Tribhuvan University

Institute of Science and Technology


Bachelor Level / second-semester / Science

Computer Science and Information Technology( CSC167 )


Full Marks: 60 + 20 + 20

Pass Marks: 24 + 8 + 8

Time: 3 Hours

Candidates are required to give their answers in their own words as far as practicable.

The figures in the margin indicate full marks.

Group A

Attempts any TWO questions


Explain instruction cycle, machine cycle and T-states. Draw timing diagram of IN instruction with brief description.


Draw block diagram of 80286 microprocessor and explain its main four functional sub-units. Differentiate between Real Address Mode and Protected Virtual address mode.


Explain LXI and CMP instruction. Write an assembly language program for 8-bit microprocessor to divide 8 bit data stored in memory location 8050 by 8 bit data stored in 8051 and store the quotient in 8052 and remainder in 8053.

Group B

Attempts any EIGHT questions


What are the different modes of parallel communication? Construct a control word for 8255 PPI for following configuration:

Port A and Port Cupper – mode 0

Port B and Port Clower  – mode 0

Port A and Port Cupper as input port

Port B and Port Clower as output port


Differentiate between interrupt based I/O and DMA based I/O. Explain based DMA operation in brief


Differentiate between PUSH and POP instruction with example illustrating the use of these instruction.


Write an assembly language program for 16 bit microprocessor to reverse the string “This is  Microprocessor”


What is the use of AD7 – AD0 in 8085 microprocessor? Explain address de-multiplexing process in 8085 microprocessor with suitable diagram.


What is mean by addressing mode? Explain all the addressing mode available in 8085 microprocessor.


Explain Register Organization in 80386 microprocessor.


Draw a logic diagram showing generation of memory and I/O read/write control signals in 8085 microprocessor


Write short notes on (Any two):

  1. Program Counter
  2. Von-Neumann Architecture
  3. Interrupt Masking