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I'd like to connect Ethernet between devices through magnetics without the FPGA or processor involved. For example, I have several off board (PWB) Ethernet signals coming onto my board and then onto other boards in the system (stack). If the Ethernet addresses are known (source-destination path), do I need to have some sort of processor or FPGA (MAC) in the path at all? In other words, can I truly have a point to point connection? I need to have both the purple and the black paths shown in the picture. Both CCA 2 and CCA3 have Ethernet with magnetics. What do I need to do to ensure that the black path is designed correctly such that it does not require the FPGA/Processor? Thanks - I hope this is clear enough. enter image description here

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  • \$\begingroup\$ It's not clear enough, no! You say you want to have the purple path but without the FPGA? What is running in the FPGA? I see that you have used the LAN9303, which is a switch. So for the Ethernet part, theoretically you don't need something else. But who will control the switch? You need some external processing unit for this. I suppose that's why you have the FPGA there. \$\endgroup\$ – nickagian Jul 24 '17 at 6:17
  • \$\begingroup\$ The 9303 needs to be configured in order to operate, which is probably what the FPGA is doing, but I believe you can probably achieve that with just an EEPROM connected to it. \$\endgroup\$ – Finbarr Jul 24 '17 at 7:24
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It is not so clear what you are asking, but if I understand correctly you want to operate both paths without using the FPGA.

You need to ask yourself why is the FPGA anyway used for. Since it is not so clear from your description nor the block diagram, I suppose you use it to manage the LAN9303 switch and the PHY.

If that's all indeed, then you can apply the switch configurations you need during boot, by using an external EEPROM, as the datasheet describes.

You could also apply the required PHY configuration using its special GPIOs for this purpose.

So, all in all, since the LAN9303 is an Ethernet switch, theoretically no external CPU is required for the Ethernet functionality, unless you need to apply special configuration or change the default configuration during operation.

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