readme_threadx.txt
1 Microsoft's Azure RTOS ThreadX for Cortex-M0
2
3 Using the IAR Tools
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51. Building the ThreadX run-time Library
6
7Building the ThreadX library is easy. First, open the Azure RTOS workspace
8azure_rtos.eww. Next, make the TX project the "active project" in the
9IAR Embedded Workbench and select the "Make" button. You should observe
10assembly and compilation of a series of ThreadX source files. This
11results in the ThreadX run-time library file tx.a, which is needed by
12the application.
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14
152. Demonstration System
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17The ThreadX demonstration is designed to execute under the IAR
18Windows-based Cortex-M0 simulator.
19
20Building the demonstration is easy; simply make the sample_threadx.ewp project
21the "active project" in the IAR Embedded Workbench and select the
22"Make" button.
23
24You should observe the compilation of sample_threadx.c (which is the demonstration
25application) and linking with tx.a. The resulting file sample_threadx.out is a
26binary file that can be downloaded and executed on IAR's Cortex-M0 simulator.
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293. System Initialization
30
31The entry point in ThreadX for the Cortex-M0 using IAR tools is at label
32__iar_program_start. This is defined within the IAR compiler's startup code.
33In addition, this is where all static and global preset C variable
34initialization processing takes place.
35
36The ThreadX tx_initialize_low_level.s file is responsible for setting up
37various system data structures, and a periodic timer interrupt source.
38By default, the vector area is defined at the top of cstartup_M.s, which is
39a slightly modified from the base IAR file.
40
41The _tx_initialize_low_level function inside of tx_initialize_low_level.s
42also determines the first available address for use by the application, which
43is supplied as the sole input parameter to your application definition function,
44tx_application_define. To accomplish this, a section is created in
45tx_initialize_low_level.s called FREE_MEM, which must be located after all
46other RAM sections in memory.
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48
494. Register Usage and Stack Frames
50
51The following defines the saved context stack frames for context switches
52that occur as a result of interrupt handling or from thread-level API calls.
53All suspended threads have the same stack frame in the Cortex-M0 version of
54ThreadX. The top of the suspended thread's stack is pointed to by
55tx_thread_stack_ptr in the associated thread control block TX_THREAD.
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57
58 Stack Offset Stack Contents
59
60 0x00 LR Interrupted LR (LR at time of PENDSV)
61 0x04 r4
62 0x08 r5
63 0x0C r6
64 0x10 r7
65 0x14 r8
66 0x18 r9
67 0x1C r10 (sl)
68 0x20 r11
69 0x24 r0 (Hardware stack starts here!!)
70 0x28 r1
71 0x2C r2
72 0x30 r3
73 0x34 r12
74 0x38 lr
75 0x3C pc
76 0x40 xPSR
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78
795. Improving Performance
80
81The distribution version of ThreadX is built without any compiler
82optimizations. This makes it easy to debug because you can trace or set
83breakpoints inside of ThreadX itself. Of course, this costs some
84performance. To make it run faster, you can change the ThreadX library
85project to enable various compiler optimizations.
86
87In addition, you can eliminate the ThreadX basic API error checking by
88compiling your application code with the symbol TX_DISABLE_ERROR_CHECKING
89defined.
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91
926. Interrupt Handling
93
94ThreadX provides complete and high-performance interrupt handling for Cortex-M3
95targets. There are a certain set of requirements that are defined in the
96following sub-sections:
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98
996.1 Vector Area
100
101The Cortex-M3 vectors start at the label __vector_table and is defined in cstartup_M.s.
102The application may modify the vector area according to its needs.
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104
1056.2 Managed Interrupts
106
107ISRs for Cortex-M using the IAR tools can be written completely in C (or assembly
108language) without any calls to _tx_thread_context_save or _tx_thread_context_restore.
109These ISRs are allowed access to the ThreadX API that is available to ISRs.
110
111ISRs written in C will take the form (where "your_C_isr" is an entry in the vector table):
112
113void your_C_isr(void)
114{
115
116 /* ISR processing goes here, including any needed function calls. */
117}
118
119ISRs written in assembly language will take the form:
120
121 PUBLIC your_assembly_isr
122your_assembly_isr:
123
124 PUSH {lr}
125
126 ; ISR processing goes here, including any needed function calls.
127
128 POP {r0}
129 MOV lr, r0
130 BX lr
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132
1337. IAR Thread-safe Library Support
134
135Thread-safe support for the IAR tools is easily enabled by building the ThreadX library
136and the application with TX_ENABLE_IAR_LIBRARY_SUPPORT. Also, the linker control file
137should have the following line added (if not already in place):
138
139initialize by copy with packing = none { section __DLIB_PERTHREAD }; // Required in a multi-threaded application
140
141The project options "General Options -> Library Configuration" should also have the
142"Enable thread support in library" box selected.
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144
1458. Revision History
146
147For generic code revision information, please refer to the readme_threadx_generic.txt
148file, which is included in your distribution. The following details the revision
149information associated with this specific port of ThreadX:
150
15104-02-2021 Release 6.1.6 changes:
152 tx_port.h Updated macro definition
153
15403-02-2021 The following files were changed/added for version 6.1.5:
155 tx_thread_schedule.s Added low power feature
156
15709-30-2020 Initial ThreadX version 6.1 for Cortex-M0 using IAR's ARM tools.
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159
160Copyright(c) 1996-2020 Microsoft Corporation
161
162
163https://azure.com/rtos
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