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222 lines
8.6 KiB
Plaintext
222 lines
8.6 KiB
Plaintext
Microsoft's Azure RTOS ThreadX for Renesas RXv3
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Using the IAR Tools
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1. Building the ThreadX run-time Library
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Please see the Samples repository on GitHub for the Azure RTOS demonstrations
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for the RXv3.
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2. Demonstration System
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Please see the Samples repository on GitHub for the Azure RTOS demonstrations
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for the RXv3.
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3. System Initialization
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The system entry point using the IAR tools is at the label __iar_program_start.
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The vector area is setup in the file tx_initialize_low_level.s. This file is also
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responsible for setting up various system data structures, interrupt vectors, and
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the periodic timer interrupt. This file is also an ideal place add hardware
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initialization code.
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The ThreadX demonstration for the RXv3 utilizes CMT0 as a periodic timer interrupt
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source. The CMT0 interrupt is typically setup for 10ms periodic interrupts and the
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interrupt priority level is set to level 7. You may change any of the timer
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parameters as needed.
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In addition, _tx_initialize_low_level determines the first available address for use
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by the application, which is supplied as the sole input parameter to your application
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definition function, tx_application_define. The first available memory is determined
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by the location of the FREEMEM section so it should be placed AFTER all other RAM
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sections in your linker control file.
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4. Context Switch, Register Usage and Stack Frames
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The RXv3 port for ThreadX uses the first software interrupt, SWINT, i.e., interrupt #17,
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to perform context switch. This ISR is thus reserved when using ThreadX and the SWINT
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should not be manipulated in any way by the application. The port will setup the
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interrupt within _tx_initialize_low_level and the compiler will automatically install
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the necessary interrupt vector. As such no additional initialization is necessary by the
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application.
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The following defines the saved context stack frame used by the ThreadX port. The
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state of the CPU registers at the time of a context switch is saved on the running
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thread's stack The top of the suspended thread's stack is pointed to by
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tx_thread_stack_ptr in the associated thread control block TX_THREAD.
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Offset Stack Frame
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0x00 ACC0
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0x04 ACC1
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0x08 R6
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0x0C R7
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0x10 R8
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0x14 R9
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0x18 R10
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0x1C R11
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0x20 R12
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0x24 R13
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0x28 FPSW
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0x2C R14
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0x30 R15
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0x34 R3
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0x38 R4
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0x3C R5
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0x40 R1
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0x44 R2
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0x48 PC - return address
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0x4C PSW
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Offset Stack Frame with DFPU Register
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0x00 DPSW
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0x04 DCMR
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0x08 DECNT
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0x0C DEPC
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0x10 DR0
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0x14 DR1
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0x18 DR2
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0x1C DR3
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0x20 DR4
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0x24 DR5
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0x28 DR6
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0x2C DR7
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0x30 DR8
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0x34 DR9
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0x38 DR10
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0x3C DR11
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0x40 DR12
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0x44 DR13
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0x48 DR14
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0x4C DR15
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0x50 ACC0
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0x54 ACC1
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0x58 R6
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0x5C R7
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0x60 R8
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0x64 R9
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0x68 R10
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0x6C R11
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0x70 R12
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0x74 R13
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0x78 FPSW
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0x7C R14
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0x80 R15
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0x84 R3
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0x88 R4
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0x8C R5
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0x90 R1
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0x94 R2
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0x98 PC - return address
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0x9C PSW
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Note: By default IAR does not save the state of the accumulator registers ACC0 and ACC1
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when entering an ISR. This means that if the ISR uses any of the DSP instructions the
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content of those registers could be corrupted. Saving and restoring of the acummulators
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can be enabled by adding the --save_acc command line option.
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5. Double Precision FPU Instructions Support
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The RXv3 architecture supports an optional set of double precision instructions which
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makes use of a new set of registers that must be saved and restored during context
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switches. This feature can be accessed by setting the size of double to 64 bit in the
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compiler options. To reduce the overhead of saving and restoring the FPU registers
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for all threads the RXv3 port allows each thread to enable and disable saving and
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restoring the DFPU registers. By default the feature is disabled for new threads.
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To enable the feature tx_thread_fpu_enable() must be called within the context of every
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thread that will perform FPU operation. The saving and restoring of DFPU registers can
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be disabled again by calling tx_thread_fpu_disable(). This can be useful if a thread
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only makes occasional use of the FPU.
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6. Improving Performance
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The distribution version of ThreadX is built without any compiler optimizations. This
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makes it easy to debug because you can trace or set breakpoints inside of ThreadX itself.
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Of course, this costs some performance. To make ThreadX run faster, you can change the
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ThreadX Library project to disable debug information and enable the desired optimizations.
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In addition, you can eliminate the ThreadX basic API error checking by compiling your
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application code with the symbol TX_DISABLE_ERROR_CHECKING defined before tx_api.h
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is included.
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7. Timer Processing
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Timer processign is performed by calling __tx_timer_interrupt(). This should usually be done
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from within the callback of a periodic timer with a period of 100Hz. In the sample projects
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a Renesas Fit CMT periodic timer module (rx_cmt) is used as the timer source.
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8. Interrupt Handling
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Interrupt handling is unaffected by the ThreadX port as such user interrupts can be
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written according to the toolchain's documentation. It is recommended not to use interrupt
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priority 15 as this is the priority of the context switch interrupt. However using interrupt
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priority 15 won't cause any negative side effectd but doing so may may slightly reduce
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performance. Please refer to the toolchain documentation for additional details on how to
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define interupt service routines.
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9. Execution Profiling
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The RX port adds support for the Execution Profiling Kit (EPK). The EPK consists
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of the files tx_execution_profile.c and tx_execution_profile.h. See the documentation
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of the EPK for generic usage details.
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To add the EPK to your RXv3 release make the following modifications:
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* Enable the following define for both the Threadx library and the application
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TX_EXECUTION_PROFILE_ENABLE
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* Setup CMT1 as a free running 16 bit timer.
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* In tx_execution_profile.h, change following around line 52:
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#ifdef TX_EXECUTION_64BIT_TIME
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typedef unsigned long long EXECUTION_TIME;
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#define TX_EXECUTION_MAX_TIME_SOURCE 0xFFFFFFFFFFFFFFFF
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#else
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typedef unsigned long EXECUTION_TIME;
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#define TX_EXECUTION_MAX_TIME_SOURCE 0xFFFF
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#endif
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/* Define basic constants for the execution profile kit. */
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#define TX_EXECUTION_TIME_SOURCE (EXECUTION_TIME) *((USHORT *) 0x8800A)
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Rebuild the Threadx library and the application.
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Refer to the EPK documentation how to interpret the results.
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10. Revision History
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For generic code revision information, please refer to the readme_threadx_generic.txt
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file, which is included in your distribution. The following details the revision
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information associated with this specific port of ThreadX:
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01-31-2022 Release 6.1.10 changes:
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tx_port.h Removed system state macro, and added
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missing interrupt control defines
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tx_timer_interrupt.src Added missing thread preemption logic
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10-15-2021 Release 6.1.9 changes:
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tx_port.h Added FPU support
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tx_thread_context_restore.s Added FPU support
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tx_thread_schedule.s Added FPU support
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06-02-2021 Initial ThreadX release for the RXv3using IAR tools, version 6.1.7
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Copyright(c) 1996-2022 Microsoft Corporation
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https://azure.com/rtos |