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Altera_Forum's avatar
Altera_Forum
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15 years ago

Question about the HandBook

Hi, all:

In "quartus II, HB 10.1, Vol 3, quartus II, HB 10.1, Vol 3, Chap 6 The Quartus II TimeQuest Timing Analyzer", there's Equation 7-1:

input delayMAX = ( cd_extMIN – cd_altrMAX) + tco_extMAX + ddMAX

input delayMIN = (cd_extMAX – cd_altrMIN) + tco_extMIN + ddMIN

I think it should be like this:

input delayMAX = (cd_extMAX – cd_altrMIN) + tco_extMAX + ddMAX

input delayMIN = (cd_extMIN – cd_altrMAX) + tco_extMIN + ddMIN

The attachment is the figure.https://www.alteraforum.com/forum/attachment.php?attachmentid=4413

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Wow. The output delay looks incorrect too. I believe it should be:

    output delayMAX = ddMAX + tsu_ext + cd_altrMAX – cd_extMIN

    output delayMIN = ddMIN – th_ext + cd_altrMin – cd_extMAX
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    I don't think so. I believe the equations are correct.

    input delayMAX (IMD) = tCO_extMAX + ddMAX - tCS_MIN

    input delayMIN (ImD) = tCO_extMIN + ddMIN - tCS_MAX

    where tCS_MIN (minimum clock skew) = MAX tCLK (destination) - MIN tCLK (source)

    = cd_altrMAX - cd_extMIN (for inputs)

    and tCS_MAX (maximum clock skew) = MIN tCLK (destination) - MAX tCLK (source)

    = cd_altrMIN - cd_extMAX

    therefore,

    input_delayMAX = tCO_extMAX + ddMAX - tCS_MIN

    = tCO_extMAX + ddMAX - (cd_altrMAX - cd_extMIN)

    = tCO_extMAX + ddMAX + cd_extMIN - cd_altrMAX

    and

    input_delayMIN = tCO_extMIN + ddMIN - tCS_MAX

    = tCO_extMIN + ddMIN - (cd_altrMIN - cd_extMAX)

    = tCO_extMIN + ddMIN + cd_extMAX - cd_altrMIN

    Similar equations apply to the output delays.
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    @nju044,

    Rysc and I have discussed this at length offline, and I now agree with him. The equations in the Handbook (and also on my "cheat sheet" which was copied from the Handbook many years ago) appear to be incorrect.