Microprocessor Interview Questions - 1

1. What is a Microprocessor?
Answer

A microprocessor is a programmable digital electronic component that incorporates the functions of a central processing unit (CPU) on a single semi conducting integrated circuit (IC). Instructions are fetched from memory, the they are decoded, and finally executed.

2. Why does microprocessor contain ROM chips?
Answer

Microprocessor uses ROM chips to store instructions, which are used to execute data.

3. What is the difference between a microprocessor and a microcontroller?
Answer

Microprocessor contains more op-codes, and few bit handling instructions. Where as a microcontroller contains few op-codes and more bit handling instructions. It can be called as a computer on a chip. In addition to all arithmetic and logic elements of a general purpose microprocessor, the microcontroller usually also integrates additional elements such as read-only and read-write memory, and input/output interfaces.

4. Give examples for 8, 16, and 32 bit microprocessors.
Answer

8-bit processors: MC6800, Intel 8008, Intel 8080, Z80.
16-bit processors: MC68000, Intel 8086.
32-bit processors: Intel 80386, Intel 80486, Z8000.

5. Give an example of a microprocessor, whose structure is pipelined.
Answer

All x86 processors have pipelined structure. Intel 8086, Intel 80386, etc.

6. What is flag? Give some examples of a flag.
Answer

Flag is a flip-flop used to store the information about the status of a microprocessor and the status of the last executed instruction.
Examples: Z - Zero flag, it is 1 if the last executed value is zero.
N - Negative flag, it is set if the result of operation in negative.
V - Overflow flag, it is set if the operation produced an overflow.
These are generally the bits of Condition Code Register (CCR).

7. What are most common registers present in a microprocessor?
Answer

Accumulator registers, Data registers, Temporary registers, Instruction registers, Stack Pointer, Program Counter and Condition Code Register.

8. Why is address bus unidirectional?
Answer

The address bus is unidirectional because the address is always given by the microprocessor, to address a memory location of an I/O device. Only microprocessor can write a value onto address bus, I/O devices can only read address bus.

9. Why is data bus bidirectional?
Answer

The data bus is bidirectional because the it is used by microprocessor, memory units, and I/O devices for both to transfer and receive data.

10. Expand RAM, ROM, PROM, EPROM, EEPROM.
Answer

RAM: Random Access Memory.
ROM: Read Only Memory.
PROM: Programmable Read Only Memory.
EPROM: Erasable Programmable Read Only Memory..
EEPROM: Electrically Erasable Programmable Read Only Memory.

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