MICROPROCESSOR VIVA QUESTIONS AND ANSWERS
MICROPROCESSOR VIVA QUESTIONS AND ANSWERS
1. What is a Microprocessor?
Microprocessor is a CPU fabricated on a single chip, program-controlled device, which fetches
the instructions from memory, decodes and executes the instructions.
2. What is Instruction Set?
It is the set of the instructions that the Microprocessor can execute.
3. What is Bandwidth ?
The number of bits processed by the processor in a single instruction.
4. What is Clock Speed ?
Clock speed is measured in the MHz and it determines that how many instructions a processor
can processed. The speed of the microprocessor is measured in the MHz or GHz.
5. What are the features of Intel 8086 ?
Features:
Released by Intel in 1978
Produced from 1978 to 1990s
A 16-bit microprocessor chip.
Max. CPU clock rate:5 MHz to 10 MHz
Instruction set: x86-16
Package: 40 pin DIP
16-bit Arithmetic Logic Unit
16-bit data bus (8088 has 8-bit data bus)
20-bit address bus - 220 = 1,048,576 = 1 meg
The address refers to a byte in memory.
In the 8088, these bytes come in on the 8-bit data bus. In the 8086, bytes at even
addresses come in on the low half of the data bus (bits 0-7) and bytes at odd addresses come in
on the upper half of the data bus (bits 8-15).
The 8086 can read a 16-bit word at an even address in one operation and at an odd
address in two operations. The 8088 needs two operations in either case.
The least significant byte of a word on an 8086 family microprocessor is at the lower
address.
6. What is Logical Address?
• A memory address on the 8086 consists of two numbers, usually written in hexadecimal
and separated by a colon, representing thesegment and the offset. This combination of segment
and offset is referred to as a logical address
• Logical address=segment: offset
7. What is The Effective Address:
• In general, memory accesses take the form of the following example:
• Mov ax, [baseReg + indexReg + constant]
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, MICROPROCESSOR VIVA QUESTIONS AND ANSWERS
• This example copies a word sized value into the register AX.
• Combined, the three parameters in brackets determine what is called the effective address,
which is simply the offset referenced by the instruction
8. What is Physical Address?
Physical memory address pointed by SEGMENT:OFFSET pair is calculated as:
Physical address = (<Segment Addr> * 10) + <Offset Addr>
9.What are the flags in 8086?
In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag,
Interrupt flag, Direction flag, and Sign flag.
10.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.
11.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.
12.What happens when HLT instruction is executed in processor?
The Micro Processor enters into Halt-State and the buses are tri-stated.
13.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.
14.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 / bits.
15. Name the processor lines of two major manufacturers?
High-end: Intel - Pentium (II, III, 4), AMD - Athlon. Low-end: Intel - Celeron, AMD - Duron.
64-bit: Intel - Itanium 2, AMD - Opteron.
16. How many bit combinations are there in a byte?
Byte contains 8 combinations of bits.
17. Have you studied buses? What types?
There are three types of buses.
Address bus: This is used to carry the Address to the memory to fetch either Instruction or Data.
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, MICROPROCESSOR VIVA QUESTIONS AND ANSWERS
Data bus : This is used to carry the Data from the memory.
Control bus : This is used to carry the Control signals like RD/WR, Select etc.
18. What is the Maximum clock frequency in 8086?
5 Mhz is the Maximum clock frequency in 8086.
19. What is meant by Maskable interrupts?
An interrupt that can be turned off by the programmer is known as Maskable interrupt.
20. What is Non-Maskable interrupts?
An interrupt which can be never be turned off (ie. disabled) is known as Non-Maskable interrupt
21. What are the different functional units in 8086?
Bus Interface Unit and Execution unit, are the two different functional units in 8086.
22. What are the various segment registers in 8086?
Code, Data, Stack, Extra Segment registers in 8086.
23. What does EU do?
Execution Unit receives program instruction codes and data from BIU, executes these
instructions and store the result in general registers.
24. Which Stack is used in 8086? k is used in 8086?
FIFO (First In First Out) stack is used in 8086.In this type of Stack the first stored information is
retrieved first.
25. What are the flags in 8086?
In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag,
Interrupt flag, Direction flag, and Sign flag.
26. What is SIM and RIM instructions?
SIM is Set Interrupt Mask. Used to mask the hardware interrupts.
RIM is Read Interrupt Mask. Used to check whether the interrupt is Masked or not.
27. 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).
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