ROM,PROM and EPROM
ROM, PROM and EPROM
ROM (Read Only Memory) is a non-volatile memory that stores permanent data and instructions. The data is written during manufacturing and cannot be modified later. It is mainly used to store firmware such as the booting program of a computer.
PROM (Programmable Read Only Memory) is also non-volatile but differs from ROM in that it is initially blank. The user can program it once using a special device. After programming, the data becomes permanent and cannot be erased or altered.
EPROM (Erasable Programmable Read Only Memory) is an advanced type of PROM that allows data to be erased and reprogrammed multiple times. The stored data can be erased by exposing the chip to ultraviolet (UV) light, after which it can be reused.
| Feature | ROM | PROM | EPROM |
|---|---|---|---|
| Full Form | Read Only Memory | Programmable ROM | Erasable Programmable ROM |
| Nature | Permanent | Programmable once | Reusable |
| Programming | Manufacturer | User (once) | User (multiple times) |
| Erasing | Not possible | Not possible | UV Light |
| Usage | Firmware | Custom programming | Testing & development |
ROM stores fixed data, PROM allows one-time programming, and EPROM allows multiple reprogramming after erasing.
Spontaneous Vs Simulated Emission of Radiation
Spontaneous vs Stimulated Emission
In atomic physics, electrons occupy discrete energy levels. Let E₁ be the ground state and E₂ be the excited state. When electrons transition between these levels, energy is either absorbed or emitted as photons. The emission of light occurs in two distinct ways: Spontaneous Emission and Stimulated Emission.
Spontaneous Emission
Spontaneous emission is the natural, unforced process by which an excited atom returns to its stable ground state.
- Mechanism: An electron is initially in the excited state E₂.Since higher energy states are unstable, the electron naturally drops to the lower energy state E₁ after a very short lifetime (typically 10⁻⁸ s).
-
The energy difference is released as a photon according to the equation:
ΔE = E₂ − E₁ = hν
-
Characteristics:
- Randomness: The exact time of emission and the direction of the emitted photon are completely random.
- Incoherence:Because millions of atoms emit photons independently at different times and in different directions, the resulting light waves are out of phase.
Stimulated Emission
Stimulated emission is the artificial, forced process of emission triggered by an external photon. This is the fundamental principle behind LASER operation.
- Mechanism: An electron is already in the excited state (E₂). An incident external photon, having an exact energy of hν=E₂−E₁, interacts with the excited atom.
- Energy Released: This interaction forces the electron to drop to the ground state (E₁) prematurely. As it drops, it releases a photon.
-
Characteristics:
- Multiplication: The process starts with one incident photon and ends up with two photons (the incident one + the newly emitted one)
- Coherence: start with one incident photon and end up with two photons (the incident one + the newly emitted one)
Key Differences
| Parameter | Spontaneous Emission | Stimulated Emission |
|---|---|---|
| Trigger mechanism | No external trigger required; happens naturally. | Requires an external incident photon to trigger the drop. |
| Photon Output | One photon emitted per transition. | Two identical photons exit for every one incident photon. |
| Phase Relationship | Photons are out of phase (Incoherent). | Photons are perfectly in phase (Coherent). |
| Directionality | Multi-directional and scattered. | Highly directional and parallel. |
| Light Intensity | Low intensity (e.g., standard light bulbs, neon). | Extremely high intensity (e.g., Lasers). |
| Thermodynamic State | Dominant in thermal equilibrium. | Requires Population Inversion (more atoms in $E_2$ than $E_1$). |
Simple 8085 Programs
8085 Assembly Language Programs - For Exam
1. 8-bit Addition
| Instruction | Explanation |
|---|---|
| LDA 2000H | Load first number into A |
| MOV B,A | Store in B |
| LDA 2001H | Load second number |
| ADD B | A = A + B |
| STA 2002H | Store result into memory |
| HLT | Stop execution |
2. 16-bit Addition
| Instruction | Explanation |
|---|---|
| LHLD 2000H | Load first 16-bit number into HL register pair |
| XCHG | Exchange HL with DE (store first number in DE) |
| LHLD 2002H | Load second 16-bit number into HL |
| DAD D | Add DE to HL (HL = HL + DE) |
| SHLD 2004H | Store result from HL into memory |
| HLT | Stop execution |
Fig: 8-bit and 16-bit Addition in 8085 Assembly Language
3. Subtraction (8-bit)
| Instruction | Explanation |
|---|---|
| LDA 2000H | Load first number into accumulator |
| MOV B,A | Copy first number into register B |
| LDA 2001H | Load second number into accumulator |
| SUB B | Subtract B from A (A = A - B) |
| STA 2002H | Store result in memory |
| HLT | Stop execution |
4. Multiplication
| Instruction | Explanation |
|---|---|
| MVI B,05H | Load multiplier into register B |
| MVI C,03H | Load multiplicand into register C |
| MVI A,00H | Clear accumulator |
| LOOP: ADD C | Add multiplicand to accumulator |
| DCR B | Decrement counter |
| JNZ LOOP | Repeat until B becomes zero |
| STA 2000H | Store result |
| HLT | Stop execution |
5. Division
| Instruction | Explanation |
|---|---|
| MVI B,03H | Load divisor into register B |
| LDA 2000H | Load dividend into accumulator |
| MVI C,00H | Initialize quotient to zero |
| LOOP: CMP B | Compare A with divisor |
| JC END | If A < B, jump to END |
| SUB B | Subtract divisor from A |
| INR C | Increment quotient |
| JMP LOOP | Repeat loop |
| END: STA 2001H | Store remainder |
| MOV A,C | Move quotient to accumulator |
| STA 2002H | Store quotient |
| HLT | Stop execution |
6. Largest Number
| Instruction | Explanation |
|---|---|
| LXI H,2000H | Load address of array |
| MOV C,M | Load count into register C |
| INX H | Point to first element |
| MOV A,M | Assume first element as largest |
| LOOP: INX H | Move to next element |
| CMP M | Compare with current largest |
| JNC SKIP | If A ≥ M skip update |
| MOV A,M | Update largest value |
| SKIP: DCR C | Decrease counter |
| JNZ LOOP | Repeat loop |
| STA 2100H | Store result |
| HLT | Stop execution |
7. Smallest Number
| Instruction | Explanation |
|---|---|
| LXI H,2000H | Load array address |
| MOV C,M | Load count |
| INX H | Point to first element |
| MOV A,M | Assume smallest |
| LOOP: INX H | Next element |
| CMP M | Compare values |
| JC SKIP | If A < M skip |
| MOV A,M | Update smallest |
| SKIP: DCR C | Decrease count |
| JNZ LOOP | Repeat |
| STA 2100H | Store result |
| HLT | Stop execution |
8. BCD → ASCII
| Instruction | Explanation |
|---|---|
| LDA 2000H | Load BCD value |
| ANI 0FH | Mask upper bits |
| ADI 30H | Add ASCII offset |
| STA 2001H | Store ASCII result |
| HLT | Stop execution |
9. ASCII → BCD
| Instruction | Explanation |
|---|---|
| LDA 2000H | Load ASCII value |
| SUI 30H | Subtract ASCII offset |
| STA 2001H | Store BCD result |
| HLT | Stop execution |
Consolidated Question Bank - DIGITAL ELECTRONICS AND MICROPROCESSOR 8085 - 23BPH6E1
Digital Electronics and Microprocessor 8085
COURSE CODE : 23BPH6E1
Question Bank
[Questions which are marked with a ★ at the end are doubly important,
marked with cyan color are important]
UNIT I – Number Systems & Logic Gates
Part A – Two Marks
1. Define Binary number system.
2. Define Octal number system.
3. Define Hexadecimal number system.
4. What is BCD code?
5. What is Gray code? Mention one use.
6. What is Excess-3 code?
7. Define code conversion.
8. What is 1’s complement?
9. What is 2’s complement?
10. Define 9’s complement.
11. Define 10’s complement.
12. What is binary addition?
13. What is binary subtraction?
14. State Boolean algebra laws.
15. State De Morgan’s theorems.
16. What are basic logic gates?
17. What are universal logic gates?
18. Define SOP representation.
19. Define POS representation.
20. What is Karnaugh Map?
21. Why NAND and NOR gates are called universal gates?★
Part B – Five Marks
1. Convert (101101) in binary to decimal.
2. Convert (347) in octal to binary.
3. Convert (9A) in hexadecimal to decimal.
4. Explain BCD code with an example.
5. Explain Gray code and its advantages.
6. Convert binary to Gray code - (10111010)
7. Convert Gray code to binary - (1110101101)
8. Perform binary subtraction using 1’s complement.
(11101101)-(11010101)
9. Perform binary subtraction using 2’s complement.
(110101101)-(100010101)
10. State and Prove De Morgan’s theorem.
11. Explain NAND gate with truth table.
12. Explain NOR gate with truth table.
Part C – Ten Marks
1. Explain number systems and conversions with examples.
2. Discuss BCD, Gray and Excess-3 codes with suitable examples.
3. Explain complements and subtraction methods.
4. Prove De Morgan’s theorems using truth tables.
5. Describe how NAND and NOR gates can be used as universal gates. ★
6. Explain SOP and POS representation of logic functions.
7. Simplify Boolean functions using 3-variable K-map.
8. Simplify Boolean functions using 4-variable K-map. [Problem]
UNIT II – Combinational Circuits
Part A – Two Marks
1. Define Half Adder.
2. Define Full Adder.
3. Define Half Subtractor.
4. Define Full Subtractor.
5. What is Parallel Binary Adder?
6. Define Magnitude Comparator.
7. What is Multiplexer?
8. What is Demultiplexer?
9. Define Encoder.
10. Define Decoder.
11. What is 4:1 Multiplexer?
12. What is 1:4 Demultiplexer?
13. Define 8-to-3 Encoder.
14. Define 3-to-8 Decoder.
15. What is BCD to seven segment decoder?
Part B – Five Marks
1. Explain Half Adder with logic diagram and truth table.
2. Explain Full Adder with logic diagram and truth table.
3. Explain Half Subtractor with truth table.
4. Explain Full Subtractor with logic diagram.
5. Discuss the working of Parallel Binary Adder.
6. Explain the function of Magnitude Comparator.
7. Explain 4:1 Multiplexer with truth table.
8. Explain 1:4 Demultiplexer with truth table.
9. Describe the working of 8-to-3 Encoder.
10. Describe the function of 3-to-8 Decoder with suitable diagrams.
11. Explain BCD to seven segment decoder.
Part C – Ten Marks
1. Explain Half Adder and Full Adder with diagrams and truth tables.
2. Explain the function of Half Subtractor and Full Subtractor.
3. Explain 4-bit parallel binary adder.
4. Explain Magnitude Comparator with logic circuit.
5. Explain Multiplexer and Demultiplexer with applications.
6. Explain Encoder and Decoder with diagrams.
7. Describe the operation of BCD to seven segment decoder with neat diagram and truth table
UNIT III – Sequential Circuits & Memory
Part A – Two Marks
1. Define Flip-Flop.
2. What is SR Flip-Flop?
3. What is JK Flip-Flop?
4. What is D Flip-Flop?
5. What is T Flip-Flop?
6. What is race around condition?
7. What is Master-Slave Flip-Flop?
8. Define Register.
9. Define SISO register.
10. Define PIPO register.
11. Define Counter.
12. Define MOD of counter.
13. Define Ring Counter.
14. What is ROM?
15. What is RAM?
Part B – Five Marks
1. Explain SR Flip-Flop with truth table and logic diagram.
2. Explain JK Flip-Flop with truth table and logic diagram.
3. Explain D Flip-Flop with truth table and logic diagram.
4. Explain T Flip-Flop with logic diagram.
5. Explain Master-Slave Flip-Flop with a suitable diagram and truth table.
6. Explain Serial In Serial Out register.
7. Explain Parallel In Parallel Out register.
8. Explain MOD-8 asynchronous counter.
9. Explain MOD-10 counter.
10. Explain Ring counter.
11. Explain Static RAM and Dynamic RAM.
12. Explain ROM, PROM and EPROM.
Part C – Ten Marks
1. Explain different types of flip-flops with truth tables.
2. Explain registers and shift registers.
3. Explain asynchronous counters with examples.
4. Explain synchronous counters.
5. Explain ring counter operation with state diagram.
6. Explain ROM, RAM and memory organization.
7. Explain EPROM, EEPROM and EAROM.
8. Explain RTL, DTL, TTL and CMOS logic families.
9. Explain CMOS NAND and NOR gates.
10. Explain Programmable Logic Devices (PLA and PAL).
UNIT IV – 8085 Microprocessor
Part A – Two Marks
1. Define Microprocessor.
2. What is 8085 microprocessor?
3. Define ALU.
4. What is an Accumulator?
5. What is Program Counter?
6. What is Stack Pointer?
7. Define PSW.
8. List 8085 flags.
9. Define interrupt.
10. List 8085 interrupts.
11. What addressing modes?
Part B – Five Marks
1. Describe the the architecture of 8085 with a neat diagram.★
2. Explain register organization.
3. Explain pin configuration of 8085 microprocessor IC with a diagram.
4. Explain PSW.
5. Explain interrupts and priority.
6. Explain various addressing modes of 8085 microprocessor.
7. Explain instruction set classification.
8. Write a program for 8-bit addition.
9. Write a program for 16-bit addition.
10. Write a program for 8-bit subtraction.
11. Write a program for multiplication of two 8 bit numbers
12. Write a program for division of two 8 bit numbers.
Part C – Ten Marks
1. Explain architecture of 8085 with diagram.
2. Explain the pin configuration of 8085 with a neat figure. ★
3. Explain instruction set classification.
4. Write program for 16-bit subtraction.
5. Write program to find largest number in array.
6. Write program to find smallest number in array.
7. Write program for BCD to ASCII conversion.
8. Write program for ASCII to BCD conversion.
UNIT V – I/O Interfaces
Part A – Two Marks
1. Define I/O interface.
2. What is 8251 USART?
3. Define serial communication.
4. Define parallel communication.
5. What is 8255 PPI?
6. What is 8253 timer?
7. What is 8279 keyboard controller?
8. What is DMA?
9. What is 8237 DMA controller?
Part B – Five Marks
1. Explain 8251 USART with neat diagrams.
2. Explain architecture of 8255.
3. Explain 8255 modes of operation.
4. Explain 8253 programmable timer.
5. Explain 8279 keyboard display controller.
6. Explain DMA transfer process.
Part C – Ten Marks
1. Explain architecture and operation of 8251 USART.
2. Explain architecture and modes of 8255 PPI.
3. Explain 8253 programmable interval timer.
4. Explain 8279 keyboard display controller.
5. Explain 8237 DMA controller.
6. Explain interfacing of 8255 with 8085.
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