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EDMA3 PaRAM Link - PaRAM load time

Shintaro
Intellectual 400 points

Hi.

I have a question about EDMA3 of C6747 DSP.

 

I configured two PaRAMs so that PaRAM (a) links to PaRAM (b). 

When a transfer of PaRAM (a) completes, PaRAM (b) is loaded to PaRAM (a) field.

My question is that can I estimate the time of  loading PaRAM (b) to PaRAM (a) field?

If it is possible, how long it would be?

 

I use EDMA3 to transfer received SPI data to IRAM. The SPI is slave mode, and the clock rate is about 15MHz.

I want to make PaRAM Link during continues SPI transfer from the host device.

I suppose that a 16-bit word may be dropped if PaRAM load takes more than 1.06 micro-sec. ( 1 second / 15MHz * 16bit  = 1.06 micro-sec.)

 

Thank you in advance.

 

Shintaro NOGUCHI

  • 0
    TI__Guru 54572 points

    Shintaro,

    The PaRAM link is just a handful of cycles. 

    The overall loop for your usecase is:

    - New sample arrives in SPI

    - Event asserted to EDMA

    - EDMA CC submits TR to EDMA TC (PaRAM Link occurs in background of this)

    - TC issues read to SPI

    - TC issues write to IRAM.

    Assuming 375 MHz part, the interconnect and EDMA runs at 187 MHz or roughly 5 ns per edma cycle.  The above loop will take around 100 EDMA cycles, or 0.5 us.  Given your budget of 1 us, this should be feasible.  However, if other activity is using the EDMA, or if contention occurs on the bus, the EDMA cycles can be higher.

    That said, you should consider building in a mechanism into your system software that detects overflow of the SPI receive buffer, and asks the host to resend a message.

    Regards

    Kyle

  • 0 in reply to kcastille
    Intellectual 400 points

    Kyle,

    Thank you for your reply.

    It is very helpful for me.

     

    Regards

    Shintaro NOGUCHI