This laboratory aims to get you familiar with basic logic gates and combinational circuit design. You will simplify the circuit that is explained below and draw the circuit using Logisim tool with the given gates.
- 74LS04 (Inverter)
- 74LS08 (AND)
- 74LS32 (OR)
3 Lab Work
In this assignment, you are expected to perform the operations described in the following section.
Suppose A and B are 2-bit binary input numbers and X and Y are 1-bit binary output numbers. A and B are represented with A1, A0, B1 and B0 bits respectively where A1 and B1 are the most significant bits and A0 and B0 are the least significant bits of the relevant number. Your circuit will take A and B as inputs and give the outputs X and Y with the following instructions:
PS: ⊕ stands for the XOR operation.
|A − B| stands for the absolute value of A minus B.
You have to use ”input pins” and ”output pins” for your inputs and outputs, respectively, from the Toolbar at the top of Logisim. Set their labels correctly using the following names. Please, only set “label” property of the “pin” objects, do not add a “label” object onto the Logisim canvas.
Input pins: A1, A0, B1, B0. Output pins: X, Y.
Each pin corresponds to a digit in a 2-bit binary number. If it is set, then the value of the digit is 1 if reset, then the value of the digit is 0.
3.2 Input Output Examples
- Suppose A1A0 = 00 and B1B0 = 10. In this case, A=0 and B=2 in decimal.
|A − B| = 2
Since |A − B| > 1 holds, the output X is 1.
- Suppose A1A0 = 10 and B1B0 = 01. In this case, A=2 and B=1 in decimal. |A − B| = 1
Since |A − B| > 1 does not hold, the output X is 0.
- Suppose A1A0 = 01 and B1B0 = 01. In this case, A=1 and B=1 in decimal. (A ∗ B) = 1
Since (A ∗ B) = 1 is not prime, the output Y is (A0 ⊕ B0) = (1 ⊕ 1) = 0 .
- Suppose A1A0 = 01 and B1B0 = 10. In this case, A=1 and B=2 in decimal. (A ∗ B) = 2
Since (A ∗ B) = 2 is prime, the output Y is 0.
4 Free Session
There will be a ”free session week” after the week which the lab is announced. You will have 2 hours in your free session slot. During the free session, you will try to build your circuit on a breadboard by using IC components, and you will practice how to handle possible problems related to physical circuit.
5 Demo Session
There will be a 2-hour-long ”demo session week” following the free session week. In demo session:
- You will take a short quiz about the logic concepts that involve the coverage of this lab.
- You will reconstruct your circuit on your breadboard.
- You will show that the circuit drawn in Logisim works as specified.