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DP83TC812S-Q1: some questions

Part Number: DP83TC812S-Q1

Hi team,

My customer Marelli use 812s in their lighting domain control projects, and have some questions maybe need your help. Thanks!

  1. Is it possible to complete the automatic setting of the entire RMII mode through autonomous operation?
  2. Do I need to reset before and after autonomous operation?
  3. For the read operation of the 0x18B register, the read data (0x1C4B) is not same with the indicated value in the register map.
    1. Read/write steps: 0xD 0x1F; 0xE 0x18B; 0xD 0x401F; read/write 0xE. Is there a problem with the operation?
    2. There is the same problem when reading and writing other MMD1F registers.
  4. When configuring RMII mode, can it be set only for RMII_CTRL_1 Register and RMII_OVERRIDE_CTRL Register? Need to manually disable some related registers in other modes?
    1. Current setting step
      1. PHY HW Reset
      2. autonomous operation(addr0x18B,data0x0040)
      3. Set Mode: Slave(addr0x1834,BIT14=0)
      4. RMII CTRL Register Setup(addr0x648,BIT5,6=1)
  5. Do we have some configuration step for RMII mode?


  • Hi Jiawei,

    By automatic setting, do you mean setting the RMII mode through straps? Both autonomous mode and RMII mode can be configured through steps.
    The default read value of register 0x18B is 0x1C4B. So you are reading as expected. The device is in autonomous mode by default and you need not write any registers.

    To configure RMII mode, through straps, please place straps on RX_D1 or RX_D0 as mentioned in section 8.5.1 in the datasheet.