ES210, Digital Design Lab
Reporter Name:
Date:
Partner Names
Group No.:
Lab 7: Half-Adder and Full-Adder
A. Objectives
1. Learn what a half adder is and its operation.
2. Implement the half-adder on the protoboard.
3. Build the Verilog design and test bench programs for a half-adder and simulate it for the input and output waveforms.
B. Introduction
A half-adder is used to add two bits that can result in a sum bit and sometimes a carry bit that represents the most
significant bit. Below is the truth table for the half-adder.
A
0
0
1
1
B
0
1
0
1
Sum
0
1
1
0
Carry
0
0
0
1
When more bits are added together the carry from each position will add to the bits in the next position. In that case we
need to use a full-adder (see the textbook).
C. Parts needed

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



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A Digital Multimeter
A +5 V power supply
A breadboard/protoboard
Wires
One 7408 Quad 2-input AND gates
One 7483, 4-Bit Binary Adder with Fast Carry
One 7486 Quad XOR gates
Datasheets of the gates from the Internet
D. Procedure
1. Use table above to express a half-adder in terms of its inputs A and B and outputs S (Sum) and C (Carry) using AND
and XOR gates. Draw the diagram in your logbook and below. Show your design on paper to the instructor.
Express Sum and Carry in Half-Adder
Diagram for Half-Adder
2. Implement the binary half-adder on the bread/protoboard using the AND and XOR gates. Use switches for the inputs
and LEDs to display the outputs. Show the results in the following table.
VA
0.0 V
0.0 V
5.0 V
5.0 V
VB
0.0 V
5.0 V
0.0 V
5.0 V
VSum (Volts)
VCarry (Volts)
3.
a. Refer to IC 7483 datasheet
and explain what it does.
b. Explain what fast carry
does.
4.
a. In 7483 express Sum1 for A1 and B1 inputs with
C0=0 in terms of minterms of A and B.
Dr. Ali Kujoory
6/30/2016
1
b. Explain whether this is what you expect.
5. Set up a 7483 IC, 4-Bit Full-Adder circuit on the protoboard. Connect C0 (input carry) of the IC to ground. Use the
eight switches to enter A4, A3, A2, A1, B4, B3, B2, B1, and five LEDs to represent C4, S4 (Sum4), S3, S2, S1,
respectively. Set the following values to the switches, observe the LEDs, and complete the following table.
A4
0
0
0
1
1
A3
0
1
1
0
0
A2
1
0
1
0
0
Input Switches
A1
B4
1
0
0
0
1
0
0
0
1
1
B3
0
1
1
1
0
B2
1
0
1
1
0
B1
1
0
1
1
1
C4
S4
Output LEDs
S3
S2
S1
6. Write a Verilog design program in the table below to simulate a half-adder and compile it to assure it is error-free.
7. Then, write the corresponding Verilog test bench program in the table below and compile it to assure it is error-free.
Include all combinations for A and B with 50 ms delay between each combination entry in the program for 200ms
duration.
8. Simulate the program to display the waveforms of the inputs and outputs (S and C) and copy the display in the table
below. Show your displays to the instructor.
//half_adder.v program module
//half_adder_tb.v program module
Waveforms of inputs and outputs
E. Feedback/Comments (your comments will help improving this lab)
Was the instruction clear enough? Any error?
How difficult was it for you?
Do you have any observations to make?
F. Report
1. Insert the answers and the display of waveforms you obtained in the tables above. You do not need to include the
unnecessary parts such as the objectives, instructions, and procedures in your report.
2. Each member should submit the Verilog section separately in the report to make sure that you do the Verilog on
your own.
Dr. Ali Kujoory
6/30/2016
2