ICS 331-L Project 2

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You will only get credit for this lab if the TA checks you off for the lab assignments listed below, and no later than Wednesday, September 17.

You may do this lab individually, if enough protoboards and chips are available, or in groups of up to four people. All team members must participate in the design and construction, and must be present for the evaluation.

The datasheet for all the circuits used in this lab are available from Texas Instruments.

De Morgan's Laws

For this exercise, you will use a voltmeter, power supply, and NOR gates (74LS02 or similar).

Build the following three circuits using only NOR gates:

  1. an inverter
  2. an AND gate
  3. an OR gate

You must design the circuits yourself, using De Morgan's laws where appropriate. Seven NOR gates should be sufficient to build all three circuits.

Once the circuits are built, check that they work using switches for inputs, and a voltmeter to check the output voltage. Once everything works, demonstrate this to the TA.

LEDs to show inputs and outputs

Place an LED in series with a 1KOhm resistor connected to Vcc, and connect the "lower" end of the LED to the output of a 74LS05 (or equivalent) inverter with open-collector output (open collector or open drain means the circuit connected to the output forms the top half of a voltage divider, and a transistor internal to the circuit forms the lower half). This LED will show the output of the circuit. Note that the LED will be on when the output is low, that is, when the input of the inverter is high.

Place another LED in series with a 1KOhm resistor. The LED is connected to ground, and the other end of the resistor is connected to to a switch (whose other end is connected to ground), to the input to the inverter, and to a 500-Ohm resistor to Vcc (since we do not have 500-Ohm resistors, create one by using two 1K-Ohm resistors in parallel). This LED will light when the switch is open (disconnected), so that the input to the inverter is high, and be dark when the switch is closed (connected), so that the input to the inverter is low.

This part of the lab is only for you to gain experience using LEDs and LED drivers. You do not need to get checked off by the TA for this part, but you will use your experience in the next section. The full circuit for this part of the lab is shown in the following diagram, where each resistor has a value of 1000 Ohm (1KOhm).

Controlled inverter

For this exercise, you will use 9 LEDs, 5 input switches, 4 XOR gates (74LS86 or similar), and 4 open-collector inverters (74LS05 or similar).
  1. build a 4-bit controlled inverter as explained in class.
  2. connect an LED and a switch as in the previous section to each of the 5 inputs (4 data inputs and one control input) to the controlled inverter.
  3. connect the 4 outputs of the controlled inverter to the input of 4 open-collector inverter drivers, and the output of the drivers to 4 LEDs, as in the previous section.
  4. be sure to make your circuit neat so it is clear which LEDs represent data inputs, the control inputs, and outputs
  5. bring your circuit to the TA and let him test your circuit to get credit for this part of the lab.