Microprocessor VIVA Questions with Answers

Most Recently Asked MPMC Viva Questions with 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.

6.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.

7.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.

8.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.

9.What happens when HLT instruction is executed in processor?
The Micro Processor enters into Halt-State and the buses are tri-stated.

10.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.

11.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.

12.What is the Maximum clock frequency in 8086?
5 Mhz is the Maximum clock frequency in 8086.

13.What is meant by Maskable interrupts?
An interrupt that can be turned off by the programmer is known as Maskable interrupt.

14.What is Non-Maskable interrupts?
An interrupt which can be never be turned off (ie. disabled) is known as Non-Maskable interrupt

15.What are the different functional units in 8086?
Bus Interface Unit and Execution unit, are the two different functional units in 8086.

16.What are the various segment registers in 8086?
Code, Data, Stack, Extra Segment registers in 8086.

17.What does EU do?
Execution Unit receives program instruction codes and data from BIU, executes these instructions and store the result in general registers.

18.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.

19.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.

20.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.

21.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 maskable interrupts are recognized by the CPU.
D-Direction Flag:-Is set for autoincrementing or autodecrementing 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 setif the result of a signed operation is large enough to be accommodated in a destination register.

22.Write the flags of 8086?
The 8086 has nine flags and they are
1. Carry Flag (CF)                6. Overflow Flag (OF)
2. Parity Flag (PF)                 7. Trace Flag (TF)
3. Auxiliary carry Flag (AF)   8. Interrupt Flag (IF)
4. Zero Flag (ZF)                  9. Direction Flag (DF)
5. Sign Flag (SF)

23. What are the interrupts of 8086?
The interrupts of 8085 are INTR and NMI. The INTR is general maskable interrupt and NMI is non-maskable interrupt.

24. How clock signal is generated in 8086? What is the maximum internal clock frequency of 8086?
The 8086 does not have on-chip clock generation circuit. Hence the clock generator chip, 8284 is connected to the CLK pin of8086. The clock signal supplied by 8284 is divided by three for internal use. The maximum internal clock frequency of8086 is 5MHz.

25. Write the special functions carried by the general purpose registers of 8086?
The special functions carried by the registers of 8086 are the following.
Register Special function
1. AX 16-bit Accumulator
2. AL 8-bit Accumulator
3. BX Base Register 4. CX Count Register 5. DX .Data Register

26.What is the need for Port?
The I/O devices are generally slow devices and their timing characteristics do not match with processor timings. Hence the I/O devices are connected to system bus through the ports.

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

28.What is processor cycle (Machine cycle)?
The processor cycle or machine cycle is the basic operation performed by the processor. To execute an instruction, the processor will run one or more machine cycles in a particular order.

29.What is Instruction cycle?
The sequence of operations that a processor has to carry out while executing the instruction is called Instruction cycle. Each instruction cycle of a processor indium consists of a number of machine cycles.

30.What is fetch and execute cycle?
In general, the instruction cycle of an instruction can be divided into fetch and execute cycles. The fetch cycle is executed to fetch the opcode from memory. The execute cycle is executed to decode theinstruction and to perform the work instructed by the instruction.