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Visitor dkendrick
Visitor
3,141 Views
Registered: ‎08-22-2017

Connecting Artix-7 to 2.5G Ethernet PHY

I am trying to connect my Artix-7 device to a NBASE-T Alliance compatible Ethernet PHY and send data at 2.5 Gbps over a Cat5e cable. Is the SGMII Core capable of doing this? In the description of the IP it mentions it can operate at 2.5 Gbps, but is this for both copper and optical connections? The datasheet does not specifically mention 2.5GBASE-T devices, but I know that Xilinx is apart of the NBASE-T Alliance and they have mentioned in this Xcell Daily Blog it mentions that the Xilinx SerDes transceivers already work well with Aquantia's 2.5G/5G BASE-T PHY.

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6 Replies
Voyager
Voyager
3,133 Views
Registered: ‎06-24-2013

Re: Connecting Artix-7 to 2.5G Ethernet PHY

Hey @dkendrick,

 

is this for both copper and optical connections?

At the SGMII level, there should be no difference between copper and fiber, the PHY has to take care of this and either use proper magnetics or fiber tranceiver.

 

Hope this helps,

Herbert

-------------- Yes, I do this for fun!
Visitor dkendrick
Visitor
3,059 Views
Registered: ‎08-22-2017

Re: Connecting Artix-7 to 2.5G Ethernet PHY

Thanks for your reply @hpoetzl,

 

I have another followup question that might help clarify some things for me, I think there is a big gap in my understanding of how the physical layer works. My initial understanding was that BASE-T/BASE-X/BASE-R classifications were referring to the MDI portion of the PHY, and then it was able to connect to any MAC device as long as they both use the same host interface. If I use a 2.5GBASE-T copper unit, am I able to use any of the available host interfaces such as 2500BASE-X or SGMII?

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Voyager
Voyager
3,055 Views
Registered: ‎06-24-2013

Re: Connecting Artix-7 to 2.5G Ethernet PHY

Hey @dkendrick,

 

Thanks for your reply

You're welcome!

 

If I use a 2.5GBASE-T copper unit, am I able to use any of the available host interfaces such as 2500BASE-X or SGMII?

The SGMII (Serial Gigabit Media Independent Interface) allows you to interface a PHY independent of the actual physical form (e.g. 1000BASE-T or 1000BASE-X). So the SGMII is the abstraction layer to interface the Ethernet MAC to the Ethernet PHY.

 

Hope this clarifies,

Herbert

-------------- Yes, I do this for fun!
Xilinx Employee
Xilinx Employee
3,020 Views
Registered: ‎05-01-2013

Re: Connecting Artix-7 to 2.5G Ethernet PHY

BASE-T is usually 4D-PAM5 signals (-2, -1, 0, +1, +2) while BASE-X is normal differential digital signal (1/0)

A7 GTP can only send/receive BASE-X data. Are you sure that you're using BASE-T cable?

Visitor dkendrick
Visitor
2,897 Views
Registered: ‎08-22-2017

Re: Connecting Artix-7 to 2.5G Ethernet PHY

Hi @guozhenp,

 

The PHY is listed as NBASE-T Alliance compatible, and it's top level block diagram shows a copper unit with 1/2.5/5GBASE-T options, and a separate host unit with USXGMII/XAUI/5GBASE-R/2500BASE-X/SGMII interface options. If the copper unit is doing the 64/65 encoding and decoding before passing the signal onto the host unit through its own internal XGMII interface, is there anything that would prevent the LogiCORE SGMII IP from receiving the signal at 2.5 Gbps?

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Xilinx Employee
Xilinx Employee
2,883 Views
Registered: ‎05-01-2013

Re: Connecting Artix-7 to 2.5G Ethernet PHY

OK. So the link would be like this.

SGMII => PHY => BASE-T

As the PHY claims that it supports BASET and 2500SGMII as well, there won't be any problem to the link.

From FPGA side, we only care about the 2.5G SGMII interface with the PHY and don't care about BASE-T which the PHY should handle.

Have you already tried it on board and can you get the SGMII link up?

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