HRT-HOOD Real-Time Systems Lecture 4 Copyright, 2002 © Adam Czajka
Contents Object types Data flow Object attributes Decomposition Classes Distributed systems
Copyright, 2002 © Adam Czajka Object types Active (A) Passive (Pa) Cyclic (C) Sporadic (S) Protected (Pr)
Copyright, 2002 © Adam Czajka Object types Passive Objects Passive object == Set of operations
Copyright, 2002 © Adam Czajka Object types Active Objects – operation types Asynchronous (ASER) Loosely Synchronous (LSER) Highly Synchronous (HSER) Functional activation constraints
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)
Copyright, 2002 © Adam Czajka Object types Active Objects – timeout constraints
Copyright, 2002 © Adam Czajka Object types Cyclic Objects Object is invoked periodically
Copyright, 2002 © Adam Czajka Object types Sporadic Objects Start operation can be raised by interrupt
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
Copyright, 2002 © Adam Czajka Data flow
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
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 :
Copyright, 2002 © Adam Czajka Exceptions
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)
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.
Copyright, 2002 © Adam Czajka Decomposition Objects Operations Whole system (1 active object) More detailed components decomposition Decomposed system (no active objects)
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 :
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.
Copyright, 2002 © Adam Czajka Decomposition Decomposition example
Copyright, 2002 © Adam Czajka Decomposition
Copyright, 2002 © Adam Czajka Environmental objects
Copyright, 2002 © Adam Czajka Classes
Copyright, 2002 © Adam Czajka Distributed systems Buffer : Real object Real object Client „stub” Client „stub” Server „stub” Server „stub”
Copyright, 2002 © Adam Czajka Summary Object types Data flow Object attributes Decomposition Classes Distributed systems