Pipelined binary encoder

Discussion in 'VHDL' started by Fred Bartoli, Nov 7, 2004.

  1. Fred Bartoli

    Fred Bartoli Guest

    Hello,

    I need to include in my design a wide (128 inputs and later 256 inputs) one
    hot to binary encoder.
    It has to run at 100MHz so I'm looking for a pipelined one (latency is no
    pb).
    I've searched almost everywhere to not avail and can't come with a good
    solution by myself.

    Does someone have hints or can point me in the right direction ?

    Oh, we need 2 of them and they will be implemented in an APEX 20KE.
    There will be lots of other stuff too, so it has to be pretty size
    efficient.


    --
    Thanks,
    Fred.
    Fred Bartoli, Nov 7, 2004
    #1
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  2. "Fred Bartoli" <fred._canxxxel_this_bartoli@RemoveThatAlso_free.fr_AndThisToo> wrote in message news:<418e15df$0$14970$>...
    > Hello,
    >
    > I need to include in my design a wide (128 inputs and later 256 inputs) one
    > hot to binary encoder.
    > It has to run at 100MHz so I'm looking for a pipelined one (latency is no
    > pb).
    > I've searched almost everywhere to not avail and can't come with a good
    > solution by myself.
    >
    > Does someone have hints or can point me in the right direction ?
    >
    > Oh, we need 2 of them and they will be implemented in an APEX 20KE.
    > There will be lots of other stuff too, so it has to be pretty size
    > efficient.


    A 256-to-8 one-hot to binary encoder is just eight 128-input OR gates,
    right? And a wide OR gate is easy to pipeline - just a tree of
    smaller OR gates, with pipeline registers at whatever levels you choose.
    The trick is to find a nice way to code it in VHDL. Recursive
    is pretty, though not all tools do a good job on recursive
    hardware descriptions.

    You may even find that the 128-in OR gate is fast enough without
    pipelining, though I doubt it.

    If you need to check that the input code is truly one-hot,
    things are much tougher.
    --
    Jonathan Bromley
    Jonathan Bromley, Nov 10, 2004
    #2
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