HDL Abstraction of Dynamic Logic

Discussion in 'VHDL' started by Alex, Sep 13, 2005.

  1. Alex

    Alex Guest

    Hi Guys,

    Maybe someone cope with similar problem and help.

    I am creating a behavioral description of an asic, and I want it to be as
    close as possible
    to what would be on a chip in the end. As it all based on dynamic logic I
    am a bit confused with
    adequate description in VHDL.

    Basically the question is how to describe the simple system which consist
    of dynamic latch and a precharged bus.
    As there are several registers connected to a bus it is necessary to keep
    latch and a bus as separate instances.

    If to decompose this problem even deeper it would sound - how to
    describe a capacitor.

    Sorry if the description is messy.
    Thanks for help.

    --
    Alex
     
    Alex, Sep 13, 2005
    #1
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  2. Alex wrote:

    > describe the simple system which
    > consist of dynamic latch and a precharged bus.


    Dynamic logic uses a capacitor and precharge circuit as
    a power supply. If you need to model these basic gates and
    flops consider spice or vhdl-ams. Once these basic cells
    are working, plain vhdl could be used for higher level
    designs.

    -- Mike Treseler
     
    Mike Treseler, Sep 13, 2005
    #2
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  3. Alex

    Alex Guest

    Thanks for your reply.

    I was considering VHDL-AMS, but I have solved this problem with simple
    usage
    of st_logic_type (as the model is only for behvioral simulation).

    So the basic idea of precharged bus is as follows - in case some one will
    need it:


    Port ( P : in std_logic; -- precharge
    O : inout std_logic -- output
    );

    architecture
    signal tmp_stor: std_logic;

    begin
    process(O,P)
    begin
    if O='0' then
    if P='1' then O<='X';
    else O<='L';
    end if;
    elsif P='1' then
    O<='H';
    end if;
    ed process

    In other words using week '0' and '1' simplify simulating such behaviour
    as precharged logic.


    Regards
    --
    Alex
     
    Alex, Sep 18, 2005
    #3
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