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I need to design an Ethernet interface.

Requirements: It should have two RJ45 connectors at 1Gbps data rate and two fiber-optic at 1Gbps rate. The system has two SoMs (Kria K26) and each one should has an ability to communicate through each one of ethernet connectors to the external PC. Kria K26 has one RGMII and one SGMII interface. No requirement that two SoM should send data to each other but it can be a nice feature. I attach a block diagram of the system and my solution using two KSZ9477 switches.

Will it work? Is it correct?

enter image description here

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1 Answer 1

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Without reading the entire 266 page datasheet for your switch, I have a couple concerns:

  • The SFP transceivers most likely need to be connected to a PHY block, on the left side of the switch, not to the GMAC on the right side.

  • Magnetic blocks are required between the PHY blocks and the RJ-45 connectors, as shown on page 253 of the datasheet. Possibly you are using RJ-45's with integrated magnetics, but you haven't indicated this in your diagram.

  • I am not sure if it's allowed to connect two PHY devices directly (without magnetics in between). However, if you move your SFP's to the left side you will be able to connect both Kria devices on the left side of a single switch and this point will be moot.

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