Question 1

Explain the role of DMA controller with neat diagram?

Accepted Answer

The DMA Controller physically bypasses the CPU to facilitate ultra-high-speed, direct data transfers between memory and I/O peripherals.

Question 2

What is the role of accumulator in microprocessor?

Accepted Answer

The Accumulator (Register A) is the primary 8-bit working register universally mandated for all arithmetic and logical operations.

Question 3

Define general purpose registers.

Accepted Answer

General purpose registers are internal, high-speed SRAM memory cells (B, C, D, E, H, L) used for temporary data storage.

Question 4

Why AD0 and AD7 lines are multiplexed?

Accepted Answer

AD0-AD7 are physically multiplexed to drastically reduce the total pin count of the IC, saving silicon real estate.

Question 5

What is the use of ALE signal?

Accepted Answer

The ALE (Address Latch Enable) signal is a critical timing pulse used to demultiplex the shared AD0-AD7 lines.

Question 6

Define Instruction and instruction set.

Accepted Answer

An instruction is a binary command, and the instruction set is the complete vocabulary of commands the CPU understands.

Question 7

List some technical features of 8085 microprocessor?

Accepted Answer

The 8085 is an 8-bit, 40-pin NMOS microprocessor operating at 3 MHz with a 16-bit address bus.

Question 8

What do you mean by input port and output port?

Accepted Answer

Input/Output ports are hardware interfaces allowing the microprocessor to communicate with the external physical world.

Question 9

What is the role of Instruction Register in 8085 microprocessor?

Accepted Answer

The Instruction Register securely holds the fetched opcode while the internal decoder mathematically translates it.

Question 10

What is the role of stack pointer (SP) and program counter (PC)?

Accepted Answer

The PC tracks the memory address of the next instruction, while the SP manages the LIFO memory stack.

Question 11

Draw and explain the pin diagram of 8085 µP

Accepted Answer

A rigorous structural classification of the 8085 microprocessor's 40 pins, organizing them into power, clock, address/data buses, advanced control signals, and interrupt management groups.

Question 12

Explain various flags available in 8085 µP.

Accepted Answer

A comprehensive logical analysis of the 8085's 8-bit Flag Register, detailing the precise mathematical conditions that trigger the Sign, Zero, Auxiliary Carry, Parity, and main Carry flags.

Question 13

Explain the different types of buses in 8085 µP with neat diagram.

Accepted Answer

A detailed structural breakdown of the microprocessor System Bus architecture, defining the unidirectional Address Bus, bidirectional Data Bus, and the complex, unsynchronized Control Bus.

Question 14

What is Subroutine? Explain the use of stack in CALL and RETURN Instructions …

Accepted Answer

A deep architectural explanation of Subroutines, detailing how the CALL instruction mathematically pushes the return address onto the Stack, and how RETURN sequentially pops it back into the Program Counter.

Question 15

Differentiate between Microcontroller and Microprocessor.

Accepted Answer

A rigorous architectural comparison separating Microprocessors (CPU-only, highly expandable) from Microcontrollers (System-on-a-Chip, deeply embedded, highly integrated).

Question 16

Explain various addressing modes in 8085 µP with suitable examples.

Accepted Answer

An exhaustive breakdown of 8085 addressing modes, defining Immediate, Register, Direct, Indirect, and Implied modes with precise binary instruction examples.

Question 17

Explain the following opcodes with suitable examples: a) LDA b) ADD c) ADC d)…

Accepted Answer

A precise operational breakdown of five critical 8085 opcodes (LDA, ADD, ADC, SHLD, MVI), detailing their data flow, addressing modes, and flag register impacts.

Question 18

How will you demultiplex the address and data bus in 8085 µP? How can you int…

Accepted Answer

A technical hardware synthesis detailing the exact latch circuitry required to demultiplex AD0-AD7 using the ALE signal, followed by a precise address decoding strategy to interface a 1KB RAM chip.

Question 19

Explain the architecture of 8251 (USART) and explain the components.

Accepted Answer

A detailed structural analysis of the 8251 USART, breaking down its internal architecture into the Transmitter, Receiver, Modem Control, and Read/Write logic sections for robust serial communication.

Question 20

Draw the architecture diagram of 8085 µP and explain the components.

Accepted Answer

A deep internal architectural breakdown of the 8085 microprocessor, detailing the ALU, Register Array, Instruction Decoder, and the massive Timing and Control Unit.

Question 21

Explain interrupts of 8085 µP in detail.

Accepted Answer

An exhaustive analysis of the 8085 interrupt architecture, rigidly categorizing the five hardware interrupts by vector address, maskability, and absolute priority (TRAP to INTR).

Question 22

Write an assembly language program to add two 8-bit numbers with carry.

Accepted Answer

A fully functional, deeply commented 8085 assembly language program specifically engineered to add two 8-bit numbers and successfully capture any resulting 16-bit carry overflow.

Question 23

Explain 8255 programmable peripheral interface in detail.

Accepted Answer

A rigorous technical breakdown of the 8255 Programmable Peripheral Interface, exploring its three 8-bit I/O ports and detailing its operational modes (BSR, I/O Mode 0, 1, and 2).

Question 24

Draw the timing diagram of the instruction MVI A, 32H.

Accepted Answer

A precise, clock-by-clock derivation of the timing diagram for the MVI A, 32H instruction, analyzing the 4-T state Opcode Fetch cycle and the subsequent 3-T state Memory Read cycle.

Question 25

Write short note on any 2 of the following: a) Memory in 8085 µP b) RIM and S…

Accepted Answer

A concise technical exploration covering the 8085 memory map constraints, the hardware-level programming of RIM/SIM maskable interrupts, and the software logic required to construct delay counters.

Microprocessor and Microcontroller