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DP83640: DP83640 Strapping Overwrite

Part Number: DP83640


We have our device setup to use RMII. We have both RX_DV and TXD_3 strapped HIGH. However, the resistors were improperly spec'd to 10K. We are seeing on occasion that the system boots without ethernet working and suspect that the PUs are not hitting the required logic level to enable RMII. We have made a change to those to be 2.2K, but in the mean time I am looking at ways to reconfigure the registers of the PHY to set the mode to RMII regardless of the strap resistors.

To test, I have removed the PU on RX_DV (using internal PD) and I have written to the RMII Bypass register (0x17) and set bits 14 and 5 high. This works well with only RX_DV removed. If I remove the PU on TXD_3 and replace the 10K PU on RX_DV the Bypass register writes do not work.

Am I missing another register write? I would appreciate some guidance.

Thank you,