Digital Logic Design Lab
CPE- YU
Task
Title
Section
05
Arithmetic circuits design and implementation
Objectives
-
To familiarize students with the functionality of digital adder-subtractor circuit.
Use different implementation approaches to perform arithmetic operations.
Use Binary full adder with fast carry IC
THEORY
Introduction
In electronics, an adder or summer is a digital circuit that performs addition of numbers. In many
computers and other kinds of processors, adders are used not only in the arithmetic logic unit(s), but
also in other parts of the processor, where they are used to calculate addresses, table indices, and
similar.
This experiment will describe some of the main arithmetic operations.
1. Half Adder
Half adder is a combinational circuit that adds only two one bit numbers, since there are two inputs (x
and y), only four possible combinations of inputs can be applied.
Truth table
Block Diagram
2. Full Adder
The circuit that performs addition of three bits (two significant bits and a previous carry) and produces
the sum and carry is called. Full adders are used to add three bits where one of them is the carry from
the preceding adder. They have two outputs: the sum and the carry to the next stage.
Digital Logic Design Lab
CPE- YU
Truth table
Block Diagram
3. Half Subtractor
The half-subtractor is a combinational circuit which is used to perform subtraction of two bits. It has
two inputs, X (minuend) and Y (subtrahend) and two outputs D (difference) and B (borrow).
Truth table
Block Diagram
Digital Logic Design Lab
CPE- YU
4. Full subtractor
The full-subtractor is a combinational circuit which is used to perform subtraction of three bits. It has
three inputs, X (minuend) and Y (subtrahend) and Z (subtrahend) and two outputs D (difference) and B
(borrow).
Truth table
Block Diagram
5. 4-bit Adder –Subtractor:
In digital circuits, an adder–subtractor is a circuit that is capable of adding or subtracting numbers (in
particular, binary). Below is a circuit that does adding or subtracting depending on a control signal. It is
also possible to construct a circuit that performs both addition and subtraction at the same time.
Digital Logic Design Lab
CPE- YU
M: controller, adding when M=0 and Subtracting when M=1.
Adding: A+B. Sub: A-B.
V: overflow flag, denote that an overflow happened when V=1.
Digital Logic Design Lab
CPE- YU
IC DESCRIPTION
IC :74LS83 4-BIT BINARY FULL ADDER WITH FAST CARRY
Logic Symbol
Table
Pins
Diagram Pins
Digital Logic Design Lab
CPE- YU
PRE-LAB
1.
2.
3.
4.
5.
6.
Review chapter 4 of (Morris Mano, Digital Design, Fourth Edition).
Study the datasheets for 74LS83.
All circuits on the Pre-lab must be constructed using circuit maker.
Submit your circuit maker file online, and name the file with your name and ID.
Add all circuits in Pre-Lab in one circuit maker file.
You should be able to construct all arithmetic functions above using logic gates used and
described before (Like Mux, Nand, Nor …..)
Part One:
Design a Full-adder (FA) based on two different implementation approaches
a. Using decoders,
b. Using multiplexers.
. Draw the circuit using CircuitMaker
Part Two:
Use 4-bit full adder with fast carry (74LS283) to design a binary adder that adds two numbers
each with a size of 7 bits. . Draw the circuit using CircuitMaker