Experiment 2 COEN 212 PDF

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Lab Exp 2...

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Experiment 2 – Bench #18 COEN212-UM-X Combinational Logic Circuit Design

“I certify that this submission is my original work and meets the faculty’s demands of originality.”

Tariq Ahmed Khan ID# 26438407 Date performed: 2017-02-06 Date Submitted: 2017-02-27

Objectives The main objective of this lab is to gain experience in connecting digital circuits on a breadboard, esp. of a 2-bit multiplier, and to also implement modular designs from our combinational logic circuits.

Introduction Logic circuits can either be combinational or in order. A 2-bit multiplier, as seen in the experiment is a combinational logical circuit that receives 2 inputs and then multiplies these values to an output of a 4bit number. A combinational circuit in general responds to the input and then creates an output, it does this while transforming binary information from the input to the output through using logic gates. Therefore, by using truth tables we can check the input values and the output values of such a type of circuit. We can express a combinational circuit using a Boolean function. Modular design is used to make it easier for the construction of large and complicated circuits as well as debugging errors when constructing such circuits. Using modular design, we can break down the complicated circuit into smaller blocks that can be tested separately for debugging any errors.

Results & Discussion 2 – Bit Multiplier Inputs A1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1

A0 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1

B1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1

Outputs B0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

P3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

P2 0 0 0 0 0 0 0 0 0 0 1 1 0 0 1 0

P1 0 0 0 0 0 0 1 1 0 1 0 1 0 1 1 0

Table 2.1 For the 2-Bit Multiplier circuit, my results were not correct. The circuit I designed was complex and not

P0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 1

wired properly. Through out the lab, I revised and re-wired my circuit but I could still not get the correct output. Because of this, most of the time I spent in debugging my circuit so to get the correct output values. I had wires and a lot of wires all over the place, it was confusing at one point. Modular design teaches us to have efficient circuit design to avoid such tangled-up circuits.

For the second part, I did not have time to complete it (Fig. 2.1 a condensed combinational logic design). If I did, I would have made sure to construct it as simple and efficient as I could, following modularity with caution for each output bit of the 2-bit so to ensure that if one circuit is not functional, the others will not be affected. Q1: Describe in your own words the purpose of the modular design. Why do we break down circuits into modules and design them independently? The purpose of the modular design is to make it easier for us to find our mistakes and also shorten the amount of time we take to debug those mistakes. The modular design states that we break down complex circuits into simpler modules to avoid problems, it allows us to test each module as one and therefore checking for problems in the whole circuit is troublesome and long, especially in the case of a 2-bit multiplier logic circuit. Because the modular design allows us to debug only those modules that are causing the problems and not affecting other modules, we save a lot of time and worry as compare to dealing with the logic circuit by itself. Q2: The circuit in Figure 2.1 is a “condensed” design for a 2-bit multiplier. What are the advantages and disadvantages between the circuit that you have designed and the one in Figure 2.1? In your opinion, which design is better and why? Figure 2.1 logic circuit is a condensed design that has not been minimized and the outputs share common sum or product expressions. An advantage this circuit had was that it used fewer integrated circuits than mine, and because of that I had more problems during the lab with my circuit design. A lot

of wiring and a lot of debugging I had to do on my part with my errors.

Conclusion In conclusion, I made a lot of mistakes when it came to building the right circuit design for the lab. I am not happy with my results since they did not meet the truth table values for the 2-bit multiplier logical circuit. For next time, I need to properly construct my circuit per modular design to help with debugging and with the time. Time is key, because I lost a lot of time debugging, reconstructing, replacing wires during the experiment and as result I could not do the second part of the lab. I have learned that it is important to properly draw logic circuits for a successful outcome and for time’s sake....