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DP83869HM: How to check TX and RX activity via registers

Balaji TS2
Intellectual 290 points

Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869

Greetings for the day,

I am using DP83869HM in Media Converter mode and I have configured LED_1 and LED_2 as Copper(Ethernet PHY) port Link and Activity LED's. And I have 2 seperate LED's for Fiber port Link and Activity which are connected MCU.

By accesing the 0xC01 register I get to know if link is UP or Down, based on this I can control Fiber side Link LED but I didn't find any option to control Fiber side Activity LED.

Is there way to to know activity status at Fiber Side Or Copper Side? Or is there any register available to show the TX/RX activity?

Thank You.

Regards,

Balaji TS

  • 0
    TI__Mastermind 38645 points

    Hi Balaji,

    I do not see a register on the PHY that tracks TX/RX activity. These can be tracked from the LED signals if needed.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Intellectual 290 points

    Hi Shane Hauser,

    Thank You for the quick response.

    As the board already fabricated, we can't use LED signals now.

    So we don't have any option to control Optical side Activity LED? Are there any hidden registers in this PHY which shows TX/RX Packets count?

    And I have one more doubt with respect to Copper Activity LED. When I send frames manually, Copper port activity LED  blinks but I if send the frames continously using a frame tester(Which will send frames continously in 50Mbps speed) then the Copper activity LED stays constant HIGH(it's not blinking). Is there any to configure Activity LED to blink irrespective of speed of data transmission?

    Regards,

    Balaji TS

  • 0 in reply to Balaji TS2
    TI__Mastermind 38645 points

    Hi Balaji,

    Balaji TS2 said:
    Are there any hidden registers in this PHY which shows TX/RX Packets count?

    There are no hidden packet counter registers on the PHY (I've checked on this before). I have not seen any hidden registers that denote TX/RX activity, but if I find something I will let you know in this thread.

    Balaji TS2 said:
    Is there any to configure Activity LED to blink irrespective of speed of data transmission?

    There is a setting you can apply to the LEDs that blinks on TX/RX activity. This doubles as a link indicator for the copper side as well, and is setting 'B' in register 0x18

    There is also a register to toggle the blink rate of the LED.

    By default the LEDs do not blink on activity, rather they stay high while there is activity on the line.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Intellectual 290 points

    Hi Shane Hauser,

    Thank you the 0x18 and 0x1A register suggestion worked. Now the LED is blinking irrespective of data speed.

    But there is one more issue we are facing in 100M Media Converter mode. We are implementing one way communication as shown in below image, where 1 board is TX only and Other board is RX Only. In both the boards Link Loss Pass through is disabled. In TX CARD we have set Bit 15 of 0xD4 register to enable Loopback Mode so that even without conneting the Fiber Side RX link, fiber Link will show UP. 

    We are sending continous data using EXFO Ethernet Frame Sender in 100Mbps speed and the Frame receiver is receiving the data properly. The issue is, during the continous data transmission,we have removed the RX fiber cable of RX CARD, as expected the RX Card fiber side link became DOWN. Now we have connected the RX fiber cable back but the RX Card Fiber side link is not coming UP. The Link Link will become UP only if we Stop the continous data transfer at TX Card or If we remove and reconnect the Copper port of TX Card or if we reboot the TX Card. 

    We are not able to understand what causing this issue. Please help us to resolve this issue?

    Note: This issue won't occur in 1G Media converter mode.

    Regards,

    Balaji TS

  • 0 in reply to Balaji TS2
    TI__Mastermind 38645 points

    Hi Balaji,

    If you are only needing Unidirectional communication, why not use a typical fiber connection and send data from one direction only? Is there a reason loopback and disconnecting the cable are necessary?

    Furthermore is the target application 100Mbps or 1000Mbps? DP83869 can only be set to one at a time, so I am curious why 100Mbps is being tested when 1000Mbps gives the desired behavior.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Intellectual 290 points

    Hi Shane Hauser,

    For safety purspose we have disconnected the cable becuase its a kind of Data Diode application. The loopback setting is done to spoof the RX Link to make force Link UP. And in RX_CARD, Fiber TX is disabled.

    We have few target applications which supports only 100M Speed, thats the reason we need 100M mode also.

    Regards,

    Balaji TS

  • 0 in reply to Balaji TS2
    TI__Mastermind 38645 points

    Hi Balaji,

    Let me test this in our lab with a few DP83869 EVMs and see if I can reproduce the behavior. With this being a unique mode of operation I am unsure what behavior to expect. I will try to set this up tomorrow, or Thursday at the latest.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    TI__Mastermind 38645 points

    Hi Balaji,

    I tested this in our lab and saw the same behavior. Removing the RX wire on the RX card drops the link, and the link does not come back up while data is constantly transmitting. I tried disabling fiber autonegotiation yet it still showed the same result. 

    This is not a typical use-case and as such the behavior we are seeing may be a consequence of the loopback mode. I suggest stopping data transmission if the link on the RX card drops (to allow it to link up) or having periodic pauses in the data if you cannot ascertain the link status of the RX card from the TX side.

    Alternatively, if you only need a unidirectional ethernet channel, consider transferring the copper signal to RGMII, then using a second PHY to convert this back into fiber. The reason for placing RGMII in-between is that you can leave one direction of the RGMII data lines disconnected to have a uni-directional channel. This would allow you to have uni-directional RGMII - fiber without needing to use a hidden loopback

    Best,

    Shane