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Traffic Class in PCIe

Delared Delared
Expert 1945 points

Hi,

Object: Communication PCIe between 2 DSPC6678.

In PCIe standard, the Traffic class TC is mapped to one of the available virtual channels(VC0-VC7) and The TC value determines the relative priority of a given transaction as it traverses the PCIe  fabric.

But in DSPC6678 Features it’s mentioned that:

  • Single virtual channel (VC)
  • Single traffic class (TC)

Question: Can we say tha the Single VC in DSP CorePac assure a performed transfer (traffics), Or With more VCs [VC0-VC7]  that manage transaction priority is more performed[improve QoS] ??

Thank’s

  • 0
    TI__Genius 12065 points

    With single VC and single TC, all the packets are mapped to the same VC with the same priority.

    If you need any priority control for different packets or some QoS feature for isochronous transactions, you may need to schedule the data traffic in the software level.

    I do not think we have difference in the throughput performance at the physical layer either we have single VC/TC or multiple VC/TC.

  • 0 in reply to Steven Ji
    Expert 1945 points

    Steven,

    In PCIe Standard it’s mentioned that The Configuration software must determine the port arbitration capability for a switch or RCRB and select the port arbitration scheme to be used for each enabled VC.

    and This port arbitration mechanism does not require configuration of the port arbitration table. Once selected by software, the mechanism is managed solely by hardware [Non-Configurable Hardware-Fixed]

    So, in my case (DSPC6678, 1VC/TC), I should configure the port arbitration in order to manage data flow congection  with many ports or not??

    Thank’s

  • 0 in reply to Delared Delared
    TI__Genius 12065 points

    C667x PCIe module is a single port module in both RC and EP modes. The port arbitration is not implemented in our device. 

    So the user does not need to configure it.