MICROPROCESSOR Interview Questions & Answers

Posted On:February 5, 2019, Posted By: Latest Interview Questions, Views: 1344, Rating :

Best MICROPROCESSOR Interview Questions and Answers

Dear Readers, Welcome to Microprocessor Interview Questions and Answers have been designed specially to get you acquainted with the nature of questions you may encounter during your Job interview for the subject of Microprocessor. These Microprocessor Questions are very important for campus placement test and job interviews. As per my experience good interviewers hardly plan to ask any particular questions during your Job interview and these model questions are asked in the online technical test and interview of many IT & Non IT Industries.

1) What type of architecture used in 8085 microprocessor?

Ans. 8085 has Von Neumann architecture. It is named after the mathematician John   Von Neumann. It is based on the concept of stored program control. In this architecture both the data and the program is stored in the same memory.
Interview Questions on MICROPROCESSOR

2) What is the function of accumulator?

Ans. Accumulator is an 8 bit register which stores data and performs arithmetic and logical operations. The result of the operation is stored in the accumulator. It is designated by the letter ‘A’.

3) What are the different types of flags in 8085 microprocessor?

Ans. There are 5 different flags in 8085 microprocessor. Though the flag register is of 8 bit but 3 bits are not in use. Only 5 bits are used for the different flags. They are:-
a) Sign flag(s)- This is designated by the letter ‘S’. If sign bit is 1 then the sign flag is set to 1 and if the sign bit is zero then sign flag is reset to zero.
b) Zero flag(z)- This is designated by the letter ‘z’. If the result of any arithmetic or logical operation is zero i.e. all the bits are zero then zero flag is set to 1 else it is set to zero.
c) Auxiliary carry- (AC) This flag is set to 1 only when any intermediate carry is produced. Else it is reset to 0.
d) Parity flag (P) – when the result of any operation has odd number of ones then parity flag is set to 1 else if it has even number of ones then it is reset to 0.
e) Carry flag(C) – this flag is set to 1 only when a carry is produced in the result i.e. the carry bit is 1 else if the carry bit is zero then the flag is reset to zero.

4)  What are the types of general purpose registers in 8085? 

Ans. There are 6 general purpose registers in 8085 microprocessor. They are designated by the letters – B, C, D, E, H, and L. These are 8 bit registers and are used to store data temporarily during the execution of any program. These registers can also be used to store 16 bit data by using them in pairs i.e. BC, DE and HL. These pairs cannot be changed as B cannot pair with any other register other than C.

5)  What is the length of stack pointer in 8085 microprocessor? And what is its use?

Ans. stack pointer is of 16 bits length and is used to point to the value at top of the stack for the currently executed instruction.

6)  What is the memory size of 8085 microprocessor? 

Ans. 8085 has 8 data lines and 16 address lines. The memory size of any microprocessor depends on the number of address lines. The general formula is 2^n, where n= number of address lines. For 8085 there are  2^16= 64 Kbytes memory size.
7)  How many bits is 8085 microprocessor? 
Ans. Microprocessor is named on the basis of number of data lines in it. 8085 is a bit microprocessor as it has 8 bit data lines.

8)  What are the various interrupts in 8085 microprocessor? Which is the highest priority interrupt?

There are 6 types of interrupts in 8085. They are
b) RST 7.5
c) RST 6.5
d) RST 5.5
f) Interrupt acknowledgment (INTA(bar)).
TRAP has the highest priority among all the interrupts.

9)  Which type of cycle is used for fetch and execute instruction? 

 Ans. Instruction cycle is used for the fetch and execute instruction.
In this cycle the instruction is fetched, decoded and executed to produce the required output.

10)  How many address lines are there in 8085 microprocessor? 

Ans. There are 16 address lines in 8085. They are multiplexed address and data lines. Address bus of 8085 is of 16 bits. During the first machine cycle these address lines are used as data lines and in the next machine cycle all the 16 lines act as address lines.
The multiplexed 8 address and data lines refer to lower order address bit and the rest 8 for higher order address bits.

11) What is a Microprocessor?

Ans:- Microprocessor is a program-controlled device, that fetches the instructions from memory, decode it & executes the instructions. Generally Microprocessor are single- chip devices.

12) Why crystal is  being preferred as a clock source?

Ans:- Reasons-high stability, large Q (Quality Factor) & the frequency that doesn’t drift with aging. so crystal is used as a clock source most of the times.

13) Name High order / Low order Register in 8085 microprocessor?

Ans:-Flag is called Low order register & Accumulator is called High order Register in 8085 microprocessor.

14) Describe Tri-state logic?

Ans:- Three Logic Levels are used and they are known as High, Low, High impedance state. The high and low are said to be normal logic levels where as high impedance state is electrical open circuit conditions. Tri-state logic has a enable line as third line

15) What will happen if HLT instruction is executed in processor?

Ans:- The Micro Processor will enter into Halt-State and the buses will be tri-stated.

16) Which Stack is used in 8085?

Ans:- LIFO (Last In First Out) stack is used in 8085.In this type of Stack the information which is stored last will be taken out or retrieved first.

17)  Describe briefly Program counter?

Ans:- Program counter does either of the two things that is it 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 was not completely fetched. In both the cases it is incremented automatically one by one as the instruction bytes will be fetched. Program register also keeps the next instruction address.

18) Name the 1st / 2nd / 3rd / 4th generation processor?

Ans:-The processor are made of PMOS / NMOS / HMOS / HCMOS technology  which is called 1st / 2nd / 3rd / 4th generation processor, and  that is made up of 4 / 8 / 16 / 32 bits respectively.

19)  Name the processor lines of two major manufacturers?

Ans:-  The Processor lines names of two major manufacturers are as follows:- At High-end: Intel – Pentium (II, III, IV), AMD – Athlon. At Low-end: Intel – Celeron, AMD – Duron. 64-bit: Intel – Itanium 2, AMD – Opteron

20)  Mention the speed and device maximum specs for Firewire?

Ans:-IEEE 1394 (Firewire) with speeds up to 400 Mbps can support the maximum of 63 connected devices

21) Where’s MBR located on the disk?

Ans:- The place where MBR is situated is in sector 0, track 0, head 0, cylinder 0 of the primary active partition.

22) Where does CPU Enhanced mode originate from?

Ans:- Intel’s 80386 was the first 32-bit processor, and so the company had to backward-support the 8086. All the modern Intel-based processors run in the enhanced mode which are capable to switch in between real mode and protected mode, which is the current mode of operation.


23) What are the types of buses?

Ans:- Three types of buses are there:-
Address bus: It carries the Address to the memory to fetch either instruction..
Data bus : It carries data from the memory.
Control bus : It carries the control signals like RD/WR, Select etc.

24) What does EU do?

Ans:- Execution Unit receives both program instruction codes & data from Bus Interface Unit and then executes these instructions and the result is being stored in registers.

25) Mention RST for the TRAP?

Ans:- RST 4.5

26) Can an RC circuit be used as clock source for 8085?

Ans:-Yes,RC circuit can be used as clock source if in case an accurate clock frequency is not required. The cost of RC is low as compared to LC.
Microprocessor interview questions on 8086

27) What are the types of flags in 8086?

Ans:- In 8086 there are 9 types of flags which are as follows Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.

28) What are the various interrupts in 8086?

Ans:- Two types of interrupts:-Maskable interrupts, Non-Maskable interrupts.

29) What is meant by Maskable interrupts?

Ans:- An interrupt that can be turned off by the programmer is known as Maskable interrupts are those interrupts which can be turned off by the programmer or can be ignored by the programmer.


30) What is Non-Maskable interrupts?

Ans:- A processor interrupt which can be never be turned off (i.e.disabled) or cannot be ignored by the programmer is known as Non-Maskable interrupt.

31) Which interrupts are generally used for critical events?

Ans:- Non-Maskable interrupts are generally used in critical events. For example- Power failure, Emergency, Shut off etc.

32) Give some examples for Maskable interrupts?

Ans:- Some examples for maskable interrupts are as follows:- RST 7.5, RST6.5, RST5.5

33) Give  some example for Non-Maskable interrupts?

Ans:- Trap is called as Non-Maskable interrupts, which is used during emergency condition.

34) What is the Maximum clock frequency in 8086?

Ans:- 5 Mhz

35) Name the various segment registers in 8086?

Ans:- The various segment registers in 8085 are- Code, Data, Stack, Extra Segment registers.

36) Which Stack is used in 8086?

Ans:- FIFO (First In First Out) stack is used in 8086.In this type of Stack the information which is stored first is taken out or  retrieved first.

37) What is SIM and RIM instructions?

Ans:- SIM is Set Interrupt Mask. which is used to mask the hardware interrupts. RIM is Read Interrupt Mask which is used to check whether the interrupet is masked or not.

38) Which is the tool which is used to connect the user and the computer?

Ans:- Interpreter

39) What is the position of the Stack Pointer after the PUSH instruction?

Ans:- The address line is 02 less than the earlier value.

40) What is the position of the Stack Pointer after the POP instruction?

Ans:- The address line is 02 greater than the earlier value.
These are some of the interview questions and answers on Microprocessor. If you want to add some more, please mention in the comment section of the post.