I have a SOC that has a KSZ9031RN PHY, that is a Gigabit PHY. But I'm going to use only in 10/100 Mode with 4 wires.

Gigabit PHY datasheet recommends a magnetic for Gigabit Ethernet, that are different from Fast Ethernet magnetics.

Can I use 4 Wire Fast Ethernet magnetic with that Gigabit PHY if I'm going to use it only in 10/100 Mode?


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    \$\begingroup\$ The devil's in the detail and I see none. \$\endgroup\$ – Andy aka Aug 28 '19 at 12:57
  • \$\begingroup\$ What do you refer to? \$\endgroup\$ – Indexer Aug 29 '19 at 6:56

Short answer: Yes you can use the KSZ9031RN with only 10/100 magnetics.

Read the Support datasheet and note section 3.8.

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So you will have to program the devices to ensure it does not attempt to size 4-pair as opposed to 2-pair connections.

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