Stats

  • Locked Locked
  • Replies 3
  • Subscribers 143
  • Views 2424
  • 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

Force db update/refresh regarding connectivity and pcell parameters

frankliu

Problem statement:

1. In layout XL create a (metal) rectangle and add a net name to it.

2. In skill add a (same layer) rectangle that abuts or overlaps this rectangle

3. Query the associated nets with this new rectangle in skill

   Result: its net name does not get updated

   Expected result : the net name associated with 1.



Note:

If instead of 2. you manually create a rectangle from the layout editor, then the query in 3., works as intended.

If I put a breakpoint between 2 and 3 then 3. works

If I add a dbSave between 2 and 3 then 3. works



I would like to avoid using dbSave, since this is too heavy handed and slows down my script.  I would like the connectivity information to be updated at the end of 2.  Please let me know if there is a way of updating this information.



Note:

In the title I also mention pcell parameters, this also happens with pcells, I know that in some cases you have to call the callback function associated with a parameter in the pcell, and I have, but a similar situation happens.  For example in a transistor pcell, when I change the number of fingers, and then query for the geometry of the poly, I don't get an updated number, and as in the connectivity example above, if I insert a breakpoint or perform a dbSave then the information gets updated.  Clearly something must be called within dbSave or when restarting from a breakpoint to update the connectivity / cell parameters.



Sorry if this is not clear, please let me know if you need further details.

  • Hi Frank,

    The feature of updating abutted or overlapping shapes is an interactive Layout XL feature, and thus it does not occur for non-interactive SKILL code. I believe that this is part of the (VLS-XL) connectivity extractor that is keeping track of connectivity and either warning of shorts, for example, or updating these abutting/overlapping shapes. I don't think that there is a public SKILL API to access this functionality either. To emulate this (simplistically, at least) you would need to look at abutted or overlapping shapes to your new object and obtain connectivity from these and apply back to the new shape. This shouldn't be too hard, but could slow down the code because of the additional search needed (dbGetOverlaps, dbProduceOverlap, dbShapeQuery ...)

    Hope this helps you!

    Best regards,

    Lawrence.

  • Thanks Lawrence, I agree with you that I can check for overlaps, and change the connectivity, yes this could be a work around, but I don't have a work around for pcell parameters.

    That is, if I change a parameter like number of fingers, and I call the related callback function, from skill, and then query for the geometry of the fingers, I don't get the updated list of rectangles. Note I used Andrew's code: CCSinvokeCdfCallbacks(geGetEditCellView())

    And as mentioned previously, if I do a dbSave or put a breakpoint after changing the number of fingers, things work correctly.

    I need geometry information of the underlying pcell after a change of parameters and I don't know how this can be obtained otherwise.

    But in either case, it seems that some kind of refreshing the db function should be provided.

  • For the VLS XL connectivity extraction (the first problem), the issue is that the connectivity extractor normally gets called as part of the interactive update loop. You may need to call the extractor (lceExtract) yourself?

    For the pcell change, this should happen directly - if you change the parameters of a pcell, then the master should get updated to a new subMaster. I'm assuming you are not doing something like this:

    inst=...
    master=inst~>master
    inst~>fingers=...

    and then look at master? That won't work, because if a pcell parameter changes (assuming that fingers is a pcell parameter), the instance will then point at a new subMaster of the pcell and you'd still be looking at the original subMaster. If you re-access inst~>master you should see the updated shapes...

    There's nothing special you need to do to do a database refresh in this case.

    Regards,

    Andrew.

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.