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Maximum RTI/DMA frequency

matteo lucarelli
Genius 3265 points

Other Parts Discussed in Thread: HALCOGEN

Hi,

I'm working on a square wave generation using RTI to drive DMA :

  • My RTI generate DMA request at a fixed frequency using compare 0
  • the DMA on every request writes 32 bits from a pre filled system buffer to the DOUT pins

My proble is that, using HalCoGen I cannot elevate the writing frequency at more than ~5MHz. If I set the RTI compare 0 interval at less than 0.0002ms the DMA output remain approx at 5-5.2MHz. I can see the output with an oscilloscope.

Is this a system limit? And in case: Is this a DMA, RTI or DOUT refresh limit?

I'm working on a TMS570LS31HDK.

Thank you

  • 0
    TI__Expert 4580 points

    Hello:

    I'll forward your request to one of our experts to provide some feedback.

    Regards.

  • 0
    TI__Mastermind 49120 points

    Hi Matteo,

    You can configure the RTI independent of HALCoGen and should be able to generate an interrupt much faster than 5MHz. The actual limit is RTICLK frequency / 2.

    This assumes that you will interrupt the CPU at this high frequency and that the CPU will be able to clear the interrupt flag before the RTI sets the flag again. Alternatively you could use the built-in interrupt flag clearing mechanism inside the RTI module. HALCoGen does not yet support the configuration of this feature.

    In your system, you may even run into the theoretical limit for the time taken by the DMA to copy 4 bytes from the CPU RAM (assumption) to the DOUT port. Based on this limit, you will need to reduce the frequency at which you generate the DMA requests, so that the DMA can keep up with the request rate.

    Regards, Sunil