Microprocessor Q&A
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. Tristate 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.
What is clock frequency for 8085?
3 MHz is the maximum clock frequency for 8085.
Give an example of one address microprocessor?
8085 is a one address microprocessor.
Give examples for 8 / 16 / 32 bit Microprocessor?
8-bit Processor - 8085 / Z80 / 6800; 16-bit Processor - 8086 / 68000 / Z8000; 32-bit
Processor - 80386 / 80486
What is meant by a bus?
A bus is a group of conducting lines that carriers data, address, & control signals.
What are the various registers in 8085?
Accumulator register, Temporary register, Instruction register, Stack Pointer, Program
Counter are the various registers in 8085
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.
Name 5 different addressing modes?
Immediate, Direct, Register, Register indirect, Implied addressing modes
In what way interrupts are classified in 8085?
In 8085 the interrupts are classified as Hardware and Software interrupts.
What is the difference between primary & secondary storage device?
In primary storage device the storage capacity is limited. It has a volatile memory. In
secondary storage device the storage capacity is larger. It is a nonvolatile memory. Primary
devices are: RAM / ROM. Secondary devices are: Floppy disc / Hard disk.
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 is the RST for the TRAP?
RST 4.5 is called as TRAP.
What are level-triggering interrupt?
RST 6.5 & RST 5.5 are level-triggering interrupts.
Which interrupt is not level-sensitive in 8085?
RST 7.5 is a raising edge-triggering interrupt.
What are Software interrupts?
RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7.
What are the various flags used in 8085?
Sign flag, Zero flag, Auxiliary flag, Parity flag, Carry flag.
In 8085 name the 16 bit registers?
Stack pointer and Program counter all have 16 bits.
What is Stack Pointer?
Stack pointer is a special purpose 16-bit register in the Microprocessor, which holds the
address of the top of the stack.
What happens when HLT instruction is executed in processor?
The Micro Processor enters into Halt-State and the buses are tri-stated.
What does Quality factor mean?
The Quality factor is also defined, as Q. So it is a number, which reflects the lossness of a
circuit. Higher the Q, the lower are the losses.
How many interrupts are there in 8085?
There are 12 interrupts in 8085.
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. Tristate logic has a third line called enable line.
Which interrupt has the highest priority?
TRAP has the highest priority
What are Hardware interrupts?
TRAP, RST7.5, RST6.5, RST5.5, INTR
Can an RC circuit be used as clock source for 8085?
Yes, it can be used, if an accurate clock frequency is not required. Also, the component cost
is low compared to LC or Crystal.
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--------------------------------------------------------------------------------------http://www.indiabix.com/digital-electronics/microprocessor-fundamentals/
1. The devices that provide the means for a computer to communicate with the user or other
computers are referred to as:
A. CPU
B. ALU
C. I/O
D.none of the above
2. The software used to drive microprocessor-based systems is called:
A. assembly language
B. firmware
C. machine language code
D.BASIC interpreter instructions
3. The circuits in the 8085A that provide the arithmetic and logic functions are called the:
A. CPU
B. ALU
C. I/O
D.none of the above
4. How many buses are connected as part of the 8085A microprocessor?
A.2
B. 3
C. 5
D.8
1. The devices that provide the means for a computer to communicate with the user or
other computers are referred to as:
A. CPU
B. ALU
C. I/O
D.none of the above
View Answer Workspace Report Discuss in Forum
2. The software used to drive microprocessor-based systems is called:
A. assembly language
B. firmware
C. machine language code
D.BASIC interpreter instructions
View Answer Workspace Report Discuss in Forum
3. The circuits in the 8085A that provide the arithmetic and logic functions are called
the:
A. CPU
B. ALU
C. I/O
D.none of the above
View Answer Workspace Report Discuss in Forum
4. How many buses are connected as part of the 8085A microprocessor?
A.2
B. 3
C. 5
D.8
View Answer Workspace Report Discuss in Forum
5. The ________ ensures that only one IC is active at a time to avoid a bus conflict
caused by two ICs writing different data to the same bus.
A. control bus
B. control instructions
C. address decoder
D.CPU
Source: http://blog.oureducation.in/interview-questions-on-microprocessor/
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.
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?
Interview Sample paper question answer on 8085 Microprocessor.
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
a) TRAP
b) RST 7.5
c) RST 6.5
d) RST 5.5
e) INTR
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? Sample Paper
Interview question answer
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? Sample Paper Interview
question answer
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. 64bit: 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 backwardsupport 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 interrupt 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.
Source: http://careerride.com/microprocessor-interview-questions.aspx
1. What is the difference between microcontrollers and microprocessor?
2. What is the function of bit slice processor?
3. How intel microprocessor different from other microprocessors?
4. What is the difference between core 2 duos and core 2 quads?
5. What is Microprocessor logic?
6. What are the basic functionalities that are being performed by
microprocessor?
7. What are the components present in a microprocessor?
8. What are the different control lines that are present?
9. What is the use of control lines?
10. What is the process of communicating Memory with the Microprocessor?
11. What are the different types of instructions that are present in
microprocessor?
12. What is the function of LOADA mem and LOADB mem?
13. Which language is used to write microprocessor instructions?
14. What are the steps that are taken to decode an instruction code?
15. What is the difference between pipelined architecture and non-pipelined
architecture?
16. How the address space is defined for different processors?
17. What are the features provided by intel microprocessors?
18. What are the different types of cache that is used by intel microprocessor?
19. How hyper-threading technology is provided with intel microprocessor?
20. What are the different types of processors used in intel microprocessor?
21. What is the difference between CISC and RISC processor?
22. What are the different types of flag registers used in intel microprocessor?
23. Explain the architecture of intel microprocessor?
24. What is the difference between 32 bit or 64 bit microprocessor?
25. What are the different addressing modes that are used in intel
microprocessor?
26. What are the different types of instructions that are present in
microprocessor?
27. What is the difference between SIM and RIM?
28. How to measure the quality factor of the microprocessor?
29. What are the different triggers present?
30. What is the difference between edge trigger and level trigger?
31. How to measure the clock frequency for 8086 intel microprocessor?
32. How tri-state logic defined?
33. What the difference is between stack and program counter?
34. What are the different functional units that are present in
microprocessor?
35. What is the difference between Maskable and non-maskable interrupt?
36. What are the different types of flags that are available in microprocessor?
37. What is the difference between AMD processors and Intel
microprocessors?
38. What are the steps involved in 5-stage pipelining?
39. What is the difference between stack and subroutine?
40. How to define the physical address of the microprocessor?
41. What is the function of linker and loader?
42. What is the function of control unit?
43. How to find out the architecture of microprocessor?
44. What is the difference between direct and indirect addressing mode?
45. How 8086 is different from 80386 microprocessor?
46. What is the difference between high order and low order registers?
47. How many types of buses that are required to transfer the data in the
system?
48. What are the devices that directly communicate with the microprocessor?
49. What is the term MESI signifies?
50. What is the difference between parallel and direct microprocessor?
51. Explain in Pentium processors how memory management has been
improved?
- By adding a paging unit and a new system in the memory system the management of it has
been improved upon.
- Paging Unit: The paging mechanism works on 4KB memory pages or with a
new extension available to the Pentium with 4MB memory pages.
- Memory-management mode: The system memory-management mode (SMM) is on
the equal levels such as the protected mode, real mode, and virtual mode. Still the memory
management mode function as a manager. High-level system functions
such as power management and security are taken care of by it._
52. What do you understand by MACRO? Explain the various conditional
constructs used while programming a macro?
- Macro can be considered to be a sequence of instructions to which a name is assigned.
- For short sequence of instructions which are of fixed nature Macros are used.
- They can execute faster as compared to subroutines.
- The MACRO directives are used to inform the assembler the starting of a macro.
- In order to enclose a macro the ENDM directive is used.
- The general format of the MACRO directive is :
Macro Name MACRO ARG1, ARG2 , …..,ARG N.
- To create macro sequences conditional assembly language statements are used. Theses
statements control the flow of the program and are variations of the IF-THEN, IF-THENELSE, DO-WHILE, and REPEAT-UNTIL constructs used in high-level language
programming languages.
53. Briefly explain following instructions in 8086 family:
a) CWD
b) LOOP
c) IMUL
d) SAR
- CWD also known as the Convert signed Word to signed Double word instruction, it is used
to extend the sign bit of a word in AX register to all the bits of the DX register. Generally
used before a signed word in AX. Then it is divided by another signed word using IDIV
instruction. It does not affect any flag.
- LOOP: (Jump to specified label until CX = 0): As the name suggests the loop instruction is
used to repeat a sequence of instructions for a specified number of time. It does not affect any
flag and the number of times the loop is to be repeated is stored in the CX register.
- IMUL: This instruction is used for the multiplication of two signed numbers.The result of
imul between two signed numbers is signed as well. The OF (Over flow) and CF (Carry flag)
flags get affected by this instruction.
- SAR: Also known as Shift each bit of operand right, this instruction shifts each bit of the
operand in a register or memory location, right by the number of bits specified. The carry flag
is affected by this operation.
54. Explain segments their pro`s and a method for their implementation.
- The division of address space into logical sections is known as segmentation and each such
space is known as a segment.
- In order to access a specific memory location, a program must specify both the segment
number and the offset contained in that segment. Segment memory addressing divides the
memory into many segments.
- One of the advantages of memory segmentation is that only 16 bit registers are
required to both store segment base address as well as offset address. Due to this the
designing of the memory is simple.
- By using segmentation there is the advantage of relocability as well.
55. Briefly explain DMA and its various addressing modes.
- The DMA or the direct memory access is a type of process in which the System bus control
is accessed and controlled by an external device in place of the CPU.
- It is primarily used for the high speed transfer of data from mass storage devices.
- The DMA functions by directly transferring data to and from from the memory to the
devices.
- The various modes of operation of the DMA are as follows: Demand mode, Single mode,
Block mode and Cascade mode.
- The characteristic of the demand mode is that it can transfer data until the Dreq input
becomes inactive.
56. Briefly explain the functions of Debugger, Assembler and the Linker.
- Debugger: As its name suggests the debugger is used to test and debug programs. The
debugger allows a user to test a program step by step, so that the problem points or steps can
be identified and rectified. It allows the user to inspect the registers and the memory locations
after a program has executed.
- Assembler: The assembler is used to convert assembly language written by a user or a
program into a machine recognizable format.
- Linker: There are certain programs which are large in size and cannot be executed at one go
simultaneously. Such programs are divided into subprograms also known as modules. The
linker is used to link such small programs to form one large program.
57. Explain the characteristics of the RS232C and RS422A standards.
The characteristics of RS232C are as follows:
- This standard has been defined for communication that is asynchronous. The timing
between data bits are specified whereas the timing between two characters is not fixed.
- This standard guarantees 50 ft coverage and 25 signal lines are defined by it.
- For each direction only a single wire is defined.
The characteristics of the RS422A standard are as follows:
- The data rate of this standard is 10Mbits/sec.
- In this standard every signal is considered to be a pair of wires and the voltage difference
between them is sensed by the receiver.
58. Briefly explain any 4 modes of operation of the 8254 interval timer.
The following are the modes of operation of the programmable timer 8254:
- Mode 0: Also known as the interrupt on terminal count. In this mode the output is initially
low. Once the count of terminal is reached the output becomes high.
- Mode 1: Programmable one shot is also known as the hardware triggered one-shot. For it to
happen, the count registers must be loaded and the A 0-1 pulse has to be sent to the Gate
input in order to trigger the counter.
- Mode 2: Rate generator, this process is repeated indefinitely.
- Mode 3: Square wave generator, when gate=1, The out is a square wave where the high
pulse is equal to the low pulse of N is an even number. In case the N is an odd number the
high pulse is longer. The mode-3 is commonly used for as frequency divider.
59. What are the various types of addressing modes for microprocessors?
The various types of addressing modes for microprocessors are as follows:
- Direct Mode: In this mode of addressing the instruction in itself includes memory access.
This can be accessed by the CPU directly.
- Indirect Mode: In this type of addressing the address which has been specified within the
instruction contains the address of the operands.
- Register direct and indirect modes: In this mode as the name suggests no addresses are
specified in this mode instead registers are specified.
- Immediate Mode: In this type of addressing mode the operand itself is the data.
- Relative Mode: In this mode the operand specified in the instruction is an offset address and
not the actual address.
60. In assembly language, write the program to search for the largest number
among n numbers which are stored in the memory.
The program to detect the largest number among n numbers stored in the memory are as
follows:
Step 1>>MOV AX, 0000
Step 2>>MOV SI, 0200
Step 3>>MOV CX, [SI]
Step 4>>BACK : INC SI
Step 5>>INC SI
Step 6>>CMP AX, [SI]
Step 7>>JAE GO
Step 8>>MOV AX, [SI]
Step 9>>GO: LOOP BACK
Step 10>>MOV [0251], AX
Step 11>>INT 3
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8086 MICROPROCESSOR INTERVIEW QUESTIONS&ANSWERS
---------------------------------------------------------------------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 is the difference between microprocessor and microcontroller?
The major difference is microprocessor doesn’t have inbuilt memory but micro-controller has inbuilt
memory .In Microprocessor more op-codes, few bit handling instructions. But in Microcontroller:
fewer op-codes, more bit handling Instructions. Micro-controller can be defined as a device that
includes micro processor, memory, & input / output signal lines on a single chip.
Give examples for 8 / 16 / 32 bit Microprocessor?
8-bit Processor - 8085 / Z80 / 6800;
16-bit Processor - 8086 / 68000 / Z8000;
32-bit Processor - 80386 / 80486.
Why 8085 processor is called an 8 bit processor?
Because 8085 processor has 8 bit ALU (Arithmetic Logic Review).
Expand HCMOS?
High-density n- type Complimentary Metal Oxide Silicon field effect transistor.
What does microprocessor speed depend on?
The processing speed depends on DATA BUS WIDTH.
What is the Maximum clock frequency in 8086?
5 Mhz is the Maximum clock frequency in 8086
Is the address bus unidirectional? Is the data bus is Bi-directional?
The address bus is unidirectional because the address information is always given by the Micro
Processor to address a memory location of an input / output devices.
The data bus is Bi-directional because the same bus is used for transfer of data between Micro
Processor and memory or input / output devices in both the direction.
What is the disadvantage of microprocessor?
It has limitations on the size of data. Most Microprocessor does not support floating-point
operations.
What is the difference between primary & secondary storage device?
In primary storage device the storage capacity is limited. It has a volatile memory. In secondary
storage device the storage capacity is larger. It is a nonvolatile memory. Primary devices are: RAM /
ROM.
Secondary devices are: Floppy disc / Hard disk.
Difference between SRAM and DRAM?
Static RAM: No refreshing, 6 to 8 MOS transistors are required to form one memory cell, Information
stored as voltage level in a flip flop.
Dynamic RAM: Refreshed periodically, 3 to 4 transistors are required to form one memory cell,
Information is stored as a charge in the gate to substrate capacitance.
What is an interrupt?
Interrupt is a signal send by external device to the processor so as to request the processor to
perform a particular work.
What are the different types of interrupts?
Maskable and Non-maskable interrupts.
What is cache memory?
Cache memory is a small high-speed memory. It is used for temporary storage of data & information
between the main memory and the CPU (center processing unit). The cache memory is only in RAM.
Expand DMA?
Direct Memory Access
Differentiate between RAM and ROM?
RAM: Random Access Memory. Read / Write memory, High Speed, Volatile Memory. ROM: Read
only memory, Low Speed, Non Volatile Memory
What is NV-RAM?
Nonvolatile Read Access Memory, also called Flash memory.
What is a flag?
Flag is a flip-flop used to store the information about the status of a processor and the status of the
instruction executed most recently
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 meant by Maskable interrupt?
An interrupt that can be turned off by the programmer is known as Maskable interrupt.
What is Non-Maskable interrupt?
An interrupt which can be never be turned off (ie.disabled) is known as Non-Maskable interrupt.
Which interrupts are generally used for critical events?
Non-Maskable interrupts are used in critical events. Such as Power failure, Emergency, Shut off etc.
Give examples for Maskable interrupts?
RST 7.5, RST6.5, RST5.5 are Maskable interrupts
Give example for Non-Maskable interrupts?
Trap is known as Non-Maskable interrupts, which is used in emergency condition.
What are the various segment registers in 8086?
Code, Data, Stack, Extra Segment registers in 8086.
Which Stack 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 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 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.
Give an example of one address microprocessor?
8085 is a one address microprocessor.
In what way interrupts are classified in 8085?
In 8085 the interrupts are classified as Hardware and Software interrupts.
What are Hardware interrupts?
TRAP, RST7.5, RST6.5, RST5.5, INTR.
What are Software interrupts?
RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7.
Which interrupt has the highest priority?
TRAP has the highest priority.
Name 5 different addressing modes?
Immediate, Direct, Register, Register indirect, Implied addressing modes.
How many interrupts are there in 8085?
There are 12 interrupts in 8085.
What is the RST for the TRAP?
RST 4.5 is called as TRAP.
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.
SAIL Interview questions & details for a Computer Science Candidate is given here...
The Interview will be about 30-40 minutes. There will be 4-5 members in the panel. One person will
be from HR department .The questions can come from the entire span of engineering. But if you are
a fresher, be prepared to explain about your engineering project in detail. For experienced people, if
you are from related field of work, expect questions from your domain.
Some of the questions were...
What are the components of LAN?
How do we connect the systems in a LAN?
What is UTP? (Unshielded Twisted Pair)
How much distance it supports?
How much distance does a Fiber optic supports?
What is the throughput of the Ethernet LAN?
Describe about OSI Layers?
In which layer encryption can be done? And other than presentation layer?
What is the function of Bridge? Router?
Which layer is responsible for end 2 end connection?
What is RAID? (Redundant Array of Inexpensive Disks)
For what it is used for?
How can achieve fault tolerance through RAID?
Where the Static variable stored in C?
What are the functions of the OS?
Which OS you are familiar with?
What is the process?
What r its attributes?
How the process interacts with each others?
What r the mechanisms for inter process communication?
What is semaphore?
What is critical region?
How can semaphore avoid conflicts?
What is a virtual function?
What is late binding?
What is scope resolution operator?
Differentiate between testing and debugging?
Distinguish black box testing and white box testing?
What is unit testing?
How can u control the lost acknowledgement issue?
Is there is any difference between switch and hub? Which is good?
Principle behind the working of zener diode?
Give examples for 8 / 16 / 32 bit Microprocessors?
Why an 8 bit processor is called so?
Define HCMOS?
What is a Compiler?
Differentiate between Compiler and Interpretor?
What are the various interrupts in 8086? Explain each?
What is SIM and RIM instructions?
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