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Altera_Forum
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16 years ago

Explanation of "COMP" value in TimeQuest When PLL Is In No Comp Mode

Looking at the "Data Available" report in TimeQuest of a path where the data is launched by a PLL within the design. The PLL is in 'No Compension Mode'.

In looking at the delay through the PLL in that report, there is still a value of type "COMP" of ~1.8ns.

If the PLL is in 'No Compensation Mode', where does this value come from and what is being compensated for?

Thanks!

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    There is always a feedback path delay in the PLL and that is what the “COMP” delay refers to. “No compensation” mode means that the feedback path delay is not guaranteed to be any particular value since the PLL is not trying to compensate any particular clock path (e.g. as in “normal mode” where the PLL tries to make the full clock path delay 0ns).

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    So the COMP value in No Compensation Mode accounts for the delay through the PLL itself. Whereas the COMP value Normal Mode accounts for both the PLL and the clock path delay?