An_Introduction_Logic_Design_Lecture_Notes

An_Introduction_Logic_Design_Lecture_Notes - An...

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1 An Introduction to Logic Design California State University, Northridge EE 320 R. Roosta
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2 Chapter 1: Introduction 1.1 Background Information Digital computers have been around since the 1940s, and have been in widespread commercial use since the 1960s. Yet only in the past 10 to 20 years has the digital revolution spread to many other aspects of life. Examples of once analog systems that now have gone digital include the following: Audio recordings. Once made exclusively by impressing analog waveforms onto vinyl or magnetic tape, audio recordings now commonly use digital compact discs (CDs) and digital audiotape (DAT). ACD or DAT stores music as a sequence of 16-bit numbers corresponding to samples of the original analog waveform, one sample every 22 microseconds or so. A typical CD contains over 5 billion bits of information. Automobile carburetors. Once controlled strictly by mechanical linkages, automobile engines are controlled by embedded microprocessors. Various electronic and electromechanical sensors convert engine conditions into numbers that the microprocessor can examine to determine how to control the flow of fuel and oxygen to the engine. The microprocessor output is a time-varying sequence of numbers that operate electromechanical actuators, which, in turn, control the engine. Telephone system. It started out a hundred years ago with analog microphones and receivers connected to the ends of pair of copper wires. Even today most homes and businesses still use analog telephones, which transmit analog signals to the phone company’s central office (CO). However, in the majority of COs, these analog signals are converted into digital format before they are routed to their destinations, be they in the same CO or across the continent or the world. Traffic lights. Signal lights used to be controlled by electromechanical timers that would give the green light to each direction for a predetermined amount of time. Later, relays were used in controllers that could activate the lights according to the pattern of traffic detected by sensors embedded in the pavement. Today’s controllers use microprocessors, and can control the light in ways that maximize vehicle throughput. Movie effects. Miniature clay models, stop action, trick photography, and numerous overlays of film on a frame-by-frame basis were used exclusively to create special effects. Today, spaceships, creatures, other worldly scenes are synthesized using digital computers.
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3 The electronic revolution has been going on for quite some time now and the solid state revolution began with analog devices and applications like transistors and transistor radios. The reason for this sudden spurt in digital circuit design versus analog design is due to many advantages that digital circuits offer over analog ones: Reproducibility of results. Given the same set of inputs, a properly designed digital circuit is consistent with its results. The outputs of analog circuit may vary
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An_Introduction_Logic_Design_Lecture_Notes - An...

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