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Altera_Forum's avatar
Altera_Forum
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16 years ago

Lvds Vs Ddr

Hi all, I have a question.

I have a design using lvds interface. Currently it is implemented with ALTDDR_in IP but no ALTLVDS. The input of ddr_in is mapped to a pin labeled with LVDS in pin assignment.

Now I see something about the ALTLVDS IP, and it can be used with the same function as ddr_in. I wonder which way is more efficient, in the power point of view.

Thanks~~~~~~~~~~:)

4 Replies

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

    What's your SERDES rate? If it's /1 or /2, then the altlvds megafunction will build it's logic out of the altddio primitives, and it's essentially the same thing. If it's a larger factor, say /4, then the dedicated LVDS logic is used. It will have better timing margins and dedicated for LVDS. (From a power point of view, I'm guessing it should be lower power, but probably not in a measurable manner. They're both using dedicated structures in the silicon, and should be insignificant in the grand scheme of things.)

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

    Dedicated SERDES hardware is only provided with Stratix and Arria FPGAs. On Cyclone chips, ALTD_LVDS uses software SERDES based on DDIO hardware.

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

    --- Quote Start ---

    Hi all, I have a question.

    I have a design using lvds interface. Currently it is implemented with ALTDDR_in IP but no ALTLVDS. The input of ddr_in is mapped to a pin labeled with LVDS in pin assignment.

    Now I see something about the ALTLVDS IP, and it can be used with the same function as ddr_in. I wonder which way is more efficient, in the power point of view.

    Thanks~~~~~~~~~~:)

    --- Quote End ---

    Another question. Does LVDS has a high impedance output state besides '0' and '1'. Because it consumes a lot static power......

    Thanks~~~~~