Digital Logic Tutorial and Design

Июль 26, 2022

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Digital Logic Tutorial and Design

Содержание

2. Digital Logic Lab (A mini-lab experience) We are going to build both a combination lock and
3. Some Definitions Definition: Discrete System - a system with a finite number of sizes or measures
4. 0 5 Analog Waveform Time Voltage (V) 0 5 Digital Waveform Time Voltage (V) 1 0
5. AND Operator Let’s look at the relationship between the semantic and logical operator known as the
6. Digital AND We can build an electrical device that performs the logical AND operation on voltage
7. OR Operator Another basic operator is the OR Consider: If I have cash OR a credit
8. NOT Operator/Inverter Gate The NOT gate reverses the input NOT Operator Truth Table All digital computers
9. XOR (Exclusive OR) Operator Let’s look at the relationship between the semantic and logical operator known
10. Digital XOR We can build an electrical device that performs the logical XOR operation on voltage
11. Digital Combination Lock Design and Software Simulation
12. Multi-Input AND Gate AND gates can be built with any number of inputs Consider the symbol
13. Digital Combination Lock Using 3 two-input AND gates, we could build a combination lock that requires
14. Digital Combination Lock We could build a combination lock that only uses the AND gate, but
15. Digital Combination Lock Let’s build a combination lock whose input (key code) combination is 0 1
16. “Picking” a Digital Lock Use the truth table below to record the lock outputs for the
17. Digital Railroad Crossing Signal Design and Software Simulation
18. Digital Railroad Crossing Signal Now, let’s develop a digital circuit whose output changes over time We
19. Railroad Crossing Signal Design Here we will need some type of timing signal that will tell
20. Railroad Crossing Signal Turn-on voltage puts out a constant +5 volts Square wave is being repeatedly
22. Скачать презентацию

Слайд 2

Digital Logic Lab (A mini-lab experience)
We are going to build both a

combination lock and a flashing railroad crossing signal using digital logic devices
To build these circuits we will draw upon knowledge or resources developed by several areas of electrical engineering
First, we will need to learn a little about digital logic

Слайд 3

Some Definitions
Definition: Discrete System - a system with a finite number

of sizes or measures
Shoes, Dresses, Pants, Bolts, Pencils
Definition: Digital System - a Discrete System with only two values of system variables: 1 and 0
True/False; Yes/No; Male/Female; On/Off
Let’s compare digital and continuous (analog) systems
Digital signals are binary; analog signals are real-valued numbers
Digital is less susceptible to noise

Слайд 4

0
5
Analog Waveform
Time
Voltage (V)
0
5
Digital Waveform
Time
Voltage (V)
1
0
1

Слайд 5

AND Operator
Let’s look at the relationship between the semantic and logical

operator known as the AND operator
Consider:
If the car is fueled AND the engine works,
then the engine will start

AND Operator
Truth Table

AND means that both conditions must be true in order for the conclusion to be true

Слайд 6

Digital AND
We can build an electrical device that performs the logical

AND operation on voltage equivalents of logic values
An AND gate has the
electrical schematic:

For digital logic:
True = 1 is 5 volts
False = 0 is 0 volts

Practice with the Excel spreadsheet

Слайд 7

OR Operator
Another basic operator is the OR
Consider:
If I have cash OR

a credit card,
then I can pay the bill
OR works such that the output is true, if either of the two inputs is true

OR Operator
Truth Table

Слайд 8

NOT Operator/Inverter Gate
The NOT gate reverses the input
NOT Operator
Truth Table
All digital

computers are built using only three gate types: AND, OR, and NOT

Слайд 9

XOR (Exclusive OR) Operator
Let’s look at the relationship between the semantic

and logical operator known as the XOR operator
Consider a biological example:
If gender A XOR gender B,
then reproduction is possible
XOR works such that output is activated (equal to one) if both inputs are of a different value
Try the Excel spreadsheet exercise

Слайд 10

Digital XOR
We can build an electrical device that performs the logical

XOR operation on voltage equivalents of logic values
An XOR gate has the
electrical schematic:

XOR Operator
Truth Table

Слайд 11

Digital Combination Lock
Design and Software Simulation

Слайд 12

Multi-Input AND Gate
AND gates can be built with any number of

inputs
Consider the symbol for the 4-input AND gate

F is true only when all the inputs are true (1’s)
Using the Excel workbook “EE-WISE-DigitalLab”, open the “Digital Locks” worksheet, and test this circuit

Слайд 13

Digital Combination Lock
Using 3 two-input AND gates, we could build a

combination lock that requires a four-digit code, specifically: 1 1 1 1
The number of inputs could be increased by using more and more AND gates

Слайд 14

Digital Combination Lock
We could build a combination lock that only uses

the AND gate, but that would be of little use since everyone would know our combination, namely 1 1 1 1
To build a more interesting combination lock, we will utilize the NOT (inverter) gate

Слайд 15

Digital Combination Lock
Let’s build a combination lock whose input (key code)

combination is 0 1 1 0

Is there any other combination that works?

AND

Слайд 16

“Picking” a Digital Lock
Use the truth table below to record the

lock outputs for the different lock combinations in the “Pick the Locks” worksheet

Слайд 17

Digital Railroad Crossing Signal
Design and Software Simulation

Слайд 18

Digital Railroad Crossing Signal
Now, let’s develop a digital circuit whose output

changes over time
We are all familiar with a railroad crossing signal that alternates flashing red lights
In addition to constructing the digital combination lock, we will build the railroad crossing signal in the lab, so let’s begin by designing the circuit

Слайд 19

Railroad Crossing Signal Design
Here we will need some type of timing

signal that will tell the lights when to turn on and off
The problem is that we seemingly need two timing signals since one light is on while the other is off, and vice versa
A digital logic implementation can allow us to save cost by using only a single timing signal
The design effort is then one of considering which gate(s) need to be used to achieve the alternating signal patterns

Слайд 20