8085 Microprocessor Interview Questions

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8085 Microprocessor Interview Questions

  1. What is flip-flop?

A flip-flop is a binary cell capable of storing one bit of information. It has two outputs; one for the normal value and one for the complement value of the bit stored in it. . It has the property to remain in one state indefinitely until it is directed by an input signal to switch over to the other state. It is also called bistable multivibrator. The basic formation of flip flop is to store data.

  1. What is D-flip flop?
    The D-flip flop is a slight modification of the SR-flip flop. A SR flip flop is converted to a D flip-flop by inserting an inveter between ‘S’ and ‘R’ and assigning the symbol ‘D’ to the single input. The D type flip flop has one input D for data or delay and a clock input. D flip-flops are used to eliminate the indeterminate state that occurs in SR Flip-flop. D flip-flop ensures that S and R are never equal to one at the same time. The output does not change its state unless it is enabled by a clock pulse. It stores value that is on the data line and this is why it is also viewed as a memory cell.
  2. What is registers ?
    A Register is a group of flip flop with each flip flop capable of storing one bit of information . It is a local storage area in a processor that holds data is to be processed by the CPU. Any kind of data must first be identified by the register before it can be manipulated. For example- if an arithmetic operation is performed on two numbers then the input and outputs are stored in a register. In the Memory Hierarchy it occupies the top most position, providing a high-speed storage space and fast access to data. It includes the address of the memory location instead of the data itself. They are generally measured in BITS to determine the amount of data that it can hold.
  3. What is program counter?
    Program counter holds the address of the next instruction to be executed. It is the 16-bit register. It point the memory location.
  4. What is decoder ?
    A decoder is a combinational circuit that converts binary information from the ‘n’ coded inputs to a maximum of 2n unique outputs.
  5. What is accumulator?
    An accumulator is a 8-bit register that stores intermediate arithmetic and logic results in a CPU. Each operation that we perform is always carried out with an accumulator that helps to speed up the processing time as to access main memory each time for a process to take input from and store output to is very time consuming.
  6. What is stack ?
    A stack is a storage device that store information in such a manner that the item stored last is the first item retrieved. It is also called LIFO.
  7. What is stack pointer?
    The register that holds the address for the stack is called stack pointer(SP) because its value always points at the top item in the stack.
  8. What is Multiplexer and Demultiplexer?
    A multiplexer is a combinational circuit that receives binary information from one of the ‘2n’ input data lines and directs it to a single output line. They are generally used for sending one or more analogue or digital signals over a common transmission line at different times or speeds.
    A Demultiplexer is a combinational circuit that receives single binary information and produce ‘2n’ output data lines. It is used when a circuit wishes to send a signal to one of many devices. A de-multiplexer converts a serial data signal at the input to a parallel data at its output lines.
  9. What is ALU?
    ALU is the arithmetic logic unit that performs the required micro-operation for executing the instruction. The control unit supervises the transfer of information among the registers and instructs the ALU as to which operation to perform. The ALU has a direct access to the I/O devices, main memory and the processor.
  10. What is Conductor?
    An electrical conductor is a substance in which electrical charge carries usually electrons, move easily from atom to atom with the application of voltage. In a conductor the outer electrons of an atom are loosely bound and are free to move through the material.
  11. Why we use Capacitors?

We use capacitor because with the help of capacitor we hold or release the electrical charge. It is similar to a battery but is completely different in its working as it does not produce new electrons, it only stores them.

  1. What is a memory cell?
    A memory cell is a small block of memory where data are stored inside the register.
  2. What is Encoder?
    An encoder is a digital circuit that performs the inverse operation of a decoder. An encoder has ‘2n’ inputs and n output lines. it converts the input data into an equivalent binary code as its output.
  3. What is Instruction Register?
    Instruction register is an element in the CPU of a computer or other device that holds the programming instruction that will be executed at the start of the next clock cycle as directed by other parts of CPU.
  4. What is Instruction Decoder?
    Instruction decoder (ID) takes bits stored in instruction register and decodes it and tells to CPU what it need to do for it and enable the components for the operation. Simply, instruction decoder is like a dictionary. It tells the meaning of the instruction.
  5. What is Interrupt ?
    An interrupt is a signal from a device attached to a computer or from a program within the computer that causes the main program that operates the computer to stop and figure out what to do next. It gives the priority based to the program, where higher priority is allowed first than lower priority.
  6. What is Serial and Parallel transmission?

Serial transmission:-  Bits are send sequentially on the same channel which reduces costs for channel but also slows the speed of transmission .
Parallel transmission:-  Multiple bits are send simultaneously  on different channels within the same cable, or radio path, and synchronized to a clock.

  1. What is Oscillator? Why we use crystal oscillator?
    The main purpose of Oscillator is generating a signal. Crystal oscillator is used to provide a stable clock run for the micro-controller which is real time dependent.
  2. What is the meaning of Baud rate?
    Baud rate is the measurement of data communication from source to destination where the transferred rate is measured per second.
  3. What is the use of clock frequency?
    Clock frequency is used to measure the pulses at a predetermined rate and interval.
  4. What is the meaning of enable pin?
    The enable pins means to provide the power supply to the processors.
  5. What is the use of enable pin?
     The enable pins are used to switch ON the output pins. Logic chips have two states for their outputs, i.e. ‘0’ and ‘1’. When the outputting is ‘0’, the output is switch towards the ground line. When the output is ‘1’, the output is switched towards the supply line.
  6. Why we use heat sink?
    The heat sink is used to cool the graphics processors and central processing units. It is passive heat exchanger that cools a device by dissipating heat into the surrounding medium.
  7. Why below 2000 address is not used in most of 8085 microprocessor kit?
    In most of the processors we cannot use addresses below 2000 to store any user defined data or results as these addresses are generally assigned to the hardware attached to that microcomputer such as keyboard.
  8. Explain LIFO and FIFO concept?

The concept of LIFO is that the last element to be inserted is the first to be executed i.e. Last in First Out. It is used in stacks.

The concept of FIFO is that the first element to be inserted is first to be executed i.e. First in First Out. It is used in queues.

  1. Explain EPROM?

EPROM (Erasable programmable read-only memory) is programmable read-only memory that can be erased and reused. It is a type of memory that retains its data when the power supply is switched off. It is non-volatile memory.

  1. What is RAM?

RAM(Random Access Memory) is a computer memory which can be accessed randomly. In RAM any byte of memory can be accessed without touching the previous bytes. It is the most common type of memory found in computers and other devices.

  1. Explain PPI?

Programmable Peripheral Interface (PPI) device designed for the use in Intel microcomputer systems. Its function is that of a general purposes I/O component to Interface peripheral devices with the microprocessor.

  1. What is PKI?

Programmable Keyboard Interface (PKI) scans and encodes up to 64-key keyboard and controls upto a 16-digit numerical display. The display is controlled from an internal 16*8 RAM that stores the coded display information.

  1. What is Programmable Timer?

Programmable Timer is a counter that generates an output signal when it reaches a programmed count. The output signal may trigger an interrupt.

  1. What is Zener Diode?

Zener diode is a diode which allows the current to flow in the forward direction as the other diodes but it also allow current to flow in the reverse direction when the voltage is above a certain value. This breakdown voltage is known as zener voltage.

  1. What are Transistors?

A transistor is a semi-conductor device which is used to amplify and switch electric signals and electric power. It is composed of semiconductor material with at least three terminals for connection to an external circuit.

By |2015-01-29T14:04:37+00:00January 29th, 2015|8085 Microprocessor, Uncategorized|0 Comments

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January 29th, 2015

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