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marked dont_use in the library

naderi

Hello,

In Encounter, when I use pad cells from library I get some warnings that those cells are marked dont_use in the library. Why is it marked and who could change it?

I searched Google for this message. It seems there was such problem already discussed in www.cdnusers.org. but the it's history is removed after merging with cadence community. my search result is following:

about the error of "checkDesign -all" > Forums > www.cdnusers.org

**ERROR: Input netlist has a cell PX2 which is marked dont_use in the library. * *ERROR: Input netlist has a cell PI which is marked dont_use in the library. ...
www.cdnusers.org/Forums/tabid/52/forumid/19/postid/9231/view/topic/Default.aspx - 56k -

 

Thanks,

Ali 

  •  Hi Ali,

     The dont_use marking typically comes from one of two places: the .lib file or the .sdc file. It's not unusual for cells like IO pads, RAMs, PLLs, etc. to be marked dont_use. You can usually ignore the warnings in this case because Encounter would not use these cells during optimization anyway (and you wouldn't want it to). The cells appear in the design, but we don't want any optimization tool to mess with them. 

     The case where I would be concerned is if, for example, a certain strength cell is marked dont_use, like an X18 or X24 and you do have some of these cells in your netlist. High-drive strength cells are often marked dont_use for power/ir drop/current limit considerations, so you want to be aware if they are in the netlist when they shouldn't be. That's why it's always a good idea to run checkDesign and examine the report.

    - Kari 

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