CPSC220: Introduction to Computer Architecture (Fall 2013)

Assignment #2

Due at the start of class on Wednesday, 09/18/2013

This assignment provides some experience in designing and simulating logic circuits, using the open-source logic< simulator, Logisim.

To do

  1. Download a copy of Logisim from its distribution site at http://ozark.hendrix.edu/~burch/logisim/index.html.
  2. Get to know the icons on the application's toolbar. If you hoverthe cursor over an icon, a brief description will pop up.
  3. Open the HELP menu, and read through the steps in the "Beginner's Tutorial". This will walk you through the creation of an XOR gate. Followup the steps therein.
  4. Create a folder for this assignment, hw2, and save your XOR circuit as hw2-xor.circ.
  5. Now move on to creating subcircuits. Study the "Subcircuits section of the Tutorial, and construct the 4-to-1 multiplexor described there. Save this in the file hw2-mux.circ
  6. In yesterday's class, we showed how to make a 1-bit full adder circuits, using only AND, XOR, and OR gates. Since we know how to make an XOR gate using only AND, OR, and NOT, it is possible to make a full adder using only these three gates. Build two versions of this subcircuit, 1-bit adder, one using XOR, AND, and OR, and the other using only AND, OR, and NOT.
  7. Using either of your 1-bit add implementations, construct a 4-bit add subcircuit.
  8. Build a 4-bit sub circuit, which implements 4-bit subtraction.

Turn in:

To hand in your files: