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GDeXi's avatar
GDeXi
Icon for Occasional Contributor rankOccasional Contributor
5 years ago
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AN477 Question

Hello, I just feel strange with AN477 doc below:

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/an/an477.pdf

page 12

why the

Calculated output maximum delay = tsu of external register = –0.9 ns

is not -tsu of external register ?

or = 0.9 ns ?

thanks for your help

  • KennyT_altera's avatar
    KennyT_altera
    5 years ago

    This is because


    1) The multicycle assignments are used to create a setup relationship of 0ns and a hold relationship of -1/2*period.

    2) The value for set_output_delay -max is now negative due to the 0ns setup relationship set by the multicycle then the setup requirement (max data delay).



6 Replies

  • KennyT_altera's avatar
    KennyT_altera
    Icon for Super Contributor rankSuper Contributor
    5 years ago

    This is because


    1) The multicycle assignments are used to create a setup relationship of 0ns and a hold relationship of -1/2*period.

    2) The value for set_output_delay -max is now negative due to the 0ns setup relationship set by the multicycle then the setup requirement (max data delay).



    • GDeXi's avatar
      GDeXi
      Icon for Occasional Contributor rankOccasional Contributor
      5 years ago

      Sorry,

      I have thought for a long time, but I still don't understand. Could you describe it in detail? thank you

    • User1574410249703619's avatar
      User1574410249703619
      Icon for New Contributor rankNew Contributor
      5 years ago

      For personal reasons, I'm sorry to reply you so late.

      For AN411,I have read page 32.

      I can understand why Multicycle set , for same edge launch and latch. I don't understand why max data delay now is negative.

      Q1:

      i don't understand max data delay is negative has some related to Multicycle. and why data delay is negative.

      Q2:

      Is it analyzed according to this formula?

      I'm sorry for the trouble！

      Have a good day.