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 #include <sys/asm.h>
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67 #include "ISR_Support.h"
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73 .extern pxCurrentTCB
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74 .extern vTaskSwitchContext
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75 .extern vPortIncrementTick
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76 .extern xISRStackTop
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78 .global vPortStartFirstTask
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79 .global vPortYieldISR
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80 .global vPortTickInterruptHandler
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83 /******************************************************************/
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87 .ent vPortTickInterruptHandler
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89 vPortTickInterruptHandler:
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93 jal vPortIncrementTick
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98 .end vPortTickInterruptHandler
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100 /******************************************************************/
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104 .ent vPortStartFirstTask
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106 vPortStartFirstTask:
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108 /* Simply restore the context of the highest priority task that has been
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110 portRESTORE_CONTEXT
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112 .end vPortStartFirstTask
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116 /*******************************************************************/
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124 /* Make room for the context. First save the current status so it can be
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125 manipulated, and the cause and EPC registers so thier original values are
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127 mfc0 k0, _CP0_CAUSE
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128 addiu sp, sp, -portCONTEXT_SIZE
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129 mfc0 k1, _CP0_STATUS
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131 /* Also save s6 and s5 so we can use them during this interrupt. Any
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132 nesting interrupts should maintain the values of these registers
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136 sw k1, portSTATUS_STACK_LOCATION(sp)
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138 /* Interrupts above the kernel priority are going to be re-enabled. */
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143 /* s5 is used as the frame pointer. */
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146 /* Swap to the system stack. This is not conditional on the nesting
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147 count as this interrupt is always the lowest priority and therefore
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148 the nesting is always 0. */
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149 la sp, xISRStackTop
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152 /* Set the nesting count. */
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153 la k0, uxInterruptNesting
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157 /* s6 holds the EPC value, this is saved with the rest of the context
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158 after interrupts are enabled. */
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161 /* Re-enable interrupts. */
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162 mtc0 k1, _CP0_STATUS
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164 /* Save the context into the space just created. s6 is saved again
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165 here as it now contains the EPC value. */
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185 sw s6, portEPC_STACK_LOCATION(s5)
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186 /* s5 and s6 has already been saved. */
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194 /* s7 is used as a scratch register as this should always be saved across
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195 nesting interrupts. */
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201 /* Save the stack pointer to the task. */
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202 la s7, pxCurrentTCB
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206 /* Set the interrupt mask to the max priority that can use the API. The
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207 yield handler will only be called at configKERNEL_INTERRUPT_PRIORITY which
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208 is below configMAX_SYSCALL_INTERRUPT_PRIORITY - so this can only ever
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209 raise the IPL value and never lower it. */
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211 mfc0 s7, _CP0_STATUS
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213 ori s6, s7, ( configMAX_SYSCALL_INTERRUPT_PRIORITY << 10 ) | 1
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215 /* This mtc0 re-enables interrupts, but only above
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216 configMAX_SYSCALL_INTERRUPT_PRIORITY. */
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217 mtc0 s6, _CP0_STATUS
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219 /* Clear the software interrupt in the core. */
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220 mfc0 s6, _CP0_CAUSE
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222 mtc0 s6, _CP0_CAUSE
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224 /* Clear the interrupt in the interrupt controller. */
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229 jal vTaskSwitchContext
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232 /* Clear the interrupt mask again. The saved status value is still in s7. */
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233 mtc0 s7, _CP0_STATUS
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235 /* Restore the stack pointer from the TCB. */
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236 la s0, pxCurrentTCB
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240 /* Restore the rest of the context. */
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251 /* s5 is loaded later. */
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273 /* Protect access to the k registers, and others. */
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276 /* Set nesting back to zero. As the lowest priority interrupt this
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277 interrupt cannot have nested. */
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278 la k0, uxInterruptNesting
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281 /* Switch back to use the real stack pointer. */
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284 /* Restore the real s5 value. */
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287 /* Pop the status and epc values. */
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288 lw k1, portSTATUS_STACK_LOCATION(sp)
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289 lw k0, portEPC_STACK_LOCATION(sp)
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291 /* Remove stack frame. */
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292 addiu sp, sp, portCONTEXT_SIZE
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294 mtc0 k1, _CP0_STATUS
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