I210 <-> BCM5241: Link to BCM PHY works, no link from PHY to I210

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We have a simple on board I210 in copper 10/100 mode connected to a BCM5241 PHY. The BCM PHY sees link at 100M from the I210, but the I210 cannot see link from the BCM PHY. So, TX from the I210 functions, but RX on the I210 has no link. We have attempted turning off and on internal RX AC bypass caps on the I210, but still do not see link.

The MDI traces are connected directly to one another on the the PCB. I210 MDI0 is the TX and I210 MDI1 is the RX. There are no magnetics in-between.

The signal from the I210 looks good on a scope, but looking at the receive side, it is very noisy. Has anyone encountered this issue?

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Hi Ewaugh,

Thank you for posting at Wired Communities. What is the brand and model of your board where the I210 is embedded? Thanks,sharon

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Hi Sharon,

The I210 is embedded on a custom board we built. We found that the BCM PHY required a pull-up in it's MDI TX lines to drive the signal, the I210 now sees link. It appears that these pull-ups must be internal to the I210 for it's TX MDIs. We have resolved the issue by adding a pull-up.

Thank you,

Eric