2 FreeRTOS.org V4.2.1 - Copyright (C) 2003-2007 Richard Barry.
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4 This file is part of the FreeRTOS.org distribution.
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6 FreeRTOS.org is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 2 of the License, or
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9 (at your option) any later version.
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11 FreeRTOS.org is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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16 You should have received a copy of the GNU General Public License
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17 along with FreeRTOS.org; if not, write to the Free Software
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18 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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20 A special exception to the GPL can be applied should you wish to distribute
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21 a combined work that includes FreeRTOS.org, without being obliged to provide
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22 the source code for any proprietary components. See the licensing section
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23 of http://www.FreeRTOS.org for full details of how and when the exception
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26 ***************************************************************************
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27 See http://www.FreeRTOS.org for documentation, latest information, license
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28 and contact details. Please ensure to read the configuration and relevant
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29 port sections of the online documentation.
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31 Also see http://www.SafeRTOS.com for an IEC 61508 compliant version along
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32 with commercial development and support options.
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33 ***************************************************************************
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37 /*-----------------------------------------------------------
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38 * Implementation of functions defined in portable.h for the Atmel AT91R40008
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41 * Components that can be compiled to either ARM or THUMB mode are
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42 * contained in this file. The ISR routines, which can only be compiled
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43 * to ARM mode are contained in portISR.c.
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44 *----------------------------------------------------------*/
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46 /* Standard includes. */
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49 /* Scheduler includes. */
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50 #include "FreeRTOS.h"
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53 /* Hardware specific definitions. */
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54 #include "AT91R40008.h"
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59 /* Constants required to setup the task context. */
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60 #define portINITIAL_SPSR ( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
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61 #define portTHUMB_MODE_BIT ( ( portSTACK_TYPE ) 0x20 )
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62 #define portINSTRUCTION_SIZE ( ( portSTACK_TYPE ) 4 )
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63 #define portNO_CRITICAL_SECTION_NESTING ( ( portSTACK_TYPE ) 0 )
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64 #define portTICK_PRIORITY_6 ( 6 )
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65 /*-----------------------------------------------------------*/
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67 /* Setup the timer to generate the tick interrupts. */
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68 static void prvSetupTimerInterrupt( void );
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71 * The scheduler can only be started from ARM mode, so
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72 * vPortISRStartFirstSTask() is defined in portISR.c.
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74 extern void vPortISRStartFirstTask( void );
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76 /*-----------------------------------------------------------*/
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79 * Initialise the stack of a task to look exactly as if a call to
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80 * portSAVE_CONTEXT had been called.
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82 * See header file for description.
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84 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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86 portSTACK_TYPE *pxOriginalTOS;
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88 pxOriginalTOS = pxTopOfStack;
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90 /* Setup the initial stack of the task. The stack is set exactly as
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91 expected by the portRESTORE_CONTEXT() macro. */
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93 /* First on the stack is the return address - which in this case is the
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94 start of the task. The offset is added to make the return address appear
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95 as it would within an IRQ ISR. */
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96 *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;
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99 *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa; /* R14 */
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101 *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
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103 *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212; /* R12 */
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105 *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111; /* R11 */
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107 *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010; /* R10 */
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109 *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909; /* R9 */
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111 *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808; /* R8 */
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113 *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707; /* R7 */
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115 *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606; /* R6 */
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117 *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505; /* R5 */
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119 *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404; /* R4 */
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121 *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303; /* R3 */
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123 *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202; /* R2 */
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125 *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101; /* R1 */
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128 /* When the task starts is will expect to find the function parameter in
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130 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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133 /* The last thing onto the stack is the status register, which is set for
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134 system mode, with interrupts enabled. */
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135 *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;
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137 #ifdef THUMB_INTERWORK
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139 /* We want the task to start in thumb mode. */
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140 *pxTopOfStack |= portTHUMB_MODE_BIT;
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146 /* Some optimisation levels use the stack differently to others. This
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147 means the interrupt flags cannot always be stored on the stack and will
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148 instead be stored in a variable, which is then saved as part of the
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150 *pxTopOfStack = portNO_CRITICAL_SECTION_NESTING;
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152 return pxTopOfStack;
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154 /*-----------------------------------------------------------*/
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156 portBASE_TYPE xPortStartScheduler( void )
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158 /* Start the timer that generates the tick ISR. Interrupts are disabled
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160 prvSetupTimerInterrupt();
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162 /* Start the first task. */
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163 vPortISRStartFirstTask();
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165 /* Should not get here! */
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168 /*-----------------------------------------------------------*/
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170 void vPortEndScheduler( void )
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172 /* It is unlikely that the ARM port will require this function as there
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173 is nothing to return to. */
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175 /*-----------------------------------------------------------*/
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178 * Setup the tick timer to generate the tick interrupts at the required frequency.
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180 static void prvSetupTimerInterrupt( void )
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182 volatile unsigned portLONG ulDummy;
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184 /* Enable clock to the tick timer... */
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185 AT91C_BASE_PS->PS_PCER = portTIMER_CLK_ENABLE_BIT;
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187 /* Stop the tick timer... */
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188 portTIMER_REG_BASE_PTR->TC_CCR = TC_CLKDIS;
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190 /* Start with tick timer interrupts disabled... */
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191 portTIMER_REG_BASE_PTR->TC_IDR = 0xFFFFFFFF;
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193 /* Clear any pending tick timer interrupts... */
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194 ulDummy = portTIMER_REG_BASE_PTR->TC_SR;
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196 /* Store interrupt handler function address in tick timer vector register...
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197 The ISR installed depends on whether the preemptive or cooperative
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198 scheduler is being used. */
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199 #if configUSE_PREEMPTION == 1
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201 extern void ( vPreemptiveTick )( void );
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202 AT91C_BASE_AIC->AIC_SVR[portTIMER_AIC_CHANNEL] = ( unsigned portLONG ) vPreemptiveTick;
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204 #else // else use cooperative scheduler
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206 extern void ( vNonPreemptiveTick )( void );
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207 AT91C_BASE_AIC->AIC_SVR[portTIMER_AIC_CHANNEL] = ( unsigned portLONG ) vNonPreemptiveTick;
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211 /* Tick timer interrupt level-sensitive, priority 6... */
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212 AT91C_BASE_AIC->AIC_SMR[ portTIMER_AIC_CHANNEL ] = AIC_SRCTYPE_INT_LEVEL_SENSITIVE | portTICK_PRIORITY_6;
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214 /* Enable the tick timer interrupt...
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216 First at timer level */
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217 portTIMER_REG_BASE_PTR->TC_IER = TC_CPCS;
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219 /* Then at the AIC level. */
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220 AT91C_BASE_AIC->AIC_IECR = (1 << portTIMER_AIC_CHANNEL);
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222 /* Calculate timer compare value to achieve the desired tick rate... */
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223 if( (configCPU_CLOCK_HZ / (configTICK_RATE_HZ * 2) ) <= 0xFFFF )
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225 /* The tick rate is fast enough for us to use the faster timer input
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226 clock (main clock / 2). */
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227 portTIMER_REG_BASE_PTR->TC_CMR = TC_WAVE | TC_CLKS_MCK2 | TC_BURST_NONE | TC_CPCTRG;
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228 portTIMER_REG_BASE_PTR->TC_RC = configCPU_CLOCK_HZ / (configTICK_RATE_HZ * 2);
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232 /* We must use a slower timer input clock (main clock / 8) because the
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233 tick rate is too slow for the faster input clock. */
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234 portTIMER_REG_BASE_PTR->TC_CMR = TC_WAVE | TC_CLKS_MCK8 | TC_BURST_NONE | TC_CPCTRG;
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235 portTIMER_REG_BASE_PTR->TC_RC = configCPU_CLOCK_HZ / (configTICK_RATE_HZ * 8);
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238 /* Start tick timer... */
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239 portTIMER_REG_BASE_PTR->TC_CCR = TC_SWTRG | TC_CLKEN;
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241 /*-----------------------------------------------------------*/
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