EET380 Lab 2.4 Line Code Zachary Trotter

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EET380 Digital Communications I Instructor: Michael Blythe Campus: Lab 2.4 Line Codes Student Name(s): Zachary Trotter Click or tap here to enter text.

2 Contents Honor Pledge: .............................................................................................................................................. 2 Abstract ....................................................................................................................................................... 3 Introduction ................................................................................................................................................. 3 Procedures .................................................................................................................................................. 3 Conclusion ................................................................................................................................................. 17 References ................................................................................................................................................. 18 Honor Pledge: I pledge to support the Honor System of ECPI. I will refrain from any form of academic dishonesty or deception, such as cheating or plagiarism. I am aware that as a member of the academic community, it is my responsibility to turn in all suspected violators of the honor code. I understand that any failure on my part to support the Honor System will be turned over to a Judicial Review Board for determination. I will report to the Judicial Review Board hearing if summoned. Date: 12/15/2023 12/20/2023 Zach Trotter

3 Abstract In this lab we learn the basic construction and concepts for several different line codes and how those code react to each other in the forms of a logic analyzer Introduction Line codes are used in many communications and storage systems for the following reasons: - Removing DC level from code - Error detection and correction capability - Synchronization at receiver - Shaping the spectrum and limiting the bandwidth of the signal - Reduction of hardware complexity of receiver Line codes are used in many communication technologies such as TDM-carriers, Ethernet family, frame relay, ATM, optical wireless systems, etc. The main load of this lab is reviewing the digital systems and circuit course. It is suggested that before starting this lab, you review the functions of the basic logic gates such as AND, OR, NOT, NAND, NOR, XOR and XNOR. Besides the gates, you need to know the function of the latch and flip-flops. When the line codes are ternary such as bipolar RZ code, we use analog parts such as analog switch (4016 or 4066 - you already worked with it in Unit 1 – Labs 1 and 2). Procedures Part A. Non-return to zero (NRZ) NRZ codes probably are the simplest line codes. NRZ codes have almost the shortest bandwidth and do not provide synchronization information at receiver. NRZ codes have no error detection or correction capability. NRZ-L NRZ-L does not need any encoder or decoder, which means send a high pulse for a “1” and a LOW for a “0”. 12/20/2023 Zach Trotter

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4 NRZ-M Download the NRZ_M.ms11 file. You should be able to see the following circuit. In case you want to make the circuit by yourself, make sure to put random patterns on Word Generator (XWG1 in this circuit). As you see the encoder and decoder use the same clock because NRZ code does not provide synchronization for the receiver. Experiment A.1 : Run the simulation and look at the logic analyzer screen (double click on XLA1). Describe your observation briefly. 12/20/2023 Zach Trotter

5 The original data and the decoder output have the same logic they both go high and low at the same time for the same length of time, the output from the decoder does differ from the other two Snapshot: Place the snapshot of the Logic Analyzer here and add the name of each pulse stream to it. Please, crop the snapshot to fit it in the place properly. The Blue line is the original data, the brown line is encoder and the green is the decoder 12/20/2023 Zach Trotter

6 Activity-1: What you need to do now is to prepare the transition table or truth table of the NRZ-M code first to find out how the encoder and decoder work. Encoder Decoder B O P 1 0 0 1 1 1 0 1 0 1 0 1 B O G 1 0 0 1 1 1 0 1 1 1 0 0 NRZ-S Download the NRZ_S.ms11 file. You should be able to see the following circuit. In case you want to make the circuit by yourself, make sure to put random patterns on Word Generator (XWG1 in this circuit). As you see the encoder and decoder use the same clock because NRZ code does not provide synchronization for the receiver. 12/20/2023 Zach Trotter

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7 Experiment A.2 : Run the simulation and look at the logic analyzer screen (double click on XLA1). Describe your observation briefly. The original data and the decoder use the same clock so they go high and low at the same time. The Encoder data will only pulse when the original data transitions low if the original data is high then the encoder will stay high until the original data goes low, this should be because of the XNOR gate used at the encoder Snapshot: Place the snapshot of the Logic Analyzer here and add the name of each pulse stream to it. Please, crop the snapshot to fit it in the place properly. 12/20/2023 Zach Trotter

8 Red is the original data, Yellow is the encoder and Green is the decoder Activity-2: What you need to do now is to prepare the transition table or truth table of the NRZ-S code first to find out how the encoder and decoder work. Encoder Decoder B O Y B O G 1 1 1 12/20/2023 Zach Trotter

9 1 1 0 1 1 0 0 0 1 1 1 1 1 1 1 0 0 0 1 1 1 Bipolar NRZ codes: It is also possible to make Bipolar NRZ, which eliminated the average DC component from the line code. To do so, you need to use a comparator with non-zero level as shown below. The following circuit is an example of this comparator that you had in EET121. Be careful: 741 is a general purpose OpAmp which is mainly used for low frequency amplification. For comparator in digital systems, a comparator OpAmp with very good Slew-rate is suggested, otherwise you will observe glitches at the output. Bipolar to Unipolar: To convert Bipolar to Unipolar, the following diode circuit can be used. 12/20/2023 Zach Trotter

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10 Part B. Return to zero (RZ) RZ codes need twice bandwidth as much as NRZ codes need, however, as RZ codes provide a level of synchronization information, they might be considered. Unipolar NRZ Download the Unipolar_RZ.ms11 file. You should be able to see the following circuit. In case you want to make the circuit by yourself, make sure to put random patterns on Word Generator. 12/20/2023 Zach Trotter

11 Experiment B.1 : Run the simulation and look at the logic analyzer screen (double click on XLA1). Describe your observation briefly. The original data which comes from pin 0 on XWG1 and the decoder share the same clock so they both transition from high to low at the same time, the decoder signal only pulses when the original signal goes high if the original signal is low then the decoder does not pulse. This is do to the and gate located in the encoder. Snapshot: Place the snapshot of the Logic Analyzer here and add the name of each pulse stream to it. Please, crop the snapshot to fit it in the place properly. 12/20/2023 Zach Trotter

12 Since the original signal and the decoder share a color I will label them by pin number 3= original signal 5=encoder 6 = decoder Activity-3: What you need to do now is to prepare the transition table or truth table of the Unipolar RZ code first to find out how the encoder and decoder work. Encoder Decoder B O Y 1 1 1 1 1 0 0 0 0 B O R 1 1 1 1 0 0 0 1 1 1 0 0 12/20/2023 Zach Trotter

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13 1 0 0 Bipolar RZ: The difference between bipolar RZ and Unipolar is that bipolar RZ is a ternary code, while unipolar RZ is a binary code, which means in bipolar RZ, the line code has 3 voltage levels, unlike the 2 levels of unipolar RZ. For this reason, digital gates are not sufficient to create bipolar RZ. The following circuit shows how a simple comparator and an analog switch (4066) can be used to make bipolar RZ. As it was explained before, use the following simple circuit at receiver then use the same decoder which is used for unipolar RZ. 12/20/2023 Zach Trotter

14 Alternate Mark Inversion: AMI is complex line code to encode and to decode. For this reason, it is not discussed in this lab. Part C. Manchester code Manchester code is the code which is suggested in IEEE 802.3 for Ethernet. There are a few implications and implementations for Manchester code. In this lab, you will work with one of them. Download the Manchester.ms11 file. You should be able to see the following circuit. In case you want to make the circuit by yourself, make sure to put random patterns on Word Generator (XWG1 in this circuit). 12/20/2023 Zach Trotter

15 Experiment C.1 : Run the simulation and look at the logic analyzer screen (double click on XLA1). Describe your observation briefly. Much like the other circuits the original data and the decoder share the same clock so they go high and low at the same time. The encoder pluses at a constant rate until the original data transitions, at the transition from high to low or vise versa it will either stay high longer or stay low longer. Snapshot: Place the snapshot of the Logic Analyzer here and add the name of each pulse stream to it. Please, crop the snapshot to fit it in the place properly. Red is the original data, blue is the encoder and yellow is the decoder 12/20/2023 Zach Trotter

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16 12/20/2023 Zach Trotter

17 Activity-4: What you need to do now is to prepare the transition table or truth table of the Manchester code first to find out how the encoder and decoder work. Encoder Decoder B O BL 1 0 1 1 1 1 0 1 1 1 1 0 B O Y 1 0 0 1 1 1 0 1 1 1 1 1 Conclusion  Compare RZ codes with NRZ codes, briefly. o RZ Code: Divides each bit period into positive and negative pulses, ensuring regular transitions. Offers clearer 0s and 1s distinction but requires more bandwidth due to additional transitions. o NRZ Code: Maintains signal levels throughout bit periods without returning to zero within them. NRZ is more bandwidth- efficient than RZ but may face synchronization challenges in long bit sequences.  What is difference between binary and ternary codes? What kinds of circuits do you need for the ternary codes? Binary codes use a base-2 system with two symbols (0 and 1), while ternary codes use a base-3 system with three symbols to represent information. Ternary codes require circuits capable of handling three distinct logic levels, including ternary logic gates, arithmetic circuits, memory cells, and signal processing circuits specifically designed for processing and manipulating ternary signals. These circuits are more complex than their binary counterparts due to the increased number of logic levels.  Describe Manchester codes briefly. 12/20/2023 Zach Trotter

18 Manchester coding: It's a line coding method used in digital communication. Each bit is divided into two halves, with a transition at the midpoint representing the bit value. A high-to-low (or low-to-high) transition denotes a 1, and a low-to-high (or high-to-low) transition represents a 0. This self- clocking method aids in synchronization and provides inherent clock recovery. Manchester coding ensures a balanced spectrum and is commonly used in Ethernet and other systems where synchronization and data integrity are essential. References Frenzel, L. E. (2016). Principles of electronic communication systems . Mcgraw-Hill Education. 12/20/2023 Zach Trotter

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