• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 100 subscribers
  • Views 606 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Data transfer from EMIF to DARAM via DMA

Olek
Prodigy 110 points

Dear community,

Currently I use VC5505 DSP und have following application question: I try to transfer a data from EMIF to DARAM via DMA. During this transfer an order of the words in the double word massage will be change. It means, if I have data in external SRAM: 1,2,3,4,5,6… After transmission DMA place in DARAM corresponding data sequence 2,1,4,3,6,5... Is this procedure correct? How can I get the right order of data in DARAM?

Thank you for an answer,

 

Olek

  • 0
    Expert 2605 points

    Hi,

    It seems like the issue is due to DMA word swap. On VC5505 DSP, DMA swaps the words in the data buffer during the data transfer. If you are writing the data using DMA and read it back using DMA then you see no issues. But if you write data using DMA and read it without using DMA or vice versa you will observe the word swap. Please refer to the silicon errata for your DSP version.

    Pratap.

  • 0 in reply to Pratap Reddy M V
    TI__Genius 14965 points

    Hi,

     

    Also the swap ordering is 4,3,2,1,8.7,6,5....

    Regards,

    Hyun

  • 0 in reply to Pratap Reddy M V
    Prodigy 110 points

    Normal 0 21 false false false DE X-NONE X-NONE MicrosoftInternetExplorer4

    Normal 0 21 false false false DE X-NONE X-NONE MicrosoftInternetExplorer4

    Hi Pratap,


    Thank you for your briefing. One thing I don’t yet understand. I observe the word swap only if I write data from EMIF (SARAM) to DARAM. During data transfer inside one memory type (from SARAM to SARAM or from DARAM to DARAM) I didn’t see this effect. Is it also correct?


    Olek


    PS: Oh..., I found the answer in the silicon errata.

  • 0 in reply to Hyun Kim
    Prodigy 110 points

    Hi,

     

    DMA swap only two words 2,1,4,3.... The nambers are in Int16 format.

    Regards,

    Olek

  • 0 in reply to Olek
    TI__Expert 8065 points

    Olek,

    Since you said that you are using VC5505, I need to explain the endianness based on the VC5505. Please keep in mind that the C5505 has different peripheral endianness.

    DMA has not intelligent on data endianess, so DMA does not swap data order. It is depending on the peripheral that uses the DMA. In the VC5505, the RAM (DARAM and SARAM) is big endian but EMIF is little endian. Whenever DMA transfer data between two modules that have different endianness, it results in word or byte swap. When you transfer data EMIF to EMIF, you won't see this issue.

    Please carefully review the device errata in the apspect of endianness.

     

    FYI, in the C5505, EMIF is big endian.

    Best Regards,

    Peter Chung

     

  • 0 in reply to Peter Chung
    Prodigy 110 points

    Hi Peter,

    Thanks for you explanation.

    Best Regards,

     

    Olek

  • 0 in reply to Olek
    TI__Expert 8065 points

    Olek,

    I am glad that I can help.

    Best Regards,

    Peter Chung