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Altera_Forum's avatar
Altera_Forum
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14 years ago

One question in TimeQuest User Guide from Wiki

I am reading TimeQuest user guide from wiki. It is great for beginner. But I have a small question in it:

In page 35, about Determining Default Setup and Hold Relationships in Three Steps, in (3)

"3) The default hold relationship comes from the closest edges where Launch Edge + Setup Relationship < Latch Edge"

But in page 39, the example to show the default hold relationship, it is :

"For the hold relationship, we will similarly assume that every launch edge sends data. So

start with the first launch edge in the waveform, moving forward by the amount of the Setup

Relationship, and then look for the first Latch Edge before that."

Why is the first latch edge before that? If Launch Edge + Setup Relationship < Latch Edge,

why not the first latch edge after that?

Hope my question posted is clear. Thanks.

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    Yes, and I think I have the equation wrong. It should be:

    Launch Edge + Setup Relationship > Latch Edge

    To be honest, I think most people ignore the equation. I know I do. I think the "process" of looking at setup relationships and moving back to find the hold is easier, and the whole theory of finding relationships is more difficult than doing it in real designs, since the clocks are usually pretty related.

    Thanks for pointing it out though, I'll make the change and update.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    --- Quote Start ---

    Yes, and I think I have the equation wrong. It should be:

    Launch Edge + Setup Relationship > Latch Edge

    To be honest, I think most people ignore the equation. I know I do. I think the "process" of looking at setup relationships and moving back to find the hold is easier, and the whole theory of finding relationships is more difficult than doing it in real designs, since the clocks are usually pretty related.

    Thanks for pointing it out though, I'll make the change and update.

    --- Quote End ---

    Thanks so much, Rysc. Yes, the new equation make sense.

    Another question is in your TimeQuest Guide, from section 6 to section 10, nearly all of them only have titles, do you have plan to fill them in future or you already did but my version is not latest one?

    Thanks very much.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    You're up to date. I put that in there as a placeholder, but it's been years and I haven't gotten around to it. I don't really want to take it out though, as that'd pretty much be admitting defeat that I won't get around to it. : )