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Unformatted text preview: 1 Chapter 2 Logic Functions and Gates 2 Chapter 2 Homework 2.1, 2.3, 2.5, 2.7, 2.9, 2.11, 2.17, 2.19, 2.21, 2.39 3 Basic Logic Functions • The three basic logic functions are: – AND – OR – NOT Y = AB 4 Logic Function Representation • Logic functions can be represented: – algebraically – using truth tables – using electronic circuits. 5 Algebraic Representation • Uses Boolean algebra. • Boolean variables have two states (binary). • Boolean operators include AND, OR, and NOT. 6 Truth Table Representation • Defines the output of a function for every possible combination of inputs. • A system with n inputs has 2 n possible combinations. 7 Electronic Circuit Representation • Uses logic gates to perform Boolean algebraic functions. • Gates can be represented by schematic symbols. • Symbols can be either distinctiveshape or rectangularoutline. 8 Distinctive Shape Schematic Symbols • Uses different graphic representations for different logic functions. • Uses a bubble (a small circle) to indicate a logical inversion. 9 RectangularOutline Schematic Symbols • All functions are shown in rectangular form with the logic function indicated by standard notation inside the rectangle. • The notation specifying the logic function is called the qualifying symbol. • Inversion is indicated by a 1/2 arrowhead. 10 NOT Function • One input and one output. • The output is the opposite logic level of the input. • The output is the complement of the input. 11 NOT Function Boolean Representation • Inversion is indicated by a bar over the signal to be inverted. A Y = 12 NOT Function Electronic Circuit • Called a NOT gate or, more usually, an INVERTER. • Distinctiveshape symbol is a triangle with inversion bubble. • Rectangularshape symbol uses “1” and the inversion 1/2 arrowhead. 13 NOT Function Electronic Circuit 14 AND Function • Two or more inputs, one output. • Output is HIGH only when all of the inputs are HIGH. • Output is LOW whenever any input is LOW. 15 A B Y 1 1 1 1 1 AND Function 16 AND Boolean Representation • AND symbol is “•” or nothing at all....
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This note was uploaded on 04/15/2008 for the course ETEC ENGR 2720 taught by Professor Grubbs during the Spring '08 term at North Texas.
 Spring '08
 Grubbs

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