Request Help - Good example of resolution function

Discussion in 'VHDL' started by Daku, Jan 25, 2010.

  1. Daku

    Daku Guest

    Could some VHDL guru please help me ? Could you please direct me to a
    good example of a resolution function for multiple drivers ? I have
    tried synthesis on Xilinx ISE 11.1 with Spartan 3 and I am getting
    multiple drivers problem. Any hints, suggestions would be of immense
    help.
    Thank you.
     
    Daku, Jan 25, 2010
    #1
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  2. Daku

    Tricky Guest

    On Jan 25, 6:31 am, Daku <> wrote:
    > Could some VHDL guru please help me ? Could you please direct me to a
    > good example of a resolution function for multiple drivers ? I have
    > tried synthesis on Xilinx ISE 11.1 with Spartan 3 and I am getting
    > multiple drivers problem. Any hints, suggestions would be of immense
    > help.
    > Thank you.


    A resolution function will not solve this problem. What it means is
    you have 2 signals driving the same register, which wont work without
    a tri-state driver (which internally synthesises to a mux). Id re-
    asses your needs and think more about the underlying hardware rather
    than functions to "solve" your problem.

    As for great examples of resolution functions - look in the
    ieee.std_logic_1164 package - its full of all the resolution functions
    for the std_logic type.
     
    Tricky, Jan 25, 2010
    #2
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  3. Daku

    Dave Pollum Guest

    On Jan 25, 1:31 am, Daku <> wrote:
    > Could some VHDL guru please help me ? Could you please direct me to a
    > good example of a resolution function for multiple drivers ? I have
    > tried synthesis on Xilinx ISE 11.1 with Spartan 3 and I am getting
    > multiple drivers problem. Any hints, suggestions would be of immense
    > help.
    > Thank you.


    If you have multiple processes driving the same signal, you will get
    this error.
    -Dave Pollum
     
    Dave Pollum, Jan 25, 2010
    #3
  4. Daku <> writes:

    > Could some VHDL guru please help me ? Could you please direct me to a
    > good example of a resolution function for multiple drivers ? I have
    > tried synthesis on Xilinx ISE 11.1 with Spartan 3 and I am getting
    > multiple drivers problem. Any hints, suggestions would be of immense
    > help.
    > Thank you.


    In *theory* this works - it's a well defined solution in
    simulation. The problem is that in *practice* the synthesizers of the
    world don't bother to try to implement the behaviour of a resolution
    function. They typically just give you an error that multiple drivers
    exist on the same signal.

    You'll have to restructure your design instead.

    - Kenn
     
    Kenn Heinrich, Jan 25, 2010
    #4
  5. Daku wrote:
    > Could some VHDL guru please help me ? Could you please direct me to a
    > good example of a resolution function for multiple drivers ?


    The standard types already have resolution functions.
    That is not your problem.

    -- Mike Treseler
     
    Mike Treseler, Jan 25, 2010
    #5
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