Project Report

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School

Northern Virginia Community College *

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150

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Electrical Engineering

Date

Apr 3, 2024

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Objective The objective of Learning Experience B was to design a digital circuit the takes in four- bit values as inputs and sends out seven-bit values as the outputs to drive a seven-segment LED display. This learning experience involves designing a character set, encoding the characters into a binary code, implementing the logic circuit to decode the binary code, and finally, simulating and implementing the driver circuits on the DE10-Lite Board. After completing this learning experience, I will be able to design, simulate, and d implement a multiple-output combinational logic circuit from a specification. Requirements and Constraints The requirements of this learning experience are that my character set must have nine to thirteen characters. Every segment of the LED must light up at least once and must be dark at least once. I also can not repeat characters. I must assign unique characters four-bit binary code to each character. Implement the logic circuit to decode the binary code and drive the seven- segment LED display. Another requirement is to test the circuit through simulation and implement it on the DE10-Lite Board. Design Approach I must design a character set that has to be displayed on the LED display. The characters in the character set must be unique. So, I assigned a four-bit binary to each character in the set. Then I designed a logic circuit to decode the binary codes and drive them to the LED display. I also designed k-maps for each of the seven outputs, then made sum of products equations for each of the k-maps. Then I designed a Verilog code from the sum of products equations. After that I ran the Verilog code through waveform to verify the outputs of the code. Equations Derived To get my equations I first set up a table with every possible input. Then I made k-maps for each of the inputs and made a sum of products for each of the outputs. I did this to minimize the logic of the circuit. I made sure to keep the K-maps group as low as possible. Then I used the sum of products equation to develop a logic circuit using NOT, AND, and OR gates. Then I decided to use NAND gates to further reduce the circuit. Doing this reduces the amount of the overall number of transistors used in the circuit. Before the switch to NAND gates the original circuit used about 143 transistors. After the switch the circuit used 106 transistors. I also made sure that the design was combinational. ABCD 0 1 2 3 4 5 6 0000 1 0 0 0 0 1 1

0001 x x x x x x x 0010 0 1 0 0 1 0 1 0011 x x x x x x x 0100 1 1 0 0 0 1 0 0101 0 0 0 1 0 0 0 0110 0 0 1 0 0 0 1 0111 x x x x x x x 1000 x x x x x x x 1001 x x x x x x x 1010 0 0 0 1 1 0 1 1011 x x x x x x x 1100 0 0 1 0 0 1 1 1101 0 0 0 1 1 0 0 1110 0 0 1 0 0 0 0 1111 1 1 0 0 0 0 1 Output [0] AB\CD 00 01 11 10 00 1 x x 0 01 1 0 x 0 11 0 0 1 0 10 x x x 0 0 = A’C’D’ + CD Output [1] AB\CD 00 01 11 10 00 0 x x 1 01 1 0 x 0 11 0 0 1 0 10 x x x 0 1 = CD + A’BC’D’ + A’B’C’ Output [2] AB\CD 00 01 11 10 00 0 x x 0 01 0 0 x 1 11 1 0 0 1 10 x x x 0 2 = ABD’ + BCD’ Output [3]

AB\CD 00 01 11 10 00 0 x x 0 01 0 1 x 0 11 0 1 0 0 10 x x x 1 3 = AB’ + C’D Output [4] AB\CD 00 01 11 10 00 0 x x 1 01 0 0 x 0 11 0 1 0 0 10 x x x 1 4 = B’C + AC’D Output [5] AB\CD 00 01 11 10 00 1 x x 0 01 1 0 x 0 11 1 0 0 0 10 x x x 0 5 = C’D’ Output [6] AB\CD 00 01 11 10 00 1 x x 1 01 0 0 x 1 11 1 0 1 0 10 x x x 1 6 = B’ + A’C + CD + AC’D’ NOT 4 8 2 input AND 6 36 3 input AND 6 48 4 input AND 1 10 2 input OR 4 24 3input OR 1 8 4 input OR 1 10 Transistor count 143 NOT 4 8

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2 input NAND 10 40 3 input NAND 7 42 4 input NAND 2 16 Transistor count 106 Simulation Results I simulated the logic circuit through the waveform to verify that the circuit made the correct outputs corresponding to the binary inputs. I verified if the simulation applied all possible valid inputs. Then I corrected any behaviors that did not match the desired behavior of the circuit. Evaluation of the Implementation I implemented the circuit on to the DE10-Lite Board. I tested my character sets through the circuit by using the switches on the board to make sure I had thirteen unique characters. I verified the characters by corresponding the input codes to what was displayed on the LED. The design met the requirements, because I ensured that each character in the set had their own binary code and displayed correctly on the LED display. I made sure I performed the technology mapping efficiently to minimize the circuit by reducing the transistor count for better

implementation. The simulation results corresponded with the design of the circuit for each of the valid combinations. Conclusion This learning experience gave me great experience in designing, simulating, and implementing a circuit that has multiple outputs and is combinational. By following the requirements and constraints, I was able to design a character set, use technology mapping, create a driver circuit, and verify functionality of the circuit through simulation. This learning experience provided me with a better understanding of circuits, how circuits work and their applications.