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I have Ethernet PHY from Marvell (88E1111-B2-BAB1I000) and Ethernet transformer (S558-5999-AT-F). By mistake the MDI P&N connection got interchanged on the transformer side. Will it work?

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  • \$\begingroup\$ Does your PHY have the option to flip diff-pair polarity internally? \$\endgroup\$ – uint128_t Jun 10 '16 at 15:34
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The 88E1111 Product Brief (which is the only interesting document I found), says "Automatic polarity correction" in the features. So it seems you're fine. However, they don't mention it later on, so we don't know how it works and if there are restrictions.

Overall, I wouldn't recommend lauching a 10000 production run without having made sure first, but if you are in prototyping phase, it's definitely worth a try. And if your prototype has problems, you can always make a custom RJ45 cable with flipped P/N wires to make it work.

Note it also does auto MDI/MDIX, so you could have flipped the pairs as well (just sayin').

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