Labs

Lab 7.1: Leggo my Logg-O

Logg-O Help

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The program upon which most of the exercises for this module are based, named Logg-O provides you with an automated "breadboard," a board upon which you can layout, hook together, and test out combinations of gates1. The program provides you with supplies of six different gates (AND, NAND, OR, NOR, NOT, AND XOR), as well as switches (which serve as input that you can set), clocks (which serve as inputs that toggle themselves between on and off), lights (which serve as output devices to show us the net effect of a circuit), and terminals for connecting wires together.

1pp. 240–241, 242

Clicking on the "hand" tool (at the bottom of the window) lets you drag elements from the supply bin onto the breadboard. You can position gates wherever you want them, and can move them at any time using the hand tool to drag them.

Gates are connected together using the "connection" tool (shaped like a wire with terminals on each end). The terminal(s) on the left side of a gate represent its inputs; those to its right are the outputs from the gate. Clicking and dragging from one terminal to another with the connection tool places a wire between the two elements involved. These wires can be cut, and gates deleted, using the "scissors" tool.

So, a simple circuit can be constructed as follows:

  1. Place switches (for now) on the board to serve as input devices.

  2. Place the desired gates on the board so that they can be connected as needed.

  3. Place lights on the board to serve as output devices.

Steps (1) - (3) are accomplished using the hand tool. Then, select the "connect" tool and

  1. connect the input switches to their terminals on one or more of the gates (a given switch can connect to more than one terminal),

  2. connect the gates together by connecting output terminals to input terminals, and

  3. connect the gate terminals that serve as circuit outputs to lights

Once a gate has been constructed in this manner, it can be tested as follows:

  1. Click on the "run" tool

  2. Set the input switches to be "on"> or "off", as desired.

  3. Observe the status of the lights, as the represent the output of the circuit. A light that is turned on represents a logical value of true; lights that are off, stand for logical false.

  1. Now, you are ready to use Logg-O. Design and test circuits that demonstrate the following: (Note that "T" stands for TRUE/ON, and "F" stands for FALSE/OFF)
    1. T AND F is F
    2. T AND T is T
    3. F OR T is T
    4. F OR F is F
    5. NOT T is F
    6. NOT F is T

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