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Lab 1: Logic Simulation Basics

1) This lab introduces students to Logisim, an open-source digital circuit design software, to simulate basic logic gates like inverters. 2) Students are instructed to build a CMOS inverter in Logisim using transistors, power/ground components, and inputs/outputs. 3) The document provides step-by-step instructions to construct the inverter and observe its truth table functionality. Students are then asked to create a library of additional logic gates to implement full and multi-bit adders.

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Singam Setty S A Deshik
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288 views3 pages

Lab 1: Logic Simulation Basics

1) This lab introduces students to Logisim, an open-source digital circuit design software, to simulate basic logic gates like inverters. 2) Students are instructed to build a CMOS inverter in Logisim using transistors, power/ground components, and inputs/outputs. 3) The document provides step-by-step instructions to construct the inverter and observe its truth table functionality. Students are then asked to create a library of additional logic gates to implement full and multi-bit adders.

Uploaded by

Singam Setty S A Deshik
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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INDIAN INSTITUTE OF TECHNOLOGY PATNA

CS210-Computer Architecture

Lab 1: Logic simulation basics

In this lab, you will begin to familiarise yourself with Logisim and simulate some blocks. This
will help you learn more about logic, and build the fundamental components used in any digital
system.

Using Logisim

Logisim is a Java application, it can be obtained from http://sourceforge.net/projects/circuit/.

Simply download and run it (tutorial is available help->tutorial).

Exercise : Inverter (NOT gate)

To build a CMOS inverter, you will need the following Logisim components: • A power source.
• A ground. • A P-type transistor, facing south. • An N-type transistor, facing north. • A constant
generator, to provide an input value. • A probe to read the output value.

If you follow the steps below and build a circuit, you should end up with a working inverter.

1. Place a P-type transistor, facing south, on the drawing area.


2. Place an N-type transistor, facing north, below the P-type. You will notice the P-type has a
small round circle at its gate and a directional arrow pointing down, whilst the N-type has no
circle, and a directional arrow pointing up.
3. Now place a power component above the top transistor.
4. Next, place a ground component below the bottom transistor.
5. Place a constant component to the left of the transistors (or a pin input), this is equivalent to
the input A
6. Place a probe on the right of the circuit. This is equivalent to the output Z
7. Connect the components with wires
(see Figure)

Now, by clicking on the constant component and pressing either the 1 or 0 key on your
keyboard, (by clicking on the pin if you used a pin input ) , you can change the logic value that it
generates. At the same time, you should see the value at the probe change, in accordance with the
logic function NOT. If your circuit does not work as expected, make sure the components are
wired correctly, and that the type and orientation of your transistors are correct. If they are not
correct, you may see X at the output for a particular input value. Save your work before
continuing.
Fig: A CMOS inverter

Fig: A CMOS NAND GATE


Assignment:

1. Using the same approach for the gates shown, create a library of gates(NAND, NOR,
XOR, AND, OR, multiple input logic gates etc).
Using your own library implement a full adder and 2 bit adder and 4 bit adder.
(Design and simulate , verify the truth table). (100 points)

Submission:

Show your simulation to TAs. All circuits should be included in your record. Submit your
single library (roll_number.circ file) to the link below before 12 PM.

 https://u.pcloud.com/#page=puplink&code=E3WkZBqjQ39X3hz5RB1dfoXpPHfI9w9Xk 

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