H-tree CTS

  1. nitin kala
    nitin kala
    Hi All,
    Please tell how to do manual H-tree Clock Tree Synthesis. If possible, please share the scripts and useful documents as well.
  2. ro9ty
    Hi Nitin,

    Clock Tree Synthesis is the most important step in PnR and hence quite extensive too.
    Which tool are you using. Usually all the CAD toolmakers provide templates for CTS and other stages, get that and you will be good to go. But to give you a jist
    You will need a placed database (placement complete with congestion in check), you will need the SDC or constraints file with all clock-definitions and false paths etc... the libraries should be properly set (target and link both). Once you do that you can write out a file from the tool which will have the root and leaf pin details according to your SDC etc... The tool has its own understanding of root and leaf pins but if you feel that it needs some ore constraints like through pins etc.. which have by-mistake taken as leaf pin by the tool then you will have to modify it.
    Source the script and analyze the skew. The main thing in CTS is analysis.
    Ex: Sometimes building clock tree for generated clocks is not optimal so you might have to make the clock generation point a through_pin and then propagate the master_clock.
  3. nitin kala
    nitin kala
    Hi ro9ty,
    Thanks for sharing info. I have the setup with me. I have build clock tree as well and analyzed things as well. Just want to know how to build HTree automatically on my top design in encounter.
    Please share if you have any working sample script for it.

    Thanks and Regards,
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