Lab #2 Familiarity with LogicWorks and Schematics

 
Start during lab and finish on your own time.
 
In the lab room, you don’t need to install LogicWorks.  However, if you wish to install on your own PC to work outside of class, see the instruction on Blackboard under “Course Information.” (this is the first time we have used Blackboard in the course, but everyone is enrolled in the SI232 course.  See www.blackboard.usna.edu).
 

Requirements for Logic Works Circuits:

1)      All inputs must be labeled and have switches (or hex keyboards) attached.

2)      All outputs must be labeled and have probes attached.

3)      The circuits must work.

4)      The files you submit must exactly match the printouts you turn in.

It is highly recommended that you label and probe/switch your signals first, rather than at the end, to facilitate testing.
 
Be sure to save your files on your X drive, not on the local computer, or else you may lose your work.
 
0. Complete the LogicWorks Tutorial.
    See /Users/cs/lmcdowel/courses/si232/logicworks
 
1. Using LogicWorks, implement and test a circuit for the following:
 
        
 
You must use binary switches for inputs A, B, and C.
 
Suggested method: 
               Select your components and add them to the schematic
               Add switches for I/O
               Add and label wires to connect the devices
               Add probes for outputs and label the outputs.
               Test your circuit

Label the circuit and the page in accordance with the specifications in the tutorial. Then print the circuit.

 

Name your file as follows: Lab2-Part1-section-lastname.cct.  Example: 
Lab2-Part1-1001-smith.cct.  You will submit this file later, together with part 2.

 
(continued on back)
2. (When you are ready, start a new file – do not include this in your previous file).  You wish to compare two 2-bit numbers and decide if the first is less than the second.
Inputs:  A (high order bit of number #1), B (low order bit of number #1), 
             C (high order bit of number #2), D (low order bit of number #2),
Output: LessThan – true if AB < CD.
 
Example #1:  A=1, B=0, C=0, D=1 à 10 is not less than 01, so LessThan is 0.
Example #2:  A=0, B=1, C=0, D=1 à 01 is not less than 01, so LessThan is 0.
Example #3:  A=0, B=1, C=1, D=1 à 01 is less than 11, so LessThan is 1.
 
Required steps:
1.      Draw a truth table for this function.
2.      Minimize the function using a K-map
3.      Implement and test the circuit using Logic Works.
 
Do not use binary switches for the inputs A, B, C, D. Instead, use two “Hex Keyboards” (available under the “Simulation IO” library).  This keyboard has 4 outputs on the right hand side – the lowest one is the least significant bit.  Specifics:
1.      Look at the example Hex keyboard at /Users/cs/lmcdowel/courses/si232/logicworks/ Note: this example just demonstrates how the hex keyboard works – it is not exactly how you will use it (see details below).
2.      Hook A and B up to the two least significant outputs of one Hex keyboard (the other two outputs will not be connected to anything). You’ll need to decide exactly which output goes to A and which to B.  Ignore the single input on the bottom of the hex keyboard.
3.      Hook C and D up to a different Hex keyboard, like you did for A and B.
4.      Test using 0, 1, 2, and 3 on the hex keyboards.  For instance, to test if 102 is less than 112, you would click on the “2” on the first (AB) hex keyboard and click on “3” on the second (CD) hex keyboard and observe the output.

Label the circuit and the page in accordance with the specifications in the tutorial. Then print the circuit.  Name your file as follows: Lab2-Part2-section-lastname.cct.  Example: 
Lab2-Part2-2001-smith.cct. 

Deliverables:

  1. Coversheet (10 pts)
  2. Save files from part 1 and part 2 in a new “Lab2” folder under “SI232” in your X drive. Be sure to read circuit requirements at top of page 1.(20 pts)
  3. Print-out of your working circuit for part 1 (20 pts)
  4. Truth table for part 2 (10 pts)
  5. K-Map and simplified equations for part 2 (20 pts)
  6. Print-out of your working circuit for part 2 (with inputs AB=01, CD=10) (20 pts)

Extra Credit (up to 10 pts)

Option 1: Expand your circuit for Part 2 so that it also computes two additional signals: Equal and GreaterThan, defined in the obvious ways.  You can include this in your file for Part 2.

Option 2: Improve your computation for LessThan so that it can compare 3-bit or 4-bit numbers.  It’s not required that your circuit be minimal.  You can explore other LogicWorks components to try and find easy ways to do this, but the most credit will be earned for solutions just using basic gates.  Turn this is in as a separate file: Lab2-Extra-section-name.cct.