Error please Help

Discussion in 'VHDL' started by Isaac, Aug 13, 2003.

  1. Isaac

    Isaac Guest

    Hi Mates I am getting following errors when I start simulating my
    design.

    Delta count overflow - stopped. Try to increase the iterations limit
    in simulator preferences.
    # Fatal error occurred during simulation.


    How to remove this error ?

    Thanking you in advance .

    Isaac
     
    Isaac, Aug 13, 2003
    #1
    1. Advertising

  2. Isaac

    Jim Wu Guest

    If you're using ModelSim, you can change the iteration limit from the
    Simuluation Options window. You can also change it in modelsim.ini file.

    Jim Wu



    "Isaac" <> wrote in message
    news:...
    > Hi Mates I am getting following errors when I start simulating my
    > design.
    >
    > Delta count overflow - stopped. Try to increase the iterations limit
    > in simulator preferences.
    > # Fatal error occurred during simulation.
    >
    >
    > How to remove this error ?
    >
    > Thanking you in advance .
    >
    > Isaac
     
    Jim Wu, Aug 13, 2003
    #2
    1. Advertising

  3. Isaac

    Ian Poole Guest

    This is usually caused by an error in the original VHDL that results in an
    infinite loop which consumes zero simulation time. Raising the maximum delta
    limit is fairly pointless, since you probably have an infinite loop...

    The usual error is a process with neither a sensitivity list nor a wait
    statement eg:
    process
    begin
    if (Reset = '1') then
    sig <= '0';
    elsif (Rising_edge(Clk)) then
    sig <= D;
    end if;
    end process;

    Processes with feedback can cause errors. Try this concurrent statement and
    see what happens!:
    sig <= not sig;

    Alternatively, you may have a process with wait statments inside a while
    loop/if statement etc that means the wait is bypassed for some reason eg:

    process
    begin
    if (Ready = '1') then
    -- do something
    wait for 10 ns;
    end if;
    end process;

    What happens to this process if Ready /= '1' ???

    Also test bench processes which are supposed to run only once and terminate,
    but have a missing wait; at the end. This particular example won't give a
    delta limit error, but illustrates what I mean:
    stim:process
    begin
    A <= "000";
    wait for 10 ns;
    A <= "010";
    wait for 10 ns;
    A <= "100";
    -- wait; -- this effectively stops this process
    end process;

    HTH

    Ian


    "Isaac" <> wrote in message
    news:...
    > Hi Mates I am getting following errors when I start simulating my
    > design.
    >
    > Delta count overflow - stopped. Try to increase the iterations limit
    > in simulator preferences.
    > # Fatal error occurred during simulation.
    >
    >
    > How to remove this error ?
    >
    > Thanking you in advance .
    >
    > Isaac
     
    Ian Poole, Aug 13, 2003
    #3
  4. The given process will never stop executing but it will NOT generate the
    delta count overflow.
    (In the example the tool probably raised a warning missing wait statement
    during compilation/analyzing).

    A simple example that generates delta count is the following CONCURRENT
    statement:
    y <= NOT y;

    In general increasing the upper limit of the delta count will not help.
    Check the
    VHDL description. If you can not find the 'loop' it maybe possible to
    perform a
    step by step simulation (in combination with a break), depending on your
    simulation environment.

    Egbert Molenkamp

    >
    > The usual error is a process with neither a sensitivity list nor a wait
    > statement eg:
    > process
    > begin
    > if (Reset = '1') then
    > sig <= '0';
    > elsif (Rising_edge(Clk)) then
    > sig <= D;
    > end if;
    > end process;
    >
     
    Egbert Molenkamp, Aug 13, 2003
    #4
  5. Isaac

    Jim Wu Guest


    > This is usually caused by an error in the original VHDL that results in an
    > infinite loop which consumes zero simulation time. Raising the maximum

    delta
    > limit is fairly pointless, since you probably have an infinite loop...


    For Modelsim, even a not very big loop would cause the problem as the
    default limit is 5000.

    Jim Wu
     
    Jim Wu, Aug 13, 2003
    #5
    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. Replies:
    4
    Views:
    520
    Chris Uppal
    May 5, 2005
  2. KK
    Replies:
    2
    Views:
    590
    Big Brian
    Oct 14, 2003
  3. MuZZy
    Replies:
    7
    Views:
    1,762
    Mike Hewson
    Jan 7, 2005
  4. Replies:
    4
    Views:
    320
    Martin Ambuhl
    Nov 14, 2007
  5. mera
    Replies:
    7
    Views:
    1,111
Loading...

Share This Page