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MicroProcessor Interview Questions

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.

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.

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.

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.

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.

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

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

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.

What are the various registers in 8085?
Accumulator register, Temporary register, Instruction register, Stack Pointer, Program Counter are the various registers in 8085

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.

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.

What?s the speed and device maximum specs for Firewire?
IEEE 1394 (Firewire) supports the maximum of 63 connected devices with speeds up to 400 Mbps. Where?s MBR located on the disk? Main Boot Record is located in sector 0, track 0, head 0, cylinder 0 of the primary active partition.

Where does CPU Enhanced mode originate from?
Intel?s 80386 was the first 32-bit processor, and since the company had to backward-support the 8086. All the modern Intel-based processors run in the Enhanced mode, capable of switching between Real mode (just like the real 8086) and Protected mode, which is the current mode of operation.

How many bit combinations are there in a byte?
Byte contains 8 combinations of bits.

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.
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.

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

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

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

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

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

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

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.

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.

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.

What is the difference between 8086 and 8088?
The BIU in 8088 is 8-bit data bus & 16- bit in 8086.Instruction queue is 4 byte long in 8088and 6 byte in 8086.

Give example for Non-Maskable interrupts?
Trap is known as Non-Maskable interrupts, which is used in emergency condition.

Give examples for Micro controller?
Z80, Intel MSC51 &96, Motorola are the best examples of Microcontroller.

ABB Placement Papers

TECHNICAL PAPER-40 QUESTION, 45- MINUTES

(1)in a ckt. We r giving voltage of 50 Hz as well as 60. then what will be  the resultant frequency.

(a)less than 50     (b) more than 60    (c)    in between 50 & 60
(d)  none..........according to our conclusion answer will be none because if  we apply two frequency component resultant frequency we can not say with  such an ease's should confirm the answer

2.In a ckt a single resistor is connected across a d.c. source, what will be  the effect on current in first resistor if we connect one more resistance in  parallel with earlier one....

Answer.. no change since it is a parallel combination.

3.why we don,t like flashover in transmission line (t-line)-  (a ) it may create earth fault(b )it reduces the life of insulator.....
Read something about flashover & puncture.

4.total no of strands in a acsr conductor is 81, then what is the no. of  conductor in its outer layer....(a)36 (b)18 (c)24.......Also read some more  on acsr.

5.Two questions based on p.u. calculation like , p.u. calculation is given  with respect to some old base and u have to calculate it with reference to  new base.  (new resistance/old)=(mva new /mva old)*(old voltage/new voltage)2

Other question is based upon transfer of p.u calculation in transformer i.e.  how base changes when we we move from primary to secondary or like wise.read  some more on p.u calculation.

6.which table is referred for sag calculation-

(a)stringing chart......answer

7.in a R-L ckt a ac voltage is applied , such that instantaneous power is  negative for 2ms, then what will be the power factor.

(a) 9 deg, (b) 18 deg, (c) 36 Deg...........(I don,t know the correct ans)

8. In an incandescent lamp

(a) luminous intensity is more than non-luminous intensity    (b) ,, ,, ,, less ,, ,, ,,

Ans: Since efficiency is less than 100%, hence ans is (b), u should confirm it further.

9. In which motor no-load to full-load diff. is lowest

(a) series motor,     (b) shunt motor,     (c) Compound motor

Ans: (b)

10. In a 60Hz induction motor full load speed is 850 rpm then what is the  Synchronous speed. (a) 900 rpm, (b) 950 rpm, (c) 1600rpm...

.Ans: (a)

11. A sync. Motor is running at synch. Speed, if al of sudden D.C.  excitation is removed, then

(a) it will rotate at slip speed,     (b) it will stop,     (c) it will continue to  rotate at sync. Speed

Ans: (a), because actually it will acts as Induction motor.

12. A transmission line is designed for 50Hz, 440KV. If we want to transfer  power at 60Hz, 440 KV, then the power transfer capability will

(a) decrease,     (b) Increase,     (c) None

Ans: (a) ...as P=( |Vt| |Ef| sin (delta) ) / X, where (delta) is torque angle.

13. Increased rotor resistance in rotor ckt of induction motor is related  with

(a) high starting torque,     (b) more speed variation,.....................Ans: (a)

14. In the formulae E = 4.44 f N ?, ? is

(a) Avg value,     (b) Rms value,     (c) Maximum value.....................Ans: (a)...[confirm it]

15. Voltage & current in a ckt is given by V= V1+j V2 and I= I1 +j I2, then rms power is.......(refer book by Administrator on NETWORK ..)

16. Input impedence of MOSFET is

(a) more than BJT........(Ans)

17, 18. Remember truth table of AND, NOR, NAND, OR, EX-OR ETC...

19. Conversion of Binary number into Equivalent decimal No.

20. Megger is used for the measurement of (a) Insulation resistance,    (b)Conductor resistance.............Ans: (a)

21. Form factor for sinusoidal as well as DC

22. Formulae of Regulation (Vs- Vr)* 100/ Vr, then transmission line is

(a) short transmission line,     (b) long, (    c) medium...................Ans: (a)

23. Improvement in power factor reduces

(a) power consumed by consumer,    (b) power generation,    (c) both a & b...........Ans: (c) [Confirm it]

24. Read about field test of Series Motor...

25. No-load test for Synchronous motor, the graph is drawn

(a) stator open ckt emf Vs field current.......................................(Ans: a)

26. An AC voltage of 50Hz is impressed in a resistive ckt, the oscillating  power has a frequency (a) 50 Hz, (b) 100, (c) no oscillating power is there  in resistive ckt......Ans: (a)
27. Insulation used in transformer ___________leakage flux.

(a) increases, (b) decreases............Ans: (b)

28.After rain what happens to Insulator (a) break-down strength of Insulator  decreases, (b)Arch length reduces, ......Ans: (b)..[Confirm it]

29.Diversity factor helps to ............(what ?)  [Read diversity factor, load factor, Reserve capacity factor in depth, with calculation]

30. Why capacitance is shown as a Shunt element in analysis of transmission  line

(a) it is between Conductor & earth,    (b) because Admittance is used for  calculation of capacitive reactance.....................Ans: (a)

31. B-R-Y sequence is followed in three phase system, if phase voltage in  B-phase is Vm sin 100, then the phase voltage in R-phase would be (a) Vm  sin (-20)            Ans:(a)

32. In a particular ckt I = Im Sin (wt -270) and V = Vm Sin wt, then type of  ckt is (a) pure resistive ckt

33. In a L-R ckt energy lost = 2000 W, energy conserved = 500W, then what is  the time constant...........Ans: time constant = L/R = 0.5

34. In electro-dynamometer A,meter & wattmeter the type of scale is

Ans:Non-uniform
35. For the same current carrying capacity corona loss of ACSR will be  ________than copper conductor.
  (a) more,     (b) less,    (c) equal.     Ans: (b)

36. A R-C ckt , supplied with DC, a bulb is connected across the Capacitor,  then what happens to the illumination, if we change the capacitance.

Ans: No change at all

37. Read about surge impendence of over-head and under-ground cable, Surge  impedence formula = sqrt(L/C)

[N.B] We are not mentioning the options in sequence, and do not think  that ans for the most questions is option (a). Read all options very  carefully as all are very close to each other.

QUANTITATIVE PAPER + PCM paper

45 Questions ---------45 minutes

1. About 10 quanti questions ( based on Mixture, Work etc. of very easy  type)

2. What is GDP ?

3. Vector algebra, codition for Co-planer vector etc.

4. Gravitation, geo-synchronous satellite( it,s hight, orbit , radius etc.), escape velocity, how g (gravitational accln) varies, about  gravitational potential.

5. Basic electricity and Magnetism----Biot-savart law, current carrying  conductor properties.

6. Nuclear physics, Bohr,s constant, and Other theories related .

7. Problem based on VIBGYOR , how wave length and frequency is varying.

8. Questions based on Plank,s Theory, E =hv

9. V=u + at , V2=u2 + 2as and W = mgh  questions based on above theory

10. Faraday,s laws of electrolysis, m = Zit

11. Heat conduction problem.

12. Co lour-coding of resistor (BBROYGBVGW)

13. How velocity of light changes in different medium while frequency remain  unchanged.

14. statistics , calculation of mode, co-efficient regression (3-4  Questions)

15. f(x) = Sin x + Cos x, find the maximum value of the function.......Ans:  sqrt (2)

16. Formulae for parallel plate capacitor and force between plates