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DP83TG720S-Q1: How to implement an interrupt when link down on DP83TG720S-Q1?

cao qi
Intellectual 786 points
Part Number: DP83TG720S-Q1
Other Parts Discussed in Thread: TDA4VH

I need to use the DP83TG720S-Q1 PHY chip to implement an interrupt when link down. In my tests, I found that register[0x12].13(Link status change interrupt status) is set and the INT_N is set low only when link up. I don't find the relevant register for link downconfiguration , does this PHY support this function?

  • 0
    TI__Genius 14006 points

    Hi Cao,

    Are you saying that INT_N is LOW when link is up and HIGH when link is down?

    You can enable the link status change interrupt through register 0x12[5] and adjust the interrupt pin polarity in register bit 0x11[3]. 

    Best regards,

    Melissa

  • 0 in reply to Melissa Chang
    Intellectual 786 points

    Hi Melissa,

    I wonder whether the act of removing the 1000BASE-T1 cable (link down) can trigger the PHY interrupt on INT_N, currently it seems that only connecting the T1 cable (link up) can trigger the interrupt.

    Regards, Cao

  • +1 in reply to cao qi
    TI__Genius 14006 points

    Hi Cao,

    Once an interrupt event flag is set, register access is required to clear the interrupt event. So you will need to read register 0x12 to clear the interrupt. 

    The INT_N pin will be able to detect any change in link status as long as the register is cleared.

    Best regards,

    Melissa

  • 0 in reply to Melissa Chang
    Intellectual 786 points

    Hi Melissa,

    Thank you, I just solved my problem. It is a problem from PHY's state machine.

    In the ti-processor-sdk-rtos-j784s4-evm-09_01_00_06 environment of TDA4VH, when disconnecting the 1000BASE-T1 cable, the PHY state will switch from LINKED state to FOUND state. This state will perform a hardware reset, causing register 0x12 [13] bit to be reset. This can explain that I can observe 0x12 [13]=1 and INT_N=0 only when connecting the 1000BASE-T1 cable.

    In addition, I found a phenomenon that a hardware reset will temporarily set the INT_N of DP83TG720S to 0, while DP83TC812S will not.

    Regards, Cao