Abstract: A method and apparatus for efficiently viewing selected cells using a database editor tool. By using a cell selection list that identifies a number of selected components, the present invention may allow the user to sequentially view the selected components by using a number of pre-defined “hot-keys”. In addition, the present invention may automatically set the design hierarchy in the database editor tool to an appropriate level so that the component being viewed can be easily manipulated by the circuit designer.

Abstract: A method and apparatus for associating selected circuit instances, and for allowing a later group manipulation thereof. Prior to entering a database editor tool, selected instances may be associated with one another, and the association may be recorded in the circuit design database. The database editor tool may then read the circuit design database and identify the selected instances and the association therebetween. The associated instances may be called a group, or preferably a stack. The database editor tool may then perform a group operation on the instances associated with the stack.

Abstract: A placement tool that may import and export cell substitution and/or cell selection lists. The cell substitution and/or cell selection lists may be used by the placement tool to substitute and/or modify the placement design database, rather than the original schematic or behavioral database. This may eliminate the need to re-synthesize the circuit design during each design iteration. The present invention further contemplates providing a reset feature which may reset the circuit design database to a previous state, if desired.

Abstract: A method and apparatus for efficiently selecting cells within a circuit design database. The invention includes four primary features for selecting cells including (1) selecting only those cells that are in a pre-identified region and within a pre-identified selection area; (2) maneuvering through the circuit design hierarchy and selecting cells or regions at selected levels of hierarchy by using predetermined up and down hot-keys; (3) sorting selected cells by instance name, and manually selecting a desired cell or region from the resulting sorted list; and (4) sorting selected cells by a corresponding net name, and manually selecting a desired cell or region from the resulting sorted list.

Abstract: A method and apparatus for selectively viewing nets within a database editor tool. The present invention provides four primary features for selectively viewing nets. First, the present invention contemplates selecting a number of objects, and viewing only those nets that are either driven from or received by the selected objects. In a preferred embodiment, the number of objects are placed objects within a placement tool. Second, for those nets that are selected, and that are also coupled to un-placed cells, the present invention contemplate providing fly-wires from the corresponding selected objects to a predetermined location representative of an approximate expected location for the un-placed cells. Third, the present invention contemplate providing a vector filter which may permit only vectored nets with a selected bus width range to be viewed.

Abstract: A method and apparatus for optimizing a circuit design having multi-cycle paths therein. In an exemplary embodiment, a circuit design having a number of multi-cycle paths may be optimized by: identifying at least one of the number of multi-cycle paths within the circuit design, and identifying the corresponding qualified clocks associated therewith; replacing selected ones of the corresponding clocks with replacement clocks; and optimizing the circuit design using the replacement clocks. By using a replacement clock that has a clock period equal to the corresponding clock, which is typically a qualified clock, a standard optimization tool may correctly optimize the circuit design.

Abstract: A method and apparatus for distributing clock drivers within a hierarchical circuit design, wherein the clock drivers are concentrated in locations where they are actually needed rather than uniformly distributed throughout the circuit design. In an exemplary embodiment, the actual clock loads within a selected hierarchical region are determined, and a sufficient number of clock drivers are added as children objects to the selected hierarchical region. Since many placement tools may place the children objects within an outer boundary of the corresponding parent object, the clock drivers, as children objects of the selected hierarchical region, may be placed within the outer boundary of the selected hierarchical region. Accordingly, the clock drivers may be concentrated in the locations where actually needed.

Abstract: Method for performing critical path timing analysis on a circuit design having different timing constraints for multiple parallel paths. Method includes clearing the state of the circuit design, setting control lines in the circuit design to a selected set of control signals, and identifying blocking nets of the circuit design to be flagged for timing analysis by simulating the circuit design with the selected set of control signals as input signals. Identified blocking points are added to a list which identifies paths in the circuit design to be analyzed. All possible sets of control signals are processed. Timing analysis is then performed on the circuit design using the list as input data. A critical step is the identification of the blocking points. Blocking points are identified for each net input to a gate in the circuit design having an unknown value, and a known value on an output net from the gate for the selected set of control signals.

Abstract: A method used by an electronic design automation system for stabilizing the names of components and nets of an integrated circuit from one design version to another. A previous integrated circuit design version and a current integrated circuit design version are partitioned into multiple cones of logic design. Each cone of logic design is defined by a path from a logic designer-defined apex net to a logic designer-defined base net affecting the apex net. Selected cones of logic design are compared. If the selected cones have identical logical structure, the component and net names of the previous integrated circuit design version are transferred to the current integrated circuit design version.

Abstract: A method used by a computer-aided design system for placing logic functions and cells in a floor plan of a very large scale integrated circuit chip. The structure of a set of selected logic functions and cells to be placed is compared to a set of selected logic functions and cells which have previously been placed in the floor plan. If the number of cells and the structure of the sets are analogous, the selected logic functions and cells to be placed are automatically assigned physical positions in the floor plan based on the physical position and structure of the selected logic functions and cells that have already been placed, and on an orientation mode. The orientation mode provides for the reflection of the placement of the selected logic functions and cells about the horizontal axis, the vertical axis, or both the horizontal and vertical axes.