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Altera_Forum's avatar
Altera_Forum
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13 years ago

External memory access for beginner

Hello guys,

I've been learning to use external memory interface. I want to read some data from DDR2 SDRAM (assume data is there already), store them in on-chip RAM and do some calculation, then the result will be written back to SDRAM.

I'm lost after instantiating the DDR2 memory controller. I have no idea how to control the I/O signals to make it work.

I also see example design that use Nios to control the whole process which makes me even more confused.

Please give me some suggestions or pointer so that I can learn this topic more properly.

Thanks a lot!

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    You will not find a lot of training material / tutorials / examples on how to directly instantiate and interface with the external memory cores. They mostly expect you to just read the datasheet / manual for the IP core and connect the signals properly.

    But, you will find lots of material on creating Qsys components and some of them will cover Avalon-MM Master interfaces.

    So for a beginner, I would suggest creating a new Qsys module with Avalon-MM Master port which can then be placed into a Qsys sytem with other components like on-chip memory and DDR2 controller.

    Just because Qsys systems commonly use a NIOS processor, you don't have to.

    Here are some links:

    http://www.altera.com/support/examples/design-entry-tools/qsys/exm-qsys-tut.html

    http://www.altera.com/support/examples/nios2/exm-avalon-mm.html

    http://www.alterawiki.com/wiki/using_the_usb-blaster_as_an_sopc/qsys_avalon-mm_master_tutorial
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Thanks Ted!

    I shall start with getting familiar with qsys.

    In a tutorial about DDR3 SDRAM controller with UniPHY using qsys, I see a DMA controller is added in the qsys hierarchy. I'm not clear about this, since from other documents I see that external memory controller can be directly connected to other qsys components through avalon MM bus, then what is DMA controller for here?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    --- Quote Start ---

    Thanks Ted!

    I shall start with getting familiar with qsys.

    In a tutorial about DDR3 SDRAM controller with UniPHY using qsys, I see a DMA controller is added in the qsys hierarchy. I'm not clear about this, since from other documents I see that external memory controller can be directly connected to other qsys components through avalon MM bus, then what is DMA controller for here?

    --- Quote End ---

    Anything with an Avalon-MM Master interface can connect to the external memory. The tutorials typically show a NIOS and DMA controller simply because that is a common / desirable elements of a system. From your initial post, your system might only have 3 components in it (your new component, the on-chip memory, the memory controller).