CAD Framework Research Articles

Towards modelling of assemblies for product design

Current cad systems provide exhaustive capabilities for specifying detailed component geometry in support of the product-design process. However, before detailed geometric designs are finally produced, the designer must first map the product requirements into functional specifications, and realize the functional specifications in the form of conceptual designs. While it may not be possible to automate these more creative steps fully in the design process, cad systems can support the design process better, by consistently representing and maintaining the functional intent of the designer. To provide such support, the cad systems must address the assembly level, since only at this level is it possible to model the functionality of the design in terms of the functionally significant geometry and assembly relations. The literature survey first establishes basic information requirements for a cad framework in support of the broader design process. The literature is reviewed in the context of this framework. The following areas are reviewed: the choice of modelling primitives for the specification of assembly information, the choice of various model structures for the aggregation of the assembly information and the use of this information for design analysis, and the choice of strategies for relative part positioning for the computation of the final assembly configuration. Even though research is well developed in individual aspects of assembly modelling, there are major gaps that must be addressed before cad systems can make use of assembly modelling as an integrated framework for product design.

Statistical simulation and optimization of high-speed VLSI interconnects

In the manufacturing process of printed circuit boards (PCB) and multichip modules (MCM), tolerances in VLSI interconnects and material properties lead to variations in critical interconnect performances which in turn can result in reduced production yield. This article presents a new CAD approach integrating multidimensional correlated Monte Carlo analysis and l 1 optimization with lossy transmission line network simulations. Electrical and physical-oriented models for both uniform and nonuniform transmission lines are incorporated. A systematic description is provided to theoretically link several simulation techniques for linear/nonlinear, lumped/distributed network simulations. A CAD framework is developed for statistical analysis and yield optimization of high-speed VLSI interconnects. Physical/geometrical based hierarchical Monte Carlo analysis and yield optimization examples are presented.

Design methodology management

Design methodology management is an emerging technology in the world of electrical computer aided design. It has spawned considerable research over the past decade, and a firm belief in many people's minds that it is the key to significant productivity enhancements in the next. How close are we to seeing this belief fulfilled? In this paper, we define the concepts that are important to design methodology management systems and explain how these systems relate to CAD frameworks. We then examine and characterize 23 notable design methodology management systems of the last 15 years in order to understand the state of the art. Finally, we describe and analyze the trends we have seen in these systems and propose where this technology is headed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Semiconductor wafer representation for TCAD

This work describes the Semiconductor Wafer Representation (SWR) for representing and manipulating wafer state during process and device simulation. The goal of the SWR is to provide an object-oriented interface to a collection of functions designed for developing and integrating Technology CAD (TCAD) applications. By providing functions which can be common across many applications, we aim to greatly reduce tool development and integration time. Corporate, vendor, and university TCAD developers have worked together under the auspices of the CAD Framework Initiative to create an architecture and C++ programming interface for an SWR 1.0 draft standard. Here we describe this architecture and the results of creating and using a prototype implementation of the standard both to integrate existing TCAD tools and to develop simple new tools. >

A design methodology for the correct specification of VLSI systems

Time to market is a key factor to beat competitors as it measures the ability to satisfy the market demands at the proper time. Innovative design methodologies based on formal methods can positively affect this parameter allowing rigour of design practice and guaranteeing correctness of implementations. In this paper we introduce the methodological approach (∗) (∗) Partially supported by ESPRIT III Project FORMAT based on the use of the specification language VHDL/S and of the related formal based tools. The final goal is to provide an environment able to support the designer in the specification phase with the generation of correct and verified VHDL code. The integration of this formal based design phase into a standard CAD design flow is managed through the restriction to the VHDL subset supporting logical synthesis. Finally the encapsulation into a commercial CAD framework guarantees the unified approach to design required by final users.

Integrated CAD frameworks: Tolerance representation scheme in a solid model

The major objective of this paper is to develop a representational scheme for geometric tolerances that are to be interfaced with a solid model. This includes the development of (i) an efficient user interface system for input of tolerance information, (ii) a suitable tolerancing data module (to be attached to the solid model), and (iii) an information retrieval system from the stored database for future tolerance analysis. This user interactive environment which enables the user to input the tolerance information in both the unevaluated (CSG) and the evaluated (B-Rep) databases, requires an effective linking mechanism between the CSG and the B-Rep data models at each stage of the object development. This has been achieved through the development of a reference face list. Tolerance information has been attached with this face list as “constraint nodes”, which are formed and updated after each “set operation.” Several functions have also been developed to retrieve essential information from the data structure in order to answer various queries. The prototype system has been implemented on a polyhedral solid modeler based on this representational scheme.

Structuring and automating hardware proofs in a higher-order theorem-proving environment

In this article we present a structured approach to formal hardware verification by modeling circuits at the register-transfer level using a restricted form of higher-order logic. This restricted form of higher-order logic is sufficient for obtaining succinct descriptions of hierarchically designed register-transfer circuits. By exploiting the structure of the underlying hardware proofs and limiting the form of descriptions used, we have attained nearly complete automation in proving the equivalences of the specifications and implementations. A hardware-specific tool called MEPHISTO converts the original goal into a set of simpler subgoals, which are then automatically solved by a general-purpose, first-order prover called FAUST. Furthermore, the complete verification framework is being integrated within a commercial VLSI CAD framework.

A utility-based integrated system for process simulation

An integrated process simulation system which uses functional utilities to integrate disparate 2-D simulation tools is described. The software utilities provide mechanisms for simulator input generation and user interaction, for mapping between different cross-section formats, and for output visualization. The specific utilities are described. With this approach, several process simulators for lithography, etching, deposition, and thermal processing have been integrated into a unified system, SIMPL-IPX (simulation of profiles from the layout-integrated process simulation environment with X-Windows). Simulation examples for metal l planarization, bipolar technology with a polysilicon , collector 5 plug, and advanced lithography are presented to demonstrated 7 the usefulness of this approach to technology CAD tool 8 integration. Methods for improved data management using 9 a CAD framework are described. >

A CAD framework for simulation and optimization of high-speed VLSI interconnections

A CAD framework addressing three specific aspects of the high-speed interconnect problem, namely, simulation, sensitivity analysis, and performance optimization, is described. Distributed interconnect models represented by uniform or nonuniform lossy coupled transmission lines are supported. The CAD framework incorporates parallel processing capabilities. It also provides a design environment for integrating accurate simulations or waveform estimation, sensitivity analysis, design specifications, and numerical optimization. Approaches enhancing the accuracy and ensuring the stability of moment-matching techniques used in the asymptotic waveform evaluation (AWE) are introduced. Also described are a parallel implementation of numerical inversion of the Laplace transform (NILT) and parallel interconnect optimization, resulting in substantial CPU speedup over existing NILT simulation and optimization.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A taxonomy of standards

Objectivity, Inc., markets an engineering database management system that is an OODBMS. We are committed to the idea that standards are beneficial for all players in the industry. We have played active roles in several standardization efforts, including the CAD Framework Initiative (CFI). This proposal discusses the motivation for a standardization effort, suggests a direction for its development, discusses cooperation with other such efforts, and offers some concrete starting suggestions.

Object programming for CAD

The use of object-oriented programming to simplify the design and implementation of CAD systems is discussed. The three features common to all languages that support object-oriented programming data abstraction, inheritance, and runtime-function determination are examined. Examples are given to illustrate the advantages of object-oriented methods. How to build an embryonic CAD framework and when to use an object-oriented language are addressed. Object-oriented databases are defined. >

Computer graphics and layout design in documentation processes

Although drafting has been strongly supported by user-friendly, highly interactive graphical systems, today there is a challenge for a further, more sophisticated development. The aim of this development has to be a better integration of documentation processes into the entire framework of CAD. Such an aim can only be achieved by a higher degree of automation of documentation processes, by a derivation of documents (either on paper or as computer-internal representations) from more comprehensive models as basic results of CAD. In the case of graphical documents, this is a challenge for the inclusion of tools for automatic layout design into corresponding computer graphics systems. This paper considers problems arising from this challenge. The generation of graphical schematics requires the placement of symbols and the routing of connection lines. A program system is described that automatically transforms formal (textual) descriptions of certain industrial control processes into corresponding logic schematics by solving complex layout problems. A further topic is the automatic routing of connection lines in more general types of schematics by another software tool. The industrial application of these sophisticated computer graphics systems is discussed. With respect to workshop drawings, the paper concentrates on the layout of dimensions within views derived from 3D models. The paper concludes with an outlook on future work.

An object-oriented VLSI CAD framework

It is shown, in the context of an actual prototype VLSI CAD framework called Cbase, how concepts such as data abstraction, property and operation inheritance, object specialization/generalization, code reusability, and polymorphism offered by object-oriented database management systems (OODBMSs) support rapid prototyping. The work was conducted on Vbase, a commercially available OODBMS, but the results and conclusions apply to any database with comparable capabilities. To implement the prototype user interface, the X11 toolkit, a windowing package that is also built around the object paradigm, was used. >