2 FreeRTOS V7.4.0 - Copyright (C) 2013 Real Time Engineers Ltd.
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4 FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME. PLEASE VISIT
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5 http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 ***************************************************************************
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9 * FreeRTOS tutorial books are available in pdf and paperback. *
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10 * Complete, revised, and edited pdf reference manuals are also *
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13 * Purchasing FreeRTOS documentation will not only help you, by *
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14 * ensuring you get running as quickly as possible and with an *
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15 * in-depth knowledge of how to use FreeRTOS, it will also help *
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16 * the FreeRTOS project to continue with its mission of providing *
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17 * professional grade, cross platform, de facto standard solutions *
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18 * for microcontrollers - completely free of charge! *
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20 * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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22 * Thank you for using FreeRTOS, and thank you for your support! *
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24 ***************************************************************************
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27 This file is part of the FreeRTOS distribution.
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29 FreeRTOS is free software; you can redistribute it and/or modify it under
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30 the terms of the GNU General Public License (version 2) as published by the
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31 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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33 >>>>>>NOTE<<<<<< The modification to the GPL is included to allow you to
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34 distribute a combined work that includes FreeRTOS without being obliged to
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35 provide the source code for proprietary components outside of the FreeRTOS
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38 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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39 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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40 FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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41 details. You should have received a copy of the GNU General Public License
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42 and the FreeRTOS license exception along with FreeRTOS; if not itcan be
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43 viewed here: http://www.freertos.org/a00114.html and also obtained by
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44 writing to Real Time Engineers Ltd., contact details for whom are available
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45 on the FreeRTOS WEB site.
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49 ***************************************************************************
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51 * Having a problem? Start by reading the FAQ "My application does *
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52 * not run, what could be wrong?" *
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54 * http://www.FreeRTOS.org/FAQHelp.html *
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56 ***************************************************************************
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59 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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60 license and Real Time Engineers Ltd. contact details.
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62 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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63 including FreeRTOS+Trace - an indispensable productivity tool, and our new
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64 fully thread aware and reentrant UDP/IP stack.
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66 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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67 Integrity Systems, who sell the code with commercial support,
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68 indemnification and middleware, under the OpenRTOS brand.
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70 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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71 engineered and independently SIL3 certified version for use in safety and
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72 mission critical applications that require provable dependability.
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75 /*-----------------------------------------------------------
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76 * Implementation of functions defined in portable.h for the ARM CM3 port.
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77 *----------------------------------------------------------*/
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80 #include <intrinsics.h>
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82 /* Scheduler includes. */
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83 #include "FreeRTOS.h"
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86 #if configMAX_SYSCALL_INTERRUPT_PRIORITY == 0
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87 #error configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to 0. See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html
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90 #ifndef configSYSTICK_CLOCK_HZ
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91 #define configSYSTICK_CLOCK_HZ configCPU_CLOCK_HZ
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94 /* Constants required to manipulate the core. Registers first... */
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95 #define portNVIC_SYSTICK_CTRL_REG ( * ( ( volatile unsigned long * ) 0xe000e010 ) )
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96 #define portNVIC_SYSTICK_LOAD_REG ( * ( ( volatile unsigned long * ) 0xe000e014 ) )
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97 #define portNVIC_SYSTICK_CURRENT_VALUE_REG ( * ( ( volatile unsigned long * ) 0xe000e018 ) )
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98 #define portNVIC_INT_CTRL_REG ( * ( ( volatile unsigned long * ) 0xe000ed04 ) )
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99 #define portNVIC_SYSPRI2_REG ( * ( ( volatile unsigned long * ) 0xe000ed20 ) )
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100 /* ...then bits in the registers. */
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101 #define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
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102 #define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )
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103 #define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )
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104 #define portNVIC_SYSTICK_COUNT_FLAG_BIT ( 1UL << 16UL )
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105 #define portNVIC_PENDSVSET_BIT ( 1UL << 28UL )
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106 #define portNVIC_PENDSVCLEAR_BIT ( 1UL << 27UL )
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107 #define portNVIC_PEND_SYSTICK_CLEAR_BIT ( 1UL << 25UL )
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109 #define portNVIC_PENDSV_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )
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110 #define portNVIC_SYSTICK_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )
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112 /* Constants required to set up the initial stack. */
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113 #define portINITIAL_XPSR ( 0x01000000 )
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115 /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is
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116 defined. The value 255 should also ensure backward compatibility.
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117 FreeRTOS.org versions prior to V4.3.0 did not include this definition. */
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118 #ifndef configKERNEL_INTERRUPT_PRIORITY
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119 #define configKERNEL_INTERRUPT_PRIORITY 0
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122 /* Each task maintains its own interrupt status in the critical nesting
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124 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
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127 * Setup the timer to generate the tick interrupts. The implementation in this
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128 * file is weak to allow application writers to change the timer used to
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129 * generate the tick interrupt.
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131 void vPortSetupTimerInterrupt( void );
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134 * Exception handlers.
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136 void xPortSysTickHandler( void );
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139 * Start first task is a separate function so it can be tested in isolation.
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141 extern void vPortStartFirstTask( void );
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143 /*-----------------------------------------------------------*/
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146 * The number of SysTick increments that make up one tick period.
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148 #if configUSE_TICKLESS_IDLE == 1
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149 static unsigned long ulTimerReloadValueForOneTick = 0;
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153 * The maximum number of tick periods that can be suppressed is limited by the
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154 * 24 bit resolution of the SysTick timer.
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156 #if configUSE_TICKLESS_IDLE == 1
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157 static unsigned long xMaximumPossibleSuppressedTicks = 0;
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158 #endif /* configUSE_TICKLESS_IDLE */
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161 * Compensate for the CPU cycles that pass while the SysTick is stopped (low
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162 * power functionality only.
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164 #if configUSE_TICKLESS_IDLE == 1
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165 static unsigned long ulStoppedTimerCompensation = 0;
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166 #endif /* configUSE_TICKLESS_IDLE */
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168 /*-----------------------------------------------------------*/
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171 * See header file for description.
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173 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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175 /* Simulate the stack frame as it would be created by a context switch
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177 pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
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178 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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180 *pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* PC */
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182 *pxTopOfStack = 0; /* LR */
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183 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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184 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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185 pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */
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187 return pxTopOfStack;
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189 /*-----------------------------------------------------------*/
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192 * See header file for description.
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194 portBASE_TYPE xPortStartScheduler( void )
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196 /* Make PendSV and SysTick the lowest priority interrupts. */
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197 portNVIC_SYSPRI2_REG |= portNVIC_PENDSV_PRI;
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198 portNVIC_SYSPRI2_REG |= portNVIC_SYSTICK_PRI;
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200 /* Start the timer that generates the tick ISR. Interrupts are disabled
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202 vPortSetupTimerInterrupt();
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204 /* Initialise the critical nesting count ready for the first task. */
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205 uxCriticalNesting = 0;
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207 /* Start the first task. */
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208 vPortStartFirstTask();
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210 /* Should not get here! */
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213 /*-----------------------------------------------------------*/
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215 void vPortEndScheduler( void )
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217 /* It is unlikely that the CM3 port will require this function as there
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218 is nothing to return to. */
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220 /*-----------------------------------------------------------*/
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222 void vPortYieldFromISR( void )
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224 /* Set a PendSV to request a context switch. */
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225 portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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227 /*-----------------------------------------------------------*/
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229 void vPortEnterCritical( void )
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231 portDISABLE_INTERRUPTS();
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232 uxCriticalNesting++;
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234 /*-----------------------------------------------------------*/
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236 void vPortExitCritical( void )
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238 uxCriticalNesting--;
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239 if( uxCriticalNesting == 0 )
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241 portENABLE_INTERRUPTS();
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244 /*-----------------------------------------------------------*/
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246 void xPortSysTickHandler( void )
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248 /* If using preemption, also force a context switch. */
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249 #if configUSE_PREEMPTION == 1
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250 portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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253 /* Only reset the systick load register if configUSE_TICKLESS_IDLE is set to
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254 1. If it is set to 0 tickless idle is not being used. If it is set to a
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255 value other than 0 or 1 then a timer other than the SysTick is being used
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256 to generate the tick interrupt. */
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257 #if configUSE_TICKLESS_IDLE == 1
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258 portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick;
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261 ( void ) portSET_INTERRUPT_MASK_FROM_ISR();
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263 vTaskIncrementTick();
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265 portCLEAR_INTERRUPT_MASK_FROM_ISR( 0 );
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267 /*-----------------------------------------------------------*/
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269 #if configUSE_TICKLESS_IDLE == 1
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271 __weak void vPortSuppressTicksAndSleep( portTickType xExpectedIdleTime )
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273 unsigned long ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickIncrements;
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274 portTickType xModifiableIdleTime;
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276 /* Make sure the SysTick reload value does not overflow the counter. */
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277 if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
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279 xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
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282 /* Calculate the reload value required to wait xExpectedIdleTime
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283 tick periods. -1 is used because this code will execute part way
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284 through one of the tick periods, and the fraction of a tick period is
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285 accounted for later. */
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286 ulReloadValue = ( ulTimerReloadValueForOneTick * ( xExpectedIdleTime - 1UL ) );
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287 if( ulReloadValue > ulStoppedTimerCompensation )
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289 ulReloadValue -= ulStoppedTimerCompensation;
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292 /* Stop the SysTick momentarily. The time the SysTick is stopped for
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293 is accounted for as best it can be, but using the tickless mode will
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294 inevitably result in some tiny drift of the time maintained by the
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295 kernel with respect to calendar time. */
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296 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;
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298 /* Adjust the reload value to take into account that the current
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299 time slice is already partially complete. */
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300 ulReloadValue += ( portNVIC_SYSTICK_LOAD_REG - ( portNVIC_SYSTICK_LOAD_REG - portNVIC_SYSTICK_CURRENT_VALUE_REG ) );
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302 /* Enter a critical section but don't use the taskENTER_CRITICAL()
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303 method as that will mask interrupts that should exit sleep mode. */
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304 __disable_interrupt();
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306 /* If a context switch is pending or a task is waiting for the scheduler
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307 to be unsuspended then abandon the low power entry. */
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308 if( eTaskConfirmSleepModeStatus() == eAbortSleep )
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310 /* Restart SysTick. */
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311 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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313 /* Re-enable interrupts - see comments above __disable_interrupt()
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315 __enable_interrupt();
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319 /* Set the new reload value. */
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320 portNVIC_SYSTICK_LOAD_REG = ulReloadValue;
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322 /* Clear the SysTick count flag and set the count value back to
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324 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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326 /* Restart SysTick. */
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327 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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329 /* Sleep until something happens. configPRE_SLEEP_PROCESSING() can
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330 set its parameter to 0 to indicate that its implementation contains
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331 its own wait for interrupt or wait for event instruction, and so wfi
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332 should not be executed again. However, the original expected idle
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333 time variable must remain unmodified, so a copy is taken. */
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334 xModifiableIdleTime = xExpectedIdleTime;
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335 configPRE_SLEEP_PROCESSING( xModifiableIdleTime );
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336 if( xModifiableIdleTime > 0 )
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340 configPOST_SLEEP_PROCESSING( xExpectedIdleTime );
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342 /* Stop SysTick. Again, the time the SysTick is stopped for is
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343 accounted for as best it can be, but using the tickless mode will
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344 inevitably result in some tiny drift of the time maintained by the
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345 kernel with respect to calendar time. */
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346 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;
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348 /* Re-enable interrupts - see comments above __disable_interrupt()
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350 __enable_interrupt();
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352 if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
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354 /* The tick interrupt has already executed, and the SysTick
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355 count reloaded with the portNVIC_SYSTICK_LOAD_REG value.
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356 Reset the portNVIC_SYSTICK_LOAD_REG with whatever remains of
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357 this tick period. */
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358 portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );
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360 /* The tick interrupt handler will already have pended the tick
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361 processing in the kernel. As the pending tick will be
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362 processed as soon as this function exits, the tick value
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363 maintained by the tick is stepped forward by one less than the
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364 time spent waiting. */
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365 ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
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369 /* Something other than the tick interrupt ended the sleep.
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370 Work out how long the sleep lasted. */
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371 ulCompletedSysTickIncrements = ( xExpectedIdleTime * ulTimerReloadValueForOneTick ) - portNVIC_SYSTICK_CURRENT_VALUE_REG;
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373 /* How many complete tick periods passed while the processor
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375 ulCompleteTickPeriods = ulCompletedSysTickIncrements / ulTimerReloadValueForOneTick;
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377 /* The reload value is set to whatever fraction of a single tick
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379 portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1 ) * ulTimerReloadValueForOneTick ) - ulCompletedSysTickIncrements;
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382 /* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG
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383 again, then set portNVIC_SYSTICK_LOAD_REG back to its standard
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385 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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386 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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388 vTaskStepTick( ulCompleteTickPeriods );
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392 #endif /* #if configUSE_TICKLESS_IDLE */
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393 /*-----------------------------------------------------------*/
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396 * Setup the systick timer to generate the tick interrupts at the required
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399 __weak void vPortSetupTimerInterrupt( void )
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401 /* Calculate the constants required to configure the tick interrupt. */
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402 #if configUSE_TICKLESS_IDLE == 1
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404 ulTimerReloadValueForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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405 xMaximumPossibleSuppressedTicks = 0xffffffUL / ( ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL );
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406 ulStoppedTimerCompensation = 45UL / ( configCPU_CLOCK_HZ / configSYSTICK_CLOCK_HZ );
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408 #endif /* configUSE_TICKLESS_IDLE */
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410 /* Configure SysTick to interrupt at the requested rate. */
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411 portNVIC_SYSTICK_LOAD_REG = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;;
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412 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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414 /*-----------------------------------------------------------*/
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