Microprocessors and Microcontroller Lab viva Questions with Answers:

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1.What is a Microprocessor?

It is a CPU fabricated on a single chip, program-controlled device, which fetches the instructions from memory, decodes and executes the instructions.

2. Define bit, byte and word.

Bit is either 0 or 1.

Byte is group of 8 bits.

Word is group of 16 bits.

3.What are the different functional units in 8086?

2 units-Bus Interface Unit (BIU) and Execution unit (EU)

4. What is the function of BIU ?

It is used to generate the 20-bit physical address and is responsible for performing all external bus operations.

5. What is the function of EU?

Execution Unit receives program codes and data from BIU, executes these instructions and store the result.

6. What is the maximum size of segment in 8086 microprocessor?

 64KB.

7. What is general purpose registers in 8086?

There are 4 general purpose registers are there.

AX-ACCUMULATOR

 BX- BASE

CX- COUNT

DX-DATA (Extended accumulator)

8. What are the functions of General purpose Registers?

AX register as 16-bit accumulator, stores all arithmetic and logical operation's results.

BX register is used as an offset address Storage.

CX register is used as counter. Especially used in loop, shift, rotate instructions.

DX register is used in port operations (IN and OUT)

9. What is special purpose registers in 8086?

CS- CODE SEGMENT

DS-DATA SEGMENT

ES-EXTRA SEGMENT

SS-STACK SEGMENT

BP-BASE POINTER

IP-INSTRUCTION POINTER

SP- STACK POINTER

SI-SOURCE INDEX

DI-DESTINATION INDEX

FLAG REGISTER

10. What are the functions of base Registers?

CS stores program code,

DS stores data

ES sores extra data

SS stores stack data.

11. Name the pin in 8086 microprocessor that is used for selecting mode of operation?

29^th pin-MN/MX'

If MN/MX'=0 then maximum mode is selected.

MN/MX'=1 then minimum mode is selected.

12. What is Segment address in 8086?

The part of the segment starting address stored in a segment register is called the segment address.

13. What are the flags in 8086?

In 8086, 9 flags are there. Out of 9, 6 are conditional (status) flags and 3 control flags.

Conditional (status) flags:

Carry flag (CF), Parity flag (PF), Auxiliary carry flag (CF), Zero flag (ZF), Overflow flag (OF),  and Sign flag(SF)

Control flags:

Trap flag (TF), Direction flag (DF), Interrupt flag (IF),

14. What is Tri-state logic?

Three Logic Levels are used and they are High (logic 1), Low(logic 0), High impedance(Z) state. The high and low are normal logic levels & high impedance state is electrical open circuit conditions.

15. What is system bus?

Group of address, data and control buses.

Address bus:  carry the Address to the memory to fetch either Instruction or Data.

Data bus:  carry the Data from the memory.

Control bus: carry the Control signals like RD/WR, reset, ready etc.

16. What is the difference between Maskable interrupts and Non-Maskable interrupts?

An interrupt that can be turned off by the programmer is known as Maskable interrupt.

An interrupt which can be never be turned off (i.e. disabled) is known as Non-Maskable interrupt.

17. What are the different types of Addressing Modes?

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

1 Immediate:-The Immediate data is a part of instruction.

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.

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.

18. What is baud rate?

The baud rate is the rate at which the serial data are transmitted. Units- symbols per second.

19. What is a port?

The port is a buffered I/O, which is used to hold the data transmitted from the processor to I/O device or vice-versa.

20. What is 8255?

It is PPI- Programmable Peripheral Interface. it is used to connect I/O devices to microprocessor and supports parallel communication.

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