University of Bahrain
College of Information Technology
Department of Computer Engineering
ITCE 112 Digital Design and ITCE 250 Digital Logic
Experiment No. 3
Combinational Logic Circuit: Design of Parallel Adder
Objective:
To design and simulate a Parallel Adder logic circuit.
Introduction:
Figure 1 shows the truth table and the logic symbol for a full adder:
Figure 1
From the truth table above, the boolean function of the full adder can be written and simplefied
as given below:
Equipment Required:
Tinkercad simulator, Breadboard
(One) IC Type 7432 Quad 2-Input OR Gate
(Two) IC Type 7486 Quad EXCLUSIVE-OR Gate
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(Two) IC Type 7408 quad 2-input AND Gate
LEDs, Resistors (220 ohms), Power Supply
Experimental Procedure
1. Write the Boolean expression for the Sum and Carry Out of the full adder such that you can
use 2-half adder and OR Gate.
2. Construct the full adder circuit shown in Figure 2 on the breadboard.
3. Test the full adder circuit, and then create 1 more full adders.
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4. For the design of 2-bit parallel adder using full adder, connect the 2-full adders logic block
and logic circuit as shown Figure:
5. Connect the 5-inputs (A1-A0, B1-B0, and Ci) to switches, and the 3-outputs (S1-S0, and Co) to
3 LEDs.
6. Connect the internal carries as shown in the figure.
7. Test your circuit for different binary values of (A, B, and Ci), and check the outputs (S and
Co). Construct a truth table.
Assignment:
Modify the circuit to work as 4-bit adder subtractor in 2's complement.
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