Section1.5 Software Aspects of Digital Design 9 景WAKE Figure 1-3 c-design template. yright 1976 by Micro Syste 1.5 Software Aspects of Digital Design Digital design need not involve any software tools.For example,Figure 1-3 shows the primary tool of the"old school"of digital design-a plastic template for drawing logic symbols in schematic diagrams by hand (the designer's name was engraved into the plastic with a soldering iron). Today,however,software tools are an essential part of digital design Indeed,the availability and practicality of hardware description languages (HDLs)and accompanying circuit simulation and synthesis tools have changed the entire landscape of digital design over the past several years.We'll make extensive use of HDLs throughout this book. In computer-aided design (CAD)various software tools improve the designer's productivity and help to improve the correctness and quality of designs.In a competitive world,the use of software tools is mandatory to obtain high-quality results on aggressive schedules.Important examples of software tools for digital design are listed below. Schematic entry.This is the digital designer's equivalent of a word proces- sor.It allows schematic diagrams to be drawn"on-line,"instead of with paper and pencil.The more advanced schematic-entry programs also check for common,easy-to-spot errors,such as shorted outputs,signals that don't go anywhere,and so on.Such programs are discussed in greater detail in Section 12.1. .HDLs.Hardware description languages,originally developed for circuit modeling.are now being used more and more for hardware design.They can be used to design anything from individual function modules to large, multi-chip digital systems.We'll introduce two HDLs.ABEL and VHDL. at the end of Chapter 4,and we'll provide examples in both languages in the chapters that follow. HDL compilers,simulators,and synthesis tools.A typical HDL software package contains several components.In a typical environment,the designer writes a text-based"program,"and the HDL compiler analyzes Copyright 1999 by John F.Wakerly Copying ProhibitedSection 1.5 Software Aspects of Digital Design 9 DO NOT COPY DO NOT COPY DO NOT COPY DO NOT COPY DO NOT COPY DO NOT COPY DO NOT COPY DO NOT COPY DO NOT COPY Copyright © 1999 by John F. Wakerly Copying Prohibited 1.5 Software Aspects of Digital Design Digital design need not involve any software tools. For example, Figure 1-3 shows the primary tool of the “old school” of digital design—a plastic template for drawing logic symbols in schematic diagrams by hand (the designer’s name was engraved into the plastic with a soldering iron). Today, however, software tools are an essential part of digital design. Indeed, the availability and practicality of hardware description languages (HDLs) and accompanying circuit simulation and synthesis tools have changed the entire landscape of digital design over the past several years. We’ll make extensive use of HDLs throughout this book. In computer-aided design (CAD) various software tools improve the designer’s productivity and help to improve the correctness and quality of designs. In a competitive world, the use of software tools is mandatory to obtain high-quality results on aggressive schedules. Important examples of software tools for digital design are listed below: • Schematic entry. This is the digital designer’s equivalent of a word proces￾sor. It allows schematic diagrams to be drawn “on-line,” instead of with paper and pencil. The more advanced schematic-entry programs also check for common, easy-to-spot errors, such as shorted outputs, signals that don’t go anywhere, and so on. Such programs are discussed in greater detail in Section 12.1. • HDLs. Hardware description languages, originally developed for circuit modeling, are now being used more and more for hardware design. They can be used to design anything from individual function modules to large, multi-chip digital systems. We’ll introduce two HDLs, ABEL and VHDL, at the end of Chapter 4, and we’ll provide examples in both languages in the chapters that follow. • HDL compilers, simulators, and synthesis tools. A typical HDL software package contains several components. In a typical environment, the designer writes a text-based “program,” and the HDL compiler analyzes Figure 1-3 A logic-design template. Quarter-size logic symbols, copyright 1976 by Micro Systems Engineering computer-aided design (CAD)