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OMAPL138 EDMA3 Chain trigger

Ali Reeza
Expert 1250 points

Hi.

I am using chained trigger of three channels on omap l138 DSP.  The first and second chained channel transfer complete correctly. But third one not.

I there a limitation for chainning only two channel?

 

 

  • 0
    TI__Genius 14545 points

    Alireza,

     Have you checked the Transfer Completion Code (TCC) from the PaRAM Set to make sure it is set for the corresponding 3rd transfer? Also - have you looked at the Event Missed Register for a missed event?

  • 0 in reply to dabuan
    Expert 1250 points

    Thanks for your reply and sorry that I missed it in my inbox for long time!

    I did the job in another way at that time which proved to be more efficient.

    What I noticed then was when I define two chained event its ok. Defining the third one acutully cause the second to be ignored but first and third complete.

    Regards

     

  • 0 in reply to Ali Reeza
    TI__Genius 14545 points

    Alireza,

    Thanks for the response.

    That shouldn't be the case. A chained event for a particular channel is triggered by a returned Transfer Completion Code (TCC). If your 2nd event had a valid PaRAM Set Entry, then the 2nd event would be queued up in the appropriate queue, submitted to the Transfer Controller, and then it's TCC returned to initiate the 3rd transfer once the 2nd event is complete.

    Now there is a dummy PaRAM set which will effectively cause a TCC to be returned by the Transfer Controller indicating a valid completion without any actual data transfers, however this required you to specifically set up the PaRAM Set Entry for a dummy transfer - which I don't think is the case in your application. Is this correct?

    I'm glad to hear you resolved your issue.

     

     

  • 0 in reply to dabuan
    TI__Guru*** 125430 points

    For the record there is nothing that limits chaining to only 2 transfers.  Something was setup incorrectly if it did not work.