2 FreeRTOS V8.1.1 - Copyright (C) 2014 Real Time Engineers Ltd.
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6 ***************************************************************************
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8 * FreeRTOS tutorial books are available in pdf and paperback. *
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9 * Complete, revised, and edited pdf reference manuals are also *
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12 * Purchasing FreeRTOS documentation will not only help you, by *
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13 * ensuring you get running as quickly as possible and with an *
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14 * in-depth knowledge of how to use FreeRTOS, it will also help *
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15 * the FreeRTOS project to continue with its mission of providing *
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16 * professional grade, cross platform, de facto standard solutions *
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17 * for microcontrollers - completely free of charge! *
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19 * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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21 * Thank you for using FreeRTOS, and thank you for your support! *
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23 ***************************************************************************
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26 This file is part of the FreeRTOS distribution.
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28 FreeRTOS is free software; you can redistribute it and/or modify it under
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29 the terms of the GNU General Public License (version 2) as published by the
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30 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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31 >>>NOTE<<< The modification to the GPL is included to allow you to
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32 distribute a combined work that includes FreeRTOS without being obliged to
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33 provide the source code for proprietary components outside of the FreeRTOS
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34 kernel. FreeRTOS is distributed in the hope that it will be useful, but
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35 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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36 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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37 more details. You should have received a copy of the GNU General Public
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38 License and the FreeRTOS license exception along with FreeRTOS; if not it
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39 can be viewed here: http://www.freertos.org/a00114.html and also obtained
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40 by writing to Richard Barry, contact details for whom are available on the
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45 http://www.FreeRTOS.org - Documentation, latest information, license and
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48 http://www.SafeRTOS.com - A version that is certified for use in safety
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51 http://www.OpenRTOS.com - Commercial support, development, porting,
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52 licensing and training services.
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62 /* Hardware registers. */
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67 /* Variables and functions. */
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68 .extern ulMaxAPIPriorityMask
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69 .extern _freertos_vector_table
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70 .extern pxCurrentTCB
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71 .extern vTaskSwitchContext
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72 .extern vApplicationIRQHandler
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73 .extern ulPortInterruptNesting
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74 .extern ulPortTaskHasFPUContext
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76 .global FreeRTOS_IRQ_Handler
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77 .global FreeRTOS_SWI_Handler
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78 .global vPortRestoreTaskContext
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79 .global vPortInstallFreeRTOSVectorTable
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84 .macro portSAVE_CONTEXT
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86 /* Save the LR and SPSR onto the system mode stack before switching to
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87 system mode to save the remaining system mode registers. */
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88 SRSDB sp!, #SYS_MODE
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92 /* Push the critical nesting count. */
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93 LDR R2, ulCriticalNestingConst
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97 /* Does the task have a floating point context that needs saving? If
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98 ulPortTaskHasFPUContext is 0 then no. */
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99 LDR R2, ulPortTaskHasFPUContextConst
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103 /* Save the floating point context, if any. */
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109 /* Save ulPortTaskHasFPUContext itself. */
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112 /* Save the stack pointer in the TCB. */
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113 LDR R0, pxCurrentTCBConst
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119 ; /**********************************************************************/
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121 .macro portRESTORE_CONTEXT
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123 /* Set the SP to point to the stack of the task being restored. */
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124 LDR R0, pxCurrentTCBConst
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128 /* Is there a floating point context to restore? If the restored
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129 ulPortTaskHasFPUContext is zero then no. */
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130 LDR R0, ulPortTaskHasFPUContextConst
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135 /* Restore the floating point context, if any. */
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141 /* Restore the critical section nesting depth. */
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142 LDR R0, ulCriticalNestingConst
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146 /* Ensure the priority mask is correct for the critical nesting depth. */
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147 LDR R2, ulICCPMRConst
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151 LDRNE R4, ulMaxAPIPriorityMaskConst
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155 /* Restore all system mode registers other than the SP (which is already
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159 /* Return to the task code, loading CPSR on the way. */
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167 /******************************************************************************
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168 * SVC handler is used to start the scheduler.
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169 *****************************************************************************/
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171 .type FreeRTOS_SWI_Handler, %function
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172 FreeRTOS_SWI_Handler:
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173 /* Save the context of the current task and select a new task to run. */
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175 LDR R0, vTaskSwitchContextConst
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177 portRESTORE_CONTEXT
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180 /******************************************************************************
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181 * vPortRestoreTaskContext is used to start the scheduler.
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182 *****************************************************************************/
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183 .type vPortRestoreTaskContext, %function
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184 vPortRestoreTaskContext:
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185 /* Switch to system mode. */
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187 portRESTORE_CONTEXT
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190 .type FreeRTOS_IRQ_Handler, %function
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191 FreeRTOS_IRQ_Handler:
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192 /* Return to the interrupted instruction. */
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195 /* Push the return address and SPSR. */
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200 /* Change to supervisor mode to allow reentry. */
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203 /* Push used registers. */
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206 /* Increment nesting count. r3 holds the address of ulPortInterruptNesting
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207 for future use. r1 holds the original ulPortInterruptNesting value for
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209 LDR r3, ulPortInterruptNestingConst
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214 /* Read value from the interrupt acknowledge register, which is stored in r0
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215 for future parameter and interrupt clearing use. */
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216 LDR r2, ulICCIARConst
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220 /* Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
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226 /* Call the interrupt handler. */
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228 LDR r1, vApplicationIRQHandlerConst
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237 /* Write the value read from ICCIAR to ICCEOIR. */
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238 LDR r4, ulICCEOIRConst
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242 /* Restore the old nesting count. */
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245 /* A context switch is never performed if the nesting count is not 0. */
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247 BNE exit_without_switch
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249 /* Did the interrupt request a context switch? r1 holds the address of
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250 ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
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252 LDR r1, =ulPortYieldRequired
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255 BNE switch_before_exit
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257 exit_without_switch:
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258 /* No context switch. Restore used registers, LR_irq and SPSR before
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267 switch_before_exit:
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268 /* A context swtich is to be performed. Clear the context switch pending
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273 /* Restore used registers, LR-irq and SPSR before saving the context
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274 to the task stack. */
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282 /* Call the function that selects the new task to execute.
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283 vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
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284 instructions, or 8 byte aligned stack allocated data. LR does not need
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285 saving as a new LR will be loaded by portRESTORE_CONTEXT anyway. */
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286 LDR R0, vTaskSwitchContextConst
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289 /* Restore the context of, and branch to, the task selected to execute
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291 portRESTORE_CONTEXT
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293 ulICCIARConst: .word ulICCIAR
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294 ulICCEOIRConst: .word ulICCEOIR
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295 ulICCPMRConst: .word ulICCPMR
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296 pxCurrentTCBConst: .word pxCurrentTCB
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297 ulCriticalNestingConst: .word ulCriticalNesting
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298 ulPortTaskHasFPUContextConst: .word ulPortTaskHasFPUContext
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299 ulMaxAPIPriorityMaskConst: .word ulMaxAPIPriorityMask
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300 vTaskSwitchContextConst: .word vTaskSwitchContext
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301 vApplicationIRQHandlerConst: .word vApplicationIRQHandler
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302 ulPortInterruptNestingConst: .word ulPortInterruptNesting
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