DP83822HF: No access to internal register through MD interface

Dear Sir/Madam,

Using Boundary Scan we are trying to read the internal register of two transceivers connected to AM3356, one in default address, the other one with 1K96 pulldown resistor in PHYAD0. Our algorithm try to read reg 0 from address 0 to 32. The fact is that we read FFFF in all addresses. We are leaving 500 ms between deasserted nreset and first pulse of MDC. The Ethernet transceiver IO power supply is 3.3V. The oscillator in pin XI is a 3,3V 25 MHz. In XO we can check the 25 MHz output but in the 1.8V range. The pullup in MDIO is 2k2. Nreset has an external 10k pullup.

We have tested MDC from 20 MHz to some kHz without any difference. It seems like they are always in reset state or similar. This algorithm works fine with other Ethernet transceivers. Could you please tell me any hint to try on communicating the MD interface?

Thanks in advance