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Cork Institute of Technology
Bachelor of Science (Honours) in Computer Applications – Award
(Bachelor of Science in Computer Applications – Award)
Bachelor of Science (Honours) in Software Development and Computer Networking
– Award
(Bachelor of Science in Software Development and Computer Networking – Award)
(NFQ – Level 8)
Autumn 2005
Real-Time Systems
(Time: 3 Hours)
Answer any THREE questions.
Note: Question 1 = 34 marks. All other questions = 33 marks. Real-Time Systems Reference Booklet available.
Examiners: Dr. J. Creagh Dr. D. Chambers Mr. P. O’Connor Mr. E. A. Parslow
Q1. (a) “OS-9 provides a complete development environment for the development of embedded systems. This includes HAWK and OS-9 on the target”. Discuss. Firstly, list a set of points that you wish to make. Then, expand on each point in your list. Clear examples required. (14 marks) (b) (i) Signals in OS-9 can be used for interprocess communication. Describe how to structure a process in OS-9 so that it may receive/handle signals. Give an example where signal numbers 400,401 and 402 are dealt with. (7 marks) (ii) Write a generic program, which uses argv/argc to send a signal to any process. (4 marks) (iii) Explain how you would test your program in part (b)(ii) above. (2 marks)
(c) “OS-9 provides events, which may be used to provide mutual exclusion or synchronisation”. Describe, with aid of your own example, how to structure OS- programs to provide mutual exclusion. (7 marks)
Q2. (a) (i) What are the advantages and disadvantages of the CAN field bus? Justify each point you make. (4 marks) (ii) Explain the CAN mechanism via an example: 4 nodes Q, R, S and T each transmit a single message at the same time; however, the priorities of the messages are 12 for Q, 7 for R, 10 for S, and 6 for T. Briefly, describe how CAN works with reference to the above example. (8 marks) (iii) Some network protocols are not suitable for real-time systems solutions. Discuss, giving examples. (4 marks)
(b) (i) Using an aeroplane as an example, justify why a distributed solution is often necessary. Diagrams are required. (4 marks) (ii) Reliability is vital for distributed solutions. List and explain, in detail, three areas of reliability. (9 marks) (iii) Discuss the issue of programming language support for distributed and real-time systems. (4 marks)
Q4. (a) Referring to fault tolerance, compare TMR and NMR. (3 marks)
(b) (i) Describe N-Version programming. Give an example and diagram(s). (6 marks) (ii) In your own words, describe the problem of frequency with which comparisons are made for N-Version programming. (3 marks) (iii) In your own words, and with your own example, explain the threshold problem when comparisons are made due to inexact results. Algorithms required. (5 marks) (c) (i) One phase of the software dynamic redundancy technique is error detection. List the different areas of error detection techniques. Give clear examples of each. (8 marks) (ii) Regarding the error recovery phase, write a report on this phase. (8 marks)
Q5. (a) (i) Consider the following process set:
Process T D C P 1 18 16 3 P 2 10 8 2 P 3 40 40 6 P 4 20 18 3 Test for schedulability using the utilisation-based schedulability test. (4 marks) (ii) Write an algorithm for the “Response Time Analysis with DEADLINES”. Explain your algorithm. (6 marks) (iii) Compare both utilisation-based and response time analysis tests. (4 marks)
(b) Regarding scheduling, describe time-line diagrams. Specify an example, specify each element of a time-line diagram structure and justify the use/value of time line diagrams. (7 marks) (c) (i) Describe the main points of the OCPP protocol. (3 marks) (ii) Describe the main points of the ICPP protocol. (3 marks)
(d) (i) Compare FPS with EDF scheduling. (3 marks) (ii) Explain with an example the problem of the domino effect with EDF. (3 marks)
