2 FreeRTOS V8.1.1 - Copyright (C) 2014 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 ***************************************************************************
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9 * FreeRTOS provides completely free yet professionally developed, *
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10 * robust, strictly quality controlled, supported, and cross *
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11 * platform software that has become a de facto standard. *
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13 * Help yourself get started quickly and support the FreeRTOS *
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14 * project by purchasing a FreeRTOS tutorial book, reference *
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15 * manual, or both from: http://www.FreeRTOS.org/Documentation *
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19 ***************************************************************************
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21 This file is part of the FreeRTOS distribution.
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23 FreeRTOS is free software; you can redistribute it and/or modify it under
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24 the terms of the GNU General Public License (version 2) as published by the
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25 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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27 >>! NOTE: The modification to the GPL is included to allow you to !<<
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28 >>! distribute a combined work that includes FreeRTOS without being !<<
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29 >>! obliged to provide the source code for proprietary components !<<
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30 >>! outside of the FreeRTOS kernel. !<<
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32 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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33 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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34 FOR A PARTICULAR PURPOSE. Full license text is available from the following
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35 link: http://www.freertos.org/a00114.html
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39 ***************************************************************************
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41 * Having a problem? Start by reading the FAQ "My application does *
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42 * not run, what could be wrong?" *
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44 * http://www.FreeRTOS.org/FAQHelp.html *
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46 ***************************************************************************
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48 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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49 license and Real Time Engineers Ltd. contact details.
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51 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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52 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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53 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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55 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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56 Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS
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57 licenses offer ticketed support, indemnification and middleware.
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59 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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60 engineered and independently SIL3 certified version for use in safety and
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61 mission critical applications that require provable dependability.
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69 + usCriticalNesting now has a volatile qualifier.
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72 /* Standard includes. */
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76 /* Scheduler includes. */
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77 #include "FreeRTOS.h"
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80 /*-----------------------------------------------------------
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81 * Implementation of functions defined in portable.h for the MSP430 port.
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82 *----------------------------------------------------------*/
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84 /* Constants required for hardware setup. The tick ISR runs off the ACLK,
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86 #define portACLK_FREQUENCY_HZ ( ( TickType_t ) 32768 )
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87 #define portINITIAL_CRITICAL_NESTING ( ( uint16_t ) 10 )
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88 #define portFLAGS_INT_ENABLED ( ( StackType_t ) 0x08 )
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90 /* We require the address of the pxCurrentTCB variable, but don't want to know
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91 any details of its type. */
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93 extern volatile TCB_t * volatile pxCurrentTCB;
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95 /* Most ports implement critical sections by placing the interrupt flags on
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96 the stack before disabling interrupts. Exiting the critical section is then
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97 simply a case of popping the flags from the stack. As mspgcc does not use
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98 a frame pointer this cannot be done as modifying the stack will clobber all
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99 the stack variables. Instead each task maintains a count of the critical
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100 section nesting depth. Each time a critical section is entered the count is
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101 incremented. Each time a critical section is left the count is decremented -
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102 with interrupts only being re-enabled if the count is zero.
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104 usCriticalNesting will get set to zero when the scheduler starts, but must
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105 not be initialised to zero as this will cause problems during the startup
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107 volatile uint16_t usCriticalNesting = portINITIAL_CRITICAL_NESTING;
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108 /*-----------------------------------------------------------*/
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111 * Macro to save a task context to the task stack. This simply pushes all the
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112 * general purpose msp430 registers onto the stack, followed by the
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113 * usCriticalNesting value used by the task. Finally the resultant stack
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114 * pointer value is saved into the task control block so it can be retrieved
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115 * the next time the task executes.
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117 #define portSAVE_CONTEXT() \
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118 asm volatile ( "push r4 \n\t" \
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130 "mov.w usCriticalNesting, r14 \n\t" \
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132 "mov.w pxCurrentTCB, r12 \n\t" \
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133 "mov.w r1, @r12 \n\t" \
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137 * Macro to restore a task context from the task stack. This is effectively
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138 * the reverse of portSAVE_CONTEXT(). First the stack pointer value is
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139 * loaded from the task control block. Next the value for usCriticalNesting
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140 * used by the task is retrieved from the stack - followed by the value of all
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141 * the general purpose msp430 registers.
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143 * The bic instruction ensures there are no low power bits set in the status
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144 * register that is about to be popped from the stack.
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146 #define portRESTORE_CONTEXT() \
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147 asm volatile ( "mov.w pxCurrentTCB, r12 \n\t" \
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148 "mov.w @r12, r1 \n\t" \
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150 "mov.w r15, usCriticalNesting \n\t" \
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163 "bic #(0xf0),0(r1) \n\t" \
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166 /*-----------------------------------------------------------*/
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169 * Sets up the periodic ISR used for the RTOS tick. This uses timer 0, but
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170 * could have alternatively used the watchdog timer or timer 1.
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172 static void prvSetupTimerInterrupt( void );
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173 /*-----------------------------------------------------------*/
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176 * Initialise the stack of a task to look exactly as if a call to
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177 * portSAVE_CONTEXT had been called.
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179 * See the header file portable.h.
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181 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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184 Place a few bytes of known values on the bottom of the stack.
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185 This is just useful for debugging and can be included if required.
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187 *pxTopOfStack = ( StackType_t ) 0x1111;
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189 *pxTopOfStack = ( StackType_t ) 0x2222;
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191 *pxTopOfStack = ( StackType_t ) 0x3333;
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195 /* The msp430 automatically pushes the PC then SR onto the stack before
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196 executing an ISR. We want the stack to look just as if this has happened
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197 so place a pointer to the start of the task on the stack first - followed
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198 by the flags we want the task to use when it starts up. */
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199 *pxTopOfStack = ( StackType_t ) pxCode;
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201 *pxTopOfStack = portFLAGS_INT_ENABLED;
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204 /* Next the general purpose registers. */
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205 *pxTopOfStack = ( StackType_t ) 0x4444;
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207 *pxTopOfStack = ( StackType_t ) 0x5555;
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209 *pxTopOfStack = ( StackType_t ) 0x6666;
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211 *pxTopOfStack = ( StackType_t ) 0x7777;
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213 *pxTopOfStack = ( StackType_t ) 0x8888;
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215 *pxTopOfStack = ( StackType_t ) 0x9999;
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217 *pxTopOfStack = ( StackType_t ) 0xaaaa;
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219 *pxTopOfStack = ( StackType_t ) 0xbbbb;
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221 *pxTopOfStack = ( StackType_t ) 0xcccc;
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223 *pxTopOfStack = ( StackType_t ) 0xdddd;
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225 *pxTopOfStack = ( StackType_t ) 0xeeee;
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228 /* When the task starts is will expect to find the function parameter in
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230 *pxTopOfStack = ( StackType_t ) pvParameters;
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233 /* The code generated by the mspgcc compiler does not maintain separate
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234 stack and frame pointers. The portENTER_CRITICAL macro cannot therefore
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235 use the stack as per other ports. Instead a variable is used to keep
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236 track of the critical section nesting. This variable has to be stored
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237 as part of the task context and is initially set to zero. */
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238 *pxTopOfStack = ( StackType_t ) portNO_CRITICAL_SECTION_NESTING;
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240 /* Return a pointer to the top of the stack we have generated so this can
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241 be stored in the task control block for the task. */
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242 return pxTopOfStack;
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244 /*-----------------------------------------------------------*/
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246 BaseType_t xPortStartScheduler( void )
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248 /* Setup the hardware to generate the tick. Interrupts are disabled when
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249 this function is called. */
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250 prvSetupTimerInterrupt();
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252 /* Restore the context of the first task that is going to run. */
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253 portRESTORE_CONTEXT();
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255 /* Should not get here as the tasks are now running! */
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258 /*-----------------------------------------------------------*/
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260 void vPortEndScheduler( void )
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262 /* It is unlikely that the MSP430 port will get stopped. If required simply
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263 disable the tick interrupt here. */
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265 /*-----------------------------------------------------------*/
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268 * Manual context switch called by portYIELD or taskYIELD.
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270 * The first thing we do is save the registers so we can use a naked attribute.
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272 void vPortYield( void ) __attribute__ ( ( naked ) );
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273 void vPortYield( void )
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275 /* We want the stack of the task being saved to look exactly as if the task
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276 was saved during a pre-emptive RTOS tick ISR. Before calling an ISR the
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277 msp430 places the status register onto the stack. As this is a function
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278 call and not an ISR we have to do this manually. */
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279 asm volatile ( "push r2" );
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282 /* Save the context of the current task. */
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283 portSAVE_CONTEXT();
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285 /* Switch to the highest priority task that is ready to run. */
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286 vTaskSwitchContext();
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288 /* Restore the context of the new task. */
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289 portRESTORE_CONTEXT();
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291 /*-----------------------------------------------------------*/
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294 * Hardware initialisation to generate the RTOS tick. This uses timer 0
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295 * but could alternatively use the watchdog timer or timer 1.
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297 static void prvSetupTimerInterrupt( void )
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299 /* Ensure the timer is stopped. */
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302 /* Run the timer of the ACLK. */
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305 /* Clear everything to start with. */
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308 /* Set the compare match value according to the tick rate we want. */
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309 TACCR0 = portACLK_FREQUENCY_HZ / configTICK_RATE_HZ;
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311 /* Enable the interrupts. */
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314 /* Start up clean. */
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320 /*-----------------------------------------------------------*/
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323 * The interrupt service routine used depends on whether the pre-emptive
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324 * scheduler is being used or not.
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327 #if configUSE_PREEMPTION == 1
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330 * Tick ISR for preemptive scheduler. We can use a naked attribute as
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331 * the context is saved at the start of vPortYieldFromTick(). The tick
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332 * count is incremented after the context is saved.
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334 interrupt (TIMERA0_VECTOR) prvTickISR( void ) __attribute__ ( ( naked ) );
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335 interrupt (TIMERA0_VECTOR) prvTickISR( void )
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337 /* Save the context of the interrupted task. */
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338 portSAVE_CONTEXT();
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340 /* Increment the tick count then switch to the highest priority task
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341 that is ready to run. */
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342 if( xTaskIncrementTick() != pdFALSE )
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344 vTaskSwitchContext();
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347 /* Restore the context of the new task. */
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348 portRESTORE_CONTEXT();
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354 * Tick ISR for the cooperative scheduler. All this does is increment the
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355 * tick count. We don't need to switch context, this can only be done by
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356 * manual calls to taskYIELD();
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358 interrupt (TIMERA0_VECTOR) prvTickISR( void );
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359 interrupt (TIMERA0_VECTOR) prvTickISR( void )
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361 xTaskIncrementTick();
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