8/10/2019 ECEN 248 Lab 4

1/8

Lab 4: Rudimentary Adder

CircuitsRebecca SontheimerECEN 248-511

TA: Mehnaz Rahman

Date: October 8, 2014

8/10/2019 ECEN 248 Lab 4

2/8

ObjectiveThe purpose of this lab is to understand the different types of adder circuits. I

learned how to design a half adder, a full adder, and a 2-bit Ripple Carry adder. Each of

these builds on top of the previous ones and I will be able to create a full adder from theconcept of two half adders and the Ripple carry adder from the concept of two full

adders. In this lab, we had to design and test our adder circuits based on a set of rules,

which gave me good practice in designing my own simple circuit.

DesignHalf Adder

Truth Table:

X Y C0 S

0 0 0 00 1 0 1

1 0 0 1

1 1 1 0

Karnaugh Maps:

Logic Expressions with XOR:

S = XY

C = X*YLogic Expressions without XOR:

S = X*Y+X*Y

C = X*Y

Schematic:

Full Adder

Truth Table:

C X Y C0 S

0 0 0 0 0

0 0 1 0 1

Sum Y

X 0 1

0 0 1

1 1 0

C0 Y

X 0 1

0 0 0

1 0 1

8/10/2019 ECEN 248 Lab 4

3/8

0 1 0 0 1

0 1 1 1 0

1 0 0 0 1

1 0 1 1 0

1 1 0 1 0

1 1 1 1 1

Karnaugh Maps:

S XY

C 00 01 11 10

0 0 1 0 1

1 1 0 1 0

Logic with XOR:

S = XYC

C0 = (XY)*C + (X*Y)

Logic without XOR:

S = (X*Y*C)+(X*Y*C)+(X*Y*C)+(X*Y*C)

C0 = X*Y + X*C + Y*C

Schematic:

Two Bit Ripple Carry Adder

C0 XY

C 00 01 11 10

0 0 0 1 0

1 0 1 1 1

8/10/2019 ECEN 248 Lab 4

4/8

When Cin=0 When Cin=1

A0 B0 A1 B1 S0 S1 Cout S0 S1 Cout

0 0 0 0 0 0 0 1 0 0

0 0 0 1 0 1 0 1 1 0

0 0 1 0 0 1 0 1 1 0

0 0 1 1 0 0 1 1 0 1

0 1 0 0 1 0 0 0 1 0

0 1 0 1 1 1 0 0 0 1

0 1 1 0 1 1 0 0 0 1

0 1 1 1 1 0 1 0 1 1

1 0 0 0 1 0 0 0 1 0

1 0 0 1 1 1 0 0 0 1

1 0 1 0 1 1 0 0 0 1

1 0 1 1 1 0 1 0 1 1

1 1 0 0 0 1 1 1 1 0

1 1 0 1 0 0 1 1 0 1

1 1 1 0 0 0 1 1 0 1

1 1 1 1 0 1 1 1 1 1

Schematic:

8/10/2019 ECEN 248 Lab 4

5/8

ResultsThis lab focused more on our ability to read schematics and build circuits rather

than collecting any data. We had to test the circuit to make sure that it gave the correct

output, which involved a lot of trouble-shooting and making sure my wiring was notmessy or confusing. I found that once I had figured out the truth tables and schematics,

that the circuits were actually very simple. However, each circuit brought its own

challenges. This lab taught me that color-coding wires is very useful because after awhile all of them start looking alike, especially when many wires are coming from the

same pin and the pins around them. The wires are long and get to be very confusing if

you dont keep track of what wire is where on the schematic and what has already beenplaced and what has been forgotten. For example, while implementing the two-bit ripple

carry adder, I had accidently not wired the Vcc of one of the ICs to the power supply.

This caused me to check the circuit many times and I became frustrated because

everything seemed right, when in reality I had just made a simple mistake. Below are

pictures of the finished products.

Half Adder

Full Adder

8/10/2019 ECEN 248 Lab 4

6/8

Two Bit Ripple Carry Adder

ConclusionIn conclusion, this was simple and straightforward. No actual data had to be

taken, but rather the lab was a test of skills. I also became more comfortable with

8/10/2019 ECEN 248 Lab 4

7/8

designing an efficient circuit. I feel as though this lab was a major learning experience

after all of the issues and simple mistakes I ran into.

Questions

1.

All of the design items can be found in the design section of this lab.

2. Worst case propagation delay for a full adder design. Each of the colored paths

denoted below show the maximum delay path because each gate is a delay unit of

1 and each of the paths go through the maximum of three gates.

3. This diagram shows a ripple carry adder diagram using the concept of 4 half

adders to create the same circuit that is shown above in the design section.

Feedback

8/10/2019 ECEN 248 Lab 4

8/8

1. I like making my own designs and circuits because it helps me to truly understand

the lab. This lab would have been easier if we had shorter wires or wire clippers.

2. Nothing about the lab manual was unclear.3. I really think having wire clippers or shorter wires in the lab would make it much

easier to learn because then we could see our circuits more clearly and actually

see the paths that the wires are taking.