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Interactive time-driven method of component placement that more directly constrains critical paths using net-based constraints

  • US 5,666,290 A
  • Filed: 12/27/1995
  • Issued: 09/09/1997
  • Est. Priority Date: 12/27/1995
  • Status: Expired due to Fees
First Claim
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1. A method for optimizing the placement of components of an integrated circuit, the components interconnected by nets to form paths wherein each of the nets couples an output of one of the components to one or more inputs of one or more of the components, and wherein each of the paths comprises one or more segments, each of the segments of one of the paths comprising one of the components and the net coupled to the output of the component, each of the segments of one of the paths coupled by a branch of its net to an input of one of the components comprising a next segment in the path, said method comprising the steps of:

  • identifying one or more of the paths as critical;

    imposing a maximum delay constraint on each of the critical paths;

    performing an initial placement of the components which becomes the current placement;

    for each of the critical paths;

    estimating a path delay for the critical path based on the current placement; and

    assigning weight values to each of the nets which form part of the segments of the critical path, said assigned weight values having a non-constant distribution based on location of the segment in the critical path of which each net is a part;

    assigning a default weight value to each of the nets not previously assigned a weight;

    applying a mincut algorithm to find a placement of the components that minimizes total weight of the nets crossing a cut line, the weight minimized placement becoming the current placement; and

    iterating said method from said step of estimating path delays through said step of applying a mincut algorithm until the components are optimally placed.

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