I finally got the sfp+ modules and run some tests.

1. The PCB is fine for up to 14.025Gb/s.

2. You can use the Si570 PROGRAMMABLE XO/VCXO of the board to get the reference clock you need.

3. And both iBert core and GTH cores work fine.

The only problem is that the specific sfp+ module only locks at 14.025Gb/s.

I tried with different rates from 10G/s to 16G/s and it only locked for ~14G/s.

Does anybody has any insights for this. Is this expected or am I doing something wrong?

Also 10GbE modules that came with the board locked at various Line rates from 10Gb/s to 16.3Gb/s but with decreasing BER (especially above 14G/s). 

Thank you

[allanherriman]

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@stmallios wrote:
The only problem is that the specific sfp+ module only locks at 14.025Gb/s.

I tried with different rates from 10G/s to 16G/s and it only locked for ~14G/s.

Does anybody has any insights for this. Is this expected or am I doing something wrong?

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That sounds right for an SFP that contains CDR.  (Some SFPs do; most don't.)  The CDR will only lock around a particular range of bit rates.

SFPs that contain CDR typically use the RS[1:0] pins to determine which rate to use.  Have you set them correctly?

For that matter, many multi-rate SFPs need RS[1:0] set to particular values to work even if they don't contain CDR.

The SFP datasheet will always say whether a module contains CDR (as it's an important feature).

Also, if it's a Fibrechannel SFP, try 8.5Gb/s (which is the next lower FC rate below 14.025Gb/s).

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@stmallios wrote:
Also 10GbE modules that came with the board locked at various Line rates from 10Gb/s to 16.3Gb/s but with decreasing BER (especially above 14G/s).

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Assuming you meant BER INcreasing with bitrate above 10Gb/s, that sounds about right for a multi-rate SFP.

Allan

[allanherriman · Accepted solution]

I just read the AFBR-57F5PZ datasheet.  It's one of the modules mentioned in the Original Post.

It quite clearly states "Per the requirements of 16GFC, internal clock and data recovery circuits (CDRs) are present on both electrical input and electrical output of this transceiver. These CDRs will lock at 14.025Gb/s (16GFC) but must be bypassed for operation at 8.5Gb/s (8GFC) and 4.25Gb/s (4GFC), accomplished by using two Rate Select inputs to configure transmit and receive sides."