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Altera_Forum's avatar
Altera_Forum
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15 years ago

Maximum Number of DDR2 SDRAM Interfaces Supported per FPGA with Cyclone IV

Hello,

I am trying to use the Cyclone IV E with DDR2 SDRAM interfaces.

I have a question with the Maximum Number of DDR2 SDRAM Interfaces Supported per FPGA for Cyclone IV E in the documentation (Section III. System Performance Specifications) :

When it is said that on top side, for example, the Maximum Number of DDR2 SDRAM Interfaces is "one x 48 interfaces" or "two x 8 interfaces" it is not equivalent ! You can only reach an equivalent of "one x 16 interfaces" in the second case ?

I don't clearly understand what is a "x48" or "x8 interfaces". Is it the number of bits of Data bus ?

Does that mean that you can only use on this side either one DDR2 SDRAM interface with a 48-width of Data Bus, or two with an only 8-width of Data Bus ?

Thanks

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    You didn't mention which Cyclone IV E device you are using.

    Table 7-2 of the user's guide is useful:

    http://www.altera.com/literature/hb/cyclone-iv/cyiv-5v1-02.pdf

    Yes the width refers to the number of bits on the data bus.

    There are usually 3 constraints to consider for the limitation on number of memory controllers you can support:

    1 - I/O pin limitations (this is the number of DQ groups available, and don't forget command / address pins).

    2 - PLL limitations (you need a PLL per controller I believe).

    3 - Internal resource utilization.

    So on a EP4CE115 device in the 780 pin package; you could presumably have 6 x8/x9 groups on the top and/or bottom of the device. So to me this means you could have:

    1 x48 DDR2 controller (6 groups of x8/x9)

    2 x8/x9 DDR2 controllers (1 groups of x8/x9 each)

    2 x16/x18 DDR2 controllers (2 groups of x8/x9 each)

    2 x24/x27 DDR2 controllers (3 groups of x8/x9 each)

    Now could you do 3 x8/9 interfaces. My gut tells me know. I'm thinking the PLL clocking is going to get hairy.

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

    Ok thank you very much.

    And do you know which size of DDR2 controller (1G, 2G, 4G...) is available with the Cyclone IV EP4CE115 in the 780 pin package ? What is the depth of DDR2 controller available with this device ?