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DP83825I: Troubleshooting design working at 10M but failing at 100M

Part Number: DP83825I
Other Parts Discussed in Thread: DP83825

We are troubleshooting a new design with the DP83825 PHY.  The design appears to be working reliably at 10M but failing at 100M.  We can receive at 100M but transmit always fails.  Link status at 100M toggles up and down.  Running in master mode with AM335X processor.  25MHz crystal seems to be in spec, although 50MHz REFCLK may be at 80 ppm.  REFCLK is clean, setup and hold times PHY-CPU have plenty of margin.  Using Wurth 7498210003 10/100 PoE RJ45 w/ transformer.  All loopback tests at 100M pass except for external loopback, which fails. Signal quality *seems* good when scoping at RJ45.  Spot check of register settings seems good (have not done an exhaustive review).  Using linux driver from

Any ideas for further debug?