Computer Systems and Networks

Introduction

The digital circuit designed by the use of logisim simulator. Logisim is an educational tool to support designing and simulating digital logic circuits. And it has the simple toolbar interface and simulation of circuits. It is easy to learn the concepts of logic circuits. It has the capacity to build the large circuits from small sub circuit. And it is used to draw the bundles of wires with a single mouse drag. Logisim is used to design and simulate the whole CPU for educational issues. It was designed by Carl Burch. Logisim is used by students in college at many classes. The user can draw the circuit’s logic gates using the toolbox model to drawing programs. The circuit had generated the values automatically by using major tool. And the user can change the switches and check how the circuits act in the situations.

CHAPTER 2:

  Logisim Simulator:

Logisim means logic simulator. They are used to allow the circuit design and simulation.  GUI (Graphical User Interface) are used to perform the circuit design process. Logisim are support types of operating system such as Windows, Linux, macOS. The main advantage of logisim is a free software design.

Mostly logisim are used to design the digital circuit, and also done some experimentation. Traditional drawing programs are mostly similar to the circuit design using GUI. In logisim it allows the user to edit the circuit. Suppose there was a problem in this circuit we can easily modify the circuit. This software is mainly used in educational purpose. 

2.1 Logisim Simulator Design: 

2.2 Features Of Logisim Simulator:

• Logisim supports many machines but these machines have languages and operating system like java5 and the windows or macOS.
• Logisim is open-source. So we did not need any resources.
• Toolbars are used for drawing purpose and also color coded wires are used to debug the circuits.
• Writing tool is used to draw the horizontal and vertical wires.
• The wire components are connected automatically so it can be design the circuit easily.
• At last the circuit design successfully completed, and save the circuit in the form of files or like GIF files and we must print the circuit using the printer.
• Each circuit has different components such as input, output, RAM memory, flip flop, arithmetic circuit, etc. 

CHAPTER 3:

Working Of Logisim

Logisim used to design and simulate the logic circuits. It uses the educational tool to know about the circuit work. It had four steps to explain about the work. They are,

• Design XOR gate
• Adding gates
• Adding wires
• Adding text
• Testing the circuit

3.1 Design Xor Gate

Using logisim we can make XOR circuit. The circuit has two inputs. If the input is similar we get the output as 1 else the input is different we get 0.

From these values we can make a logic circuit. It shows below,

Fig: Logic circuit for XOR gate

3.2 Adding Gates

The circuit building is easy by inserting the gates and connecting the wires. For that first we have to add two and gates. And select AND tool in the toolbar. And select the direction of AND gates by editing tools.

Fig: Creation of two AND gates using logisim simulator

In this AND gates it has some dots in that dots mentioned the wires are attached. And now add the other gates like NOT gate for that click the OR tool and pick the place for NOT gate.

Fig: Adding NOT gates and OR gates

Now add two inputs in the diagram such as x and Y. And select the input pin behind the NOT gates and add the output front of the OR gate. If we want to change any gate place click the control and see the menu and delete that and can also modify the things using the tool.

Fig: Adding inputs and outputs

3.3 Adding Wires

If the components in the canvas are blocked then we the wire are added. And select the wire tool and initiate moving from one area to another in the canvas area. And the wires appearance is in the middle of two points. In the logisim simulator wires in the form of horizontal or vertical. Logisim works to connect the wires with the gates to each other by automatically. In this picture blue and green color activity is there, in that blue indicates the note is unknown and the gray color indicates the wires are not connected to anyone.

In that it is important to connect the wires in the suitable location. In logisim it has dots indicates the wires have to connect. If the wires are connected then the wires inserted by the light color or dark green color.

3.4 Adding Text

The text adding is used to show the circuit to some others from not well understanding and in this the text act as label to show each part with clear idea to others. Pick the text tool A from the tool box and click the input pin and type and explore that as a label. And this procedure same to the output portion and we can type the one in last existing work.

Fig: Adding the text

3.5 Testing The Circuit

The finishing module of circuit design is to confirm it is really working. Logisim was stimulated the circuit in before steps.

Fig: Circuit testing

In that figure the input pins having 0s and also the output pin and in this when both inputs are zero and it compute the value as zero. The next is the combination of inputs. Here select the poke tool and click the inputs. If the input is poked the value will be moved.

If the input value is changed the logisim simulator display the values of the wires by light green color as 1 and dark green color for the value of 0. If the output value changed to 1 also it will display. Till now the testing was done for first two rows in the gates table in that the output is matched to the inputs. If the switches was poked by the combination the rows matching is easy. In that all are matches then the circuit works properly. 

CHAPTER 4

Conclusion

Logisim is the most famous educational tool. Because this tool used by the students for their educational purpose.

Which are used to simulate the digital circuit .And also we can easily understand the concept of this circuit. The designer easily learns the functionality of the circuit. And also tells the details about voltage, timing, impedance and so on.

Logisim reduce the execution timing. So the solution is generated very fast and also effective.  The main drawback in logisim is it does not support direct export of waveforms.

So we are using some mathematical operations. So using conjunction then exports the waveforms. Some countries are not familiar about this logisim tool. Especially Bulgaria has a little familiar about logisim tool.

Lack of elements are used in digital simulation like capacitors, inductors, they are mainly used for the timing purpose. Using these elements we can easily set the time constants. Finally the most important feature is fully open source’s, public easily get software.  And also freely modify the software.

CHAPTER 5

Limitations

Logisim have some limitations. The java virtual machine is the most familiar logisim limitation device. Basically logisim is platform independence. So it supports any platform. Installation process is very complicated. And also starting the program is very difficult. These are the main drawbacks.

So avoid this problem simple scripts are followed in our windows and UNIX computers. In laboratories is not a major problem but our home computers are affected.

Construction of the program is fully focused on the given efficient details. All the circuits are in moderate size. So we cannot find the problems easily in our laboratory assignment.

Two types are coursed are used one is lower-division course and another one is upper division architecture course. Logisim does not support the circuit layout issues, circuit timing, and buses.

Fixed orientation has the collections of logisim components. They are used in rotation of components. Sub circuit and surrounding circuits have a lot of pins. All the pins are in one way.