CSC231 Logic Design Lab 2014
--D. Thiebaut (talk) 10:35, 19 November 2014 (EST)
Contents
Logic Design LAB
EXPERIMENT #1: INVESTIGATING THE KIT
Overview of the Kit
The main tools for us today are the switches, the LEDs, the +5 and GND wiring plots, and the breadboard area.
Exploration
For this part, concentrate only on the flatter part of the Digital Kit, not the circuit board that is upright, facing you. Please follow the steps below.
- Power OFF. Always turn OFF the power when you are wiring circuits. This will prevent shorts and extend the life of your circuits.
- Connect a wire between the Logic Indicator L4 and the Logic Switch A.
- Power ON
- Activate Switch A, and observe the LED (Light Emitting Diode) turn ON and OFF.
- Power OFF
- Switch the wire from A to A-Bar, turn the power back ON, and see how the LED reacts .
- Same experiment, but this time replace the Logic Switch by one of the Data Switches.
- Power OFF.
- Connect one of the Logic Indicators to the Clock signal. Connect a second wire from another Logic Indicator to the Clock-bar signal. Make sure the sliding switch is on the 1Hz mark.
- Power UP. What do you observe?
- Slide the switch to 1KHz. What happens? Why? Is there any difference in the brightness of the LED? Why?
EXPERIMENT #2: INTEGRATED CIRCUITS AND LOGIC GATES
You should have the data sheets of the integrated circuits implementing the AND gate (74LS08), the OR gate (74LS32), and the XOR gate (74LS86). The XOR is not and universal gate, but its function is encountered enough times in the real world that manufacturers have built a circuit just for this function. The equation for a XOR b is ( a and not b ) or ( not a and b), which can be implemented using the simple AND, OR, and NOT.
You will be given three circuits in class, with a piece of tape hiding its part number. The circuits are labeled A, B, and C. Your job is to
- pick one gate of the circuit,
- wire up the inputs of the gate to switches,
- attach the output of the gate to an LED,
- activate the different inputs
- figure out which circuit contains AND gates, which contains OR gates, and which contains XOR gates.
Use the information shown in the Figure 1 to help you wire the circuit.
- Rule 1
- Always make sure the notch on the circuit is facing left. This way the circuit matches the diagram on the datasheets.
- Rule 2
- Always make sure that the circuit is connected to +5V through its pin 14, and to GND via its pin 7.
Figure 1:Wiring of an IC on the breadboard. Always identify pin 1 of the IC which is on the left (or below) the notch or circle embossed on the top of the chipYou may find the tables below useful for keeping notes of what is going on.
Input 1 Input 2 Output
0 0 0 1 1 0 1 1
Input 1 Input 2 Output
0 0 0 1 1 0 1 1
Input 1 Input 2 Output
0 0 0 1 1 0 1 1
2-Bit Adder
- We'll explore in class how to verify the property, both theoretically, on paper, and practically, using digital electronic circuits. The diagram below needs to be completed in class before wiring and testing.
Useful Gates
Inverter: 74LS04
AND gate: 74LS08
OR gate: 74LS32
Exclusive OR: 74LS86
Useful Boolean Axioms
- You may find these axioms useful in simplifying functions (taken from Wikipedia)
a OR (b OR c) = (a OR b) OR c a AND (b AND c) = (a AND b) AND c Associativity a OR b = b OR a a AND b = b AND a Commutativity a OR (a AND b) = a a AND (a OR b) = a Absorption a OR (b AND c) = (a OR b) AND (a OR c) a AND (b OR c) = (a AND b) OR (a AND c) Distributivity a OR NOT a = 1 a AND NOT a = 0 Complements
- Figure out how to test each axiom
- Divide the work to be done into tasks and assign each task to a group or to an individual
- Demonstrate to the class that the gates found in the integrated circuits used in the lab verify the axioms of the Boolean Algebra.
