Viva Questions and Answers in MP lab -1

1) What is Microprocessor?

A:- A Microprocessor is a multipurpose, programmable, clock-driven, register-based electronic

device that reads binary

Instructions from a storage device called memory, accepts binary data as input and processes the

data according to

Those instruction, and provides results as output.

2) What are the different types of Addressing Modes?

A:- There are 12 different types of Addressing Modes. They are:-

<1> Immediate:-The Immediate data is a part of instruction, and appears in the form of

successive bytes.

<2> Direct:-A 16-bit memory address (offset) is directly specified in the instruction as a part of

it.

<3> Register:-Data is stored in a register and it is referred using the particular register (except

IP).

<4> Register Indirect:-The address of the memory location which contains data or operand is

determined in an indirect way.

<5> Indexed:-offset of the operand is stored in one of the index registers.

<6> Register Relative:-The data is available at an effective address formed by adding an 8-bit or

16-bit displacement with the content of any one of the registers BX,BP,SI and DI in the default

(either DS or ES) segment.

<7> Based Indexed:-The effective address of the data is formed, in this addressing mode, by

adding content of a base register to the content of an index register.

<8> Relative Based Indexed:- The effective address is formed by adding an 8 or 16-bit

displacement with the sum of contents of any one of the base registers and any one of the index

registers, in the default segment.

<9> Intrasegment Direct Mode:-In this mode, the address to which the control is to bve

transferred lies in the segment in which the control transfer instruction lies and appears directly

in the instruction as an immediate displacement value.

<10> Intrasegment Indirect Mode:-In this mode, the displacement to which the control is to be

transferred, is in the same segment in which the control transfer instruction lies, but it is passed

to the instruction indirectly.

<11> Intersegment Direct:-In this mode, the address to which the control is to be transferred is in

a different segment.

<12> Intersegment Indirect:-In this mode, the address to which the control is to be transferred

lies in a different segment and it is passed to the instruction indirectly sequentially.

3) What are the General Data Registers & their uses?

A: - The Registers AX, BX,CX,DX are the general Purpose 16-bit registers. AX register as 16-

bit accumulator. BX register is used as an offset Storage.CX register is used as default or implied

counter.Dx register is used as an implicit operand or destination in case of a few instructions.

4) What are Segment Registers & their uses?

A:-There are 4 Segment Registers Code Segment (CS), Data Segment (DS), Extra Segment (ES)

& Stack Segment (SS) registers. CS is used for addressing memory location in code.DS is used

to points the data.ES refers to a segment which is essentially in another data segment.SS is used

for addressing stack segment of memory.

5) What are Flag registers?

A:-Divided into 2 parts:-Condition code or status flags and machine control flags.

S-Sign Flag:-Is to set when the result of any computation is negative.

Z-Zero Flag:-Is to set if the result of the computation or comparison performed by the previous

instruction is zero.

C-Carry Flag:-Is set when there is carry out of MSB in case of addition or a borrow in case of

subtraction.

T-Trap Flag:-Is set, the processor enters the single step execution mode.

I-Interrupt Flag:-Is set, the mask able interrupts are recognized by the CPU.

D-Direction Flag:-Is set for auto incrementing or auto decrementing mode in string manipulation

instructions.

AC-Auxiliary Carry Flag:-Is set if there is a carry from the lowest nibble during addition or

borrow for the lowest nibble.

O-Overflow Flag:-Is set if the result of a signed operation is large enough to be accommodated in

a destination register.

8085 microprocessor questions

1. What are the various registers in 8085? - Accumulator register, Temporary register, Instruction

register, Stack Pointer, Program Counter are the various registers in 8085 .

2. In 8085 name the 16 bit registers? - Stack pointer and Program counter all have 16 bits.

3. What are the various flags used in 8085? - Sign flag, Zero flag, Auxiliary flag, Parity flag,

Carry flag.

4. What is Stack Pointer? - Stack pointer is a special purpose 16-bit register in the

Microprocessor, which holds the address of the top of the stack.

5. What is Program counter? - Program counter holds the address of either the first byte of the

next instruction to be fetched for execution or the address of the next byte of a multi byte

instruction, which has not been completely fetched. In both the cases it gets incremented

automatically one by one as the instruction bytes get fetched. Also Program register keeps the

address of the next instruction.

6. Which Stack is used in 8085? - LIFO (Last in First Out) stack is used in 8085.In this type of

Stack the last stored information can be retrieved first.

7. What happens when HLT instruction is executed in processor? - The Micro Processor enters

into Halt-State and the buses are tri-stated.

8. What is meant by a bus? - A bus is a group of conducting lines that carries data, address, &

control signals.

9. What is Tri-state logic? - Three Logic Levels are used and they are High, Low, High

impedance state. The high and low are normal logic levels & high impedance state is electrical

open circuit conditions. Tri-state logic has a third line called enable line.

10. Give an example of one address microprocessor? - 8085 is a one address microprocessor.

11. In what way interrupts are classified in 8085? - In 8085 the interrupts are classified as

Hardware and Software interrupts.

12. What are Hardware interrupts? - TRAP, RST7.5, RST6.5, RST5.5, INTR.

13. What are Software interrupts? - RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7.

14. Which interrupt has the highest priority? - TRAP has the highest priority.

15. Name 5 different addressing modes? - Immediate, Direct, Register, Register indirect, implied

addressing modes.

16. How many interrupts are there in 8085? - There are 12 interrupts in 8085.

17. What is clock frequency for 8085? - 3 MHz is the maximum clock frequency for 8085.

18. What is the RST for the TRAP? - RST 4.5 is called as TRAP.

19. In 8085 which is called as High order / Low order Register? - Flag is called as Low order

register & Accumulator is called as High order Register.

20. What are input & output devices? - Keyboards, Floppy disk are the examples of input

devices. Printer, LED / LCD display, CRT Monitor are the examples of output devices.

21. Can an RC circuit be used as clock source for 8085? - Yes, it can be used, if an accurate

clock frequency is not required. Also, the component cost is low compared to LC or Crystal.

22. Why crystal is a preferred clock source? - Because of high stability, large Q (Quality Factor)

& the frequency that doesn’t drift with aging. Crystal is used as a clock source most of the times.

23. Which interrupt is not level-sensitive in 8085? - RST 7.5 is a raising edge-triggering

interrupt.

24. What does Quality factor mean? - The Quality factor is also defined, as Q. So it is a number,

which reflects the lossness of a circuit. Higher the Q, the lower are the losses.

25. What are level-triggering interrupt? - RST 6.5 & RST 5.5 are level-triggering interrupts.

X86 interview questions

these interview questions test the knowledge of x86 Intel architecture and 8086 microprocessor

specifically.

1. What is a Microprocessor? - Microprocessor is a program-controlled device, which fetches the

instructions from memory, decodes and executes the instructions. Most Micro Processor are

single- chip devices.

2. Give examples for 8 / 16 / 32 bit Microprocessor? - 8-bit Processor - 8085 / Z80 / 6800; 16-bit

Processor - 8086 / 68000 / Z8000; 32-bit Processor - 80386 / 80486.

3. Why 8085 processor is called an 8 bit processor? - Because 8085 processor has 8 bit ALU

(Arithmetic Logic Review). Similarly 8086 processor has 16 bit ALU.

4. What is 1st / 2nd / 3rd / 4th generation processor? - The processor made of PMOS / NMOS /

HMOS / HCMOS technology is called 1st / 2nd / 3rd / 4th generation processor, and it is made

up of 4 / 8 / 16 / 32 bits.

5. Define HCMOS? - High-density n- type Complementary Metal Oxide Silicon field effect

transistor.

6. What does microprocessor speed depend on? - The processing speed depends on DATA BUS

WIDTH.

7. Is the address bus unidirectional? - The address bus is unidirectional because the address

information is always given by the Micro Processor to address a memory location of an input /

output devices.

8. Is the data bus is Bi-directional? - The data bus is Bi-directional because the same bus is used

for transfer of data between Micro Processor and memory or input / output devices in both the

direction.

9. What is the disadvantage of microprocessor? - It has limitations on the size of data. Most

Microprocessor does not support floating-point operations.

10. What is the difference between microprocessor and microcontroller? - In Microprocessor

more op-codes, few bit handling instructions. But in Microcontroller: fewer op-codes, more bit

handling Instructions, and also it is defined as a device that includes micro processor, memory, &

input / output signal lines on a single chip.

11. What is meant by LATCH? - Latch is a D- type flip-flop used as a temporary storage device

controlled by a timing signal, which can store 0 or 1. The primary function of a Latch is data

storage. It is used in output devices such as LED, to hold the data for display.

12. Why does microprocessor contain ROM chips? - Microprocessor contain ROM chip because

it contain instructions to execute data.

13. What is the difference between primary & secondary storage device? - In primary storage

device the storage capacity is limited. It has a volatile memory. In secondary storage device the

storage capacity is larger. It is a nonvolatile memory. Primary devices are: RAM / ROM.

Secondary devices are: Floppy disc / Hard disk.

14. Difference between static and dynamic RAM? - Static RAM: No refreshing, 6 to 8 MOS

transistors are required to form one memory cell, Information stored as voltage level in a flip

flop. Dynamic RAM: Refreshed periodically, 3 to 4 transistors are required to form one memory

cell; Information is stored as a charge in the gate to substrate capacitance.

15. What is interrupt? - Interrupt is a signal send by external device to the processor so as to

request the processor to perform a particular work.

16. What is cache memory? - Cache memory is a small high-speed memory. It is used for

temporary storage of data & information between the main memory and the CPU (center

processing unit). The cache memory is only in RAM.

17. What is called “Scratch pad of computer”? - Cache Memory is scratch pad of computer.

18. Which transistor is used in each cell of EPROM? - Floating –gate Avalanche Injection MOS

(FAMOS) transistor is used in each cell of EPROM.

19. Differentiate between RAM and ROM? - RAM: Read / Write memory, High Speed, Volatile

Memory. ROM: Read only memory, Low Speed, Non Voliate Memory.

20. What is a compiler? - Compiler is used to translate the high-level language program into

machine code at a time. It doesn’t require special instruction to store in a memory, it stores

automatically. The Execution time is less compared to Interpreter.

21. Which processor structure is pipelined? - All x86 processors have pipelined structure.

22. What is flag? - Flag is a flip-flop used to store the information about the status of a processor

and the status of the instruction executed most recently

23.What is stack? - Stack is a portion of RAM used for saving the content of Program Counter

and general purpose registers.

24. Can ROM be used as stack? - ROM cannot be used as stack because it is not possible to write

to ROM.

25. What is NV-RAM? - Nonvolatile Read Write Memory also called Flash memory. It is also

known as shadow RAM.