DP83822EVM: When using USB-2-MDIO to set DP83822EVM Analog loopback, but it can't work

Hi team,

There are my testing step.

1. I used USB-2-MDIO to set DP83822EVM Analog loopback mode following below Register setting;

2. I sent the data=0xa5 to DP83822EVM by MII and enbale TX_EN.

But I can't catch any waveform from RX_D[0:3] pin, which mean there are not any loopback data. 

I saw the user guide that it need 100  Ω termination in TX/ RX pins.

But I saw the DP83822EVM SCH and there are two 49.9Ω pull-up in TX/ RX pins. So in my mind, it don't need 100  Ω termination in TX/ RX pins, right?

If yes, why can't I catch any waveform from RX_D[0:3] pin?

Thanks!

Register setting:

begin 001F 8000 //software reset (clears register)

0000 2100 //programs DUT to 100BASE-TX mode

0019 0021 //programs DUT to Forced MDI mode, set to 4021 for MDIX mode

0016 0108 //enables analog loopback mode

001F 4000 //digital reset (doesn’t clear register)

end