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DP83TC811R-Q1: How to boot strap the chip so that no link is established until MDIO access

Luke Korte
Prodigy 160 points
Part Number: DP83TC811R-Q1

Hi

We have a requirement where the DP83TC811R-Q1 must not try and establish a link after being pulled out of reset. 

The DP83TC811R-Q1 must only establish a link after we have accessed the MDIO and done some setup.

Currently we have tried the managed mode available, but if there is any device connected on the physical side, the PHY will always establish a link.

Is it possible to boot strap the chip so that when reset goes high, it will not establish a link until we have enabled it over MDIO?

Regards

Luke

  • 0
    TI__Mastermind 23675 points

    Hi Luke,

    If you configure the DP83TC811R-Q1 for managed mode, there is different behavior for master and slave.

    If you are in slave mode, the PHY will try and link when it detects PAM3 signals.

    If you are in master mode, the PHY will not send any PAM3 signals until you enable it to through register access.

    You can also configure the PHY for IEEE power-down right after reset by using register 0x0.

    Once the configurations are done, you can exit IEEE power-down.

  • 0 in reply to Ross Pimentel
    Prodigy 160 points

    Hi 

    I have strapped the PHY to managed mode and master mode. I then connected the PHY to another slave PHY (Marcell 88Q2112).

    Once I take the DP83TC811R-Q1 out of reset it immediately links with the 88Q2112. We are not accessing the MDIO at all.

    Is this behavior expected?

    Also, we don't want to configure the PHY while it is trying to link. This will result in a race condition which is not ideal.

    Regards

    Luke

  • 0 in reply to Luke Korte
    TI__Mastermind 23675 points

    The Marvell device must be sending some pulses then because the PHY should not come out of standby unless it detects energy from the link partner.

    If you probe the MDI, I would guess that you will see the Marvell sending some sort of pulses, which it shouldn't be if that device is indeed in slave mode.

    You can disable the MDI before you do any other configuration by setting register 0x475 to 0x8.

    After you are done configuring the PHY, you can re-enable the MDI by setting register 0x475 back to 0x0.

  • 0 in reply to Ross Pimentel
    Prodigy 160 points

    Hi Ross

    Thank you, I think this may be the case.

    Does this mean that if the DP83TC811R-Q1 detects any energy from the link partner (whether the DP83TC811R-Q1 is in Master or Slave) it will come out of standby and link?

    Is there a way to guarantee it does not link (apart from accessing the SMI interface just before) even if there is energy detected from the link partner? 

    Thank you

    Luke