Circuitos

23/08/2012

Sistemas Digitales

Floyd, Digital Fundamentals, 10th ed

© 2008 Saddle Education © 2009 Pearson Education, UpperPearson River, NJ 07458. All Rights Reserved

Compuertas Lógicas

Floyd, Digital Fundamentals, 10th ed

© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved

1

23/08/2012

Summary
The Inverter A X The inverter performs the BooleanNOT operation. When the input is LOW, the output is HIGH; when the input is HIGH, the output is LOW.
Input Output
A X LOW (0) HIGH (1) HIGH (1) LOW(0)

The NOT operation (complement) is shown with an overbar. Thus, the Boolean expression for an inverter is X = A.
Floyd, Digital Fundamentals, 10th ed © 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved

Summary
TheInverter A X Example waveforms: A X A group of inverters can be used to form the 1’s complement of a binary number: Binary number
1 0 0 0 1 1 0 1

0

1

1

1 0 0 1’s complement

1

0

Floyd, Digital Fundamentals, 10th ed

© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved

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23/08/2012

Summary
The AND Gate
A B X A B
&

X

The AND gateproduces a HIGH output when all inputs are HIGH; otherwise, the output is LOW. For a 2-input gate, the truth table is Inputs Output
A B X

0 0 1 1

0 1 0 1

0 0 0 1

The AND operation is usually shown with a dot between the variables but it may be implied (no dot). Thus, the AND operation is written as X = A .B or X = AB.
Floyd, Digital Fundamentals, 10th ed © 2009 Pearson Education, UpperSaddle River, NJ 07458. All Rights Reserved

Summary
The AND Gate
A B X A B
&

X

Example waveforms: A B X The AND operation is used in computer programming as a selective mask. If you want to retain certain bits of a binary number but reset the other bits to 0, you could set a mask with 1’s in the position of the retained bits. If the binary number 10100011 is ANDed with the mask 00001111,what is the result? 00000011
Floyd, Digital Fundamentals, 10th ed © 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved

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Figure 3–15

An AND gate performing an enable/inhibit function for a frequency counter.

th Floyd, Fundamentals, 9e Digital Digital Fundamentals, 10 ed

Thomas L. Floyd

Copyright ©2006 by Pearson Education, Inc. Upper SaddleRiver, New Jersey 07458 © 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved All rights reserved.

Figure 3–16

A simple seat belt alarm circuit using an AND gate.

th Floyd, Fundamentals, 9e Digital Digital Fundamentals, 10 ed

Thomas L. Floyd

Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 © 2009 Pearson Education, Upper SaddleRiver, NJ 07458. All Rights Reserved All rights reserved.

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Summary
The OR Gate
A B X A B
≥1

X

The OR gate produces a HIGH output if any input is HIGH; if all inputs are LOW, the output is LOW. For a 2-input gate, the truth table is Inputs Output
A B X

0 0 1 1

0 1 0 1

0 1 1 1

The OR operation is shown with a plus sign (+) between the variables. Thus, the ORoperation is written as X = A + B.
Floyd, Digital Fundamentals, 10th ed © 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved

Summary
The OR Gate
A B X A B
≥1

X

Example waveforms: A B X
The OR operation can be used in computer programming to set certain bits of a binary number to 1. ASCII letters have a 1 in the bit 5 position for lower case letters and a 0 inthis position for capitals. (Bit positions are numbered from right to left starting with 0.) What will be the result if you OR an ASCII letter with the 8-bit mask 00100000? The resulting letter will be lower case.
Floyd, Digital Fundamentals, 10th ed © 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved

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Figure 3–24

A simplified intrusion detection...