2 FreeRTOS V7.2.0 - Copyright (C) 2012 Real Time Engineers Ltd.
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5 ***************************************************************************
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7 * FreeRTOS tutorial books are available in pdf and paperback. *
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8 * Complete, revised, and edited pdf reference manuals are also *
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11 * Purchasing FreeRTOS documentation will not only help you, by *
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12 * ensuring you get running as quickly as possible and with an *
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13 * in-depth knowledge of how to use FreeRTOS, it will also help *
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14 * the FreeRTOS project to continue with its mission of providing *
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15 * professional grade, cross platform, de facto standard solutions *
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16 * for microcontrollers - completely free of charge! *
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18 * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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20 * Thank you for using FreeRTOS, and thank you for your support! *
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22 ***************************************************************************
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25 This file is part of the FreeRTOS distribution.
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27 FreeRTOS is free software; you can redistribute it and/or modify it under
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28 the terms of the GNU General Public License (version 2) as published by the
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29 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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30 >>>NOTE<<< The modification to the GPL is included to allow you to
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31 distribute a combined work that includes FreeRTOS without being obliged to
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32 provide the source code for proprietary components outside of the FreeRTOS
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33 kernel. FreeRTOS is distributed in the hope that it will be useful, but
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34 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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35 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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36 more details. You should have received a copy of the GNU General Public
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37 License and the FreeRTOS license exception along with FreeRTOS; if not it
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38 can be viewed here: http://www.freertos.org/a00114.html and also obtained
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39 by writing to Richard Barry, contact details for whom are available on the
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44 ***************************************************************************
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46 * Having a problem? Start by reading the FAQ "My application does *
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47 * not run, what could be wrong? *
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49 * http://www.FreeRTOS.org/FAQHelp.html *
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51 ***************************************************************************
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54 http://www.FreeRTOS.org - Documentation, training, latest information,
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55 license and contact details.
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57 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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58 including FreeRTOS+Trace - an indispensable productivity tool.
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60 Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell
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61 the code with commercial support, indemnification, and middleware, under
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62 the OpenRTOS brand: http://www.OpenRTOS.com. High Integrity Systems also
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63 provide a safety engineered and independently SIL3 certified version under
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64 the SafeRTOS brand: http://www.SafeRTOS.com.
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68 /* Standard includes. */
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71 /* Scheduler includes. */
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72 #include "FreeRTOS.h"
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75 /* Constants required to setup the initial task context. */
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76 #define portINITIAL_SPSR ( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
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77 #define portTHUMB_MODE_BIT ( ( portSTACK_TYPE ) 0x20 )
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78 #define portINSTRUCTION_SIZE ( ( portSTACK_TYPE ) 4 )
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79 #define portNO_CRITICAL_SECTION_NESTING ( ( portSTACK_TYPE ) 0 )
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81 /* Constants required to setup the tick ISR. */
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82 #define portENABLE_TIMER ( ( unsigned portCHAR ) 0x01 )
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83 #define portPRESCALE_VALUE 0x00
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84 #define portINTERRUPT_ON_MATCH ( ( unsigned portLONG ) 0x01 )
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85 #define portRESET_COUNT_ON_MATCH ( ( unsigned portLONG ) 0x02 )
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87 /* Constants required to setup the VIC for the tick ISR. */
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88 #define portTIMER_VIC_CHANNEL ( ( unsigned portLONG ) 0x0004 )
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89 #define portTIMER_VIC_CHANNEL_BIT ( ( unsigned portLONG ) 0x0010 )
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90 #define portTIMER_VIC_ENABLE ( ( unsigned portLONG ) 0x0020 )
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92 /* Constants required to handle interrupts. */
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93 #define portTIMER_MATCH_ISR_BIT ( ( unsigned portCHAR ) 0x01 )
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94 #define portCLEAR_VIC_INTERRUPT ( ( unsigned portLONG ) 0 )
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96 /*-----------------------------------------------------------*/
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98 /* The code generated by the Keil compiler does not maintain separate
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99 stack and frame pointers. The portENTER_CRITICAL macro cannot therefore
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100 use the stack as per other ports. Instead a variable is used to keep
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101 track of the critical section nesting. This variable has to be stored
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102 as part of the task context and must be initialised to a non zero value. */
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104 #define portNO_CRITICAL_NESTING ( ( unsigned portLONG ) 0 )
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105 volatile unsigned portLONG ulCriticalNesting = 9999UL;
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107 /*-----------------------------------------------------------*/
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109 /* Setup the timer to generate the tick interrupts. */
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110 static void prvSetupTimerInterrupt( void );
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113 * The scheduler can only be started from ARM mode, so
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114 * vPortStartFirstSTask() is defined in portISR.c.
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116 extern __asm void vPortStartFirstTask( void );
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118 /*-----------------------------------------------------------*/
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121 * See header file for description.
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123 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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125 portSTACK_TYPE *pxOriginalTOS;
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127 /* Setup the initial stack of the task. The stack is set exactly as
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128 expected by the portRESTORE_CONTEXT() macro.
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130 Remember where the top of the (simulated) stack is before we place
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132 pxOriginalTOS = pxTopOfStack;
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134 /* To ensure asserts in tasks.c don't fail, although in this case the assert
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135 is not really required. */
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138 /* First on the stack is the return address - which in this case is the
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139 start of the task. The offset is added to make the return address appear
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140 as it would within an IRQ ISR. */
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141 *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;
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144 *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa; /* R14 */
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146 *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
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148 *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212; /* R12 */
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150 *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111; /* R11 */
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152 *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010; /* R10 */
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154 *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909; /* R9 */
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156 *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808; /* R8 */
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158 *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707; /* R7 */
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160 *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606; /* R6 */
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162 *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505; /* R5 */
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164 *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404; /* R4 */
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166 *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303; /* R3 */
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168 *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202; /* R2 */
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170 *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101; /* R1 */
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172 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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175 /* The last thing onto the stack is the status register, which is set for
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176 system mode, with interrupts enabled. */
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177 *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;
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179 if( ( ( unsigned long ) pxCode & 0x01UL ) != 0x00UL )
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181 /* We want the task to start in thumb mode. */
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182 *pxTopOfStack |= portTHUMB_MODE_BIT;
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187 /* The code generated by the Keil compiler does not maintain separate
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188 stack and frame pointers. The portENTER_CRITICAL macro cannot therefore
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189 use the stack as per other ports. Instead a variable is used to keep
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190 track of the critical section nesting. This variable has to be stored
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191 as part of the task context and is initially set to zero. */
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192 *pxTopOfStack = portNO_CRITICAL_SECTION_NESTING;
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194 return pxTopOfStack;
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196 /*-----------------------------------------------------------*/
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198 portBASE_TYPE xPortStartScheduler( void )
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200 /* Start the timer that generates the tick ISR. */
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201 prvSetupTimerInterrupt();
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203 /* Start the first task. This is done from portISR.c as ARM mode must be
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205 vPortStartFirstTask();
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207 /* Should not get here! */
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210 /*-----------------------------------------------------------*/
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212 void vPortEndScheduler( void )
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214 /* It is unlikely that the ARM port will require this function as there
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215 is nothing to return to. If this is required - stop the tick ISR then
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216 return back to main. */
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218 /*-----------------------------------------------------------*/
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220 #if configUSE_PREEMPTION == 0
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223 * The cooperative scheduler requires a normal IRQ service routine to
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224 * simply increment the system tick.
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226 void vNonPreemptiveTick( void ) __irq;
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227 void vNonPreemptiveTick( void ) __irq
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229 /* Increment the tick count - this may make a delaying task ready
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230 to run - but a context switch is not performed. */
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231 vTaskIncrementTick();
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233 T0IR = portTIMER_MATCH_ISR_BIT; /* Clear the timer event */
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234 VICVectAddr = portCLEAR_VIC_INTERRUPT; /* Acknowledge the Interrupt */
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240 **************************************************************************
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241 * The preemptive scheduler ISR is written in assembler and can be found
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242 * in the portASM.s file. This will only get used if portUSE_PREEMPTION
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243 * is set to 1 in portmacro.h
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244 **************************************************************************
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247 void vPreemptiveTick( void );
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250 /*-----------------------------------------------------------*/
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252 static void prvSetupTimerInterrupt( void )
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254 unsigned portLONG ulCompareMatch;
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256 /* A 1ms tick does not require the use of the timer prescale. This is
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257 defaulted to zero but can be used if necessary. */
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258 T0PR = portPRESCALE_VALUE;
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260 /* Calculate the match value required for our wanted tick rate. */
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261 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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263 /* Protect against divide by zero. Using an if() statement still results
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264 in a warning - hence the #if. */
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265 #if portPRESCALE_VALUE != 0
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267 ulCompareMatch /= ( portPRESCALE_VALUE + 1 );
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271 T0MR0 = ulCompareMatch;
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273 /* Generate tick with timer 0 compare match. */
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274 T0MCR = portRESET_COUNT_ON_MATCH | portINTERRUPT_ON_MATCH;
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276 /* Setup the VIC for the timer. */
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277 VICIntSelect &= ~( portTIMER_VIC_CHANNEL_BIT );
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278 VICIntEnable |= portTIMER_VIC_CHANNEL_BIT;
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280 /* The ISR installed depends on whether the preemptive or cooperative
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281 scheduler is being used. */
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282 #if configUSE_PREEMPTION == 1
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284 VICVectAddr0 = ( unsigned portLONG ) vPreemptiveTick;
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288 VICVectAddr0 = ( unsigned portLONG ) vNonPreemptiveTick;
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292 VICVectCntl0 = portTIMER_VIC_CHANNEL | portTIMER_VIC_ENABLE;
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294 /* Start the timer - interrupts are disabled when this function is called
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295 so it is okay to do this here. */
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296 T0TCR = portENABLE_TIMER;
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298 /*-----------------------------------------------------------*/
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300 void vPortEnterCritical( void )
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302 /* Disable interrupts as per portDISABLE_INTERRUPTS(); */
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305 /* Now interrupts are disabled ulCriticalNesting can be accessed
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306 directly. Increment ulCriticalNesting to keep a count of how many times
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307 portENTER_CRITICAL() has been called. */
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308 ulCriticalNesting++;
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310 /*-----------------------------------------------------------*/
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312 void vPortExitCritical( void )
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314 if( ulCriticalNesting > portNO_CRITICAL_NESTING )
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316 /* Decrement the nesting count as we are leaving a critical section. */
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317 ulCriticalNesting--;
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319 /* If the nesting level has reached zero then interrupts should be
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321 if( ulCriticalNesting == portNO_CRITICAL_NESTING )
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323 /* Enable interrupts as per portEXIT_CRITICAL(). */
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328 /*-----------------------------------------------------------*/
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