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Altera_Forum's avatar
Altera_Forum
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15 years ago

Scatter-gather DMA for tse

Hi everyone,

I looked into reference designs about tse(triple-speed ethernet), and I found that all these tse applications are built around NIOSII with scatter-gather DMAs.

My question is that if I just want to build a standalone tse (I'll use some simple control logic to program tse before sending/receiving packet), should I also include scatter-gather DMA into my design? And what's purpose of scatter-gather DMA?

Thanks!

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    The purpose of DMA is to avoid loading cpu with the task of transferring rx and tx data when is needed: the sgdma will take care of that, by directly placing data to and from the memory.

    In the case of tse you can use it without sgdma but you need to connect it to a device with Avalon streaming interface in order to manage tx/rx data.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    If you put the TSE into 32-bit mode and connected the ST interfaces to FIFOs that support MM on one side and ST on the other you could manage the traffic using software. It'll be dog slow since the CPU will be directly in the data path. This would also require changes to the code which assumes there are SGDMAs moving the data around.