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TMS320C6678: TI ROM Bootloader bug?

Part Number: TMS320C6678

Good day!

I'm working with custom board with C6678 DSP. Both two DSP SGMII ports are connected at our board to AMC interface ports 0 and 1 correspondingly. I'm using the board installed at NAT NATIVE-C1 MTCA chassis with 6 AMC slots. Ports 0 and 1 of all AMC slots are connected to NAT-MCH Fabric A. NAT-MCH is connected to LAN via font-panel RJ45 connector.

I'd like to use TI ROM Bootloader (RBL) Ethernet boot at my board. I set DSP bootmode to Ethernet boot and power on the board. DSP starts sending Ethernet-ready frames without any interval, one by one, so I couldn't do anything (I cann't attach Wireshark capture file)! If I turn off AMC port 1 at NAT-MCH 1GbE switch then DSP starts sending Ethernet-ready frames as expected, with about 3 seconds interval.

My question: is this behavior of TI RBL with two DSP SGMII ports connected to the same LAN normal or is it a bug?

  • Hi Oleg,

    I've notified the bootloader experts. Their feedback will be posted here.

    Best Regards,
    Yordan
  • Oleg,

     

    The Ethernet ports connected to the C6678 on ports 1 and 2 of the backplane route to the Ethernet switch on the NAT MCH. The C6678 contains an internal Ethernet switch.  During Ethernet boot, the Ethernet switch inside the C6678 is configured for packet forwarding so that chained devices can be booted simultaneously.  If you have packet forwarding enabled within the Ethernet switch on the NAT MCH, you have created an Ethernet loop.  You will need to disable this packet forwarding in the NAT MCH or disable one of the ports to overcome this issue.  Do you need both Ethernet ports connected to the NAT MCH for data transport?

     

    Also note that the Ethernet ports on the C6678 are SGMII ports. The Ethernet ports on the MTCA chassis backplane are 1000BASE-BX ports per the standard.  These can interoperate on forced-on circuits but it violates the Ethernet standard.  A PHY should be implemented between the C6678 and the MTCA backplane for production systems.  GE Fanuc has an excellent application note titled "Ethernet Interoperability in AdvancedTCA, AdvancedMC and MicroTCA" written by Gene Juknevicius that discusses this is detail.

     

    Tom

  • Hi Tom!
    Thanks to your reply. We need both Ethernet ports connected to the NAT MCH for data transport in working system, but for Ethernet booting we need only one C6678 SGMII port 0. Why do you configure the Ethernet switch inside the C6678 in such way? Does this configuration lead to unable to boot DSP in case both SGMII ports receive data simultaneously? Is any boot parameter or anything else available to disable packet forwarding in the Ethernet switch inside the C6678?
    The modern Ethernet switches used in MTCA chassis support both SerDes and SGMII modes, so it's not needed to implement a PHY. Unfortunately I couldn't find the application note you've pointed. Could you please send me it via email or post the link to it?
    Best regards,
    Miloserdin Oleg
  • Oleg,

    I stated previously that the Ethernet switch in the C6678 is in packet forwarding mode at boot time to enable chained units to be downloaded simultaneously.  This cannot be disabled.  Later when you load your application, this functionality can be disabled.

    I cannot provide the App note from FANUC.  You will need to request it from them.  I have found it previous using GOOGLE search but it appears that those links are now gone.  Besides, if the NAT MCH ports can be configured for SGMII, you can bring the links up using SGMII as a MAC to MAC connection that is fully compliant.

    Tom