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Microsoft's Azure RTOS ThreadX for TMS320C667x
Using the TI Code Composer Tools
1. Installation
TI Code Composer Studio and the TI MCSDK must be installed prior to
building ThreadX. The following links can be used to download these
packages:
http://processors.wiki.ti.com/index.php/Download_CCS
http://software-dl.ti.com/sdoemb/sdoemb_public_sw/bios_mcsdk/latest/index_FDS.html
It is assumed the tools are installed in the default directories:
CCS path by default - c:\ti\ccsv(version number)
MCSDK path by default - c:\ti
If the packages are installed in different directories, the ThreadX project
settings must be adjusted.
2. Open the Azure RTOS Workspace
In order to build the ThreadX library and the ThreadX demonstration first open
the Azure RTOS Workspace inside your ThreadX installation directory.
3. Building the ThreadX run-time Library
Building the ThreadX library is easy; simply import the CCS project file
"tx" and then select the build button. You should now observe the compilation
and assembly of the ThreadX library. This project build produces the ThreadX
library file tx.lib.
4. Demonstration System
The ThreadX demonstration is designed to execute on the C6678EVM evaluation board.
Building the demonstration is easy; simply import the "sample_threadx_c6678evm" project.
Now select "Project -> Build Active Project" to build the ThreadX demonstration,
which produces the sample_threadx.out file in the "Debug" directory. You are now
ready to run the ThreadX demonstration on the C6678EVM evaluation board.
Please refer to Chapter 6 of the ThreadX User Guide for a complete description
of this demonstration.
5. System Initialization
The entry point in ThreadX for the TMS320C667x using the TI tools is at label
_c_int00. This is defined within the TI library. In addition, this is
where all static and global pre-set C variable initialization processing
takes place.
The ThreadX initialization file tx_initialize_low_level.asm is responsible
for setting up various system data structures, the vector area, and a periodic
timer interrupt source. By default, the vector area is defined to be located in
the "vectors" section, which is defined at the top of tx_initialize_low_level.asm.
This area is located at address 0 for the demonstration.
tx_initialize_low_level.asm is also where initialization of a periodic timer
interrupt source should take place.
In addition, _tx_initialize_low_level determines the first available address
for use by the application. By default, free memory is assumed to start after
the .zend section in RAM (defined in tx_initialize_low_level). This section
must be placed at the end of your other RAM sections. Please see sample_threadx.cmd
for an example. The address of this section is passed to the application definition
function, tx_application_define.
6. Register Usage and Stack Frames
The TI TMS320C667x compiler assumes that registers A0-A9, A16-A31, B0-B9, and
B16-B31 are scratch registers for each function. All other registers used by
a C function must be preserved by the function. ThreadX takes advantage of this
in situations where a context switch happens as a result of making a ThreadX
service call (which is itself a C function). In such cases, the saved context
of a thread is only the non-scratch registers.
The following defines the saved context stack frames for context switches
that occur as a result of interrupt handling or from thread-level API calls.
All suspended threads have one of these two types of stack frames. The top
of the suspended thread's stack is pointed to by tx_thread_stack_ptr in the
associated thread control block TX_THREAD.
Offset Interrupted Stack Frame Non-Interrupt Stack Frame
0x04 1 0
0x08 CSR CSR
0x0C IPR B3
0x10 AMR AMR
0x14 A0 A10
0x18 A1 A11
0x1C A2 A12
0x20 A3 A13
0x24 A4 A14
0x28 A5 A15
0x2C A6 B10
0x30 A7 B11
0x34 A8 B12
0x38 A9 B13
0x3C A10 ILC
0x40 A11 RILC
0x44 A12
0x48 A13
0x4C A14
0x50 A15
0x54 B0
0x58 B1
0x5C B2
0x60 B3
0x64 B4
0x68 B5
0x6C B6
0x70 B7
0x74 B8
0x78 B9
0x7C B10
0x80 B11
0x84 B12
0x88 B13
0x8C A16
0x90 A17
0x94 A18
0x98 A19
0x9C A20
0xA0 A21
0xA4 A22
0xA8 A23
0xAC A24
0xB0 A25
0xB4 A26
0xB8 A27
0xBC A28
0xC0 A29
0xC4 A30
0xC8 A31
0xCC B16
0xD0 B17
0xD4 B18
0xD8 B19
0xDC B20
0xE0 B21
0xE4 B22
0xE8 B23
0xEC B24
0xF0 B25
0xF4 B26
0xF8 B27
0xFC B28
0x100 B29
0x104 B30
0x108 B31
0x10C ILC
0x110 RILC
0x114 ITSR
7. Improving Performance
The distribution version of ThreadX is built without any compiler
optimizations. This makes it easy to debug because you can trace or set
breakpoints inside of ThreadX itself. Of course, this costs some performance.
To make it run faster, you can replace the -g compiler option
to a -O3 in the ThreadX project file to enable all compiler optimizations.
In addition, you can eliminate the ThreadX basic API error checking by
compiling your application code with the symbol TX_DISABLE_ERROR_CHECKING
defined.
8. Interrupt Handling
ThreadX provides complete and high-performance interrupt handling for
TMS320C667x targets. There are a certain set of requirements that are
defined in the following sub-sections:
8.1 Vector Area
The TMS320C667x interrupt vectors at in the section "vectors" and is defined at
the top of tx_initialize_low_level.asm. Each interrupt vector entry contains
a jump to a template interrupt processing shell.
8.2 Interrupt Service Routine Shells
The following interrupt processing shells are defined at the bottom of
tx_initialize_low_level.asm:
__tx_int4_ISR
__tx_int5_ISR
__tx_int6_ISR
__tx_int7_ISR
__tx_int8_ISR
__tx_int9_ISR
__tx_int10_ISR
__tx_int11_ISR
__tx_int12_ISR
__tx_int13_ISR
__tx_int14_ISR
__tx_int15_ISR
Each interrupt ISR is entered with B3, A0-A4 is available (these registers are
saved in the initial vector processing). The default interrupt handling
includes calls to __tx_thread_context_save and __tx_thread_context_restore.
Application ISR processing can be added between the context save/restore
calls. Note that only the compiler scratch registers are available for use
after context save return to the ISR.
High-frequency interrupt handlers might not want to perform context
save/restore processing on each interrupt. If this is the case, any
additional registers used must be saved and restored by the ISR and
the interrupt return processing must restore the registers saved by the
initial vector processing. This can be accomplished by adding the
following code to the end of the custom ISR handling:
LDW *+SP(20),A0 ; Recover A0
LDW *+SP(24),A1 ; Recover A1
LDW *+SP(28),A2 ; Recover A2
LDW *+SP(32),A3 ; Recover A3
B IRP ; Return to point of interrupt
|| LDW *+SP(36),A4 ; Recover A4
LDW *+SP(96),B3 ; Recover B3
ADDK.S2 288,SP ; Recover stack space
NOP 3 ; Delay slots
9. Revision History
For generic code revision information, please refer to the readme_threadx_generic.txt
file, which is included in your distribution. The following details the revision
information associated with this specific port of ThreadX:
04-02-2021 Release 6.1.6 changes:
tx_port.h Updated macro definition
09-30-2020 Initial ThreadX 6.1 version for TMS320C667x using TI Code Composer tools.
Copyright(c) 1996-2020 Microsoft Corporation
https://azure.com/rtos
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