8086 MICROPROCESSOR INTERVIEW QUESTIONS&ANSWERS
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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.
