- What is Adder?
- What are Full Adders?
- How is the Truth Table of Full Adder?
- How can we design Full Adder in Proteus ISIS?
- What are the uses of Full Adder?
AddersIn digital Electronics, Adders are important Circuits. We define the Adders as:
"The Adders are the Logical circuits that take the bits in as the input , sum the bits together and show the output of the sum at output terminals."Adders are present in many areas of computer architecture , but they are mainly present in the Arithmetic Logic Unit. We classify the Adders into two types:
- Half Adder.
- Full Adder.
2-bit Full Adder using Logic GatesThere are two types of Full Adders:
- 2 bit Full Adder.
- 4 Bit Full Adder.
"Two Bit Full Adders are the Logical Circuits that have two inputs for the input bits and one for the carry and as a result, Sum of the bits along with the carry are obtained at sum and carry Terminals respectively.in this way, user ( may be person or Computer) can gets a complete cycle of calculation as it can have the connection of two or more calculation. The Full Adder plays an important role in the calculation because, computer , itself is a calculating machine. thus it uses such circuits along with a complex circuitry. DID YOU KNOW???????????? We can design the adder circuit in such a way that it can add any number of bits and give us the real result as its output.
Truth Table of 2-bit Full AdderAs discussed above, there are total three inputs and two outputs of Full Adder. Therefore, the Truth Table of Full Adder also have the same criteria. The input combinations of the Truth Tables are followed through the formula:
Numbers of Combinations= 2^nwhere n is the numbers of input. In our case,
Numbers of Combinations=8We start the truth table from zero bit. The right most input has the alternative inputs after each combination. The middle contains the alternative bits after two combinations. By the same token the left most changes the input bit after four combinations. The Truth Table of Full Adder looks like this:
DID YOU KNOW????????????There exist a Logical Circuit called "Half Adder" that does the half work of the Full Adder. It take the two inputs from the user and shows the output in the form of sum and carry. Yet, it does not have any mechanism to store the carry or to use the carry of the previous calculation.
Simulation of Full Adder in Proteus ISISTo design a Full Adder in Proteus ISIS, just follow these simple steps.
- Fire up the Proteus Software.
- Take the required Material.
- XOR Gate
- AND Gate
- OR Gate
- Logic Toggle
- Ground Terminal
- Connecting Wires
- Get the first five components from the Pick Library through "P" button one after the other.
- Take two XOR Gates one by one and arrange the at working area vertically.
- Get two AND Gates and set them just below the XOR Gates.
- After the AND Gates, arrange one OR Gate.
- Connect two Logic Toggles with the inputs of switch 1.
- Connect one Logic Toggle with the 2nd input of switch three.
- Attach LED with the switch 3 and ground the LED through Ground Terminal in "Terminal Mode" presented on the left most bar of the screen.
- Repeat the above step for switch 5.
- Connect all the switches through wires according to the diagram given next:
- Change the Input bits according to the combination and record them in your own table.
- For best Understanding we'll design a Truth Table that describes the output of each switch.
Input Output Cin B A Switch1 Switch2 Switch4 Switch 3? Switch 5C0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 1 0 0 1 0 1 0 0 1 0 0 1 1 0 1 0 0 1 1 0 0 0 0 0 1 0 1 0 1 1 0 1 0 1 1 1 0 1 0 1 0 1 1 1 1 0 1 0 1 1 Carry+A+B Sum Carry out
Uses of Full Adder
- Full adders are paramount for the on chip Libraries.
- They are used in computer for table indices.
- They are used by processor to add the addresses.
- Full adders are used in Arithmetic Logic Unit.
- Full Adders are used in the Computer for the series calculations. For this purpose, they may be connected in the way given next in the image. Observe it from bottom to top.
- It can be designed so, that we can input eight bits together that collectively work as a byte.