ABSTRACT
The field of design automation technology, also commonly called computer-aided design (CAD) or computer-aided engineering (CAE), involves developing computer programs to conduct portions of product design and manufacturing on behalf of the designer. Competitive pressures to produce in less time and use fewer resources, new generations of products having improved function and performance are motivating the growing importance of design automation. The increasing complexities of microelectronic technology, shown in Figure 7.1, illustrate the importance of relegating portions of product development to computer automation [1,3]. Advances in microelectronic technology enable over 1 million devices to be manufactured on an integrated circuit substrate smaller in size than a postage stamp, yet the ability to exploit this capability remains a challenge. Manual design techniques are unable to keep pace with product design cycle demands and are being replaced by automated design techniques [2,4]. Figure 7.2 summarizes the historical development of design automation technology and computer
programs. Design automation programs are also called ‘‘applications’’ or ‘‘tools.’’ Design automation efforts started in the early 1960s as academic research projects and captive industrial programs, focusing on individual tools for physical and logical design. Later developments extended logic simulation to more detailed circuit and device simulation and more abstract functional simulation. Starting in the mid to the
late 1970s, new areas of test and synthesis emerged and commercial design automation products appeared. Today, the electronic design automation industry is an international business with a well-established and expanding technical base [5]. The electronic design automation technology base will be examined by presenting an overview of the following topical areas:
. Design entry
. Conceptual design
Design entry, also called design capture, is the process of communicating with a design automation system. Design entry involves describing a system design to a design automation system, invoking applications to analyze and=or modify the system design, and querying the results. In short, design entry is how an engineer ‘‘talks’’ to a design automation application and=or system. Any sort of communication is composed of two elements: language and mechanism. Language
provides common semantics; mechanism provides a means by which to convey the common semantics. For example, two people communicate via a language such as English, French, or German, and a mechanism, such as a telephone, electronic mail, or facsimile transmission. For design, a digital system can be described in many ways, involving different perspectives or abstractions. An abstraction is a model for defining the behavior or semantics of a digital system, i.e., how the outputs respond to the inputs. Figure 7.3 illustrates several popular levels of abstractions and the trends toward higher levels of design entry abstraction to address greater levels of complexity [10,12]. The physical level of abstraction involves geometric information that defines electrical devices and
their interconnection. Geometric information includes the shaped objects and where objects are placed relative to each other. For example, Figure 7.4 shows the geometric shapes defining a simple complementary metal-oxide semiconductor (CMOS) inverter. The shapes denote different materials, such as aluminum and polysilicon, and connections, called contacts or vias. The design entry mechanism for physical information involves textual and graphic techniques. With
textual techniques, geometric shape and placement are described via an artwork description language, such as Caltech Intermediate Form or Electronic Design Intermediate Form. With graphical techniques, geometric shape and placement are described by drawing the objects on a display terminal [13]. The electrical level abstracts geometric information into corresponding electrical devices, such as
capacitors, transistors, and resistors. For example, Figure 7.5 shows the electrical symbols denoting a CMOS inverter. Electrical information includes the device behavior in terms of terminal or pin current and voltage relationships. Device behavior also may be defined in terms of manufacturing parameters, such as resistances or chemical compositions. The logical level abstracts electrical information into corresponding logical elements, such as and
gates, or gates, and inverters. Logical information includes truth table and=or characteristic switching algebra equations and active level designations. For example, Figure 7.6 shows the logical symbol for a CMOS inverter. Notice how the amount of information decreases as the level of abstraction increases.
