Stats

  • Locked Locked
  • Replies 4
  • Subscribers 92
  • Views 13907
  • 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

Experiensing odd behaviour with encounter

Thodoros

 Hello,

I am trying to implemen t a divider using macro cells with  encounter. The LEF of a macro cell is attached.
The macro cell consists of two standard cell rows sharing the gnd! in the middle. So the macro cell starts with power (vdd!) on top,
has ground (gnd!) in middle and ends with power (vdd!) at the bottom.

With encounter (versions mainly 9.1 and also 10.1) I commit floorplan and I do specialRoute to get gnd! and vdd! rails. Than I perform a standard cell placement.

My problem is  that the cell is auto placed at a gnd! - vdd! - gnd! combination whereas it uses vdd! - gnd! - vdd! combination.
I try to move slitly the macro (i.e to the right) and when I release it, it is auto moved to the row below as to use the proper vdd! - gnd! combination. So I do not think that it is a pin problem.

  The problem does not occuse when the macro has gnd! at the bottom (and not in the middle).

 Why is encounter showing me this behaviour?

Thanks for your help (to which I am in desperate of),
My appologies for consuming your time,

Thodoros

  • Hello Thodoros,

    If this is a double-height cell then you should have double-height rows defined in your floorplan which align properly to the single-height rows so the power rails align properly. For example, typically you will have two site definitions:

    SITE CORE

      SIZE 2.8 BY 2.52 ;

      CLASS CORE ;

      SYMMETRY Y ;

    END CORE

    SITE CORE_2X

      SIZE 2.8 BY 5.04 ;

      CLASS CORE ;

      SYMMETRY Y ;

    END CORE

    Specify Floorplan will then automatically create the single and double-height rows if instances in the netlist use these sites.

    Regards,

    Brian

  •  Dear Wally,

    Thanks for your help. It was exactly what I needed to do.

    Thanks!!

  • I have a similar problem except that my cell has gnd-vdd-gnd power lines and encounter is placing them in vdd-gnd-vdd configuration. I have specified the double row site as stated. Is there a way to fix this?

     

    Thanks 

  • you might have to manually specify the start of the double-height rows. sounds like they are off by one single-row height.

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.