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CS 240 Lab 3

Learning Goals & Reflection

CS 240 Lab 3

Learning Goals

Core Goals

Students can:

  1. Work with multiplexers:
    1. Explain the purpose of a multiplexer.
    2. Design a circuit for an arbitrarily large multiplexer using AND, OR, and NOT gates.
    3. Give the formula for how many select wires are needed for a multiplexer, and explain why.
    4. Identify the select line inputs necessary to select the signal on a specific input line of a multiplexer.
    5. Explain how to use a multiplexer to build a circuit for an arbitrary truth table.
  2. Work with decoders:
    1. Explain the purpose of a decoder.
    2. Explain what a “1-hot” encoding is and how it differs from binary.
    3. Explain how the number of inputs and outputs is related for different sizes of decoder.
    4. Write the truth table for a decoder of a specific size.
    5. Design a circuit for an arbitrarily large decoder using AND and NOT gates.
  3. Work with encoders:
    1. Explain the purpose of an encoder.
    2. Explain how the number of inputs and outputs is related for different sizes of encoder.
    3. Write the truth table for an encoder of a specific size.
    4. Design a circuit for an arbitrarily large demultiplexer using OR gates.
  4. Work with demultiplexers:
    1. Explain the purpose of a demultiplexer.
    2. Write the truth table for a demultiplexer of a specific size.
    3. Explain how the number of inputs and select lines is related for different sizes of demultiplexer.
    4. Design a circuit for an arbitrarily large demultiplexer using AND and NOT gates.
  5. Build functional circuits using integrated circuits as components:
    1. Explain what “active low” means in a circuit diagram or logic diagram.
    2. Explain what an enable line is for.
    3. Build a circuit that has a specific 3-input truth table using a 74151 8x1 multiplexer chip.

Stretch goals

  1. Work with adders:
    1. Explain why a 1-bit adder needs 2 output lines.
    2. Explain the difference between a half adder and a full adder.
    3. Design a half-adder using AND and XOR gates.
    4. Design a full-adder using AND, OR, and XOR gates.
    5. Explain how to connect multiple 1-bit full adders to produce a multi-bit adder circuit.
    6. Identify how many inputs and outputs a 4-bit full adder has.
    7. Explain under what circumstances a carry-out bit indicates overflow for an N-bit adder.

Reflection

Fill out the CS 240 Lab 3 Reflection form to complete today’s lab reflection.