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Altera_Forum's avatar
Altera_Forum
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15 years ago

how to calculate the length register and the burst count port in DMA control manual

hello:

when I read the DMA control manual provided by the altera.com,I came across a question.

According to the manual at page 3 "The master Read and Write port",it says "For example, if a 32-bit data width DMA is programmed for a word transfer of 64 bytes, the length registered is programmed with 64 and the burst count port will be 16. If a 64-bit data width DMA is programmed for a doubleword transfer of 8 bytes, the length register is programmed with 8 and the burst count port will be 1."

I can't understand the meaning of the above paragraph,can anyone help me?

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    Length register == number of bytes.

    Burst count == number of transfers of full bus width.

    64 bytes (512 bits) on 32 bit bus: 512/32 = burst count of 16.

    8 byte (64 bits) on 64 bit bus: 64/64 = burst count of 1.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    --- Quote Start ---

    Length register == number of bytes.

    Burst count == number of transfers of full bus width.

    64 bytes (512 bits) on 32 bit bus: 512/32 = burst count of 16.

    8 byte (64 bits) on 64 bit bus: 64/64 = burst count of 1.

    --- Quote End ---

    Matthias Wachter:

    thank you very much,best wishes!