Lab 1

Combinational Circuit Design:
Ripple Adder, Gray-code Decoder/Encoder Circuits, MUX

Due date: Tue 10/21

Objective

In this lab, we will build a half-adder, a full-adder and a 4-bit adder from the full-adder. We will also build a gray-code encoder & decoder.

Part 1. Ripple Adder.

i. Design a full-adder starting with a half-adder. Briefly describe the design (how a 1/2 adder works and how putting together two 1/2 adders will make up a full-adder, mention the sum & carry in relation to the inputs).
ii. Use the enclosed full adder tutorial to build a full adder using xilinx program.
iii. Build a 4-bit adder using xilinx & simulate the 4-bit adder using xilinx. Simulate EXACTLY 8 different test cases to help demonstrate that your circuit works.

Part 2. Construction of a Combinational Logic for the Gray-code ENCODER

Design a combinational logic circuit that converts three-bit binary code counter to three-bit gray-code counter (Gray Code ENCODER)

abc wxy
000 000
001 001
010 011
011 010
100 110
101 111
110 101
111 100

i. Briefly describe what a gray-code encoder is.
ii. Design the encoder circuit (K-map, Algebraic expression)
iii. Build the gray-code encoder circuit & simulate the gray-code encoder using xilinx. Simulate all cases.

Part 3. Construction of a Combinational Logic for the Gray-code DECODER

wxy efg
000 000
001 001
011 010
010 011
110 100
111 101
101 110
100 111

i. Briefly describe what a gray-code decoder is.
ii. Design the encoder circuit (K-map, Algebraic expression, etc.)
iii. Build the gray-code dncoder circuit & simulate the gray-code decoder using xilinx. Simulate all cases.

Part 4. Multiplexer

Build a circuit that translate a 8-bit parallel data to a serial output using only 2:1 Muxes.
i. Define the specification for this 8-bit parallel to serial circuit. (input, output & their relationship)
ii. Briefly describe how you design this circuit.
iii. Build and simulate the circuit using xilinx. Simulate EXACTLY 8 different test cases to help demonstrate that your circuit works.

Report
Title page:
  • Names of students and due date.
  • Title of the lab and objective.
  • A brief description of each person's contribution.

Content:
  • Part 1 i, ii, iii
  • Part 2 i, ii, iii
  • Part 3 i, ii, iii
  • Part 4 i, ii, iii
  • Hint on a good report: Be descriptive but not wordy. Think of yourself as the grader but doesn't have the hand out. The grader should know what you did in the lab without looking at the hand out. **Also, remember to have a short description on what test cases you used (preferably label the test cases on the simulation print-out). Labeling 0's and 1's on your simulation timing chart will also help the grader to identify which test cases you have used.
Grading

90% will based on the completeness and correctness of the report. 10% will based on the neatness, organization, and following instruction of the report format. Please note, however, that if your report is not clear enough we may not be able to tell that it's correct either and may grade you down accordingly.