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:

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A simple priority-encoder circuits.

In this part you will wire up a simple circuit corresponding to the priority encoder we saw this morning in class. 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. (You can right click on the pictures and select "View Image" to see the full size photo)
	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.

1. Add a label (or post-it) over the switches and identify the left switch as "Mouse" and the right switch as "Printer". Add a label or post-it above the indicator and label it "INT".
2. 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.
3. Power ON
4. The switches are off, indicating that neither the mouse nor the printer are requesting attention from the processor, right?
5. Activate one of the switches. What happens to the LED?
6. Turn this switch OFF and activate the other one. Observations?
7. Power OFF.
8. You will have noticed that we have not implemented the "code" signal. Using your recently acquired knowledge of the kit, and your intuition, implement the "code" signal such that a logic indicator can be use to see its value.
9. Power ON. Verify that your completed circuit works as a priority encoder. If neither the mouse nor the printer switches are activated, then INT is low. If one is activated, INT is high, and "code" is equal to 0 or 1 depending on which peripheral is active.
10. Verify that if both peripherals are active, the "code" signal shows the Id of the peripheral with the highest priority.

• 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.

• KISS: Keep it simple, Silly!