2 FreeRTOS.org V5.1.0 - Copyright (C) 2003-2008 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 ***************************************************************************
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29 * SAVE TIME AND MONEY! We can port FreeRTOS.org to your own hardware, *
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30 * and even write all or part of your application on your behalf. *
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31 * See http://www.OpenRTOS.com for details of the services we provide to *
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32 * expedite your project. *
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34 ***************************************************************************
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35 ***************************************************************************
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37 Please ensure to read the configuration and relevant port sections of the
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38 online documentation.
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40 http://www.FreeRTOS.org - Documentation, latest information, license and
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43 http://www.SafeRTOS.com - A version that is certified for use in safety
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46 http://www.OpenRTOS.com - Commercial support, development, porting,
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47 licensing and training services.
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52 #include "FreeRTOS.h"
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55 /*-----------------------------------------------------------
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56 * Implementation of functions defined in portable.h for the AVR/IAR port.
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57 *----------------------------------------------------------*/
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59 /* Start tasks with interrupts enables. */
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60 #define portFLAGS_INT_ENABLED ( ( portSTACK_TYPE ) 0x80 )
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62 /* Hardware constants for timer 1. */
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63 #define portCLEAR_COUNTER_ON_MATCH ( ( unsigned portCHAR ) 0x08 )
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64 #define portPRESCALE_64 ( ( unsigned portCHAR ) 0x03 )
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65 #define portCLOCK_PRESCALER ( ( unsigned portLONG ) 64 )
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66 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( unsigned portCHAR ) 0x10 )
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68 /* The number of bytes used on the hardware stack by the task start address. */
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69 #define portBYTES_USED_BY_RETURN_ADDRESS ( 2 )
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70 /*-----------------------------------------------------------*/
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72 /* Stores the critical section nesting. This must not be initialised to 0.
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73 It will be initialised when a task starts. */
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74 #define portNO_CRITICAL_NESTING ( ( unsigned portBASE_TYPE ) 0 )
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75 unsigned portBASE_TYPE uxCriticalNesting = 0x50;
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79 * Perform hardware setup to enable ticks from timer 1, compare match A.
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81 static void prvSetupTimerInterrupt( void );
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84 * The IAR compiler does not have full support for inline assembler, so
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85 * these are defined in the portmacro assembler file.
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87 extern void vPortYieldFromTick( void );
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88 extern void vPortStart( void );
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90 /*-----------------------------------------------------------*/
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93 * See header file for description.
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95 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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97 unsigned portSHORT usAddress;
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98 portSTACK_TYPE *pxTopOfHardwareStack;
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100 /* Place a few bytes of known values on the bottom of the stack.
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101 This is just useful for debugging. */
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103 *pxTopOfStack = 0x11;
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105 *pxTopOfStack = 0x22;
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107 *pxTopOfStack = 0x33;
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110 /* Remember where the top of the hardware stack is - this is required
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112 pxTopOfHardwareStack = pxTopOfStack;
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115 /* Simulate how the stack would look after a call to vPortYield(). */
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117 /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
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121 /* The IAR compiler requires two stacks per task. First there is the
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122 hardware call stack which uses the AVR stack pointer. Second there is the
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123 software stack (local variables, parameter passing, etc.) which uses the
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126 This function places both stacks within the memory block passed in as the
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127 first parameter. The hardware stack is placed at the bottom of the memory
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128 block. A gap is then left for the hardware stack to grow. Next the software
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129 stack is placed. The amount of space between the software and hardware
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130 stacks is defined by configCALL_STACK_SIZE.
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134 The first part of the stack is the hardware stack. Place the start
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135 address of the task on the hardware stack. */
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136 usAddress = ( unsigned portSHORT ) pxCode;
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137 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );
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141 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );
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145 /* Leave enough space for the hardware stack before starting the software
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146 stack. The '- 2' is because we have already used two spaces for the
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147 address of the start of the task. */
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148 pxTopOfStack -= ( configCALL_STACK_SIZE - 2 );
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152 /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
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153 portSAVE_CONTEXT places the flags on the stack immediately after r0
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154 to ensure the interrupts get disabled as soon as possible, and so ensuring
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155 the stack use is minimal should a context switch interrupt occur. */
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156 *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* R0 */
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158 *pxTopOfStack = portFLAGS_INT_ENABLED;
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161 /* Next place the address of the hardware stack. This is required so
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162 the AVR stack pointer can be restored to point to the hardware stack. */
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163 pxTopOfHardwareStack -= portBYTES_USED_BY_RETURN_ADDRESS;
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164 usAddress = ( unsigned portSHORT ) pxTopOfHardwareStack;
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167 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );
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172 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );
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178 /* Now the remaining registers. */
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179 *pxTopOfStack = ( portSTACK_TYPE ) 0x01; /* R1 */
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181 *pxTopOfStack = ( portSTACK_TYPE ) 0x02; /* R2 */
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183 *pxTopOfStack = ( portSTACK_TYPE ) 0x03; /* R3 */
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185 *pxTopOfStack = ( portSTACK_TYPE ) 0x04; /* R4 */
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187 *pxTopOfStack = ( portSTACK_TYPE ) 0x05; /* R5 */
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189 *pxTopOfStack = ( portSTACK_TYPE ) 0x06; /* R6 */
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191 *pxTopOfStack = ( portSTACK_TYPE ) 0x07; /* R7 */
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193 *pxTopOfStack = ( portSTACK_TYPE ) 0x08; /* R8 */
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195 *pxTopOfStack = ( portSTACK_TYPE ) 0x09; /* R9 */
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197 *pxTopOfStack = ( portSTACK_TYPE ) 0x10; /* R10 */
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199 *pxTopOfStack = ( portSTACK_TYPE ) 0x11; /* R11 */
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201 *pxTopOfStack = ( portSTACK_TYPE ) 0x12; /* R12 */
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203 *pxTopOfStack = ( portSTACK_TYPE ) 0x13; /* R13 */
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205 *pxTopOfStack = ( portSTACK_TYPE ) 0x14; /* R14 */
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207 *pxTopOfStack = ( portSTACK_TYPE ) 0x15; /* R15 */
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210 /* Place the parameter on the stack in the expected location. */
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211 usAddress = ( unsigned portSHORT ) pvParameters;
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212 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );
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216 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );
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219 *pxTopOfStack = ( portSTACK_TYPE ) 0x18; /* R18 */
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221 *pxTopOfStack = ( portSTACK_TYPE ) 0x19; /* R19 */
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223 *pxTopOfStack = ( portSTACK_TYPE ) 0x20; /* R20 */
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225 *pxTopOfStack = ( portSTACK_TYPE ) 0x21; /* R21 */
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227 *pxTopOfStack = ( portSTACK_TYPE ) 0x22; /* R22 */
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229 *pxTopOfStack = ( portSTACK_TYPE ) 0x23; /* R23 */
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231 *pxTopOfStack = ( portSTACK_TYPE ) 0x24; /* R24 */
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233 *pxTopOfStack = ( portSTACK_TYPE ) 0x25; /* R25 */
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235 *pxTopOfStack = ( portSTACK_TYPE ) 0x26; /* R26 X */
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237 *pxTopOfStack = ( portSTACK_TYPE ) 0x27; /* R27 */
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240 /* The Y register is not stored as it is used as the software stack and
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241 gets saved into the task control block. */
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243 *pxTopOfStack = ( portSTACK_TYPE ) 0x30; /* R30 Z */
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245 *pxTopOfStack = ( portSTACK_TYPE ) 0x031; /* R31 */
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248 *pxTopOfStack = portNO_CRITICAL_NESTING; /* Critical nesting is zero when the task starts. */
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250 /*lint +e950 +e611 +e923 */
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252 return pxTopOfStack;
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254 /*-----------------------------------------------------------*/
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256 portBASE_TYPE xPortStartScheduler( void )
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258 /* Setup the hardware to generate the tick. */
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259 prvSetupTimerInterrupt();
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261 /* Restore the context of the first task that is going to run.
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262 Normally we would just call portRESTORE_CONTEXT() here, but as the IAR
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263 compiler does not fully support inline assembler we have to make a call.*/
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267 /* Should not get here! */
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270 /*-----------------------------------------------------------*/
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272 void vPortEndScheduler( void )
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274 /* It is unlikely that the AVR port will get stopped. If required simply
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275 disable the tick interrupt here. */
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277 /*-----------------------------------------------------------*/
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280 * Setup timer 1 compare match A to generate a tick interrupt.
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282 static void prvSetupTimerInterrupt( void )
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284 unsigned portLONG ulCompareMatch;
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285 unsigned portCHAR ucHighByte, ucLowByte;
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287 /* Using 16bit timer 1 to generate the tick. Correct fuses must be
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288 selected for the configCPU_CLOCK_HZ clock. */
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290 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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292 /* We only have 16 bits so have to scale to get our required tick rate. */
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293 ulCompareMatch /= portCLOCK_PRESCALER;
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295 /* Adjust for correct value. */
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296 ulCompareMatch -= ( unsigned portLONG ) 1;
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298 /* Setup compare match value for compare match A. Interrupts are disabled
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299 before this is called so we need not worry here. */
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300 ucLowByte = ( unsigned portCHAR ) ( ulCompareMatch & ( unsigned portLONG ) 0xff );
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301 ulCompareMatch >>= 8;
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302 ucHighByte = ( unsigned portCHAR ) ( ulCompareMatch & ( unsigned portLONG ) 0xff );
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303 OCR1AH = ucHighByte;
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304 OCR1AL = ucLowByte;
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306 /* Setup clock source and compare match behaviour. */
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307 ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
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308 TCCR1B = ucLowByte;
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310 /* Enable the interrupt - this is okay as interrupt are currently globally
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312 TIMSK |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
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314 /*-----------------------------------------------------------*/
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316 #if configUSE_PREEMPTION == 1
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319 * Tick ISR for preemptive scheduler. We can use a __task attribute as
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320 * the context is saved at the start of vPortYieldFromTick(). The tick
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321 * count is incremented after the context is saved.
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323 __task void SIG_OUTPUT_COMPARE1A( void )
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325 vPortYieldFromTick();
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332 * Tick ISR for the cooperative scheduler. All this does is increment the
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333 * tick count. We don't need to switch context, this can only be done by
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334 * manual calls to taskYIELD();
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336 * THE INTERRUPT VECTOR IS POPULATED IN portmacro.s90. DO NOT INSTALL
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337 * IT HERE USING THE USUAL PRAGMA.
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339 __interrupt void SIG_OUTPUT_COMPARE1A( void )
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341 vTaskIncrementTick();
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344 /*-----------------------------------------------------------*/
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346 void vPortEnterCritical( void )
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348 portDISABLE_INTERRUPTS();
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349 uxCriticalNesting++;
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351 /*-----------------------------------------------------------*/
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353 void vPortExitCritical( void )
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355 uxCriticalNesting--;
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356 if( uxCriticalNesting == portNO_CRITICAL_NESTING )
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358 portENABLE_INTERRUPTS();
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