NATIONAL OPEN UNIVERSITY OF NIGERIA

UNIVERSITY VILLAGE, PLOT 91, CASDASTRAL ZONE, NNAMDI AZIKIWE EXPRESS WAY, JABI, ABUJA.
FACULTY OF SCIENCES
OCTOBER 2019 EXAMINATION

CIT 411: MICROCOMPUTERS AND MICROPROCESSORS
TIME ALLOWED: 2HOURS
CREDIT UNIT: 2 UNITS
INSTRUCTION(S): ANSWER QUESTION 1 AND ANY OTHER THREE (3) QUESTIONS

1a.) Specify the hardware features of the CISC within the context of Microcomputers and Microprocessors. (4mks)
b.) Describe the concept of instruction and interpret its relationship with instruction set (3mks)
c.) Mention the 8085 flags (3mks)
d) Examine the main features of 8085 microprocessors (6mks)
e.) Determine examples of devices that can be used as i) servers and ii) clients (4 mks)
f.) Describe the concept of flag? State the various uses of flags in microprocessors? (5mks)

2a) With two examples each, illustrate the classes of 8085 instruction set based on word size. (7½ mks)
2b) i. What is an Interrupt?
ii. Detect the likely causes of program crashes when interrupts routines }7½mk
are used?

3a.) Deduce the actions taken by microcontroller when an Interrupts is triggered (5mks)
b.) Describe the various types of computer ports and itemize their functions (6mks)
c.) i. What is Direct Memory Access? ) 2 mks
ii. Mention any four (4) devices that make use of DMA ) 2 mks

4a.) Illustrate the effect of the following assembly language instructions:
i) ORL D, 91h
ii) MOV D, 86h
iii) ANL C, 90h ) 2 x 5 = 10 marks
ii) CPL 20h
v)) SETB 25h
b.) Demonstrate using a well labelled diagram, the Harvard architecture (5mks)

5a.) Provide the classes of instructions vis-à-vis their respective functions (5mks)
b) Determine the main sub-categories of Computer architecture (7mks)
c.) State the reasons why DMA is required, outlining how it works (3mks)