tinySA/os/ports/GCC/ARMCM3/port.dox

/*
    ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio.

    This file is part of ChibiOS/RT.

    ChibiOS/RT is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    ChibiOS/RT is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
 * @defgroup ARMCM3 ARM Cortex-M3
 * @details The ARM Cortex-M3 architecture is quite complex for a
 *  microcontroller and some explanations are required about the port choices.
 *
 * @section ARMCM3_STATES Mapping of the System States in the ARM Cortex-M3 port
 * The ChibiOS/RT logical @ref system_states are mapped as follow in the ARM
 * Cortex-M3 port:
 * - <b>Init</b>. This state is represented by the startup code and the
 *   initialization code before @p chSysInit() is executed. It has not a
 *   special hardware state associated.
 * - <b>Normal</b>. This is the state the system has after executing
 *   @p chSysInit(). In this state the ARM Cortex-M3 has the BASEPRI register
 *   set at @p BASEPRI_USER level, interrupts are not masked. The processor
 *   is running in thread-privileged mode.
 * - <b>Suspended</b>. In this state the interrupt sources are not globally
 *   masked but the BASEPRI register is set to @p BASEPRI_KERNEL thus masking
 *   any interrupt source with lower or equal priority. The processor
 *   is running in thread-privileged mode.
 * - <b>Disabled</b>. Interrupt sources are globally masked. The processor
 *   is running in thread-privileged mode.
 * - <b>Sleep</b>. This state is entered with the execution of the specific
 *   instruction @p <b>wfi</b>.
 * - <b>S-Locked</b>. In this state the interrupt sources are not globally
 *   masked but the BASEPRI register is set to @p BASEPRI_KERNEL thus masking
 *   any interrupt source with lower or equal priority. The processor
 *   is running in thread-privileged mode.
 * - <b>I-Locked</b>. In this state the interrupt sources are not globally
 *   masked but the BASEPRI register is set to @p BASEPRI_KERNEL thus masking
 *   any interrupt source with lower or equal priority. The processor
 *   is running in exception-privileged mode.
 * - <b>Serving Regular Interrupt</b>. In this state the interrupt sources are
 *   not globally masked but only interrupts with higher priority can preempt
 *   the current handler. The processor is running in exception-privileged mode.
 * - <b>Serving Fast Interrupt</b>. It is basically the same of the SRI state
 *   but it is not possible to switch to the I-Locked state because fast
 *   interrupts can preempt the kernel critical zone.
 * - <b>Serving Non-Maskable Interrupt</b>. The Cortex-M3 has a specific
 *   asynchronous NMI vector and several synchronous fault vectors that can
 *   be considered to be in this category.
 * - <b>Halted</b>. Implemented as an infinite loop after globally masking all
 *   the maskable interrupt sources. The ARM state is whatever the processor
 *   was running when @p chSysHalt() was invoked.
 * .
 * @section ARMCM3_NOTES The ARM Cortex-M3 port notes
 * The ARM Cortex-M3 port is organized as follow:
 * - The @p main() function is invoked in thread-privileged mode.
 * - Each thread has a private process stack, the system has a single main
 *   stack where all the interrupts and exceptions are processed.
 * - Only the 4 MSb of the priority level are used, the 4 LSb are assumed
 *   to be zero.
 * - The threads are started in thread-privileged mode with BASEPRI level
 *   0x00 (disabled).
 * - The kernel raises its BASEPRI level to @p BASEPRI_KERNEL in order to
 *   protect the kernel data structures.
 * - Interrupt nesting and the other advanced NVIC features are supported.
 * - The SVC instruction and vector, with parameter #0,  is internally used
 *   for commanded context switching.<br>
 *   It is possible to share the SVC handler at the cost of slower context
 *   switching.
 * - The PendSV vector is internally used for preemption context switching.
 * .
 * @ingroup ports
 */

/**
 * @defgroup ARMCM3_CONF Configuration Options
 * @brief ARM Cortex-M3 Configuration Options.
 * @details The ARMCM3 port allows some architecture-specific configurations
 * settings that can be specified externally, as example on the compiler
 * command line:
 * - @p INT_REQUIRED_STACK, this value represent the amount of stack space used
 *   by an interrupt handler between the @p extctx and @p intctx
 *   structures.<br>
 *   In the current implementation this value is guaranteed to be zero so
 *   there is no need to modify this value unless changes are done at the
 *   interrupts handling code.
 * - @p BASEPRI_USER, this is the @p BASEPRI value for the user threads. The
 *   default value is @p 0 (disabled).<br>
 *   Usually there is no need to change this value, please refer to the
 *   Cortex-M3 technical reference manual for a detailed description.
 * - @p BASEPRI_KERNEL, this is the @p BASEPRI value for the kernel lock code.
 *   The default value is 0x40.<br>
 *   Code running at higher priority levels must not invoke any OS API.<br>
 *   Usually there is no need to change this value, please refer to the
 *   Cortex-M3 technical reference manual for a detailed description.
 * - @p ENABLE_WFI_IDLE, if set to @p 1 enables the use of the @p <b>wfi</b>
 *   instruction from within the idle loop. This is defaulted to 0 because
 *   it can create problems with some debuggers. Setting this option to 1
 *   reduces the system power requirements.
 * .
 * @ingroup ARMCM3
 */

/**
 * @defgroup ARMCM3_CORE Core Port Implementation
 * @brief ARM Cortex-M3 specific port code, structures and macros.
 *
 * @ingroup ARMCM3
 */

/**
 * @defgroup ARMCM3_STARTUP Startup Support
 * @brief ARM Cortex-M3 startup code support.
 * @details ChibiOS/RT provides its own generic startup file for the ARM
 * Cortex-M3 port.
 * Of course it is not mandatory to use it but care should be taken about the
 * startup phase details.
 *
 * <h2>Startup Process</h2>
 * The startup process, as implemented, is the following:
 * -# Interrupts are masked globally.
 * -# The two stacks are initialized by assigning them the sizes defined in the
 *    linker script (usually named @p ch.ld). Stack areas are allocated from
 *    the highest RAM location downward.
 * -# An early initialization routine @p hwinit0 is invoked, if the symbol is
 *    not defined then an empty default routine is executed (weak symbol).
 * -# DATA and BSS segments are initialized.
 * -# The CPU state is switched to Privileged and the PSP stack is used.
 * -# A late initialization routine @p hwinit1 is invoked, if the symbol not
 *    defined then an empty default routine is executed (weak symbol).<br>
 *    This late initialization function is also the proper place for a
 *    @a bootloader, if your application requires one.
 * -# The @p main() function is invoked with the parameters @p argc and @p argv
 *    set to zero.
 * -# Should the @p main() function return a branch is performed to the weak
 *    symbol MainExitHandler. The default code is an endless empty loop.
 * .
 * <h2>Expected linker symbols</h2>
 * The startup code starts at the symbol @p ResetHandler and expects the
 * following symbols to be defined in the linker script:
 * - @p __ram_end__ RAM end location +1.
 * - @p __main_stack_size__ Exception stack size.
 * - @p __process_stack_size__ Process stack size. This is the stack area used
 *      by the @p main() function.
 * - @p _textdata address of the data segment source read only data.
 * - @p _data data segment start location.
 * - @p _edata data segment end location +1.
 * - @p _bss_start BSS start location.
 * - @p _bss_end BSS end location +1.
 * .
 * @ingroup ARMCM3
 * @file ARMCM3/crt0.s Startup code.
 */

/**
 * @defgroup ARMCM3_NVIC NVIC Support
 * @brief ARM Cortex-M3 NVIC support.
 *
 * @ingroup ARMCM3
 */