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DP83849IF Ethernet Ring Network

Victor Chen_HK
Expert 5130 points
Other Parts Discussed in Thread: DP83849IF

Hello,

My customer wants to build a Ethernet ring network using DP83849IF and they took http://www.ti.com/lit/an/snla086b/snla086b.pdf  as a reference.

They've encountered with an issue that during broadcasting, only port A can transmit signal. They are using 100Base-TX full duplex mode with single clock.

Attached their schematic. eth_test.pdf

Could you please take a look? Please let me know if any information needed.

Best regards,

Victor

  • 0
    TI__Mastermind 19780 points
    Hi Victor,

    Port A appears to be connected to the Cortex-M3 device and port B is connected to a device that performs conversion from SPI to MII from what I understand on the schematic.

    This is not a typical application. Can your customer verify that the W3150+ acts as a standard 802.3 MAC layer where TX_CLK and RX_CLK are inputs from the DP83849?

    I'd like to see some scope shots of the ETHB interface like RX_D0 and TX_D0 when trying to broadcast. I could not easily find a datasheet on the W3150+, so providing this will help also.

    Also your customer should change RBIAS resistor R40 from 4.7k to 4.87k. This is a critical value and will impact operation of the device within Ethernet standards. It is not the solution for the problem you asked, but it should be fixed.

    Best Regards,
  • 0 in reply to Rob Rodrigues
    TI__Expert 5130 points

    Hi Rob,

    Attached W3150+ data sheet.W3150A+.pdf

    Do you have any RMII or SCMII reference circuit since the Ethernet ring network requires RMII or SCMII mode in order to operte in broadcast transmit mode?

    Customer has  some difficulty in operating DP83849IF in one of these modes.

  • 0 in reply to Victor Chen_HK
    TI__Mastermind 19780 points
    Hi Victor,

    Could you draw me a diagram of what the customer would like to happen when they use broadcast mode? As the DP83849IF defines broadcast, the device would transmit the signal from MII port A to both network segments(RJ45 A & B).

    As configured here, the customer has a MAC connected to each port, and broadcast mode would stop one of these MII ports from working.

    Best Regards,
  • 0 in reply to Rob Rodrigues
    TI__Expert 5130 points

    Hi Rob,

    I think SCMII or RMII mode is required for broadcast mode, correct?

    They want both Port A and Port B can transmit same date from MAC A. While now they could only see data from Port A. from application note www.ti.com/.../snla086b.pdf

    Since customer is not familiar with the device, I think it's better to debug start from:

    1. Check the schematic is correct to implement SCMII mode or RMII mode, such as check those pull-ups and pull-downs

    2. Check the software code are correct.

    Best regards,

    Victor

  • 0 in reply to Victor Chen_HK
    TI__Expert 5130 points

    Hi Rob,

    Attached the 2nd version of schematic.eth_test_RMII160929.pdf

    Customer has tested that the circuit works properly in RMII mode. Both channels can transmit and receive data.

    They've also tried keeping and removing the 2nd MAC but the result is still the same, i.e. in broadcast TX MII mode, only one slaver can receive data from one channel.

    Could you please take a look at the new schematic and comment?  The R40 will be changed to 4.87k on customer side.

    Thanks and best regards,

    Victor