Digital Logic Design
Final Project Report
4-bit Arithmetic Logic Unit (ALU)
Components:
2 x 4 Bit Full Adder (7083)
4 Bit Comparator (7485)
Green, Red, Blue LEDs
Jump wires
220-ohm resistors
Breadboard
Power Supply from Trainer Board
Ground
Inputs from Trainer Board
Implementation:
4-bit Adder for addition and Subtraction:
The 7083 Adder IC has four different stages, and each stage has two normal
inputs Ax and Bx with an additional carry input called C1. Based on the values
provided to these pins the output Sx will either be high (logic 1) or low (logic 0).
The IC also has a Carry Out (CO) pin which will go high if the result has a carry. It
takes 2 4-bit number inputs and outputs its resulting addition including the
carry. The Carry Input is given 0 for addition. For subtraction, the same Full
Adder IC is used to subtract two 4-bit numbers with 1’s complement of input B.
For 1’s complement of B we used its NOT input. The Carry Input for subtraction
is 1.
4-bit Comparator:
A comparator is a combinational circuit that compares two binary numbers to
find where one binary number in this case A, is equal to B, less than B, or greater
than B. Our 4-bit comparator IC (7485) takes 2 4-bit numbers A and B as input
and has three output terminals to output conditions: A=B, A>B, A<B. The input
we gave for each condition was 1.
LEDs:
We will use red, green, and blue LEDs to show our output. 12 LEDs will be
used to output the following:
Addition (4 LEDs)
Carry Output (1 LED)
Subtraction (4 LEDs)
A=B
A<B
A>B
0
