Overview Of Degital Design With Verilog HDL part 1

Evolution of Computer-Aided Digital Design Digital circuit design has evolved rapidly over the last 25 years. The earliest digital circuits were designed with vacuum tubes and transistors. Integrated circuits were then invented where logic gates were placed on a single chipof
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Overview Of Degital Design With Verilog HDL part 1[ Team LiB ]1.1 Evolution of Computer-Aided Digital DesignDigital circuit design has evolved rapidly over the last 25 years. The earliest digitalcircuits were designed with vacuum tubes and transistors. Integrated circuits were theninvented where logic gates were placed on a single chip. The first integrated circuit (IC)chips were SSI (Small Scale Integration) chips where the gate count was very small. Astechnologies became sophisticated, designers were able to place circuits with hundreds ofgates on a chip. These chips were called MSI (Medium Scale Integration) chips. With theadvent of LSI (Large Scale Integration), designers could put thousands of gates on asingle chip. At this point, design processes started getting very complicated, anddesigners felt the need to automate these processes. Electronic Design Automation(EDA)[1] techniques began to evolve. Chip designers began to use circuit and logicsimulation techniques to verify the functionality of building blocks of the order of about100 transistors. The circuits were still tested on the breadboard, and the layout was doneon paper or by hand on a graphic computer terminal.[1] The earlier edition of the book used the term CAD tools. Technically, the termComputer-Aided Design (CAD) tools refers to back-end tools that perform functionsrelated to place and route, and layout of the chip . The term Computer-Aided Engineering(CAE) tools refers to tools that are used for front-end processes such HDL simulation,logic synthesis, and timing analysis. Designers used the terms CAD and CAEinterchangeably. Today, the term Electronic Design Automation is used for both CADand CAE. For the sake of simplicity, in this book, we will refer to all design tools as EDAtools.With the advent of VLSI (Very Large Scale Integration) technology, designers coulddesign single chips with more than 100,000 transistors. Because of the complexity ofthese circuits, it was not possible to verify these circuits on a breadboard. Computer-aided techniques became critical for verification and design of VLSI digital circuits.Computer programs to do automatic placement and routing of circuit layouts also becamepopular. The designers were now building gate-level digital circuits manually on graphicterminals. They would build small building blocks and then derive higher-level blocksfrom them. This process would continue until they had built the top-level block. Logicsimulators came into existence to verify the functionality of these circuits before theywere fabricated on chip.As designs got larger and more complex, logic simulation assumed an important role inthe design process. Designers could iron out functional bugs in the architecture before thechip was designed further.[ Team LiB ] Algorithms and Data Structures in C++ by Alan Parker CRC Press, CRC Press LLC ISBN: 0849371716 Pub Date: 08/01/93 Previous Table of Contents NextChapter 1Data RepresentationsThis chapter introduces the various formats used by computers for the representation ofintegers, floating point numbers, and characters. Extensive examples of theserepresentations within the C++ programming language are provided.1.1 Integer RepresentationsThe tremendous growth in computers is partly due to the fact that physical devices can bebuilt inexpensively which distinguish and manipulate two states at very high speeds.Since computers are devices which primarily act on two states (0 and 1), binary, octal,and hex representations are commonly used for the representation of computer data. Therepresentation for each of these bases is shown in Table 1.1. Table 1.1 Number Systems Octal Hexadecimal Decimal Binary 0 0 0 0 1 1 1 1 10 2 2 2 11 3 3 3 100 4 4 4 101 5 5 5 110 6 6 6 111 7 7 7 1000 10 8 8 1001 11 9 9 1010 12 A 10 1011 13 B 11 1100 14 C 12 1101 15 D 13 1110 16 E 14 1111 17 F 15 10000 20 10 16Operat ...