Guard

Discussion in 'VHDL' started by Kuan Zhou, Jan 24, 2005.

  1. Kuan Zhou

    Kuan Zhou Guest

    Hi,

    A newbie question: what does "guard" mean in VHDL? Can anybody kindly
    give me one example?

    Kuan
     
    Kuan Zhou, Jan 24, 2005
    #1
    1. Advertising

  2. Probably you can find a little bit more at this location
    http://www.acc-eda.com/vhdlref/refguide/language_overview/partitioning_features/blocks.htm

    Its interesting if a signal if all drivers to a signal are disconnected.
    What should be the value of that signal?
    Therefore the a signal declaration can be declared as:

    signal myobject1 : std_logic REGISTER;
    signal myobject1 : std_logic BUS;

    In case myobject1 it not driven anymore it remembers its last value.
    In case myobject2 is not driven anymore the resolution functions determines
    the value.
    see more on this at:
    http://www-asim.lip6.fr/recherche/alliance/olddoc/jumpstart/VHDL-Subset/vbe.html

    Egbert Molenkamp


    "Kuan Zhou" <> wrote in message
    news:p...
    > Hi,
    >
    > A newbie question: what does "guard" mean in VHDL? Can anybody kindly
    > give me one example?
    >
    > Kuan
     
    Egbert Molenkamp, Jan 24, 2005
    #2
    1. Advertising

  3. Kuan Zhou

    Guest

    guard is the implicit signal created when you declare a block with a
    guard expression. guard expressions are used to control operation of
    guarded signal assignments.
    ex:
    guard_ex: block (value = '1') is
    begin
    ---
    signal_a <= guarded (x and y);
    ---
    end block;
    here signal_a is a guarded signal evaluated when guard is true ie, when
    value='1'.

    -Neo
     
    , Jan 24, 2005
    #3
  4. On Mon, 24 Jan 2005 00:41:42 -0500, Kuan Zhou <>
    wrote:

    >Hi,
    >
    > A newbie question: what does "guard" mean in VHDL? Can anybody kindly
    >give me one example?


    Given that you say you're a newbie, perhaps a better answer would be:

    Guard is a keyword you won't ever use in synthesisable code, and
    probably won't use in your testbench either.

    Regards,
    Allan
     
    Allan Herriman, Jan 24, 2005
    #4
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Marcus Liddle
    Replies:
    2
    Views:
    483
  2. Samuel
    Replies:
    0
    Views:
    287
    Samuel
    Jan 14, 2007
  3. Replies:
    11
    Views:
    563
    Jack Klein
    Oct 21, 2005
  4. asdf

    header guard

    asdf, Nov 21, 2006, in forum: C++
    Replies:
    15
    Views:
    774
    Marcus Kwok
    Nov 27, 2006
  5. Barry

    Exception Safe Guard

    Barry, Sep 4, 2007, in forum: C++
    Replies:
    5
    Views:
    466
    Barry
    Sep 5, 2007
Loading...

Share This Page