DP83867E: Reg 0x0025 by Default is not RW

Hello,

We will be doing ethernet compliance testing. I have tried USB-2-MDIO and I can RW on 0x0025. In our made test script which we will use for our board with DP83867E PHY, I notice that I was not able to access or perform RW to Testmode Channel Control (TMCH_CTRL), Address 0x0025.  I mean I can write something but when I read it, the data is not the one I wrote (resulting read is 0x00). I know by default this is not RW based on the datasheet. May I ask how are we going to make REG 0x0025 a RW? I mean is there a way to make it a RW so I can perform all test modes? 

The rest of the register configurations for the test modes, it is working properly and I can RW on it.

Thanks.