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external EDMA trigger in DM8168

Andrew Dyer
Intellectual 650 points

Is there a way to trigger the EDMA block in DM8168 from an external pin?  I'm planning to have an FPGA on the GPMC bus, and I'd like for it to be able to initiate the EDMA engine.  It doesn't look like there is any event source that would do that (Table 8-34. EDMA Default Synchronization Events in SPRS614A).

  • 0
    TI__Mastermind 25055 points

    Andrew,

    I am not familiar with a way to do this.  Can you please provide more details on exactly what you want to do here and why?

    Regards,
    Marc

  • 0 in reply to MarcPyne
    Intellectual 650 points

    I am looking to create a bus bridge between the GPMC bus and an external bus via an FPGA. 

    The bus supports DMA requests from devices via a pair of request lines that cause the bus controller to initiate the DMA.  I would like to use the EDMA controllers inside the DM8168 to handle the transfers.  To do this I need a way to signal them to proceed/stop.

  • 0 in reply to Andrew Dyer
    TI__Guru*** 125430 points

    You're right -- there's no GPIO event that is capable of initiating an EDMA transfer.  Here are a couple thoughts:

    1. Generate a CPU interrupt from the FPGA and then initiate the EDMA transfer inside the ISR.
    2. Have the FPGA act as a SPI master and use the SPI event to initiate a DMA transfer.  The FPGA would have to send a complete element in order for this to create an event.  I know this is ugly, but it at least would not require CPU interaction to start the event.