PHY management register
| PHYRWDATA | PHY read write data |
| WRITE10 | Must be written with 10. |
| REGADDR | Register address - specifies the register in the PHY to access. |
| PHYADDR | PHY address. |
| OPERATION | Operation. For a Clause 45 frame: 00 is an addr, 01 is a write, 10 is a post read increment, 11 is a read frame. For a Clause 22 frame: 10 is a read, 01 is a write. |
| WRITE1 | Must be written to 1 for a valid Clause 22 frame and to 0 for a valid Clause 45 frame. |
| WRITE0 | Must be written with 0. |