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 /*-----------------------------------------------------------
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71 * Implementation of functions defined in portable.h for the ARM CM0 port.
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72 *----------------------------------------------------------*/
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74 /* Scheduler includes. */
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75 #include "FreeRTOS.h"
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78 /* Constants required to manipulate the NVIC. */
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79 #define portNVIC_SYSTICK_CTRL ( ( volatile uint32_t *) 0xe000e010 )
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80 #define portNVIC_SYSTICK_LOAD ( ( volatile uint32_t *) 0xe000e014 )
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81 #define portNVIC_INT_CTRL ( ( volatile uint32_t *) 0xe000ed04 )
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82 #define portNVIC_SYSPRI2 ( ( volatile uint32_t *) 0xe000ed20 )
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83 #define portNVIC_SYSTICK_CLK 0x00000004
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84 #define portNVIC_SYSTICK_INT 0x00000002
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85 #define portNVIC_SYSTICK_ENABLE 0x00000001
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86 #define portNVIC_PENDSVSET 0x10000000
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87 #define portMIN_INTERRUPT_PRIORITY ( 255UL )
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88 #define portNVIC_PENDSV_PRI ( portMIN_INTERRUPT_PRIORITY << 16UL )
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89 #define portNVIC_SYSTICK_PRI ( portMIN_INTERRUPT_PRIORITY << 24UL )
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91 /* Constants required to set up the initial stack. */
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92 #define portINITIAL_XPSR ( 0x01000000 )
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94 /* Let the user override the pre-loading of the initial LR with the address of
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95 prvTaskExitError() in case it messes up unwinding of the stack in the
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97 #ifdef configTASK_RETURN_ADDRESS
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98 #define portTASK_RETURN_ADDRESS configTASK_RETURN_ADDRESS
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100 #define portTASK_RETURN_ADDRESS prvTaskExitError
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103 /* Each task maintains its own interrupt status in the critical nesting
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105 static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
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108 * Setup the timer to generate the tick interrupts.
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110 static void prvSetupTimerInterrupt( void );
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113 * Exception handlers.
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115 void xPortPendSVHandler( void ) __attribute__ (( naked ));
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116 void xPortSysTickHandler( void );
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117 void vPortSVCHandler( void );
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120 * Start first task is a separate function so it can be tested in isolation.
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122 static void vPortStartFirstTask( void ) __attribute__ (( naked ));
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125 * Used to catch tasks that attempt to return from their implementing function.
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127 static void prvTaskExitError( void );
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129 /*-----------------------------------------------------------*/
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132 * See header file for description.
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134 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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136 /* Simulate the stack frame as it would be created by a context switch
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138 pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
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139 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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141 *pxTopOfStack = ( StackType_t ) pxCode; /* PC */
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143 *pxTopOfStack = ( StackType_t ) portTASK_RETURN_ADDRESS; /* LR */
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144 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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145 *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
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146 pxTopOfStack -= 8; /* R11..R4. */
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148 return pxTopOfStack;
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150 /*-----------------------------------------------------------*/
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152 static void prvTaskExitError( void )
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154 /* A function that implements a task must not exit or attempt to return to
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155 its caller as there is nothing to return to. If a task wants to exit it
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156 should instead call vTaskDelete( NULL ).
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158 Artificially force an assert() to be triggered if configASSERT() is
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159 defined, then stop here so application writers can catch the error. */
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160 configASSERT( uxCriticalNesting == ~0UL );
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161 portDISABLE_INTERRUPTS();
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164 /*-----------------------------------------------------------*/
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166 void vPortSVCHandler( void )
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168 /* This function is no longer used, but retained for backward
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171 /*-----------------------------------------------------------*/
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173 void vPortStartFirstTask( void )
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175 /* The MSP stack is not reset as, unlike on M3/4 parts, there is no vector
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176 table offset register that can be used to locate the initial stack value.
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177 Not all M0 parts have the application vector table at address 0. */
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179 " ldr r2, pxCurrentTCBConst2 \n" /* Obtain location of pxCurrentTCB. */
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181 " ldr r0, [r3] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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182 " add r0, #32 \n" /* Discard everything up to r0. */
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183 " msr psp, r0 \n" /* This is now the new top of stack to use in the task. */
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184 " movs r0, #2 \n" /* Switch to the psp stack. */
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185 " msr CONTROL, r0 \n"
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187 " pop {r0-r5} \n" /* Pop the registers that are saved automatically. */
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188 " mov lr, r5 \n" /* lr is now in r5. */
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189 " pop {r3} \n" /* Return address is now in r3. */
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190 " pop {r2} \n" /* Pop and discard XPSR. */
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191 " cpsie i \n" /* The first task has its context and interrupts can be enabled. */
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192 " bx r3 \n" /* Finally, jump to the user defined task code. */
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195 "pxCurrentTCBConst2: .word pxCurrentTCB "
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198 /*-----------------------------------------------------------*/
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201 * See header file for description.
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203 BaseType_t xPortStartScheduler( void )
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205 /* Make PendSV, CallSV and SysTick the same priroity as the kernel. */
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206 *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;
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207 *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;
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209 /* Start the timer that generates the tick ISR. Interrupts are disabled
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211 prvSetupTimerInterrupt();
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213 /* Initialise the critical nesting count ready for the first task. */
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214 uxCriticalNesting = 0;
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216 /* Start the first task. */
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217 vPortStartFirstTask();
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219 /* Should never get here as the tasks will now be executing! Call the task
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220 exit error function to prevent compiler warnings about a static function
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221 not being called in the case that the application writer overrides this
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222 functionality by defining configTASK_RETURN_ADDRESS. */
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223 prvTaskExitError();
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225 /* Should not get here! */
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228 /*-----------------------------------------------------------*/
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230 void vPortEndScheduler( void )
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232 /* Not implemented in ports where there is nothing to return to.
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233 Artificially force an assert. */
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234 configASSERT( uxCriticalNesting == 1000UL );
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236 /*-----------------------------------------------------------*/
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238 void vPortYield( void )
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240 /* Set a PendSV to request a context switch. */
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241 *( portNVIC_INT_CTRL ) = portNVIC_PENDSVSET;
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243 /* Barriers are normally not required but do ensure the code is completely
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244 within the specified behaviour for the architecture. */
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245 __asm volatile( "dsb" );
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246 __asm volatile( "isb" );
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248 /*-----------------------------------------------------------*/
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250 void vPortEnterCritical( void )
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252 portDISABLE_INTERRUPTS();
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253 uxCriticalNesting++;
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254 __asm volatile( "dsb" );
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255 __asm volatile( "isb" );
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257 /*-----------------------------------------------------------*/
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259 void vPortExitCritical( void )
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261 configASSERT( uxCriticalNesting );
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262 uxCriticalNesting--;
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263 if( uxCriticalNesting == 0 )
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265 portENABLE_INTERRUPTS();
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268 /*-----------------------------------------------------------*/
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270 uint32_t ulSetInterruptMaskFromISR( void )
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273 " mrs r0, PRIMASK \n"
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278 /* To avoid compiler warnings. This line will never be reached. */
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281 /*-----------------------------------------------------------*/
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283 void vClearInterruptMaskFromISR( uint32_t ulMask )
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286 " msr PRIMASK, r0 \n"
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290 /* Just to avoid compiler warning. */
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293 /*-----------------------------------------------------------*/
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295 void xPortPendSVHandler( void )
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297 /* This is a naked function. */
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303 " ldr r3, pxCurrentTCBConst \n" /* Get the location of the current TCB. */
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306 " sub r0, r0, #32 \n" /* Make space for the remaining low registers. */
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307 " str r0, [r2] \n" /* Save the new top of stack. */
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308 " stmia r0!, {r4-r7} \n" /* Store the low registers that are not saved automatically. */
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309 " mov r4, r8 \n" /* Store the high registers. */
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313 " stmia r0!, {r4-r7} \n"
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315 " push {r3, r14} \n"
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317 " bl vTaskSwitchContext \n"
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319 " pop {r2, r3} \n" /* lr goes in r3. r2 now holds tcb pointer. */
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322 " ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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323 " add r0, r0, #16 \n" /* Move to the high registers. */
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324 " ldmia r0!, {r4-r7} \n" /* Pop the high registers. */
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330 " msr psp, r0 \n" /* Remember the new top of stack for the task. */
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332 " sub r0, r0, #32 \n" /* Go back for the low registers that are not automatically restored. */
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333 " ldmia r0!, {r4-r7} \n" /* Pop low registers. */
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338 "pxCurrentTCBConst: .word pxCurrentTCB "
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341 /*-----------------------------------------------------------*/
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343 void xPortSysTickHandler( void )
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345 uint32_t ulPreviousMask;
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347 ulPreviousMask = portSET_INTERRUPT_MASK_FROM_ISR();
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349 /* Increment the RTOS tick. */
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350 if( xTaskIncrementTick() != pdFALSE )
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352 /* Pend a context switch. */
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353 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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356 portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );
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358 /*-----------------------------------------------------------*/
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361 * Setup the systick timer to generate the tick interrupts at the required
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364 void prvSetupTimerInterrupt( void )
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366 /* Configure SysTick to interrupt at the requested rate. */
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367 *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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368 *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
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370 /*-----------------------------------------------------------*/
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