1. HRT-HOOD Adam.Czajka@cs.put.poznan.pl Real-Time Systems Lecture 4 Copyright, 2002 © Adam Czajka

2. Contents Object types Data flow Object attributes Decomposition Classes Distributed systems

3. Copyright, 2002 © Adam Czajka Object types Active (A) Passive (Pa) Cyclic (C) Sporadic (S) Protected (Pr)

4. Copyright, 2002 © Adam Czajka Object types Passive Objects Passive object == Set of operations

5. Copyright, 2002 © Adam Czajka Object types Active Objects – operation types Asynchronous (ASER) Loosely Synchronous (LSER) Highly Synchronous (HSER) Functional activation constraints

6. Copyright, 2002 © Adam Czajka Object types Active Objects – timeout constraints Timeout constraints are related only to : TOER_HSER HSER  TOER_HSER TOER_LSER LSER  TOER_LSER (Timed Operation Execution Request)

7. Copyright, 2002 © Adam Czajka Object types Active Objects – timeout constraints

8. Copyright, 2002 © Adam Czajka Object types Cyclic Objects Object is invoked periodically

9. Copyright, 2002 © Adam Czajka Object types Sporadic Objects Start operation can be raised by interrupt

10. Copyright, 2002 © Adam Czajka Object types Protected Objects – operation types Asynchronous (PAER) - in Synchronous (PSER) – in/outs Only PSER operations can have functional activation constraints

11. Copyright, 2002 © Adam Czajka Data flow

12. Copyright, 2002 © Adam Czajka Data flow Function calling rules Active (A)  Any other object Cyclic (C), Sporadic (S)  Any other object except active (the asynchronous active operations are allowed to be called) Protected (Pr)  Only Protected or Passive (the asynchronous operations of all other objects are allowed) Passive (Pa)  Only Passive

13. Copyright, 2002 © Adam Czajka Data flow Function calling rules If A and B are passive (or protected) objects and object A calls the operation from object it is NOT allowed B, then it is NOT allowed to call any operation from object A by object B. General rule :

14. Copyright, 2002 © Adam Czajka Exceptions

15. Copyright, 2002 © Adam Czajka Object attributes DEADLINE THREAD BUDGET THREAD WCET OFFSET PRIORITY IMPORTANCE INTEGRITY PERIOD (Cyclic objects only) Minimum Arrival Time (Sporadic objects only)

16. Copyright, 2002 © Adam Czajka Object attributes OPERATION BUDGET OPERATION WCET (WCET = BUDGET + ERROR_HANDLING) CEILING PRIORITY INTEGRITY Operation attributes : Protected object attributes : Goal : To check the system schedulability.

17. Copyright, 2002 © Adam Czajka Decomposition Objects Operations Whole system (1 active object) More detailed components decomposition Decomposed system (no active objects)

18. Copyright, 2002 © Adam Czajka Decomposition Active  any other object Passive  only Passive objects Protected  Passive object + 1 Protected Sporadic  Passive, Protected, Cyclic + at least 1 Sporadic Cyclic  Passive, Protected, Sporadic + at least 1 Cyclic Object decomposition rules :

19. Copyright, 2002 © Adam Czajka Decomposition Decomposition rules (operation decomposition examples) : ASER  ASER ASER  PAER LSER  PSER PSER  PSER Decomposition is valid only if it doesn’t affect the parent object properties.

20. Copyright, 2002 © Adam Czajka Decomposition Decomposition example

21. Copyright, 2002 © Adam Czajka Decomposition

22. Copyright, 2002 © Adam Czajka Environmental objects

23. Copyright, 2002 © Adam Czajka Classes

24. Copyright, 2002 © Adam Czajka Distributed systems Buffer : Real object Real object Client „stub” Client „stub” Server „stub” Server „stub”

25. Copyright, 2002 © Adam Czajka Summary Object types Data flow Object attributes Decomposition Classes Distributed systems