Real Time Systems

Advanced State Machines

Behaviour (part 2) - 2

Outline

Simple and Composite States

Transition Segments and Junction Points

Run-to-Completion

Group Transitions and History

Self & Internal Transitions

Exercise

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Simple and Composite States

compositesimple

external view

??

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Simple and Composite States

internal view

What triggersthese transitions?

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Transition Segments

transition segments => a transition chain single trigger

State?

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Junction Points - 2 types

Termination (history)extension

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Design Tip:Unnamed Transitions / Segments

Do not leave these “unnamed” transitions in your models!!!

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Run-to Completion

a capsule exhibits run-to-completion semantics: meaning that a capsule will not be interrupted by

the run-time services library while it is executing a run-to-completion step.

when a message is received by a capsule, the entire transition chain executes (before another message is delivered);

data sent with a message is only accessible until the end of the run-to completion a local copy must be made to preserve the data

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Run-to Completion

consider event “done” while in sub-state “paint”. what is the sequence of execution code?

“Workstation” state “producing” sub-state

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Group Transitions

transitions from hierarchical states that are common to all sub-states example: “error” while in the sub-state “paint” what is the sequence of execution code?

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History (*deep)

the deepest sub-state when the containing state was last active. example: “reset” what is the sequence of execution code ?

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Self-transition

a transition “out-of” and “back-into” a state what are the consequences of getting a status

message while in the “paint” sub-state?

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Internal-transition

a self-transition which never exits the state does not fire all entry / exit code up & down the

state hierarchy; example: the new “status” transition

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Behaviour Exercise – part 1

Go to the RoseRT on-line Help Complete the animated Concept Tutorial

entitled: Capsule Hierarchical State Machines

{if you have not already done so}

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Behaviour Exercise – part 2

Refer to the following 2 state diagrams: Television Satellite Receiver – Top State Television Satellite Receiver – Operate Sub-state

Assume that initially you are in the Locked sub-state. After that follow the state machine wherever the transition chains take you: doDiagnostics followed by changeChannel followed by orderMovie followed by status followed by diag_timeout signal;

assume EvaluateTest = false

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Television Satellite Receiver – Top State

changeChannel,

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Television Satellite Receiver – Operate Sub-state