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Help, DMA when using early completion interrupt?

Marko S
Intellectual 670 points

I'm using C6748.

 

I have a question about DMA early completion interrupts.

 

Let’s say I setup parameter set 5 (McBSAMP1 Transmit event) and select early completion (TCCMODE = 1) and PaRAM set is static (STATIC = 1).

 

Do I get a transfer completion interrupt as soon as the event leaves the event queue and triggers a transfer request to the transfer controller?

 

And what happens to parameter set 5 at that time? Is parameter set 5 “consumed” at this moment so I can update it?

 

I have seen that the parameter set is a null parameter set when I enter the transfer completion interrupt, is this correct?

  • 0
    TI__Guru* 84110 points

    Marko,

    When you write up your post in a Microsoft product like Word and then use cut-and-paste to put the text into a forum post, please use the Paste From Word icon. Without it, your post does not show up in some releases of IE, which is interestingly another Microsoft product. We are working on this issue, but until you hear otherwise, please use that button. Personally, I have found that even cutting and pasting within the forum (like from the post above the Edit Box) can cause formatting problems, so I always paste anyything I need to copy into a pure text editor like Notepad, then copy it from there before pasting into the forum; but usually I just type it directly into the forum.

     

    McBSAMP1 is not a familiar term, but I assume the typo is in that name. It probably will not matter, but in case it is needed...

    Servicing McBSP with Early Completion is not a good choice because it could cause you to change or use the data before the EDMA3 has accessed that data.

    Servicing McBSP with STATIC=1 is rare, but you could come up with a scenario when you would want to use it. Why do you want to use STATIC=1?

    Marko Siponen said:

    Do I get a transfer completion interrupt as soon as the event leaves the event queue and triggers a transfer request to the transfer controller?

    Yes.

    Marko Siponen said:

    And what happens to parameter set 5 at that time? Is parameter set 5 “consumed” at this moment so I can update it?

    Once the TR is sent to the TC, the PaRAM update will be completed or the contents will be consumed.

    Marko Siponen said:

    I have seen that the parameter set is a null parameter set when I enter the transfer completion interrupt, is this correct?

    I am not trying to be a joker, but I do not know what you have seen so I cannot comment directly. I certainly assume you can recognize a null PSet when you see one. But with STATIC=0, the PSet will not be changed from whatever it was before the trigger event.

    Regards,
    RandyP

     

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