2 ; FreeRTOS V8.2.0 - Copyright (C) 2015 Real Time Engineers Ltd.
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3 ; All rights reserved
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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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41 ; FreeRTOS WEB site.
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43 ; 1 tab == 4 spaces!
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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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55 INCLUDE portmacro.inc
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57 IMPORT vTaskSwitchContext
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58 IMPORT xTaskIncrementTick
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60 EXPORT vPortYieldProcessor
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61 EXPORT vPortStartFirstTask
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62 EXPORT vPreemptiveTick
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66 VICVECTADDR EQU 0xFFFFF030
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68 T0MATCHBIT EQU 0x00000001
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71 AREA PORT_ASM, CODE, READONLY
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75 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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76 ; Starting the first task is done by just restoring the context
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77 ; setup by pxPortInitialiseStack
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78 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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92 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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93 ; Interrupt service routine for the SWI interrupt. The vector table is
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94 ; configured in the startup.s file.
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96 ; vPortYieldProcessor() is used to manually force a context switch. The
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97 ; SWI interrupt is generated by a call to taskYIELD() or portYIELD().
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98 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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100 vPortYieldProcessor
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104 ; Within an IRQ ISR the link register has an offset from the true return
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105 ; address, but an SWI ISR does not. Add the offset manually so the same
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106 ; ISR return code can be used in both cases.
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109 ; Perform the context switch.
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110 portSAVE_CONTEXT ; Save current task context
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111 LDR R0, =vTaskSwitchContext ; Get the address of the context switch function
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112 MOV LR, PC ; Store the return address
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113 BX R0 ; Call the contedxt switch function
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114 portRESTORE_CONTEXT ; restore the context of the selected task
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118 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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119 ; Interrupt service routine for preemptive scheduler tick timer
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120 ; Only used if portUSE_PREEMPTION is set to 1 in portmacro.h
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122 ; Uses timer 0 of LPC21XX Family
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123 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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129 portSAVE_CONTEXT ; Save the context of the current task.
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131 LDR R0, =xTaskIncrementTick ; Increment the tick count.
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132 MOV LR, PC ; This may make a delayed task ready
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136 BEQ SkipContextSwitch
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137 LDR R0, =vTaskSwitchContext ; Find the highest priority task that
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138 MOV LR, PC ; is ready to run.
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141 MOV R0, #T0MATCHBIT ; Clear the timer event
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145 LDR R0, =VICVECTADDR ; Acknowledge the interrupt
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148 portRESTORE_CONTEXT ; Restore the context of the highest
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149 ; priority task that is ready to run.
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