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DP83867 Configuration and Driver

Ryan.Bishop
Expert 3900 points

Hello,

I have two questions regarding the DP83867 using SGMII:

1. I'm trying to run this PHY without using the MDIO/MDC lines. I see that there are a few configurations you can set with strap resistors. For the strap setting SPEED_SEL, I only get one bit to set: 0 to advertise 10/100/1000 and 1 to advertise 100/1000. However if I wanted to also strap Autoneg Disable and turn it off, will the PHY still be able to adapt to the speed of the MDI link speeds since I can't hard set a speed?

Table 11, the BMCR register list, has bits 6 and 13 both default to a strap value, giving you the ability to actually select a specific speed with two bits. Are they able to be individually set? It not clear what straps set those bits.

My overall question is am I able to hard set 1000 speed with auto-negotiation off all without using the MDIO line? Or if not hard set, will the phy still adjust to the link speed with auto-neg off?

2. I see there is a RGMII linux driver online for this PHY. If I want to use this device with a RTOS and SGMII, is there no other option other than manually porting over the code? Just wanted to check if there were any other alternatives.

I hope that all made sense. Thank you for your help!

Ryan

  • 0
    TI__Mastermind 23675 points
    Hi Ryan,

    Here are the answers to your questions above:

    1. If you turn auto-negotiation off, the PHY will not be able to negotiate to other speeds. It will be fixed at the speed you set it to. Auto-negotiation must be enabled to do speed changes. Otherwise you need to do it through the MDIO/MDC (SMI).

    I will need to check the strap section because I agree that this is not clear.

    2. There is only one driver. You would need to modify the code to support SGMII.

    Kind regards,
    Ross
  • 0 in reply to Ross Pimentel
    TI__Expert 3900 points
    Hi Ross,

    Okay thank you very much! If you could let me know how to resistor strap in a fixed speed value once you find out that would be great.

    Thanks again,
    Ryan
  • 0 in reply to Ryan.Bishop
    TI__Mastermind 18425 points

    Hello Ryan,

    The PHY cannot be forced into any speed through straps. The speed select straps are used for controlling auto-negotiation advertisement. The name and description will be editied in the next datasheet revision. SGMII 4 wire can be enabled through strap. If the customer needs sgmii 6 wire interface, then register configuration is required.

    Do we know why they want to turn off auto-negotiation?

    -Regards,

    Aniruddha

  • 0 in reply to Aniruddha Khadye
    TI__Expert 3900 points
    Aniruddha,

    Thank you very much for your answer. That cleared up my confusion about the strap configurations. Without the ability to strap in a fixed speed, they will return to using auto-neg.

    Thank you again,
    Ryan