EE260 Lab 3

Protoboards and Programming EPROM's


Contents

1 Objectives
2 Materials that you need
3 Prelab
4 Experiment
 
  1. Playing with the Hardware
  2. Logic probes
  3. Switches
  4. Directional lights circuit
5 What to turn in for this lab

1. Objectives

The objective of this lab is for you to become familiar with the equipment in the lab in Holmes 451 and to get a little practice building some very useful circuits that you will keep on your protoboard throughout the semester.

This Experiment has three parts:


2. Materials that you need

For this experiment you will need the following equipment:


3. Prelab

1.  Get your kit.

2.  Read the Safety page before you come to the lab. Understand and remember these rules!

3.  Read over the Experiment section of this experiment. Be sure you understand what are to be done.

Task 5 of the Experiment is to build a directional lights circuit as shown in Figure 2.d below.  A block diagram of this sequential circuit is shown in Figure 1 along with its state diagram.  There are four states, a clock input, a single control input DIR, and four outputs that drive a series of lights.  At all times, only one of the lights is on.  The "on" light goes travels to the left or right depending on the DIR value.

LogicWorks Design and Simulation:  Create a state transition table for the circuit based upon the state diagram in Figure 1 (please excuse the artwork).  Then using the Truth Table program on wiliki, create a HEX file.  Using the Hex file, create a PROM in LogicWorks and check that it matches the truth table.  Create the directional lights circuit in Logicworks by using the PROM as the combinational circuit, and a 74175 as the state register.  In your Logicworks circuit, attach binary switches to the DIR input, and logic probes to the outputs.  You can attach either the clock generator or a binary switch to the clock input of the circuit.

Figure 1. Directional lights circuit.


Projected time of this lab: 3+ hours.

4. Experiment

4.1 Playing with the Hardware

This part of the lab will allow you to become more familiar with all the equipment you will be using throughout the course.

4.1.1 Protoboard and IC's

Look at the layout of your protoboard. The TA will describe how the connections are built in to the protoboard.

Task 1: Make a brief sketch of your board in your write-up, showing the connections of the various rows, columns, and holes.

The TA will also show you how to identify the IC's you have in your parts kit, how to determine the pin numbers, and how to mount the chips on your board and provide power connections.

4.1.2 Equipment in H451

In this section of the lab, your TA will go over the functionality, usage, and the precautions of all the equipment that we have in the EE260 lab.

4.2 Logic Probes

Place a 74'04 IC in the test circuit area of your board (preferably at a corner). The TA will show you how to identify pin 1 of the chip and where the power (Vcc) and the ground (Gnd) pins are. Wire these pings to the power and ground rails you have chosen.

Task 2: Construct a positive logic probe as shown in Figure 2.a. (Note that this lab used to be "Lab 2", which explains some of the references in this document, e.g., Figure 2.x.)

Verify its functionality using the test point lead.

Questions:

  1. What happens when you connect the test point to +5 V?
  2. What happens when you connect the test point to GND?
  3. What voltage does LED 1 indicate?
  4. What happens when the test point is not connected (floating)?

Task 3: Construct a negative logic probe as shown in Figure 2.b. Verify its functionality using the test point lead.

Questions:

  1. What happens when you connect the test point to +5 V?
  2. What happens when you connect the test point to GND?
  3. What voltage does LED 1 indicate?
  4. What happens when the test point is not connected (floating)?

4.3 Switches

Task 4: Place your DIP (Dual Inline Pin) switch in the test circuit area of your board. Identify four of these switches as A, B, C, and D. Wire switch A shown in Figure 2.c. (If there is time, or later on your own, you can wire the other three switches as in the figure)

Questions:

  1. Using test point 1, what is the voltage at A1 when switch A is in the OFF (open) position?
  2. Using test point 1, what is the voltage at A1 when switch A is in the ON (closed) position?
  3. What is the voltage at A2 when switch A is OFF and ON?
  4. Now connect test point 1 to A1 and test point 2 to A2. What is the status of the LED's when switch A if OFF and ON?

4.3.1 Using the Test Circuits for Logic

During the earlier part of the course, we have used the high voltage (5 volts) to represent the value "1", and the low voltage (0 volt for GND) to represent the value "0". This is called the positive logic convention. However, sometimes it is useful to have the low voltage represent "1", and the high voltage represent "0". This is called the negative logic convention. When we used both positive and negative logic conventions in a single circuit, this is called mixed logic. Mixed logic has the advantage of separating the mathematics used in defining circuits from the actual implementation. The mathematics relies on mathematical operations and the numbers {0,1}. The physical implementation relies on actual circuits and the voltages {L,H}.

To test circuits, to check if they are operating properly or not, it is useful to have "probes" that convert the voltage behavior to the mathematical meaning of the voltages. We sometimes call the mathematical meaning the logic. From the preceding experiment, you should see that LED 1 can indicate a logic value for signals under the positive logic convention. You will use the LED 1 circuit as a logic probe for positive logic signals. (LED 1 will also double as a voltage probe). Likewise, LED 2 can indicate the logic value for signals under the negative logic convention. You will use the LED 2 circuit as a logic probe for negative logic signals.

Similarly for the switches, you should see that A1 corresponds to the logic value for switch A under the positive logic convention and A2 corresponds to the logic value of switch A under the negative logic convention. We denote the positive and negative logic values for A by A.H and A.L., respectively, where ".H" and ".L" indicate positive and negative logic. This is shown in parenthesis in Figure 2.c.

4.4 Directional Lights Circuit

Task 5: The circuit that you will build is shown in Figure 2.d. It is composed of the following parts:

If you have not already done so, do the LogicWorks Design and Simulation discussed in the Prelab.  Have the TA check your circuit before proceeding.  Before demonstrating to the TA, have the appropriate binary probes, switches, and clock generators attached to the circuit.

Hardware Construction of Circuit:  You will program a 2732 EPROM.  Using your HEX file, program your 2732 EPROM using the PROM programmer (or sometimes called a PROM "burner"). The TA will help you to do this.   Configure the 2732 so that it behaves as the combinational circuit with the appropriate truth table.  Note that configuration here means to ground the high address inputs.  Test the configured EPROM.

Attach the 2732 to a 74175 circuit, signal generator, LEDs, and switches as shown in Figure 2.d (actually the figure is out of date with a 2716 EPROM rather than a 2732 but you should get the idea.  Also note that the Vpp should be set to 0 too.  Check the 2732 data sheet for the appropriate pin numbers.).  If you have any question, talk to the TA.

Before running and testing your circuit, have the TA check it. The TA will show you how this operate the signal generator. Run the clock at a sufficiently slow speed to clearly observer the outputs. If your circuit does not work, ask your TA for some tips on how to debug digital circuits. If you have any problems getting the circuit to work, document them in your write up.

Build your circuit on your protoboard. When you are ready to run your circuit, have the TA check it.


5. What to turn in for this lab

You need to complete the following:

  1. If you haven't done so already, sign and turn in your Safety Release Form.
  2. Complete each task in the Experiment section and answer all questions in the report.
  3. Show TA your working version of the Logic Probes and Switches that you built on your protoboard.
  4. Show TA your working version of the Directional Lights Circuit.
  5. Write the lab report in the format specified in the course syllabus. Turn in your report at the beginning of the following lab session.