Stats

  • Locked Locked
  • Replies 6
  • Subscribers 127
  • Views 12535
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Virtuoso router leaves steiners, routes & guides in the database

HiuMinor
Hi,

we currently experienced a strange behaviour concening the bounding boxes of routed macros.

First we created a big macro layout using the Virtuoso router. After that we re-used the layout to create some derivates using the Virtuoso layout Editor (actually smaller layouts by deleting parts of the bigger one). All the checks (DRC,ERC,LVS ...) are OK, but the bounding boxes (when instantiating the small macros) are way too large. They still have the size of the original, bigger macro.

When looking into the OA database I found a lot of objects, that seems to be remains from the initial routing of the big macro (steiners, routes & guides). Now I deleted all the objects lying outside the current macros boundary by a SKILL procedure and thus also the bounding box, when instatiating the macro, is OK again.

Now my questions:

  • Can I delete all the steiners, routes & guides, if the routing of a macro is finished, or are these objects in some way relevant for the layout cellView or the final GDS?
  • Is this the normal behaviour of the Virtuoso router to leave these objects in the database, or are they possibly remains of a crash or misuse of the tool?
  • If they can be deleted without any loss of design contents, is it possible to have a clean-up step in the Virtuoso router to get rid of them automatically?

Many thanks in advance, Ronald.

PS: I forgot to mention our tool version: IC6.1.4.500.8

 

  • Hi Ronald

    The problem of stranded steiners is actually not limited to auto-routing. It happens even when wires are chopped. The leftover steiners will make the bBox larger than the cellview. You can remove them safely using SKILL:

    foreach( steiner geGetWindowCellView()~>steiners
       dbDeleteObject(steiner)
    ) ;foreach

    Currently there are no other ways to remove stranded steiners. Would it be possible for you to file a service request with your local Cadence support to highlight the issue so that we can improve on the tool?

    Thanks
    Quek

  •  Hi Quek,

    many thanks for your reply.
    So that means, I can delete all the steiners, guides and routes from the database. It was my biggest concern, that by deleting these objects I would somehow damage the layout.

    I will file a service request with Cadence as you suggested.

    Thanks again, Ronald.

  • Hi Ronald

    You are welcome. I think the cellview bBox problem is only caused by steiners so it is fine to just remove the steiners. Removing routes is actually not a good idea because in IC61, there is a difference between wires that are contained in routes (signal nets) and those that are not in routes (special nets such as power/ground, clk, etc).

    Best regards
    Quek

  •  Hi Quek,

    thanks for the hint - when we run into this problem next time I will try out deleting the steiners only.
    For our current design I have already deleted all steiners, guides and routes with coordinares outside the prBoundary and everything is just fine.

    I have also forwarded this thread to our EDA service colleagues to file a request to Cadence for automatic clean-up.

    Best regards, Ronald.

  • Hi Quek and Ronald

    in the CADENCE Doc there is a scenario description when large bounding boxes can occur:

    One more scenario where such an issue ( that means to large Bounding-Boxes ) can happen is when you have steiners in the design. Wire Editor and assisted routing commands like P2P ( Point to Point ), Guided routing and VSR etc use steiner to ease the routing. In general deletion of a net should delete a steiner associated with a net. However, steiners may be leftover in a layout view if wires of a net get deleted due to unspecified reasons but the net was not cleaned up. In such a case one should delete the steiner after finding it out.
    ...

    These logical points ( steiners ) can be regenerated by the routing commands automatically without any user intervention. Starting ISR12 of IC6.1.5 release, when a steiner is connected to a route and we try to move the route, the steiner will move according to the new coordinate of the design or the end elements of the route.

    I also created manually steiners and guides. Both can create large bounding boxes.

    So I would also suggest to delete steiners only

    best regards

     
     

     

  • Hi Matze17

    Thank you very much for the info. It is very useful for all forum users. : )

    Best regards
    Quek

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.