162 lines
7.6 KiB
Plaintext
162 lines
7.6 KiB
Plaintext
/**
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* @defgroup ARMCM3 ARM Cortex-M3
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* @{
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* @details The ARM Cortex-M3 architecture is quite complex for a
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* microcontroller and some explanations are required about the port choices.
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*
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* @section ARMCM3_STATES Mapping of the System States in the ARM Cortex-M3 port
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* The ChibiOS/RT logical @ref system_states are mapped as follow in the ARM
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* Cortex-M3 port:
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* - <b>Init</b>. This state is represented by the startup code and the
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* initialization code before @p chSysInit() is executed. It has not a
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* special hardware state associated.
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* - <b>Normal</b>. This is the state the system has after executing
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* @p chSysInit(). In this state the ARM Cortex-M3 has the BASEPRI register
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* set at @p BASEPRI_USER level, interrupts are not masked. The processor
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* is running in thread-privileged mode.
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* - <b>Suspended</b>. In this state the interrupt sources are not globally
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* masked but the BASEPRI register is set to @p BASEPRI_KERNEL thus masking
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* any interrupt source with lower or equal priority. The processor
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* is running in thread-privileged mode.
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* - <b>Disabled</b>. Interrupt sources are globally masked. The processor
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* is running in thread-privileged mode.
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* - <b>Sleep</b>. This state is entered with the execution of the specific
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* instruction @p <b>wfi</b>.
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* - <b>S-Locked</b>. In this state the interrupt sources are not globally
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* masked but the BASEPRI register is set to @p BASEPRI_KERNEL thus masking
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* any interrupt source with lower or equal priority. The processor
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* is running in thread-privileged mode.
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* - <b>I-Locked</b>. In this state the interrupt sources are not globally
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* masked but the BASEPRI register is set to @p BASEPRI_KERNEL thus masking
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* any interrupt source with lower or equal priority. The processor
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* is running in exception-privileged mode.
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* - <b>Serving Regular Interrupt</b>. In this state the interrupt sources are
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* not globally masked but only interrupts with higher priority can preempt
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* the current handler. The processor is running in exception-privileged mode.
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* - <b>Serving Fast Interrupt</b>. It is basically the same of the SRI state
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* but it is not possible to switch to the I-Locked state because fast
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* interrupts can preempt the kernel critical zone.
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* - <b>Serving Non-Maskable Interrupt</b>. The Cortex-M3 has a specific
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* asynchronous NMI vector and several synchronous fault vectors that can
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* be considered to be in this category.
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* - <b>Halted</b>. Implemented as an infinite loop after globally masking all
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* the maskable interrupt sources. The ARM state is whatever the processor
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* was running when @p chSysHalt() was invoked.
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*
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* @section ARMCM3_NOTES The ARM Cortex-M3 port notes
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* The ARM Cortex-M3 port is organized as follow:
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* - The @p main() function is invoked in thread-privileged mode.
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* - Each thread has a private process stack, the system has a single main
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* stack where all the interrupts and exceptions are processed.
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* - Only the 4 MSb of the priority level are used, the 4 LSb are assumed
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* to be zero.
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* - The threads are started in thread-privileged mode with BASEPRI level
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* 0x00 (disabled).
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* - The kernel raises its BASEPRI level to @p BASEPRI_KERNEL in order to
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* protect the kernel data structures.
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* - Interrupt nesting and the other advanced NVIC features are supported.
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* - The SVC instruction and vector, with parameter #0, is internally used
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* for commanded context switching.<br>
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* It is possible to share the SVC handler at the cost of slower context
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* switching.
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* - The PendSV vector is internally used for preemption context switching.
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*
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* @ingroup Ports
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*/
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/** @} */
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/**
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* @defgroup ARMCM3_CONF Configuration Options
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* @{
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* @brief ARM Cortex-M3 Configuration Options.
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* @details The ARMCM3 port allows some architecture-specific configurations
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* settings that can be specified externally, as example on the compiler
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* command line:
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* - @p INT_REQUIRED_STACK, this value represent the amount of stack space used
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* by an interrupt handler between the @p extctx and @p intctx
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* structures.<br>
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* In the current implementation this value is guaranteed to be zero so
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* there is no need to modify this value unless changes are done at the
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* interrupts handling code.
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* - @p BASEPRI_USER, this is the @p BASEPRI value for the user threads. The
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* default value is @p 0 (disabled).<br>
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* Usually there is no need to change this value, please refer to the
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* Cortex-M3 technical reference manual for a detailed description.
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* - @p BASEPRI_KERNEL, this is the @p BASEPRI value for the kernel lock code.
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* The default value is 0x40.<br>
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* Code running at higher priority levels must not invoke any OS API.<br>
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* Usually there is no need to change this value, please refer to the
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* Cortex-M3 technical reference manual for a detailed description.
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* - @p ENABLE_WFI_IDLE, if set to @p 1 enables the use of the @p <b>wfi</b>
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* instruction from within the idle loop. This is defaulted to 0 because
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* it can create problems with some debuggers. Setting this option to 1
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* reduces the system power requirements.
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*
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* @ingroup ARMCM3
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*/
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/** @} */
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/**
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* @defgroup ARMCM3_CORE Core Port Implementation
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* @{
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* @brief ARM Cortex-M3 specific port code, structures and macros.
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*
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* @ingroup ARMCM3
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*/
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/** @} */
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/**
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* @defgroup ARMCM3_STARTUP Startup Support
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* @{
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* @brief ARM Cortex-M3 startup code support.
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* @details ChibiOS/RT provides its own generic startup file for the ARM
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* Cortex-M3 port.
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* Of course it is not mandatory to use it but care should be taken about the
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* startup phase details.
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*
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* <h2>Startup Process</h2>
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* The startup process, as implemented, is the following:
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* -# Interrupts are masked globally.
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* -# The two stacks are initialized by assigning them the sizes defined in the
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* linker script (usually named @p ch.ld). Stack areas are allocated from
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* the highest RAM location downward.
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* -# An early initialization routine @p hwinit0 is invoked, if the symbol is
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* notdefined then an empty default routine is executed (weak symbol).
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* -# DATA and BSS segments are initialized.
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* -# The CPU state is switched to Privileged and the PSP stack is used.
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* -# A late initialization routine @p hwinit1 is invoked, if the symbol not
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* defined then an empty default routine is executed (weak symbol).<br>
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* This late initialization function is also the proper place for a
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* @a bootloader, if your application requires one.
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* -# The @p main() function is invoked with the parameters @p argc and @p argv
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* set to zero.
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* -# Should the @p main() function return a branch is performed to the weak
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* symbol MainExitHandler. The default code is an endless empty loop.
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* .
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* <h2>Expected linker symbols</h2>
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* The startup code starts at the symbol @p ResetHandler and expects the
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* following symbols to be defined in the linker script:
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* - @p __ram_end__ RAM end location +1.
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* - @p __main_stack_size__ Exception stack size.
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* - @p __process_stack_size__ Process stack size. This is the stack area used
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* by the @p main() function.
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* - @p _textdata address of the data segment source read only data.
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* - @p _data data segment start location.
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* - @p _edata data segment end location +1.
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* - @p _bss_start BSS start location.
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* - @p _bss_end BSS end location +1.
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* .
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* @ingroup ARMCM3
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* @file ports/ARMCM3/crt0.s Startup code.
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*/
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/** @} */
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/**
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* @defgroup ARMCM3_NVIC NVIC Support
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* @{
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* @brief ARM Cortex-M3 NVIC support.
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*
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* @ingroup ARMCM3
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*/
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/** @} */
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