top cell set criteria

Comments

• ocasta

  October 8

  Isn't it the cell that was visible at the time of saving the file? Can you check? (I didn't).
• blueman_44

  October 9

  There can be multiple 'top' cells. Top just means that a cell has no parent cell. Which is usually the case when you write/export a gds file.

  Some documentation: (ctrl-f top and you'll find it)
  https://www.klayout.de/doc-qt5/programming/database_api.html

  And here's a good article about gdsII format:
  https://www.artwork.com/gdsii/gdsii/

  Sadly I don't know how kLayout picks a top cell if there are multiple of them...
• Matthias

  October 10

  I can tell

  When there are multiple top cells, KLayout picks the one with the largest bounding box for initial display. GDS does not have a way of saying which is the primary top cell. Also, GDS files with multiple top cells are common only in certain contexts (e.g. as a collection of library cells). A design ready for tapeout should never have multiple top cells.

  Matthias
• dick_freebird

  October 11

  Many orgs seem to have a habit of calling the
  top cell "TopCell". When you do part after part
  after part, you can stand to lose a few repetitive
  questions. If you get to name the baby, then you
  might develop a habit that saves thought. I will
  often designate "real important stuff" with a
  "00_blahblah" type name so that alpha ascending
  sort will bubble them to the top. That's personal,
  not common practice, but works for me. Also
  tagging stale versions with date suffix (rename
  and copy-back) gives me a "trail" that is poor boy
  "versioning".

  Or make a "TopCell" or "00_Top" layout that has
  placed, the "real" one and just push in. Change
  your mind? 00_Top2.