Logic design and integrated circuits

Logic design is the area of computer science that deals with the design of electronic circuits to carry out the operations of the control unit, the ALU, the I/O controllers, and more. For example, the addition circuit of the ALU has inputs corresponding to all the bits of the two numbers to be added and outputs corresponding to the bits of the sum. The arrangement of wires and transistors that link inputs to outputs is determined by logic-design principles. The design of the control unit provides the circuits that interpret instructions and control subsequent behaviour. Clearly, it is critical that this circuitry be as efficient as possible; logic design deals with optimizing the circuitry, not just putting together something that will work. Boolean algebra is the mathematical tool used for logic design.

An important area related to architecture is the design of computer chips, or microprocessors, a type of integrated circuit. A microprocessor is a complete CPU—control unit, ALU, and possibly some memory (especially cache)—on a single integrated circuit chip. Additional memory and I/O control circuitry are linked to this chip to form a complete computer. These thumbnail-sized devices contain thousands or millions of transistors, together with wiring, to form the processing and memory units of modern computers.

The process of very-large-scale integrated (VLSI) circuit design involves a number of stages, which characteristically are as follows: (1) creating the initial functional or behavioral specification, (2) encoding this specification into a hardware description language, (3) breaking down the design into modules and generating sizes and shapes for the eventual chip components, and (4) chip planning, which includes building a “floor plan” to indicate where on the chip the components are to be placed and how they are to be interconnected. The modularization, sizing, and planning stages are often iterated before a final design is reached. The final stage is the formulation of the instructions for the automated production of the chip through an optical lithography process. Computer scientists are involved not only in creating the computer-aided design (CAD) tools to support engineers in the various stages of chip design but also in providing the necessary theoretical results, such as how to efficiently design a floor plan with near-minimal area that satisfies the given constraints.

Date: 2015-01-12; view: 948