Chapter04 - Chapter 4 Gates and Circuits Computers and...

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Chapter 4 Gates and Circuits
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2 Computers and Electricity Gate: A device that performs a basic operation on electrical signals. Circuits: Gates combined to perform more complicated tasks.
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3 Computers and Electricity There are three different, but equally powerful, notational methods for describing the behavior of gates and circuits: Boolean expressions logic diagrams truth tables
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4 Computers and Electricity Boolean expressions: Expressions in Boolean algebra, a mathematical notation for expressing two-valued logic. This algebraic notation is an elegant and powerful way to demonstrate the activity of electrical circuits.
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5 Computers and Electricity Logic diagram: a graphical representation of a circuit Each type of gate is represented by a specific graphical symbol. Truth table: A table showing all possible input values and the associated output values.
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6 Gates Let’s examine the processing of the following six types of gates: NOT AND OR XOR NAND NOR Typically, logic diagrams are black and white, and the gates are distinguished only by their shape.
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7 NOT Gate A NOT gate accepts one input value and produces one output value. Figure 4.1 Various representations of a NOT gate
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8 NOT Gate By definition, if the input value for a NOT gate is 0, the output value is 1, and if the input value is 1, the output is 0. A NOT gate is sometimes referred to as an inverter because it inverts the input value.
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9 AND Gate An AND gate accepts two input signals. If the input values for an AND gate are both 1, the output is 1; otherwise, the output is 0. Figure 4.2 Various representations of an AND gate
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10 OR Gate If the two input values are both 0, the output value is 0; otherwise, the output is 1. Figure 4.3 Various representations of a OR gate
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11 XOR Gate XOR gate ( eXclusive OR) An XOR gate produces 0 if its two inputs are the same, and a 1 otherwise. Note the difference between the XOR gate and the OR gate; they differ only in one input situation: When both input signals are 1, the OR gate produces a 1 but the XOR produces a 0.
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12 XOR Gate Figure 4.4 Various representations of an XOR gate
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NAND and NOR Gates The NAND and NOR gates are essentially the opposite of the AND and OR gates, respectively. Figure 4.5 Various representations of a NAND gate Figure 4.6 Various representations of a NOR gate 4–15
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Review of Gate Processing A NOT gate inverts its single input value. An AND gate produces 1 if both input values
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This note was uploaded on 07/16/2010 for the course CSE CSE 1520 taught by Professor Paul during the Spring '09 term at York University.

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Chapter04 - Chapter 4 Gates and Circuits Computers and...

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