Lab #1 (02/01/05)
The lab report for the experiments below is due at the beginning of next lab, Feb 8.

© D. Thiébaut 2003

CSC270 Lab #1

EXPERIMENT 1: Investigating the Digital Training Kit

We will be using the horizontal part of the kit in the first few labs. The goal for now is to get a sense of how the different parts operate.

With your partner, going at your own pace, follow the steps outlined below.

Make sure the power switch is OFF.
Connect a wire between the Logic Indicator L3 and the Logic Switch A.
Power ON!
Activate Switch A, and observe the LED (Light Emitting Diode) turn ON and OFF. We will use these visual indicators to define the state of logic signals. A light ON will mean 1, or true. A light OFF will mean 0, or false.
Power OFF. Connect another wire from the Switch A-bar to the Logic Indicator L4.
Power ON. Activate the A Switch. How do the LEDs react?
Power OFF. Remove the wires. Put a new wire between Data Switch SW1 and Logic Indicator L4.
Power ON. Activate the switch. Observe how the LED responds to the switch.

The data and logic switches will provide ways for you to generate signals that will be "high" or "low", "1" or "0", "True" or "False", depending on the context. The logic indicators will provide ways for you to visualize the status of the signals. They will also prove useful when debugging circuits.

You will now run some simple experiments with the clock circuitry, and in particular the clock signal. The clock signal will be useful when we move from combinational circuits (first quarter of the course) to sequential circuits (second quarter).

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: A simple circuit

In this part you will wire up a simple circuit just so that you get the feel for wiring up digital circuits, and understanding how boolean logic maps to electrical signals. Do not worry too much if you don't understand much of the theory. Today we are interested in the mechanical aspect of wiring circuits.

The integrated circuit and its connections to the 5V supply are shown above. Below is a list of step by step instructions for realizing the complete wiring and testing it.

Make sure you follow the rules for good wiring as you go along (highlighted in red in the text below). More information and details will be given out during the lab.

Put the circuit (which we will sometimes refer to as chip, or IC--short for integrated circuit) with the designation 74LS32 on the breadboard area of the kit, with the notch to your left (in other words, you should be able to read the markings on the chip without problems). Make sure it sits over the middle groove.

Add wires as shown in the picture to the left. When wiring circuits up, always use short wires if possible, so as to avoid huge loops and spaghetti-type results.

Then add wires between two switches and the chip.

Then a wire between the chip and a logic indicator.

Add a label (or post-it) over the switches and identify the left switch as "In1" and the right switch as "In2". Add a label or post-it above the indicator and label it "Out".
Set the two switches in the OFF position, so that they generate a 0. If you do not remember which position generates what value, temporarily connect a wire between a switch and an LED, and activate the switch a few times to get it straight.
Power ON
The switches are off, indicating that neither the mouse nor the printer are requesting attention from the processor, right?
Activate one of the switches. What happens to the LED?
Turn this switch OFF and activate the other one. Observations?
If you assign the logic value 0 to a switch that is in the OFF position, and 1 to a switch that is on the ON position, and a value 0 for an LED that is OFF, what logic function have you implemented on the kit?

EXPERIMENT 3: The Diode. Finding the passing direction

What is the relationship between the symbol for a diode and its physical markings?
Using the multimeter, find the voltage across the resistor and the diode for both directions of the diode in the circuit.

EXPERIMENT 4: A diode and resistor AND-gate.

Figure 2 shows an AND gate implemented with two diodes and a resistor. The figure shows only the gate, and not the input and output circuits necessary to test it.

Connect the inputs to Data Switches and the output to an Indicator, and test the AND gate. Use the voltmeter to Measure the voltages at the inputs and at the output when you activate the switches and set them to all four possible combinations (00, 01, 10, 11). Record your observation in a truth table.

Look especially at the way the current flows through the output wire when the output voltage is low and when it is high. What is interesting (puzzling maybe) about the flow of information and the flow of current.

What happens when the two inputs are disconnected from the Data Switches? What signals does the circuit "see" on its inputs in that case? In other words, is a disconnected input treated as a high signal, or as a low signal?

THE END!

That's it for this lab! Translate your notes into a lab report that you will hand in next Wednesday. It will not be graded, but you will get feedback to help you better organize the next reports. When preparing your lab reports, keep these important points in mind:

Your lab report should be self-contained. Somebody should be able to redo the same experiments using the information contained in your report.
Record and report observations truthfully. If you measure a signal to be of a value different from the value you think, or know, it should have, report the value that you measure, not the value that you believe you should measure. You may (and probably should) comment on the measurement and indicate that you think the value is incorrect.
The Web documents for this class contain many graphic files showing different types of circuit and designs. Do not hesitate to use them to illustrate your own documents.
A report should be a log of your work, not an idealized version of it.
Be concise, but also complete.

	Put the circuit (which we will sometimes refer to as chip, or IC--short for integrated circuit) with the designation 74LS32 on the breadboard area of the kit, with the notch to your left (in other words, you should be able to read the markings on the chip without problems). Make sure it sits over the middle groove.
	Add wires as shown in the picture to the left. When wiring circuits up, always use short wires if possible, so as to avoid huge loops and spaghetti-type results.
	Then add wires between two switches and the chip.
	Then a wire between the chip and a logic indicator.