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DP83822IF: LED 1 options

VSS
Prodigy 160 points
Part Number: DP83822IF

Hello,

We are using the DP83822IF in 100BASE-FX mode.  In the datasheet it is recommended to use the LED_1/GPIO (pin 24) in Signal Detect mode when in FX mode.  However we also would like to control an LED with this pin.  Is it possible to use both Signal Detect and control an LED using this pin? If not what is the recommended approach?

In connection with this, if we do not use the LED_1 in Signal Detect mode how is the Fiber link-up/down detected?

Thanks.

  • 0
    TI__Genius 9920 points

    Hi,

    This pin will only act as signal detect if enabled. Would you be able to use other LED pins such as LED0 or GPIO2 or GPIO3?

    Thanks,

    Cecilia

  • 0 in reply to Cecilia Reyes
    Prodigy 160 points

    Cecilia,

    Thanks for your response.

    We are already using LED_0 to show Link status.  We require the second LED to show other status.

    Can we use both the Signal Detect function and the second LED?

    Thanks,

    VS

  • 0 in reply to VSS
    TI__Genius 9920 points

    VS, 

    Can you clarify what you mean by second LED?

    Your options could be to use GPIO2 or GPIO3 that also has the option to connect an LED 

    Thanks,

    Cecilia

  • 0 in reply to Cecilia Reyes
    Prodigy 160 points

    Cecilia,

    Since we use the PHY in MII mode, both COL/GPIO2 and RXD3/GPIO3 are used by the MII interface.  Our understanding is that GPIO2 & GPIO3 can only be used in RMII mode.  Correct?

    Thanks,

    VS

  • 0 in reply to VSS
    TI__Genius 9920 points

    Hi VS,

    That is correct. It is only used in RMII mode. I was not aware that you were using the PHY in MII mode. Another way to check the fiber link is to read the register status. Is that a viable option for confirming the link?

    Thanks,

    Cecilia

  • 0 in reply to Cecilia Reyes
    Prodigy 160 points

    Hi Cecilia,

    That was my suggestion to our software engineer.  However there is a statement in the datasheet that suggests otherwise.

    Refer section 8.4.4.2:

    If the Signal Detect is not used, if the electrical link between the fiber module and the DP83822 is broken, disconnected or otherwise disrupted, the link will recover only by initiating a soft reset through MDIO/MDC interface.

    Also when we disable the Signal Detect function, the Link-up/down status in Bit 2 of the BMSR was not correctly reflecting the status of the fiber link.

    Could you please comment on this?

    Thanks

    VS

  • 0 in reply to VSS
    TI__Genius 9920 points

    Hi VS,

    That is expected in what you are seeing. You need to connect SD pin AND enable it in Fiber mode.

    Thanks,

    Cecilia