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 Experiensing odd behaviour with encounter 

Last post Thu, Aug 1 2013 11:34 AM by Thodoros. 2 replies.
Started by Thodoros 01 Aug 2013 02:55 AM. Topic has 2 replies and 361 views
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  • Thu, Aug 1 2013 2:55 AM

    • Thodoros
    • Top 500 Contributor
    • Joined on Tue, Oct 6 2009
    • Patra, Athens Greece
    • Posts 34
    • Points 485
    Experiensing odd behaviour with encounter Reply

     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

    • Post Points: 20
  • Thu, Aug 1 2013 8:54 AM

    • wally1
    • Top 50 Contributor
    • Joined on Mon, Aug 4 2008
    • Bellevue, WA
    • Posts 148
    • Points 2,895
    Re: Experiensing odd behaviour with encounter Reply

    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

    • Post Points: 20
  • Thu, Aug 1 2013 11:34 AM

    • Thodoros
    • Top 500 Contributor
    • Joined on Tue, Oct 6 2009
    • Patra, Athens Greece
    • Posts 34
    • Points 485
    Re: Experiensing odd behaviour with encounter Reply

     Dear Wally,

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

    Thanks!!

    • Post Points: 5
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Started by Thodoros at 01 Aug 2013 02:55 AM. Topic has 2 replies.