2 FreeRTOS V7.5.2 - Copyright (C) 2013 Real Time Engineers Ltd.
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4 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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6 ***************************************************************************
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8 * FreeRTOS provides completely free yet professionally developed, *
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9 * robust, strictly quality controlled, supported, and cross *
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10 * platform software that has become a de facto standard. *
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12 * Help yourself get started quickly and support the FreeRTOS *
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13 * project by purchasing a FreeRTOS tutorial book, reference *
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14 * manual, or both from: http://www.FreeRTOS.org/Documentation *
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18 ***************************************************************************
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20 This file is part of the FreeRTOS distribution.
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22 FreeRTOS is free software; you can redistribute it and/or modify it under
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23 the terms of the GNU General Public License (version 2) as published by the
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24 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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26 >>! NOTE: The modification to the GPL is included to allow you to distribute
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27 >>! a combined work that includes FreeRTOS without being obliged to provide
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28 >>! the source code for proprietary components outside of the FreeRTOS
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31 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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32 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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33 FOR A PARTICULAR PURPOSE. Full license text is available from the following
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34 link: http://www.freertos.org/a00114.html
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38 ***************************************************************************
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40 * Having a problem? Start by reading the FAQ "My application does *
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41 * not run, what could be wrong?" *
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43 * http://www.FreeRTOS.org/FAQHelp.html *
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45 ***************************************************************************
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47 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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48 license and Real Time Engineers Ltd. contact details.
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50 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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51 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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52 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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54 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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55 Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS
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56 licenses offer ticketed support, indemnification and middleware.
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58 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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59 engineered and independently SIL3 certified version for use in safety and
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60 mission critical applications that require provable dependability.
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66 /* Standard includes. */
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69 /* Scheduler includes. */
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70 #include "FreeRTOS.h"
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73 /* Constants required to setup the initial task context. */
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74 #define portINITIAL_SPSR ( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
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75 #define portTHUMB_MODE_BIT ( ( portSTACK_TYPE ) 0x20 )
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76 #define portINSTRUCTION_SIZE ( ( portSTACK_TYPE ) 4 )
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77 #define portNO_CRITICAL_SECTION_NESTING ( ( portSTACK_TYPE ) 0 )
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79 /* Constants required to setup the tick ISR. */
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80 #define portENABLE_TIMER ( ( unsigned portCHAR ) 0x01 )
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81 #define portPRESCALE_VALUE 0x00
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82 #define portINTERRUPT_ON_MATCH ( ( unsigned portLONG ) 0x01 )
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83 #define portRESET_COUNT_ON_MATCH ( ( unsigned portLONG ) 0x02 )
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85 /* Constants required to setup the VIC for the tick ISR. */
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86 #define portTIMER_VIC_CHANNEL ( ( unsigned portLONG ) 0x0004 )
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87 #define portTIMER_VIC_CHANNEL_BIT ( ( unsigned portLONG ) 0x0010 )
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88 #define portTIMER_VIC_ENABLE ( ( unsigned portLONG ) 0x0020 )
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90 /* Constants required to handle interrupts. */
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91 #define portTIMER_MATCH_ISR_BIT ( ( unsigned portCHAR ) 0x01 )
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92 #define portCLEAR_VIC_INTERRUPT ( ( unsigned portLONG ) 0 )
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94 /*-----------------------------------------------------------*/
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96 /* The code generated by the Keil compiler does not maintain separate
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97 stack and frame pointers. The portENTER_CRITICAL macro cannot therefore
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98 use the stack as per other ports. Instead a variable is used to keep
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99 track of the critical section nesting. This variable has to be stored
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100 as part of the task context and must be initialised to a non zero value. */
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102 #define portNO_CRITICAL_NESTING ( ( unsigned portLONG ) 0 )
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103 volatile unsigned portLONG ulCriticalNesting = 9999UL;
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105 /*-----------------------------------------------------------*/
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107 /* Setup the timer to generate the tick interrupts. */
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108 static void prvSetupTimerInterrupt( void );
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111 * The scheduler can only be started from ARM mode, so
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112 * vPortStartFirstSTask() is defined in portISR.c.
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114 extern __asm void vPortStartFirstTask( void );
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116 /*-----------------------------------------------------------*/
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119 * See header file for description.
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121 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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123 portSTACK_TYPE *pxOriginalTOS;
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125 /* Setup the initial stack of the task. The stack is set exactly as
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126 expected by the portRESTORE_CONTEXT() macro.
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128 Remember where the top of the (simulated) stack is before we place
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130 pxOriginalTOS = pxTopOfStack;
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132 /* To ensure asserts in tasks.c don't fail, although in this case the assert
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133 is not really required. */
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136 /* First on the stack is the return address - which in this case is the
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137 start of the task. The offset is added to make the return address appear
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138 as it would within an IRQ ISR. */
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139 *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;
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142 *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa; /* R14 */
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144 *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
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146 *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212; /* R12 */
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148 *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111; /* R11 */
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150 *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010; /* R10 */
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152 *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909; /* R9 */
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154 *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808; /* R8 */
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156 *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707; /* R7 */
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158 *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606; /* R6 */
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160 *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505; /* R5 */
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162 *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404; /* R4 */
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164 *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303; /* R3 */
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166 *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202; /* R2 */
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168 *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101; /* R1 */
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170 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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173 /* The last thing onto the stack is the status register, which is set for
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174 system mode, with interrupts enabled. */
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175 *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;
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177 if( ( ( unsigned long ) pxCode & 0x01UL ) != 0x00UL )
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179 /* We want the task to start in thumb mode. */
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180 *pxTopOfStack |= portTHUMB_MODE_BIT;
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185 /* The code generated by the Keil compiler does not maintain separate
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186 stack and frame pointers. The portENTER_CRITICAL macro cannot therefore
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187 use the stack as per other ports. Instead a variable is used to keep
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188 track of the critical section nesting. This variable has to be stored
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189 as part of the task context and is initially set to zero. */
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190 *pxTopOfStack = portNO_CRITICAL_SECTION_NESTING;
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192 return pxTopOfStack;
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194 /*-----------------------------------------------------------*/
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196 portBASE_TYPE xPortStartScheduler( void )
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198 /* Start the timer that generates the tick ISR. */
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199 prvSetupTimerInterrupt();
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201 /* Start the first task. This is done from portISR.c as ARM mode must be
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203 vPortStartFirstTask();
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205 /* Should not get here! */
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208 /*-----------------------------------------------------------*/
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210 void vPortEndScheduler( void )
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212 /* It is unlikely that the ARM port will require this function as there
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213 is nothing to return to. If this is required - stop the tick ISR then
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214 return back to main. */
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216 /*-----------------------------------------------------------*/
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218 #if configUSE_PREEMPTION == 0
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221 * The cooperative scheduler requires a normal IRQ service routine to
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222 * simply increment the system tick.
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224 void vNonPreemptiveTick( void ) __irq;
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225 void vNonPreemptiveTick( void ) __irq
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227 /* Increment the tick count - this may make a delaying task ready
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228 to run - but a context switch is not performed. */
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229 xTaskIncrementTick();
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231 T0IR = portTIMER_MATCH_ISR_BIT; /* Clear the timer event */
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232 VICVectAddr = portCLEAR_VIC_INTERRUPT; /* Acknowledge the Interrupt */
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238 **************************************************************************
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239 * The preemptive scheduler ISR is written in assembler and can be found
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240 * in the portASM.s file. This will only get used if portUSE_PREEMPTION
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241 * is set to 1 in portmacro.h
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242 **************************************************************************
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245 void vPreemptiveTick( void );
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248 /*-----------------------------------------------------------*/
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250 static void prvSetupTimerInterrupt( void )
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252 unsigned portLONG ulCompareMatch;
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254 /* A 1ms tick does not require the use of the timer prescale. This is
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255 defaulted to zero but can be used if necessary. */
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256 T0PR = portPRESCALE_VALUE;
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258 /* Calculate the match value required for our wanted tick rate. */
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259 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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261 /* Protect against divide by zero. Using an if() statement still results
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262 in a warning - hence the #if. */
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263 #if portPRESCALE_VALUE != 0
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265 ulCompareMatch /= ( portPRESCALE_VALUE + 1 );
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269 T0MR0 = ulCompareMatch;
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271 /* Generate tick with timer 0 compare match. */
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272 T0MCR = portRESET_COUNT_ON_MATCH | portINTERRUPT_ON_MATCH;
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274 /* Setup the VIC for the timer. */
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275 VICIntSelect &= ~( portTIMER_VIC_CHANNEL_BIT );
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276 VICIntEnable |= portTIMER_VIC_CHANNEL_BIT;
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278 /* The ISR installed depends on whether the preemptive or cooperative
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279 scheduler is being used. */
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280 #if configUSE_PREEMPTION == 1
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282 VICVectAddr0 = ( unsigned portLONG ) vPreemptiveTick;
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286 VICVectAddr0 = ( unsigned portLONG ) vNonPreemptiveTick;
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290 VICVectCntl0 = portTIMER_VIC_CHANNEL | portTIMER_VIC_ENABLE;
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292 /* Start the timer - interrupts are disabled when this function is called
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293 so it is okay to do this here. */
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294 T0TCR = portENABLE_TIMER;
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296 /*-----------------------------------------------------------*/
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298 void vPortEnterCritical( void )
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300 /* Disable interrupts as per portDISABLE_INTERRUPTS(); */
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303 /* Now interrupts are disabled ulCriticalNesting can be accessed
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304 directly. Increment ulCriticalNesting to keep a count of how many times
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305 portENTER_CRITICAL() has been called. */
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306 ulCriticalNesting++;
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308 /*-----------------------------------------------------------*/
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310 void vPortExitCritical( void )
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312 if( ulCriticalNesting > portNO_CRITICAL_NESTING )
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314 /* Decrement the nesting count as we are leaving a critical section. */
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315 ulCriticalNesting--;
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317 /* If the nesting level has reached zero then interrupts should be
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319 if( ulCriticalNesting == portNO_CRITICAL_NESTING )
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321 /* Enable interrupts as per portEXIT_CRITICAL(). */
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326 /*-----------------------------------------------------------*/
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