Real-Time Embedded Systems
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Preface xiii
Book Layout xv
Acknowledgments xvii
1 Introduction to Real-Time Embedded Systems 1
1.1 Real-Time Embedded Systems 1
1.2 Example: Automobile Antilock Braking System 3
1.2.1 Slip Rate and Brake Force 3
1.2.2 ABS Components 4
1.2.2.1 Sensors 4
1.2.2.2 Valves and Pumps 5
1.2.2.3 Electrical Control Unit 7
1.2.3 ABS Control 8
1.3 Real-Time Embedded System Characteristics 10
1.3.1 System Structure 10
1.3.2 Real-Time Response 10
1.3.3 Highly Constrained Environments 11
1.3.4 Concurrency 12
1.3.5 Predictability 12
1.3.6 Safety and Reliability 13
1.4 Hard and Soft Real-Time Embedded Systems 13
Exercises 14
Suggestions for Reading 15
References 15
2 Hardware Components 17
2.1 Processors 17
2.1.1 Microprocessors 17
2.1.2 Microcontrollers 19
2.1.3 Application-Specific Integrated Circuits (ASICs) 19
2.1.4 Field-Programmable Gate Arrays (FPGAs) 19
2.1.5 Digital Signal Processors (DSPs) 20
2.1.6 Application-Specific Instruction Set Processors (ASIPs) 20
2.1.7 Multicore Processors 20
2.1.8 Von Neumann Architecture and Harvard Architecture 21
2.1.9 Complex Instruction Set Computing and Reduced Instruction Set Computing 22
2.2 Memory and Cache 23
2.2.1 Read-Only Memory (ROM) 23
2.2.2 Random-Access Memory (RAM) 24
2.2.3 Cache Memory 24
2.3 I/O Interfaces 26
2.4 Sensors and Actuators 27
2.5 Timers and Counters 29
Exercises 30
Suggestions for Reading 31
References 31
3 Real-Time Operating Systems 33
3.1 Main Functions of General-Purpose Operating Systems 33
3.1.1 Process Management 34
3.1.2 Memory Management 36
3.1.3 Interrupts Management 39
3.1.4 Multitasking 39
3.1.5 File System Management 39
3.1.6 I/O Management 41
3.2 Characteristics of RTOS Kernels 42
3.2.1 Clocks and Timers 42
3.2.2 Priority Scheduling 44
3.2.3 Intertask Communication and Resource Sharing 45
3.2.3.1 Real-Time Signals 45
3.2.3.2 Semaphores 46
3.2.3.3 Message Passing 46
3.2.3.4 Shared Memory 46
3.2.4 Asynchronous I/O 47
3.2.5 Memory Locking 47
3.3 RTOS Examples 48
3.3.1 LynxOS 48
3.3.2 Ose 49
3.3.3 Qnx 49
3.3.4 VxWorks 49
3.3.5 Windows Embedded Compact 50
Exercises 50
Suggestions for Reading 52
References 52
4 Task Scheduling 53
4.1 Tasks 53
4.1.1 Task Specification 54
4.1.2 Task States 56
4.1.3 Precedence Constraints 58
4.1.4 Task Assignment and Scheduling 59
4.2 Clock-Driven Scheduling 59
4.2.1 Structured Clock-Driven Scheduling 62
4.2.1.1 Frames 62
4.2.1.2 Task Slicing 65
4.2.2 Scheduling Aperiodic Tasks 66
4.2.3 Scheduling Sporadic Tasks 68
4.3 Round-Robin Approach 69
4.4 Priority-Driven Scheduling Algorithms 70
4.4.1 Fixed-Priority Algorithms 70
4.4.1.1 Schedulability Test Based on Time Demand Analysis 72
4.4.1.2 Deadline-Monotonic Algorithm 76
4.4.2 Dynamic-Priority Algorithms 76
4.4.2.1 Earliest-Deadline-First (EDF) Algorithm 76
4.4.2.2 Optimality of EDF 78
4.4.3 Priority-Driven Scheduling of Aperiodic and Sporadic Tasks 82
4.4.3.1 Scheduling of Aperiodic Tasks 82
4.4.3.2 Scheduling of Sporadic Tasks 85
4.4.4 Practical Factors 85
4.4.4.1 Nonpreemptivity 85
4.4.4.2 Self-Suspension 86
4.4.4.3 Context Switches 87
4.4.4.4 Schedulability Test 87
4.5 Task Assignment 89
4.5.1 Bin-Packing Algorithms 89
4.5.1.1 First-Fit Algorithm 90
4.5.1.2 First-Fit Decreasing Algorithm 91
4.5.1.3 Rate-Monotonic First-Fit (RMFF) Algorithm 91
4.5.2 Assignment with Communication Cost 92
Exercises 94
Suggestions for Reading 97
References 97
5 Resource Sharing and Access Control 99
5.1 Resource Sharing 99
5.1.1 Resource Operation 100
5.1.2 Resource Requirement Specification 100
5.1.3 Priority Inversion and Deadlocks 101
5.1.4 Resource Access Control 103
5.2 Nonpreemptive Critical Section Protocol 103
5.3 Priority Inheritance Protocol 106
5.3.1 Rules of Priority Inheritance Protocol 106
5.3.2 Properties of Priority Inheritance Protocol 109
5.4 Priority Ceiling Protocol 111
5.4.1 Rules of Priority Ceiling Protocol 112
5.4.2 Properties of Priority Ceiling Protocol 114
5.4.3 Worst-Case Blocking Time 116
5.5 Stack-Sharing Priority Ceiling Protocol 119
5.5.1 Rules of Stack-Sharing Priority Ceiling Protocol 119
5.5.2 Properties of Stack-Sharing Priority Ceiling Protocol 121
Exercises 122
Suggestion for Reading 125
References 125
6 Concurrent Programming 127
6.1 Introduction 127
6.2 POSIX Threads 128
6.3 Synchronization Primitives 133
6.3.1 Race Conditions and Critical Sections 133
6.3.2 Mutex 134
6.3.3 Condition Variables 137
6.3.4 Semaphores 142
6.4 Communication among Tasks 148
6.4.1 Message Queues 149
6.4.2 Shared Memory 155
6.4.3 Shared Memory Protection 157
6.5 Real-Time Facilities 162
6.5.1 Real-Time Signals 162
6.5.1.1 Blocking Signals 163
6.5.1.2 Dealing with Signals 164
6.5.2 Timers 165
6.5.3 Implement Periodic Tasks 169
6.5.3.1 Using sleep() Function 169
6.5.3.2 Using Timers 172
6.5.4 Implement an Application with Multiple Periodic Tasks 173
Exercises 173
Suggestions for Reading 177
References 177
7 Finite-State Machines 179
7.1 Finite State Machine Basics 179
7.2 Deterministic Finite Automation (DFA) 181
7.2.1 Moore Machines 182
7.2.2 Mealy Machines 184
7.3 Nondeterministic Finite Automation 188
7.4 Programming Finite-State Machines 188
Exercises 191
Suggestions for Reading 194
References 195
8 UML State Machines 197
8.1 States 198
8.2 Transitions 200
8.3 Events 201
8.4 Composite States 202
8.4.1 Hierarchy 203
8.4.2 Orthogonality 205
8.4.3 Submachine States 206
8.5 Pseudostates 206
8.5.1 History Pseudostates 206
8.5.2 Entry and Exit Points 208
8.5.3 Fork and Join Pseudostates 210
8.5.4 Terminate Pseudostates 210
8.6 UML State Machine of Antilock Braking System 211
Exercises 215
Suggestions for Reading 217
References 217
9 Timed Petri Nets 219
9.1 Petri Net Definition 219
9.1.1 Transition Firing 221
9.1.2 Modeling Power 222
9.2 Petri Net Properties 225
9.2.1 Behavioral Properties 225
9.2.1.1 Reachability 225
9.2.1.2 ¿ Markings 226
9.2.1.3 Reachability Analysis Algorithm 227
9.2.1.4 Boundedness and Safeness 229
9.2.1.5 Liveness 229
9.2.2 Structural Properties 230
9.2.2.1 T-Invariants and S-Invariants 230
9.2.2.2 Siphons and Traps 233
9.3 Timed Petri Nets 234
9.3.1 Deterministic Timed Petri Nets 234
9.3.1.1 Performance Evaluation Based on DTPNs 237
9.3.2 Time Petri Nets 240
9.3.2.1 States in a Time Petri Net 241
9.3.2.2 Enabling and Firing Conditions of Transitions 242
9.3.2.3 Firing Rules 243
Exercises 244
Suggestions for Reading 250
References 251
10 Model Checking 253
10.1 Introduction to Model Checking 253
10.2 Temporal Logic 254
10.2.1 Linear Temporal Logic 256
10.2.1.1 Syntax of LTL 256
10.2.1.2 Parse Trees for LTL Formulas 257
10.2.1.3 Semantics of LTL 258
10.2.1.4 Equivalencies of LTL Formulas 262
10.2.1.5 System Property Specification 263
10.2.2 Computation Tree logic 264
10.2.2.1 Syntax of CTL 264
10.2.2.2 Semantics of CTL 265
10.2.2.3 Equivalencies of CTL Formulas 268
10.2.3 LTL versus CTL 268
10.3 The NuSMV Model Checking Tool 269
10.3.1 Description Language 269
10.3.1.1 Single-Module SMV Program 269
10.3.1.2 Multimodule SMV Program 271
10.3.1.3 Asynchronous Systems 273
10.3.2 Specifications 274
10.3.3 Running NuSMV 275
10.4 Real-Time Computation Tree Logic 279
Exercises 285
Suggestions for Reading 290
References 290
11 Practical Issues 293
11.1 Software Reliability 293
11.1.1 Software Faults 293
11.1.2 Reliability Measurement 294
11.1.3 Improving Software Reliability 295
11.1.3.1 Fault Avoidance 295
11.1.3.2 Fault Removal 295
11.1.3.3 Fault Tolerance 295
11.1.3.4 Fault Recovery 296
11.2 Software Aging and Rejuvenation 296
11.3 Security 297
11.3.1 Challenges 297
11.3.2 Common Vulnerabilities 298
11.3.3 Secure Software Design 299
11.4 Safety 300
11.5 Power Conservation 301
Suggestions for Reading 302
References 302
Index 305
