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Block data move from external RAM to internal RAM

Bill Liu48
Intellectual 280 points
Other Parts Discussed in Thread: TMS320C6748

Hi There,

I am using C6748 LCDK and I want to move/copy data between external RAM to internal RAM. I tried to use DSPF_sp_blk_move function in the dsplib.

When I move data within the interal L2 RAM, the cycle count is roughly the same as the benchmark data given in the document. However, when I move data from external RAM to internal L2 RAM, the speed is about 25 times slower. Is that what we would expect? Are there any way that can make the data transfer much faster?

Many thanks,

Bill

 

  • 0
    TI__Guru* 84110 points
    Bill,

    Which document are you referencing for your cycle counts.

    This is what you would expect using this function to copy data, that it will be slower moving from external memory that from internal memory, both to internal memory.

    You can use the EDMA to move data much faster than with the CPU. And it can be done while the CPU is busy doing other things.

    Regards,
    RandyP
  • 0 in reply to RandyP
    Intellectual 280 points

    Hi RandyP,

    Thanks very much for your reply. I was referencing "TMS320C67xDSP Library Programmer's Reference Guide_spru657c" for cycle count.

    Could you point me to an EDMA example code? If I copy 16kB data from external RAM to internal L2 RAM using EDMA, including the DMA setup, how long it will take roughly?

    Best Regards,

    Bill  

  • 0 in reply to Bill Liu48
    TI__Guru* 84110 points
    Bill,

    Go back to your product folder for the TMS320C6748 and look for the Tools/Software tab. You will find links for the SYS/BIOS (TI-RTOS) SDK which contains the EDMA3 Low Level Drivers and examples for that. Alternatively, you can go to the Starterware link and use the EDMA example code and drivers that come with Starterware.

    You will also want to go back to the DSPLIB access page and get the C674x-based DSPLIB. At least I assume it has a different PRG for the C674x instead of for the C67x. There is definitely a separate library for C674x from the one for C67x.

    The speed of an EDMA3 copy from external memory to internal memory should take roughly the amount of time the external bus will need to access that amount of data. It will depend on your bus width and bus speed.

    Regards,
    RandyP
  • 0 in reply to RandyP
    Intellectual 280 points

    Thanks very much RandyP.

    Bill