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CIS-295 Computer Architecture

Course Description:
This course is intended for students who are in the computer science program or for students interested in developing a background in hardware concepts. Topics covered include number systems, logic circuits, arithmetic circuits, flip-flops, registers, memories, sample designs of simple computers and an introduction to microprogramming. The student should expect to pay for additional materials for this course.

* Project #1: Design and construct a Full Adders. A circuit that can add 3 bits. There are two outputs, SUM and CARRY. The Boolean equations are:
SUM = A xor B xor C.
Carry = AB + AC + BC.

*Reflection on project#1:
In this assignment, I have to design a logic diagram for the full adders, and then draw the circuit diagram base on the logic diagram. In this case, SUM equals A xor B xor C. CARRY equals AB or AC or BC. Therefore, SUM is 1 when the number of input 1s is odd. CARRY is a 1 when two or more inputs are 1s.

The table below summarizes the circuit action. A, B, and C are being added. If you check any entry, you will see that the circuit adds 3 bits at a time and comes up with the correct answer. For example: if A = 0, B = 0, and C = 1, it is equal to 1 in binary. Therefore, the SUM = 1 and no CARRY. If A = 1, B = 1, and C= 1, it is equal to 3, which is 11 in binary number. Therefore, SUM = 1, and CARRY = 1 also.
The simple way to construct the circuit can be using one 7408(Quad 2-input AND gate) and one 7432(Quad 2-input OR gate) which one 7486 (Quad 2-input XOR gate). However, I have a difficulty to find the AND GATE chip, so I changed the components of one AND gate to use two 7400(Quad 2-input AND gate) which work the same way.

The arithmetic-logic unit (ALU) is the number-crunching part of the computer. This means not only arithmetic operations but logic as well (OR, AND, NOT, and so forth). ALUs do not process decimal numbers. Therefore, it is important to know how ALU adds and subtracts binary numbers. I think this project is very useful, because after finishing this assignment, I was able to learn how to add binary numbers, and understand the circuits inside an ALU.

Below are my circuit diagram, logic diagram, and the Full Adder table for this assignment:

* Project #2: Design and construct a four-bit Ripple Counter. Using two 74107 (dual J-K Flip-Flop) to construct the circuit. The clock signal is supplied manually. The output is displayed with four LEDs. Include your logic diagram, circuit diagram, and the time diagram in your report.

*Reflection on project#2:
A counter is a register capable of counting the number of clock pulses that have arrived at its clock input. In its simplest form, it is the electronic equivalent of a binary odometer.

I construct the four-bit Ripple Counter with JK flip-flops. Since the J and K inputs are returned to a high voltage, each flip flop will toggle when its clock input receives a negative edge. Here is how the counter works: Each flip-flop acts like a wheel in a binary odometer; whenever it resets to 0, it sends a carry to the next higher flip-flop. Therefore, the counter is the electronic equivalent of a binary odometer. The table below summarizes the operation of the counter. Counter represents the number of clock pulses that have arrived. As you see, the counter output is the binary equivalent of the decimal count.

I build this circuit with two chip 74107 (dual J-K Flip-Flop) and connect the output with four LEDs, which is Q0, Q1, Q2, and Q3 in my circuit diagram. Below are my logic diagram, circuit diagram, and the time diagram for this project.