Microprocessor Short Questions and AnswersHello Friends Here in this section of Microprocessor Short Questions and Answers,We have listed out some of the important Short Questions with Answers which will help students to answer it correctly in their University Written Exam.


Lets have a look at below Lists of Short Descriptive type Questions that may be asked in this format in Written Exams.

1.What is the need of co- processors? Give an example?
The coprocessor is a processor which is specially designed processor to work under the control of the processor and to support special processing capabilities. For example, 8087 is a coprocessor. It works under the control of 8086 processor and has numeric processing capabilities.


2. Mention the advantages of using 8087 numeric data processor.
However, some applications require extremely fast and complex math functions which are not provided by a general purpose processor. Such functions as square  root, sine, cosine, and logarithms are not directly available in a general purpose processor. Providing fast, accurate, complex math can be quite complicated, requiring large areas of silicon on integrated circuits.


3. What are the advantages of multiprocessor system?
i.improves cost/ performance ratio of the system
ii.Tasks are divided among the modules. If failure occurs, it is easier and cheaper to find and replace the malfunctioning processor than replacing the falling part of complex processor.


4. What are the advantages of multiprocessor system?
i. Better system throughput by having more than one processor.
ii. system structure is more flexible


5. What are the instructions available in 8087?
a.Data transfer instructions
b. arithmetic instructions
c.compare instructions
d. transcendental instructions
e.load constant instructions
f. processor control instructions


6. What are the features of 8089?
a.Instructions are specially designed for I/O processing.
b. In addition to data transfer 8089 can perform arithmetic and logic operations, branches, searching and translation


7. What is mean by microcontroller?
A device which contains the microprocessor with integrated p peripherals like memory, serial ports, parallel
ports, timer/counter, interrupt controller, data acquisition interfaces like ADC, DAC is called microcontroller.


8. Why interfacing is needed for 1/0 devices?
Generally I/O devices are slow devices. Therefore the speed of I/O devices does not match with the speed of microprocessor. And so an interface is provided between system bus and I/O devices.


9. What is the difference between CPU bus and system bus?
The CPU bus has multiplexed lines but the system bus has separate lines for each signal. (The multiplexed CPU lines are demultiplexed by the CPU interface circuit to form system bus).


10. List the features of 8051 microcontroller?
The features are

  • single supply +5 volt operation using HMOS technology.
  • 4096 bytes program memory on chip (not on 8031)
  • 128 data memory on chip.
  • Four register banks.
  • Two multiple mode, 16-bit timer/counter.
  • Extensive Boolean processing capabilities.
  • 64 KB external RAM size
  • 32 bidirectional individually addressable I/O lines.
  • 8 bit CPU optimized for control applications.



11. Explain the operating mode0 of 8051 serial ports?
In this mode serial enters &exits through RXD, TXD outputs the shift clock.8 bits are transmitted/received:8 data bits(LSB first).The baud rate is fixed at 1/12 the oscillator frequency.


12. Explain the operating mode2 of 8051 serial ports?
In this mode 11 bits are transmitted (through TXD) or received (through RXD):a start bit(0), 8 data bits(LSB first),a programmable 9th data bit ,& a stop bit(1).ON transmit the 9th data bit (TB* in SCON)can be assigned the value of 0 or 1.Or for eg:, the parity bit(P, in the PSW)could be moved into TB8.On receive the 9th data bit go in to the RB8 in Special Function Register SCON, while the stop bit is ignored. The baud rate is programmable to either 1/32or1/64 the oscillator frequency.


13. Explain the mode3 of 8051 serial ports?
In this mode,11 bits are transmitted(through TXD)or received(through RXD):a start bit(0), 8 data bits(LSB first),a programmable 9th data bit ,& a stop bit(1).In fact ,Mode3 is the same as Mode2 in all respects except the baud rate. The baud rate in Mode3 is variable. In all the four modes, transmission is initiated by any instruction that uses SBUF as a destination register. Reception is initiated in Mode0 by the condition RI=0&REN=1.Reception is initiated in other modes by the incoming start bit if REN=1.


14. Explain the interrupts of 8051 microcontroller?
The interrupts are:
Vector address

  •  External interrupt 0: IE0: 0003H
  •  Timer interrupt 0: TF0: 000BH
  •  External interrupts 1: IE1: 0013H
  •  Timer Interrupt 1: TF1: 001BH
  •  Serial Interrupt Receive interrupt: RI: 0023H Transmit interrupt: TI: 0023H


15. Write A program to perform multiplication of 2 no’s using 8051?
MOV A, data 1
MOV B, #data 2
MOV DPTR, #5000
MOV @DPTR, A (lower value)


16. Write a program to mask the 0th &7th bit using 8051?
MOV A, data
ANL A, #81
MOV DPTR, #4500


17. Write program to load accumulator, DPH, &DPL using 8051?
MOV A,#30


18. Write a program to find the 2’s complement using 8051?


19. Write the features of mode 0 in 8255.
In mode 0, port A and port B can be configured as simple 8-bit input or output ports without handshaking. The two halves of port C can be programmed separately as 4-bit input or output ports.


20.What is memory mapping?
memory mapping may refer to:
Memory-mapped file, also known as mmap() Memory-mapped I/O, an alternative to port I/O; a communication between CPU and peripheral device using the same instructions, and same bus, as between CPU and memory
Virtual memory, technique which gives an application program the impression that it has contiguous
working memory, while in fact it is physically fragmented and may even overflow on to disk storage