COSC 201: Computer Organization

Lab 5: Circuit development

Purpose
Learn how to build circuits and test them with the LogiSim simulator.
Method
Create the specified circuits: a shifter and a 32-bit adder
Preparation
Read Appendix B from the text
Files to Use
           shifter8x4.circ, add.circ
What to Hand In
Completed adderXX.circ and shifter8x4XX.circ (XX are your initials or name)

1. Starting with the file shifter8x4.circ create a circuit that does a logical left shift by an amount determined by two bits, e.g. 0, 1, 2, 3, to shift an 8-bit input value to an 8-bit output value. (Hint: Use offset 8-bit forks, one that expands the 8-bit input and the second (reverse direction) that creates an offset 8-bit output, using constant 0 for the unspecified inputs to the second fork. Also use a 2-bit control for an 8-bit wide multiplexor.)

2. Starting with the add.circ file, first create a one-bit full adder (using basic logic gates and, or, xor, not), then an 8-bit adder, then a 32-bit adder. The main will test your adder against the 32-bit adder component.

3. Hard extra credit! Add circuitry for carry-look-ahead to your adder. Do not attempt this at home! This will take much longer than the rest of the lab.