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Digital Logic CPE231. Digital Fundamentals, Ninth Edition By Floyd Instructor: Eng. Tuqa Manasrah. Ch 1: Digital Concepts. Explain the basic differences between digital and analog quantities Show how voltage levels are used to represent digital quantities
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Digital Logic CPE231 Digital Fundamentals, Ninth Edition By Floyd Instructor: Eng. Tuqa Manasrah
Ch 1: Digital Concepts • Explain the basic differences between digital and analog quantities • Show how voltage levels are used to represent digital quantities • Explain the basic logic operations of NOT, AND, and OR
Introduction • Digital is derived from the way computers perform operations, by counting digits. • In past digital electronics confined to computer systems. • Today, digital technology every where.. TV, radar, medicine, communication, military, transportation..
Digital and Analog quantities • Digital quantity have discrete values • Analog quantity have continuous values • Things measured in nature in analog form (ex. temperature) • Take a temp reading every hour sampled values at discrete points (quantization) • Each sample can be represented by a digital code.
The digital advantage • Processed more efficiently and reliably • Compact storage • Greater accuracy • Does not affected by noiseas well as analog values
Binary digits • Digital electronics involves circuits with two possible states • The two states are represented by two voltage levels: High, Low • Binary digit: a two state number with two digits (0, 1). • Each of the two digits in the binary system 1 and 0 is called bit. • 1 represented by higher voltage (HIGH) • 0 represented by lower voltage (LOW) • Codes: group of bits used to represent numbers, symbols, alphabets.. etc
Voltage levels • VH(min) to VH(max) = HIGH (binary 1) • VL(min) to VL(max) = LOW (binary 0) • VL(max) to VH(min) = unacceptable for proper operation.
Digital waveforms • Consist of voltage levels that are changing back and forth between HIGH and LOW levels. • Positive going pulse. • Negative going pulse. • Leading edge (+ve edge, raising). • Trailing edge (-ve edge, falling). • A digital waveform is made up of a series of pulses. • Binary information appears as waveforms that represent a sequence of bits. • Each bit occupies a defined time interval called bit time. • Data refers to group of bits that express some type of information.
Basic logic operations • In human reasoning, logic tells you that a certain proposition is true if certain conditions are true. • In daily life you faced many yes/no statements. • Ex. “The light is ON will be true if the bulb is not burned out” • “The light is ON will be true if the bulb is not burned out and the switch is on” • In 1850, George Boole developed a mathematical system for formulating logic statements with symbols so that problems can be written and solved similar to ordinary algebra…
Continue.. • Boolean algebra is applied in the design and analysis of digital systems. • Logic is applied to digital circuits to implement logic functions. • The basic logic operations: NOT, AND, OR. • A circuit that performs the logic operations is called logic gate.