📘 Digital Electronics & Microprocessor 8085 — Important Questions (Unit-wise)

🎓 Course: B.Sc Computer Science / BCA / B.Sc Electronics
📚 Subject: Digital Electronics & Microprocessor 8085
🗓️ Year: III Year
📝 Semester: VI Semester

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📖 Introduction

Digital Electronics and Microprocessor 8085 is one of the most important subjects for Computer Science, Electronics, and BCA students. This subject covers number systems, Boolean algebra, logic gates, combinational circuits, flip-flops, counters, memory devices, and the architecture of the 8085 microprocessor.

For semester examinations, students should focus mainly on important theory questions, truth tables, circuit diagrams, and 8085 assembly language programs. The following unit-wise important questions are prepared based on previous year university examination patterns.

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🔷 UNIT I: Number Systems, Boolean Algebra & Logic Gates

1. Explain the four types of number systems (Binary, Decimal, Octal, Hexadecimal) with examples. How are conversions performed between them?
2. What are BCD, Gray, and Excess-3 codes? Explain code conversions with examples.
3. Explain binary addition and binary subtraction using 1's complement and 2's complement methods with examples.
4. State and prove De Morgan's theorems. How are they applied in logic simplification?
5. What are universal logic gates? Explain how NAND and NOR gates can be used to realize all basic logic gates.
6. Explain SOP (Sum of Products) and POS (Product of Sums) standard forms of Boolean expressions.
7. Minimize the following Boolean expressions using Karnaugh Map (K-Map) for 3 and 4 variables.
8. State and explain the fundamental Boolean laws with examples.

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🔷 UNIT II: Combinational Circuits

1. Draw the circuit, truth table, and Boolean expressions for a Half Adder and Full Adder.
2. Explain Half Subtractor and Full Subtractor with truth tables and logic diagrams.
3. What is a Parallel Binary Adder? Explain its working with a neat diagram.
4. Explain the working of a 4:1 Multiplexer and 1:4 Demultiplexer with truth tables and circuit diagrams.
5. What is the difference between a Multiplexer and a Demultiplexer? Explain with applications.
6. Explain 8-line to 3-line Encoder and 3-line to 8-line Decoder with truth tables.
7. What is a Magnitude Comparator? Explain its design and operation.
8. Explain BCD to Seven Segment Decoder with a truth table and logic diagram.

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🔷 UNIT III: Flip-Flops, Registers & Counters

1. Explain the construction and working of RS Flip-Flop using NAND gates and NOR gates. Give its truth table.
2. What is a JK Flip-Flop? How does it overcome the drawbacks of RS Flip-Flop? Explain with truth table.
3. Explain T and D type flip-flops with truth tables and circuit diagrams.
4. What is a Master-Slave Flip-Flop? Explain its working and advantages.
5. Explain Serial-In Serial-Out (SISO) and Parallel-In Parallel-Out (PIPO) shift registers with diagrams.
6. What is an Asynchronous Counter? Design Mod-8 and Mod-10 counters with circuit diagrams.
7. Explain synchronous counters, ring counters, and up-down counters with neat diagrams.
8. Explain the working of A/D (Analog-to-Digital) and D/A (Digital-to-Analog) converters.

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🔷 UNIT IV: Memory & Logic Families

1. Explain ROM and its types: PROM, EPROM, EEPROM, and EAROM with differences and applications.
2. Compare Static RAM (SRAM) and Dynamic RAM (DRAM) with respect to structure, speed, and applications.
3. What are IC logic families? Compare RTL, DTL, and TTL logic families.
4. Explain CMOS NAND gate, NOR gate, and CMOS Inverter with circuit diagrams and working.
5. What is a Programmable Logic Array (PLA)? Explain with a block diagram and example.
6. What is Programmable Array Logic (PAL)? How does it differ from PLA?
7. Describe the general memory operations and classification of memory (Primary and Secondary).

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🔷 UNIT V: 8085 Microprocessor

1. What is a microprocessor? Explain the block diagram and basic operations of a microprocessor.
2. Explain the pin configuration of the 8085 microprocessor with a neat diagram.
3. What are Flags in 8085? Explain all five flags (Sign, Zero, Auxiliary Carry, Parity, Carry) with examples.
4. Explain the general-purpose and special-purpose registers of the 8085 microprocessor.
5. What are interrupts in 8085? Explain all types of interrupts and their priority order.
6. Describe the addressing modes of 8085 with suitable examples for each mode.
7. Classify the instruction set of 8085 into different groups (data transfer, arithmetic, logical, branching) with examples.
8. Write 8085 Assembly Language Programs for:
   • (a) Addition of two 8-bit numbers
   • (b) Subtraction of two 8-bit numbers
   • (c) Multiplication of two 8-bit numbers
   • (d) Division of two 8-bit numbers

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⭐ Most Frequently Asked Exam Topics

• K-Map Simplification
• Full Adder & Full Subtractor
• JK Flip-Flop
• Synchronous and Asynchronous Counters
• RAM and ROM Differences
• CMOS Logic Gates
• 8085 Addressing Modes
• Interrupts in 8085
• 8085 Assembly Language Programs

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📝 Preparation Tips for Students

• Practice truth tables and logic gate diagrams regularly.
• Understand Boolean algebra laws and K-Map simplification techniques.
• Focus on flip-flops, counters, and register operations.
• Revise memory classification and logic family comparisons carefully.
• Practice 8085 assembly language programs repeatedly for better understanding.
• Study previous year university question papers for better exam preparation.

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📌 Conclusion

These unit-wise important questions for Digital Electronics & Microprocessor 8085 will help students prepare effectively for semester examinations and university exams. Students are advised to concentrate more on circuit diagrams, truth tables, Boolean simplification, counters, memory concepts, and 8085 programming topics for scoring better marks.

Regular revision and problem-solving practice can improve conceptual understanding and exam performance significantly.

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💡 Tip: Questions on K-Map simplification (Unit I), Full Adder/Subtractor (Unit II), JK Flip-Flop & Counters (Unit III), RAM/ROM types (Unit IV), and 8085 Assembly Programs (Unit V) are the most frequently examined topics across all units.

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⚠️ Disclaimer

The important questions provided in this post are prepared only for educational and exam preparation purposes. These questions are collected and organized based on previous year university examination patterns, syllabus analysis, and commonly repeated topics.

MH Educational Blog does not guarantee that the same questions will appear in the upcoming examinations. Students are advised to study all units thoroughly and refer to their official syllabus, textbooks, class notes, and university materials for complete preparation.

All trademarks, course names, and educational references belong to their respective owners and institutions.

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