Subject: DIGITAL SYSTEMS 2

Student: Jos Antonio Gmez Hurtado

Practice Name SIMULATING DIGITAL SYSTEMS

Practice Number 1 Length (Hours) 2

OBJECTIVE (Learning result)

The student will be able to learn how to simulate digital systems by using the simulation tool ISIS Professional. The student will
be able to add virtual instruments and common generator sources.

THEORETICAL FRAMEWORK

- Definition of: Digital system, clock generator, virtual instrument, hard and soft real time simulation, IDE

- Digital system: A digital system is a set of devices for the generation, transmission, handling, processing or storage of
digital signals. Also, unlike an analog system, a digital system is a combination of devices designed to manipulate
physical quantities or information that are represented in digital form; that is, they can only take discrete values. Digital
systems represent information using a binary system, where data can assume one of only two possible values: zero or
one.

- Clock generator: It is a circuit that produces a timing signal (known as a clock signal and behaves as such) for use in
synchronizing a circuit's operation. The signal can range from a simple symmetrical square wave to more complex
arrangements. The basic parts that all clock generators share are a resonant circuit and an amplifier.

- Virtual instrument: A program that implements functions of an instrument by computer, sensors and actuators. This
can be a program written in the LabVIEW or in other programming languages

- Hard and soft real time simulation:

The argument could be made that your iPhone or your Andriod phone is an electronic device whose goal is to operate in
real time. When you browse for an appointment or phone number, you expect the device to respond to your finger
gestures in a timely manner. However, if a particular gesture requires several seconds to respond rather than the fraction
of a second normally required, nothing catastrophic will occur. You may be a little annoyed but youll assume
something important is going on behind the scenes. Perhaps youll shut down some apps that might be stealing
computational power in the background. This type of device is an example of a soft real-time embedded device. The
term soft indicates that there is some flexibility in the real-time requirement.

All of the following are all examples of hard real-time applications. ADI technology is used in the development of
hard real-time systems, such as those in the list below.

A Full Authority Digital Engine Controller (FADEC) controls the activities of an aircraft jet engine. The FADEC design
mandates particular timing requirements. For example, if the FADEC senses that a turbine drive shaft has broken, then
the FADEC must respond with a damage mitigating action in a predetermined time.
The fly-by-wire Flight Control Computer (FCC) uses electronic signals to measure the pilot control motions and to
control the aircrafts control surfaces. The FCC must transmit the pilots intentions at a predetermined frequency. If the
fly-by-wire system cannot communicate information with sufficient determinism, the aircraft can become unstable
resulting in a crash.
A Dynamic Positioning System (DPS) found in a marine vessel or offshore drilling platform provides capability to
 automatically maintain a position or heading using propellers, rudders, and thrusters. The DPS uses a real-time
positioning control system interfaced with sensor systems, position reference systems, and thruster and power interfaces
to perform its task. If the DPS cannot execute its control strategy at the predetermined frequency then positional or
trajectional stability may be lost which could result in damage to equipment, injury, or loss of life.

- IDE:
An integrated development environment (IDE) is a software application that provides comprehensive facilities to
computer programmers for software development. An IDE normally consists of a source code editor, build automation
tools and a debugger. Most modern IDEs have intelligent code completion.

MATERIALS AND EQUIPEMENT

Software: ISIS Professional

METHODOLOGY

1.- Software presentation in order to introduce common pallets and menus.

2.- Exercise: Simulating a typical AND Gate

3.- Pick and place:

a) 74LS08 Gate
b) Switch
c) Voltage source
d) Ground
e) Voltage probe
f) Led

4.- Wire the circuit as shown in class

5.- Change one of the inputs to the AND Gate and use instead of a fixed voltage, a clock generator with a frequency of 1 Hz.

6.- Watch the results

7.- Increase the frequency and write down the maximum frequency that can be appreciated at sight

8.- Change the clock oscillator frequency by 100 Hz and use a virtual oscilloscope to monitor the AND output.

9.- Build the two challenge circuit drawn by your teacher, simulate it and write down the results.
 Results
Simulating a typical AND Gate
10 Hz, It is still visible
100 Hz, It is not still visible
PRACTICE EVALUATION

QUESTIONARY

1. Which families of microcontrollers are included in this simulation software?

2. How can a pulse length can be measured using the oscilloscope?

3. Which is the maximum switching speed of an AND Gate, can you simulate it?
It dependents on the velocity of your CPU, and the CPU load.

4. Why there is a problem when all the names of the elements on the schematic are the same?
Because the program thinks that both are the same device, so, it gets confused.

5. Add the simulated circuit and write down the results you found for the four exercises.

Conclusions

In the AND operation it is run exactly like ordinary multiplication of ones and zeros. An output equal to 1 occurs only when
in the event that all inputs are 1. Output is zero in any case where one or more inputs are 0.

One application of this gate can be a security system for a seesaw. To prevent the operator's hands are within the pressure
zone , two buttons that put a one in each entry are placed. The buttons are well spaced apart. Only when the press operator
appears a one in the output relay that operates the engine.

(Results interpretation, Was the objective reached? Possible applications, etc.)