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Participant namabo
Participant
492 Views
Registered: ‎07-27-2018

Which IP choose to drive a QSFP28 cage

Hi,

I'm evaluating to buy a dev kit with optical connection such as Xilinx Virtex UltraScale+ FPGA VCU118 Evaluation Kit,

I saw it has 2 QSFP28 cage, now one cage has following option to reach a throughput of 100Gb/s:

1) 4x25Gb/s

2) 10x10Gb/s

 

I think CMAC 100G Ethernet Subsystem is the first choice that implements the above configuration, but I want to know if the optical interface can be "partitioned", can I use 10G/25G Ethernet Subsystem just to control only one of the link, and so put 4 10/25 IP, or using two 40G/50G?

 

I guess there is a strictly relation among IPs and transceivers GTY /GTH, but I would like an explanation on the various

combination of IP that can be connected to such type of cages.

 

This because

Thank you.

 

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2 Replies
Scholar drjohnsmith
Scholar
474 Views
Registered: ‎07-09-2009

Re: Which IP choose to drive a QSFP28 cage

QSFP's have two parts,

 

the High speed serdes bits, 

    but the bits people forget, is the control, I2C and the pins,

 

The Serdes part is actually 'easy' , in that its 'just' connecting the QSFP to the SerDes pins of the fpga,

    The bit that will catch you out there is the ordering

 

depending upon the IP ,  certain SerDes can connect , 

    you need to check the IP you look at as to what serdes you can use , and the clocking they need.

 

The control and I2C, tends not to be part of the IP blocks, but left to your processor

    but this is needed to turn the QSFP on, issue resets, control the Tx power of the Optical block,

       even read the ID of the module,   

 

this is a lot more difficult to get right as information tends to be less easy to come by,

     they sort of assume you have linux or such like with drivers in place to do this comms.

 

good luck

 

 

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459 Views
Registered: ‎01-08-2012

Re: Which IP choose to drive a QSFP28 cage

I saw it has 2 QSFP28 cage, now one cage has following option to reach a throughput of 100Gb/s:

1) 4x25Gb/s

2) 10x10Gb/s

 

I skimmed through UG1224, and I'm really not sure where you found that it said that it was possible to use 10x10Gb/s connections to a QSFP28.

Each QSFP28 has four 25Gb/s lanes (known as CAUI-4).  There is no 10x10 option (known as CAUI-10) on this board.  Some legacy 100G interfaces (e.g. CFP) did support CAUI-10, but the VCU118 does not have any of those.

 

The CMAC only does 100Gb/s Ethernet.  It will not do 40G, or any other rate.  You can use a single (or multiple) lane of 10/25G on this board, but not using the CMAC - you will require other IP for those rates.

You will also need a fanout cable, perhaps something like this.

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