Modeling Software with Finite State Machines: A Practical Approach

Table of Contents

Part I
The Problems of Software

1. Evolution of Software Development
Programming Languages
A Little History, BASIC Catastrophe, C++, PLC, Script or Macro Notations, There Are Many Languages
Basic Knowledge, Specifying or Not? CASE Tools, UML, Agile Methods, Behavior Modeling
Development Tools
Recommended Reading
2. The Price of Weakness
Software Development Costs
Programming as a Hobby, Small Software Projects, Large Software Projects, Hardness of Software, Ease of Creating New Macro Languages, Do We Need So Many Programming Languages? The Specifics of Programming Languages, The Specifics of a Software Project, Software Is Expensive
Maintenance Costs
Software Errors, Software Changes, In Code We Trust, The Costs of Software Errors
The Programmers’ World
A Programmer in a Project, The Software Project Leader
Examples of Disasters
Recommended Reading
3. Software as Engineering?
Fascination with Graphics, Visual Basic Chaos, Object-Oriented Design Illusion, UML Illusion, Formal Methods, CASE Tools — Value for Money? Programming or Specification Languages?
Development Cycle
Prototyping, Specification, Software Development Steps, Software Documentation, Testing and Debugging, Maintenance and Support, Human Factors, Summary
Education Requirements
Who Is a Programmer? Education as the Basis of Skill, Missing Skill — Examples
Recommended Reading

Part II
Finite State Machines

4. Introduction, Definitions, and Notation
Finite State Machine
State Machine Models and Presentations
Transition Matrix, State Transition Diagram, Outputs (Actions), Moore and Mealy Model, State Transition Table, Example
Recommended Reading
5. Hardware Applications
Limited to Boolean Signals, Design Example — Traffic Light Control, EPROM-Based Implementations, FPLA- or CPLD-Based Implementations, Conclusions, Recommended Reading
6. Software Specific
Data and Control Flow
Any Class of Signal May "Contain" the Control Value
Digital Input Command Input Numerical Input Parameter Data Processing Result Timer State Machine External and Internal Signals What about Outputs? Digital Output Command Output Numerical Output Data Processing Output Timer Summary
Event Driven Software
Event as a Control Signal
State Machine or Combinational System?
Models of a Finite State Machine
Application-Based State Machine Models State Machine Execution Models
Coding as a Universal Solution
Table-Driven Software to Reduce Coding Effort
Limits of the Coded Solutions
Recommended Reading
7. Misunderstandings about FSM
Historical Background
Software Systems
Event-Driven Model Parser Problem State Explosion Signal Lifetime State Machine Size Interface between State Machines
A Flowchart Is Not a State Machine
Flowchart Example What Is a Flowchart For?
Recommended Reading
8. Designing a State Machine
A State Machine Models Behavior
Mealy or Moore Models
Actions (Entry, Input, Exit, Transition)
Defining States
Acknowledgment Principle (Busy and Done States)
The Role of a Timer
Error States and Alarms
Completeness of the Design
Hiding Control Information
Example — Pedestrian Traffic Lights
The Requirements The Specification The Specification Must Be Understandable
Example — Pressure Supervision
The Requirements The Specification The Output Function The State Transition Diagram
9. Systems of State Machines
Mastering Complexity
The Partitioning Criteria
The Communication Interface among State Machines
The Handshaking Rule
The (Hierarchical) Structure of the Control System
Design Procedure
Locality of the Control Problems Up-Down or Bottom-Up Design Deadlocks Loops Sins Design Rules
Example — Pumps Supervision System
Task Definition The First Approach The Second Trial The Ultimate Solution
Example — Traffic Light Control
Task Definition "Obvious" Solution The Ultimate Control Light TrafficLight Flash System for Two-Track Railway Summary
Implementation Designing a State Machine Designing a System of State Machines

Part III
StateWORKS: Principles and Practice

10. StateWORKS
Virtual Environment and Vfsm
The StateWORKS Development Environment
Positive Logic Algebra The Vfsm Execution Model Objects State Machine Defines Object Control Values Signal Lifetime Behavior Specification System Specification
The StateWORKS Execution Environment
RTDB-Based Runtime System Output Function I/O Handler User Interface
Recommended Reading
11. Digital Input and Output
A Digital Input Has Three Control Values
Setting and Clearing the Boolean Output Are Two Different Actions
DI and DO Properties
Recommended Reading
12. Other Inputs
Input Data (DAT)
Control Values Example Properties
Getting the Control Value (SWIP)
Actions Control Values Example Properties
NI Object as an Extension of DAT Type
Control Values Properties
PAR Object as a Specific Variant of DAT Type
Control Values Properties
Strings (STR) as a Specific Variant of SWIP
Actions Control Values Example Properties
Recommended Reading
13. Other Outputs
Output Data (NO)
Actions Example Properties
Output Demultiplexer (TAB)
Actions Example
Alarms (AL)
Actions Properties Example
Recommended Reading
14. Counters
A Simple Counter (CNT)
Actions Control Values Example Properties
An Event Counter (ECNT)
Example Properties
A Timer (TI)
An Up/Down Counter (UDC)
Actions Control Values Properties Example
Recommended Reading
15. VFSM and Its Interfaces
Virtual Finite State Machine Interfaces
A Virtual Finite State Machine (VFSM)
Hiding Specification Details
A Command (CMD)
An Interface to I/O Handler (UNIT)
An Interface to a User-Written Function (OFUN)
Example Properties
Just XDA
Memory for OFUN Internal Value as a Control Value
Recommended Reading
16. Debugging Vfsm
Testing Vfsm Application
System Consistency
Debugging Mode (VFSM)
Command Files
Service Mode
The Role of Documentation
17. What Is StateWORKS?
Compared with Specification Methods
Compared with Agile Methods
Application Areas
Recommended Reading
Appendix A. Case Studies
Appendix B. Microwave Oven Control — Use of StateWORKS Development Tools
Appendix C. Control — Hierarchical System of State Machines
Appendix D. Dining Philosophers Problem Example
Appendix E. Going Beyond the Limitations of IEC 61131-3
Appendix F. Traffic Light Control — Design of the Hardware Solution
Appendix G. Coding Finite State Machine — Vending Machine Counter Example
Appendix H. IOD File of the StandardUnit
Appendix I. StateWORKS Projects
Appendix J. Vending Machine Counter Project
Appendix K. Pedestrian Traffic Light Project
Appendix L. Pumps Supervision Project
Appendix M. Output Function CalcLimits()
Appendix N. Traffic Light Project
Appendix O. DI_DO Project
Appendix P. Other_Inputs Project
Appendix Q. Other_Outputs Project
Appendix R. Counters Project
Appendix S. Attributes of RTDB Objects
Appendix T. StateWORKS Tools and Components