2 FreeRTOS V9.0.0 - Copyright (C) 2016 Real Time Engineers Ltd.
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5 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 This file is part of the FreeRTOS distribution.
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9 FreeRTOS is free software; you can redistribute it and/or modify it under
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10 the terms of the GNU General Public License (version 2) as published by the
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11 Free Software Foundation >>>> AND MODIFIED BY <<<< the FreeRTOS exception.
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13 ***************************************************************************
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14 >>! NOTE: The modification to the GPL is included to allow you to !<<
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15 >>! distribute a combined work that includes FreeRTOS without being !<<
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16 >>! obliged to provide the source code for proprietary components !<<
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17 >>! outside of the FreeRTOS kernel. !<<
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18 ***************************************************************************
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20 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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21 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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22 FOR A PARTICULAR PURPOSE. Full license text is available on the following
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23 link: http://www.freertos.org/a00114.html
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25 ***************************************************************************
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27 * FreeRTOS provides completely free yet professionally developed, *
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28 * robust, strictly quality controlled, supported, and cross *
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29 * platform software that is more than just the market leader, it *
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30 * is the industry's de facto standard. *
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32 * Help yourself get started quickly while simultaneously helping *
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33 * to support the FreeRTOS project by purchasing a FreeRTOS *
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34 * tutorial book, reference manual, or both: *
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35 * http://www.FreeRTOS.org/Documentation *
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37 ***************************************************************************
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39 http://www.FreeRTOS.org/FAQHelp.html - Having a problem? Start by reading
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40 the FAQ page "My application does not run, what could be wrong?". Have you
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41 defined configASSERT()?
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43 http://www.FreeRTOS.org/support - In return for receiving this top quality
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44 embedded software for free we request you assist our global community by
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45 participating in the support forum.
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47 http://www.FreeRTOS.org/training - Investing in training allows your team to
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48 be as productive as possible as early as possible. Now you can receive
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49 FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
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50 Ltd, and the world's leading authority on the world's leading RTOS.
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52 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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53 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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54 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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56 http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
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57 Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.
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59 http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
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60 Integrity Systems ltd. to sell under the OpenRTOS brand. Low cost OpenRTOS
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61 licenses offer ticketed support, indemnification and commercial middleware.
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63 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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64 engineered and independently SIL3 certified version for use in safety and
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65 mission critical applications that require provable dependability.
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70 /* Standard includes. */
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73 /* Scheduler includes. */
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74 #include "FreeRTOS.h"
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77 #if configUSE_PORT_OPTIMISED_TASK_SELECTION == 1
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78 /* Check the configuration. */
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79 #if( configMAX_PRIORITIES > 32 )
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80 #error configUSE_PORT_OPTIMISED_TASK_SELECTION can only be set to 1 when configMAX_PRIORITIES is less than or equal to 32. It is very rare that a system requires more than 10 to 15 difference priorities as tasks that share a priority will time slice.
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82 #endif /* configUSE_PORT_OPTIMISED_TASK_SELECTION */
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84 #ifndef configSETUP_TICK_INTERRUPT
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85 #error configSETUP_TICK_INTERRUPT() must be defined in FreeRTOSConfig.h to call the function that sets up the tick interrupt.
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88 #ifndef configCLEAR_TICK_INTERRUPT
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89 #error configCLEAR_TICK_INTERRUPT must be defined in FreeRTOSConfig.h to clear which ever interrupt was used to generate the tick interrupt.
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92 /* A critical section is exited when the critical section nesting count reaches
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94 #define portNO_CRITICAL_NESTING ( ( uint32_t ) 0 )
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96 /* Tasks are not created with a floating point context, but can be given a
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97 floating point context after they have been created. A variable is stored as
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98 part of the tasks context that holds portNO_FLOATING_POINT_CONTEXT if the task
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99 does not have an FPU context, or any other value if the task does have an FPU
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101 #define portNO_FLOATING_POINT_CONTEXT ( ( StackType_t ) 0 )
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103 /* Constants required to setup the initial task context. */
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104 #define portINITIAL_SPSR ( ( StackType_t ) 0x1f ) /* System mode, ARM mode, IRQ enabled FIQ enabled. */
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105 #define portTHUMB_MODE_BIT ( ( StackType_t ) 0x20 )
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106 #define portTHUMB_MODE_ADDRESS ( 0x01UL )
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108 /* Masks all bits in the APSR other than the mode bits. */
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109 #define portAPSR_MODE_BITS_MASK ( 0x1F )
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111 /* The value of the mode bits in the APSR when the CPU is executing in user
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113 #define portAPSR_USER_MODE ( 0x10 )
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115 /* Let the user override the pre-loading of the initial LR with the address of
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116 prvTaskExitError() in case it messes up unwinding of the stack in the
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118 #ifdef configTASK_RETURN_ADDRESS
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119 #define portTASK_RETURN_ADDRESS configTASK_RETURN_ADDRESS
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121 #define portTASK_RETURN_ADDRESS prvTaskExitError
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124 /*-----------------------------------------------------------*/
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127 * Starts the first task executing. This function is necessarily written in
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128 * assembly code so is implemented in portASM.s.
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130 extern void vPortRestoreTaskContext( void );
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133 * Used to catch tasks that attempt to return from their implementing function.
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135 static void prvTaskExitError( void );
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137 /*-----------------------------------------------------------*/
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139 /* A variable is used to keep track of the critical section nesting. This
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140 variable has to be stored as part of the task context and must be initialised to
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141 a non zero value to ensure interrupts don't inadvertently become unmasked before
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142 the scheduler starts. As it is stored as part of the task context it will
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143 automatically be set to 0 when the first task is started. */
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144 volatile uint32_t ulCriticalNesting = 9999UL;
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146 /* Saved as part of the task context. If ulPortTaskHasFPUContext is non-zero then
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147 a floating point context must be saved and restored for the task. */
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148 volatile uint32_t ulPortTaskHasFPUContext = pdFALSE;
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150 /* Set to 1 to pend a context switch from an ISR. */
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151 volatile uint32_t ulPortYieldRequired = pdFALSE;
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153 /* Counts the interrupt nesting depth. A context switch is only performed if
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154 if the nesting depth is 0. */
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155 volatile uint32_t ulPortInterruptNesting = 0UL;
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157 /*-----------------------------------------------------------*/
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160 * See header file for description.
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162 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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164 /* Setup the initial stack of the task. The stack is set exactly as
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165 expected by the portRESTORE_CONTEXT() macro.
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167 The fist real value on the stack is the status register, which is set for
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168 system mode, with interrupts enabled. A few NULLs are added first to ensure
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169 GDB does not try decoding a non-existent return address. */
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170 *pxTopOfStack = ( StackType_t ) NULL;
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172 *pxTopOfStack = ( StackType_t ) NULL;
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174 *pxTopOfStack = ( StackType_t ) NULL;
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176 *pxTopOfStack = ( StackType_t ) portINITIAL_SPSR;
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178 if( ( ( uint32_t ) pxCode & portTHUMB_MODE_ADDRESS ) != 0x00UL )
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180 /* The task will start in THUMB mode. */
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181 *pxTopOfStack |= portTHUMB_MODE_BIT;
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186 /* Next the return address, which in this case is the start of the task. */
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187 *pxTopOfStack = ( StackType_t ) pxCode;
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190 /* Next all the registers other than the stack pointer. */
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191 *pxTopOfStack = ( StackType_t ) portTASK_RETURN_ADDRESS; /* R14 */
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193 *pxTopOfStack = ( StackType_t ) 0x12121212; /* R12 */
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195 *pxTopOfStack = ( StackType_t ) 0x11111111; /* R11 */
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197 *pxTopOfStack = ( StackType_t ) 0x10101010; /* R10 */
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199 *pxTopOfStack = ( StackType_t ) 0x09090909; /* R9 */
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201 *pxTopOfStack = ( StackType_t ) 0x08080808; /* R8 */
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203 *pxTopOfStack = ( StackType_t ) 0x07070707; /* R7 */
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205 *pxTopOfStack = ( StackType_t ) 0x06060606; /* R6 */
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207 *pxTopOfStack = ( StackType_t ) 0x05050505; /* R5 */
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209 *pxTopOfStack = ( StackType_t ) 0x04040404; /* R4 */
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211 *pxTopOfStack = ( StackType_t ) 0x03030303; /* R3 */
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213 *pxTopOfStack = ( StackType_t ) 0x02020202; /* R2 */
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215 *pxTopOfStack = ( StackType_t ) 0x01010101; /* R1 */
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217 *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
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220 /* The task will start with a critical nesting count of 0 as interrupts are
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222 *pxTopOfStack = portNO_CRITICAL_NESTING;
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225 /* The task will start without a floating point context. A task that uses
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226 the floating point hardware must call vPortTaskUsesFPU() before executing
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227 any floating point instructions. */
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228 *pxTopOfStack = portNO_FLOATING_POINT_CONTEXT;
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230 return pxTopOfStack;
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232 /*-----------------------------------------------------------*/
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234 static void prvTaskExitError( void )
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236 /* A function that implements a task must not exit or attempt to return to
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237 its caller as there is nothing to return to. If a task wants to exit it
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238 should instead call vTaskDelete( NULL ).
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240 Artificially force an assert() to be triggered if configASSERT() is
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241 defined, then stop here so application writers can catch the error. */
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242 configASSERT( ulPortInterruptNesting == ~0UL );
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243 portDISABLE_INTERRUPTS();
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246 /*-----------------------------------------------------------*/
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248 BaseType_t xPortStartScheduler( void )
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252 /* Only continue if the CPU is not in User mode. The CPU must be in a
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253 Privileged mode for the scheduler to start. */
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254 __asm volatile ( "MRS %0, APSR" : "=r" ( ulAPSR ) );
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255 ulAPSR &= portAPSR_MODE_BITS_MASK;
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256 configASSERT( ulAPSR != portAPSR_USER_MODE );
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258 if( ulAPSR != portAPSR_USER_MODE )
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260 /* Start the timer that generates the tick ISR. */
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261 portDISABLE_INTERRUPTS();
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262 configSETUP_TICK_INTERRUPT();
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264 /* Start the first task executing. */
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265 vPortRestoreTaskContext();
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268 /* Will only get here if vTaskStartScheduler() was called with the CPU in
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269 a non-privileged mode or the binary point register was not set to its lowest
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270 possible value. prvTaskExitError() is referenced to prevent a compiler
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271 warning about it being defined but not referenced in the case that the user
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272 defines their own exit address. */
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273 ( void ) prvTaskExitError;
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276 /*-----------------------------------------------------------*/
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278 void vPortEndScheduler( void )
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280 /* Not implemented in ports where there is nothing to return to.
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281 Artificially force an assert. */
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282 configASSERT( ulCriticalNesting == 1000UL );
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284 /*-----------------------------------------------------------*/
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286 void vPortEnterCritical( void )
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288 portDISABLE_INTERRUPTS();
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290 /* Now interrupts are disabled ulCriticalNesting can be accessed
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291 directly. Increment ulCriticalNesting to keep a count of how many times
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292 portENTER_CRITICAL() has been called. */
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293 ulCriticalNesting++;
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295 /* This is not the interrupt safe version of the enter critical function so
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296 assert() if it is being called from an interrupt context. Only API
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297 functions that end in "FromISR" can be used in an interrupt. Only assert if
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298 the critical nesting count is 1 to protect against recursive calls if the
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299 assert function also uses a critical section. */
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300 if( ulCriticalNesting == 1 )
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302 configASSERT( ulPortInterruptNesting == 0 );
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305 /*-----------------------------------------------------------*/
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307 void vPortExitCritical( void )
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309 if( ulCriticalNesting > portNO_CRITICAL_NESTING )
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311 /* Decrement the nesting count as the critical section is being
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313 ulCriticalNesting--;
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315 /* If the nesting level has reached zero then all interrupt
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316 priorities must be re-enabled. */
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317 if( ulCriticalNesting == portNO_CRITICAL_NESTING )
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319 /* Critical nesting has reached zero so all interrupt priorities
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320 should be unmasked. */
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321 portENABLE_INTERRUPTS();
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325 /*-----------------------------------------------------------*/
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327 void FreeRTOS_Tick_Handler( void )
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329 uint32_t ulInterruptStatus;
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331 ulInterruptStatus = portSET_INTERRUPT_MASK_FROM_ISR();
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333 /* Increment the RTOS tick. */
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334 if( xTaskIncrementTick() != pdFALSE )
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336 ulPortYieldRequired = pdTRUE;
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339 portCLEAR_INTERRUPT_MASK_FROM_ISR( ulInterruptStatus );
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341 configCLEAR_TICK_INTERRUPT();
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343 /*-----------------------------------------------------------*/
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345 void vPortTaskUsesFPU( void )
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347 uint32_t ulInitialFPSCR = 0;
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349 /* A task is registering the fact that it needs an FPU context. Set the
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350 FPU flag (which is saved as part of the task context). */
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351 ulPortTaskHasFPUContext = pdTRUE;
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353 /* Initialise the floating point status register. */
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354 __asm volatile ( "FMXR FPSCR, %0" :: "r" (ulInitialFPSCR) );
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356 /*-----------------------------------------------------------*/
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