Fundamentals of Digital Electronics

1 Fundamentals of Digital Electronics by Professor Barry Paton Dalhousie University March 1998 Edition Part Number 321948A-01. Fundamentals of Digital Electronics Copyright Copyright 1998 by National Instruments Corporation, 6504 Bridge Point Parkway, Austin, Texas 78730-5039. Universities, colleges, and other educational institutions may reproduce all or part of this publication for educational use. For all other uses, this publication may not be reproduced or transmitted in any form, electronic or mechanical, including photocopying, recording, storing in an information retrieval system, or translating, in whole or in part, without the prior written consent of National Instruments Corporation. Trademarks labview and The Software is the Instrument are trademarks of National Instruments Corporation.

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3 National Instruments Corporate Headquarters 6504 Bridge Point Parkway Austin, Texas 78730-5039 Tel: 512 794 0100. Contents Introduction Lab 1. Gates The AND The OR and XOR Gates ..1-2. The NAND, NOR, and NXOR Building Gates from Other Gates ..1-3. Gates with More than Two Inputs ..1-4. Masking ..1-5. Application: Data Name that Gate ..1-6. Lab 1 Library VIs ..1-6. Lab 2. Encoders and Decoders The Die ..2-2. Modulo 6 Encode ..2-4. Virtual Dice ..2-5. Lab 2 Library VIs ..2-6. Lab 3. Binary Addition Adder Expansion (Half Adder, Full Adders)..3-3. Binary Coded Decimal (BCD)..3-5. labview Challenge ..3-6. Lab 3 Library VIs ..3-6. National Instruments Corporation iii Fundamentals of Digital Electronics Contents Lab 4.

4 Memory: The D-Latch Shift labview Challenge: The Bucket Brigade ..4-4. Ring Counters ..4-4. Lab 4 Library VIs ..4-5. Lab 5. Pseudo-Random Number Generators A 6-Bit Pseudo-Random Number An 8-Bit Pseudo-Random Sequencer ..5-2. 8-Bit Pseudo-Random Number Encryption of Digital Lab 5 Library VIs ..5-7. Lab 6. JK Master-Slave Flip-Flop Binary Counters (1-Bit, 2-Bit, and 4-Bit) ..6-3. 8-Bit Binary Counter (with and without Reset)..6-5. Summary ..6-5. Lab 6 Library VIs ..6-6. Lab 7. Digital -to-Analog Converter What is a DAC? ..7-1. ALU Simulator ..7-3. Simulating a Real DAC Waveform Special Lissajous Figures ..7-7. Lab 7 Library VIs ..7-8. Lab 8. Analog-to- Digital Converters, Part I. Purpose of the Analog-to- Digital The Ramp ADC.

5 8-2. Tracking Lab 8 Library VIs ..8-6. Lab 9. Analog-to- Digital Converters, Part II. SAR Simulation ..9-3. Summary ..9-4. Lab 9 Library VIs ..9-4. Fundamentals of Digital Electronics iv National Instruments Corporation Contents Lab 10. Seven-Segment Digital Displays Seven-Segment Display ..10-1. Lab 10 Library VIs ..10-5. Lab 11. Serial Communications Serial Transmitter ..11-2. Voltage to Serial Lab 11 Library VIs ..11-5. Lab 12. Central Processing Unit Operation of the Arithmetic and Logic The Accumulator ..12-3. Addition ..12-4. Binary Lab 12 Library VIs ..12-6. National Instruments Corporation v Fundamentals of Digital Electronics Introduction Digital Electronics is one of the fundamental courses found in all electrical engineering and most science programs.

6 The great variety of labview . Boolean and numeric controls/indicators, together with the wealth of programming structures and functions, make labview an excellent tool to visualize and demonstrate many of the fundamental concepts of Digital Electronics . The inherent modularity of labview is exploited in the same way that complex Digital integrated circuits are built from circuits of less complexity, which in turn are built from fundamental gates. This manual is designed as a teaching resource to be used in the classroom as demonstrations, in tutorial sessions as collaborative studies, or in the laboratory as interactive exercises. The order of the labs follows most electronic textbooks. The first six labs cover the fundamental circuits of gates, encoders, binary addition, D-latches, ring counters, and JK flip-flops.

7 Many of the VIs are suitable for both classroom demonstration and laboratory exploration. The second set of six labs cover advanced topics such as DACs, ADCs, seven-segment displays, serial communication, and the CPU. These are best done in the context of a Digital Electronics lab, comparing the labview . simulations with real integrated circuits. In each case, you can enhance simulations presented in the text by using a National Instruments DAQ. board to interact with the real world through labview Digital I/O, analog out, analog in, and serial VIs. Labs 2, 5, and 12 are application oriented and are designed to demonstrate encoding schemes, Digital encryption, and the operation of a CPU. These labs could be presented as challenging problems in a tutorial setting or in a workshop environment.

8 The labs can also be grouped to demonstrate special relationships of advanced devices on certain basic gates. For example, the CPU operation is dependent on the concept of registers and two input operations. This manual includes a complete set of labview VIs. The text is also included on the CD so that you can customize the material. National Instruments Corporation I-1 Fundamentals of Digital Electronics Lab 1. Gates Gates are the fundamental building blocks of Digital logic circuitry. These devices function by opening or closing to admit or reject the passage of a logical signal. From only a handful of basic gate types (AND, OR, XOR, and NOT), a vast array of gating functions can be created. The AND Gate A basic AND gate consists of two inputs and an output.

9 If the two inputs are A and B, the output (often called Q) is on only if both A and B are also on.. In Digital Electronics , the on state is often represented by a 1 and the off state by a 0. The relationship between the input signals and the output signals is often summarized in a truth table, which is a tabulation of all possible inputs and the resulting outputs. For the AND gate, there are four possible combinations of input states: A=0, B=0; A=0, B=1; A=1, B=0; and A=1, B=1. In the following truth table, these are listed in the left and middle columns. The AND gate output is listed in the right column. Table 1-1. Truth Table for AND Gate A B Q=A AND B. 0 0 0. 0 1 0. 1 0 0. 1 1 1. National Instruments Corporation 1-1 Fundamentals of Digital Electronics Lab 1 Gates In labview , you can specify a Digital logic input by toggling a Boolean switch; a Boolean LED indicator can indicate an output.

10 Because the AND. gate is provided as a basic built-in labview function, you can easily wire two switches to the gate inputs and an indicator LED to the output to produce a simple VI that demonstrates the AND gate. Figure 1-1. labview AND Function Wired to I/O Terminal Boxes Run AND from the Chap VI library. Push the two input buttons and note how the output indicator changes. Verify the above truth table. The OR and XOR Gates The OR gate is also a two-input, single-output gate. Unlike the AND gate, the output is 1 when one input, or the other, or both are 1. The OR gate output is 0 only when both inputs are 0. A A. OR Q XOR Q. B B. Figure 1-2. Digital Symbols for the OR and XOR Gates A related gate is the XOR, or eXclusive OR gate, in which the output is 1.