μC/OS-III
TM
The Real-Time Kernel
User’s Manual
Weston, FL 33326
Micriμm Press
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Weston, FL 33326
USA
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ISBN: 978-0-9823375-9-2
600-uCOS-III-Users-Manual-004
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Table of Contents
Preface .................................................................................................. 13
Chapter 1 Introduction .......................................................................................... 15
1-1 Foreground/Background Systems ...................................................... 16
1-2 Real-Time Kernels ................................................................................ 17
1-3 RTOS (Real-Time Operating System) .................................................. 19
1-4 μC/OS-III ............................................................................................... 19
1-5 μC/OS, μC/OS-II and μC/OS-III Features Comparison ...................... 24
1-6 How the Book is Organized ................................................................. 26
1-7 μC/Probe .............................................................................................. 26
1-8 Conventions ......................................................................................... 27
1-9 Chapter Contents ................................................................................. 28
1-10 Licensing .............................................................................................. 32
1-11 Contacting Micrium .............................................................................. 32
Chapter 2 Directories and Files ............................................................................ 33
2-1 Application Code ................................................................................. 36
2-2 CPU ....................................................................................................... 37
2-3 Board Support Package (BSP) ............................................................ 38
2-4 μC/OS-III, CPU Independent Source Code ........................................ 39
2-5 μC/OS-III, CPU Specific Source Code ................................................ 43
2-6 μC/CPU, CPU Specific Source Code .................................................. 44
2-7 μC/LIB, Portable Library Functions ..................................................... 46
2-8 Summary .............................................................................................. 48
Chapter 3 Getting Started with μC/OS-III ............................................................ 51
3-1 Single Task Application ....................................................................... 52
3-2 Multiple Tasks Application with Kernel Objects ................................. 60
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Table of Contents
Chapter 4 Critical Sections ................................................................................... 69
4-1 Disabling Interrupts .............................................................................. 70
4-1-1 Measuring Interrupt Disable Time ....................................................... 70
4-2 Locking the Scheduler ......................................................................... 71
4-2-1 Measuring Scheduler Lock Time ......................................................... 72
4-3 μC/OS-III Features with Longer Critical Sections ............................... 73
4-4 Summary .............................................................................................. 74
Chapter 5 Task Management ............................................................................... 75
5-1 Assigning Task Priorities ..................................................................... 84
5-2 Determining the Size of a Stack .......................................................... 86
5-3 Detecting Task Stack Overflows ......................................................... 87
5-4 Task Management Services ................................................................ 91
5-5 Task Management Internals ................................................................ 92
5-5-1 Task States ........................................................................................... 92
5-5-2 Task Control Blocks (TCBs) ................................................................. 97
5-6 Internal Tasks ..................................................................................... 109
5-6-1 The Idle Task (OS_IdleTask(), os_core.c) .......................................... 109
5-6-2 The Tick Task (OS_TickTask(), os_tick.c) .......................................... 111
5-6-3 The Statistic Task (OS_StatTask(), os_stat.c) ................................... 118
5-6-4 The Timer Task (OS_TmrTask(), os_tmr.c) ........................................ 121
5-6-5 The ISR Handler Task (OS_IntQTask(), os_int.c) .............................. 122
5-7 Summary ............................................................................................ 123
Chapter 6 The Ready List ................................................................................... 125
6-1 Priority Levels ..................................................................................... 126
6-2 The Ready List ................................................................................... 130
6-3 Adding Tasks to the Ready List ........................................................ 133
6-4 Summary ............................................................................................ 134
Chapter 7 Scheduling .......................................................................................... 135
7-1 Preemptive Scheduling ...................................................................... 136
7-2 Scheduling Points .............................................................................. 138
7-3 Round-Robin Scheduling .................................................................. 140
7-4 Scheduling Internals .......................................................................... 142
7-4-1 OSSched() .......................................................................................... 143
7-4-2 OSIntExit() ........................................................................................... 144
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7-4-3 OS_SchedRoundRobin() .................................................................... 145
7-5 Summary ............................................................................................ 147
Chapter 8 Context Switching .............................................................................. 149
8-1 OSCtxSw() .......................................................................................... 152
8-2 OSIntCtxSw() ...................................................................................... 154
8-3 Summary ............................................................................................ 157
Chapter 9 Interrupt Management ....................................................................... 159
9-1 Handling CPU Interrupts .................................................................... 160
9-2 Typical μC/OS-III Interrupt Service Routine (ISR) ............................. 161
9-3 Non Kernel-Aware Interrupt Service Routine (ISR) ........................... 164
9-4 Processors with Multiple Interrupt Priorities .................................... 165
9-5 All Interrupts Vector to a Common Location .................................... 167
9-6 Every Interrupt Vectors to a Unique Location .................................. 169
9-7 Direct and Deferred Post Methods ................................................... 170
9-7-1 Direct Post Method ............................................................................ 170
9-7-2 Deferred Post Method ....................................................................... 173
9-8 Direct vs. Deferred Post Method ....................................................... 176
9-9 The Clock Tick (or System Tick) ........................................................ 177
9-10 Summary ............................................................................................ 179
Chapter 10 Pend Lists (or Wait Lists) ................................................................... 181
10-1 Summary ............................................................................................ 186
Chapter 11 Time Management ............................................................................. 187
11-1 OSTimeDly() ........................................................................................ 188
11-2 OSTimeDlyHMSM() ............................................................................ 193
11-3 OSTimeDlyResume() .......................................................................... 195
11-4 OSTimeSet() and OSTimeGet() .......................................................... 196
11-5 OSTimeTick() ...................................................................................... 196
11-6 Summary ............................................................................................ 196
Chapter 12 Timer Management ............................................................................ 197
12-1 One-Shot Timers ................................................................................ 199
12-2 Periodic (no initial delay) .................................................................... 200
