Construction & Implementation of 2-bit adder by using "Digital" (step-by-step explanation)

What Will I Learn?

In this tutorial, readers:

• will learn about full-adders
• will learn about 2-bit adders
• will learn how to construct 2-bit adder on "Digital"

Requirements

In order to complete the tutorial, readers would have:

• basic idea about logic gates and logic circuit environment
• a working PC
• "Digital" software

Difficulty

• Intermediate

Tutorial Contents

In this tutorial, I am going to explain the basics & construction steps of 2-bit full adders on the digital circuit simulator "Digital". I will start this tutorial by explaining full adders, which is necessary to construct 2-bit full adder, then move into 2-bit full adder. As a last step I will construct & simulate circuits on the software. Let me start with full-adders.

-Episode 1: What is Full Adder?

Full adder is a type of digital circuits, which similarly perfoming addition operation in mathematics. In digital environment, we are dealing with binary numbers, so any mathemathical operation that we can play with is vital for us. Full-Adder circuits is one of the most common types of the digital circuits and it is really important for us(in the case of understand & construct more complex digital circuits).

An example truth table of full adder is given below:

S corresponds to sum,whereas C corresponds to carry (which are simple addition terms).

We can simply construct the circuit by following gates & instructions (To understand this step better, one would need to know Karnough Map method, which is very common in digital circuit concept).

To obtain the overall circuit we need to use 2 XOR gates, 2 AND gates and a OR gate.

To obtain S ,we need to XOR A with B and XOR this output with Cin.

To obtain Cout ,we need to XOR A with B again and will AND this gate with Cin. And as a second gate we will AND A and B, and OR those 2 AND outputs.

-Episode 2: What is 2 bit adder?

2 bit adder is a form of adder which takes input as 2 numbers with 2 bit. And also as an other input, we have defined a Cin to identify internal carry. This is one of the most used adders in the digital area. Overall circuit diagram and truth tables are shown below:

I will explain the circuit construction steps basically on the later parts of the tutorial.

-Episode 3: Construction of circuits in the software

In this part, I will construct full-adder and 2-bit adder,respectively. To understand the function of 2-bit adder, we need to use full-adder, so it will be explained too.

• Construction of full-adder

Construction will be explained in steps.

• Step 1: Adding inputs

As a first step, I have added 3 inputs & label them.

• Step 2: Adding XOR gates

As a second step, I have added XOR gates & output as explained above.

• Step 3: Adding AND and OR gates

As a last step, I have added AND and OR gates & output as explained above.

So, we have managed to construct a full adder, as a next step I will construct 2-bit adder.

• Construction of 2-bit-adder

To construct 2 bit adder, we need 2 full adders, so we may use the duplication of first full adder. Construction will be explained in steps.

• Step 1: Duplication of full-adder

As a first step, I will duplicate full-adder.

I have used the same circuitry that I have done for the full-adder.

• Step 2: Construction of 2-bit adder

Now, we need to focus the circuit diagram that I have provided above. From here, we can easily see that, Cout1 must be connected to Cin2 to manage communication between adders. This is the main & most important part of the construction of m-bit adders by using full-adders.

So, we have managed to construct 2-bit adder circuit.

-Episode 4: Simulation of 2-bit adder circuit

We are ready for simulation, results are shown below:

The results are expected.

I have provided the files for this tutorial here. I highly recommend that the reader should work on the files that I have provided and try to understand the basics of the circuit & software. It will be benefical for he/she.

This is the end for this tutorial.Hope that you like it.

Digital is a really effective and easy to learn software, I highly recommend this software for the one who wants to make simulation in digital circuits especially. If you have any questions, please feel free to ask me on Discord (Escorn#4114)

Curriculum

I have provided the previous tutorials that I have prepared for the community:

SimulIDE	Caneda	Digital	LogiJS
Part 1	Part 1	Part 1	Part 1
Part 2	Part 2	Part 2
Part 3	Part 3	Part 3
Part 4	Part 4	Part 4
-	Part 5	Part 5
-	Part 6
-	Part 7

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Posted on Utopian.io - Rewarding Open Source Contributors

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