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DP83822I: Reset requirement on 0x041F register

Takeshi Sasaki
Expert 4480 points
Part Number: DP83822I

Hi team,

Could you give me comment on following customer questions related to 0x041F register setting?

Q1. After writing data on 0x041F register, is the software reset (0x001F, bit 15) required?

Q2. After writing data on 0x041F register, then after the reset (0x0000, bit 15) is run, will the written data on the 0x041F be kept?

Q3. Is it ok that writing data on 0x041F register right after writing 1 on the bit 15 at the 0x0000 register?

Q4. Following flow is ok? 1. writing data on 0x041F register, 2. writing 1 the bit 15 at the 0x0000 register, 3. writing data on 0x041F again

Q5. When changing the setting of the link speed and duplex during link up, will the setting run immediately? 

 

Best regards,

Takeshi Sasaki

  • 0
    TI__Mastermind 26752 points

    Hi Takeshi, 

    0x001F, bit 14 is the reset to use after making a change to register settings, which is called a digital reset. This will reset the state machine/link training process, without erasing the register settings. 0x001F bit 15 will also erase the register settings to default, which is called a software reset. It is good practice to do a digital reset after changing register settings. So to answer your questions:

    1. 0x001F bit 14 reset is recommended after writing data to 0x041F

    2. Written data on 0x041F will be kept after doing a digital reset

    3. Writing data immediately after doing a digital reset is fine. When doing a full software reset, you must wait 2ms before register access, as shown in Section 7.8 of the datasheet. 

    4. Replace step 2 with bit 14 of 0x001F, and that sequence would be fine. 

    5. Yes, these settings will run immediately. 

    Let me know if you have additional questions. 

    Thanks,

    David

  • 0 in reply to David Creger
    TI__Expert 4480 points

    Hi David,

    Thank you for your comment. Could you give me comment on additional customer question?

    Q5. Does any waiting time for assessing register requirement after the digital resetting? 

    If they need to have wait time as dozens of micro second such as 20us, 30us, they want to know such requirement for the digital resetting. 

    Best regards,

    Takeshi Sasaki

  • +1 in reply to Takeshi Sasaki
    TI__Mastermind 26752 points

    Hi Takeshi, 

    This is not a specification that we characterize, but generally you can perform another read/write immediately after a digital reset. You would have to determine this time with your own testing, though. 2ms (T2 in section 7.8 of the datasheet) would be the absolute maximum, but it is probably much lower. 

    Thanks,

    David