1. CSCI1600: Embedded and Real Time Software
Lecture 12: Modeling IV: Compositions of State Machines
Steven Reiss, Fall 2016
Hand out digital watch statechart
Without the introductory discussion of the circuit, this lecture would have run short. Might want to look at some of the material in the text and see if it can augment the lecture.

2. Circuit Review
Lecture 12: Modeling Compositions
10/31/2019

3. Modeling Tasks We can model individual tasks using FSMs
Extended FSMs, Timed automata, …
Hybrid automata to reflect state of outside world
This is sufficient for coding
We need to model the overall application
We need this to prove properties of the system
We need this to understand overall system behavior
What was in chapter 5?
Lecture 12: Modeling Compositions
10/31/2019

4. Digital Watch Lots of features Four buttons for input
How does it work?
How would you model it?
Lecture 12: Modeling Compositions
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5. Statecharts Here is one model Lets look at it in detail
Understand what it means
Map to a single FSM
How many think they could explain/understand this?
Lecture 12: Modeling Compositions
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6. Example : Concurrent Machines
This diagram is not readable. Replace
Lecture 12: Modeling Compositions
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7. Example: Concurrency
Lecture 12: Modeling Compositions
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8. Example: Concurrency
Lecture 12: Modeling Compositions
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9. Example : Communicating Tasks
Lecture 12: Modeling Compositions
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10. Example: Hierarchical
Lecture 12: Modeling Compositions
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11. Example: Hierarchical
Lecture 12: Modeling Compositions
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12. Example: Hierarchical
Lecture 12: Modeling Compositions
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13. Microwave Oven
Lecture 12: Modeling Compositions
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14. Digital Watch Can you understand this now?
Lecture 12: Modeling Compositions
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15. Example
Tic-Tac-Toe
Lecture 12: Modeling Compositions
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16. Implementing a Statechart
Handling concurrency
The FSM is in multiple states
What does this mean formally (single FSA)
What does this mean in a statechart
What do you do with an input
How is this implemented
What if the results are contradictory (set x = 1, set x = 0)
What does this mean for your implementation
Lecture 12: Modeling Compositions
10/31/2019

17. Mapping to Code Direct sequential coding Explicit state variables
Determine state from various conditions
Act accordingly
Allows common operations for multiple states
Explicit state variables
switch (state) { … }
Table-driven
Approximate the state machine
Lecture 12: Modeling Compositions
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18. Homework Read 6.1, 6.2, 6.4 Exercise 6.7
Lecture 12: Modeling Compositions
10/31/2019