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 Simulation problem: unwanted zero-width glitch 

Last post Tue, Aug 25 2009 2:27 AM by Shalom B. 3 replies.
Started by ridgemao 16 Jun 2009 07:46 PM. Topic has 3 replies and 3957 views
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  • Tue, Jun 16 2009 7:46 PM

    • ridgemao
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    Simulation problem: unwanted zero-width glitch Reply
    I'm using LDV 5.1. In simvision's waveform window, many signals have zero-width glitch. How can I avoid displaying these glitches? I know it is due to the zero-time delay of sequential logic in functional simulation, and these "zero-width glitch" won't appears in actual application because there is no zero-time delay in actual sequential logic. And I think the simulator knows all about it and It marks the "zero-width glitch" with a special sign. I don't want the simulator to display these glitches, how can I make it? Thanks.
    • Post Points: 5
  • Thu, Jul 9 2009 7:36 PM

    • ridgemao
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    Re: Simulation problem: unwanted zero-width glitch Reply
    here is a snapshot of my waveform. The zero-width glitch have a special mark, I don't want to display this kind of glitch. http://picasaweb.google.com/lh/photo/frI8o_RwPqxbRX_YCj6Kkw?feat=directlink
    • Post Points: 20
  • Mon, Aug 24 2009 9:56 PM

    • adua
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    Re: Simulation problem: unwanted zero-width glitch Reply

     

    Hi,

    You need to turn off "-event" switch when you are opening the shm waveform database. The default behavior is not to record these glitches (that you want), and it happens only when you specify "-event" option of 'database' tcl command. 

    The following is copy-paste from NCVLOG product documentation (<ius_inst_dir>/doc/ncvlog/ncvlog.pdf ) on "-event" option of database

    database Command Modifiers and Options

     -event

    Dumps all value changes to the database.

    By default, when probing to an SHM database, the simulator discards multiple value changes for an object during one simulation time and dumps only the final value at the end of that simulation time. Use -event if you want to dump all value changes to the SHM database. You can then use the SimVision waveform viewer to expand a single moment of simulation time to show the sequence of value changes that occurred at that time.

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  • Tue, Aug 25 2009 2:27 AM

    • Shalom B
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    Re: Simulation problem: unwanted zero-width glitch Reply

    As a side-note, sometimes one sees behavior that seems inexplicable, such as a flip-flop whose output changes although its data input looks constant all the time. In such cases, one should suspect a zero-width glitch and turn on -event. I had such a case just recently.

     

    Shalom

    Shalom.Bresticker@intel.com
    • Post Points: 5
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Started by ridgemao at 16 Jun 2009 07:46 PM. Topic has 3 replies.