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Clarification on OMAP4 GPMC burst write

Yannick Fortin94
Prodigy 30 points

Hi,

I want to use OMAP4460 to send data on the GPMC interface using a synchronous burst write with as many 16-bit words as possible. By "burst" I mean writing multiple data words successively during a same nCS assertion.

1. It seems like 16 words per burst is the maximum number of words that can be configured by the GPMC parameters. Is it possible to extend this limit to Nx16 words by setting the WRAPBURST bit to 1 (or by other means)?

2. Is it mandatory to use DMA in order to achieve a 16 words (or Nx16word) burst write? Or can it be achieved by looping a single-word write command?

Here are my GPMC config parameters for your reference. At this point I am only worried about GPMC WRITE transactions.

CONFIG1 0x3A001001
CONFIG2 0x00020200
CONFIG3 0x00000000
CONFIG4 0x02000A02
CONFIG5 0x0209020C
CONFIG6 0x01000000

Thank you very much.

  • 0
    TI__Guru**** 161600 points

    Hi Yannick,

    I think you are correct, 16 words is the max number of words that can be configured by the GPMC parameter.

    As for the setting fo WRAPBURST see Section 15.4.4.11.5 System Burst Versus External Device Burst Support.  WRAPBURST should be set to 1 if you want to get optimal performance from memory devices that natively support 16 Word 16-length-wrapping burst capability. That means you have to set ATTACHEDDEVICEPAGELENGTH = 16 & WRAPBURST = 1

    When memory device doesn't offer native 16 word 16-length-wrapping burst => WRAPBUSRT=0x0.

    The use of DMA depends on your specific use case. The use of DMA with GPMC is a must in the following cases:
    - prefetch and write-posting engine

    - FIFO control in prefetch mode

    - FIFO control in write-posting mode

    The GPMC is discussed in details here: http://e2e.ti.com/support/omap/f/849/p/356519/1251838.aspx#1251838

    Hope this helps.

    Best Regards,

    Yordan

  • 0 in reply to Yordan Kovachev
    Prodigy 30 points

    Thank you Yordan,

      You listed the cases where DMA is required, but can you please also enumerate the cases where GPMC burst is possible without DMA?

      I've read the TRM section on WRAPBURST but this is not clear to me. For instance, does a "wrap" mean that it will be possible to burst write out 32 words within a same nCS assertion?

     FYI; the GPMC will be connected to a Cyclone IV FPGA, and I'm trying to figure out what type of performance I can get out of it.

      Thank you,

      Yannick.

      

  • 0 in reply to Yannick Fortin94
    TI__Guru**** 161600 points

    Yannick Fortin94 said:
    I've read the TRM section on WRAPBURST but this is not clear to me. For instance, does a "wrap" mean that it will be possible to burst write out 32 words within a same nCS assertion?

    To my knowledge you can transfer maximum 16 words per burst.

    Also for transferring data from OMAP to FPGA, through the GPMC interface you need DMA.


    Best Regards,

    Yordan