2 FreeRTOS V8.1.0 - Copyright (C) 2014 Real Time Engineers Ltd.
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5 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 ***************************************************************************
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9 * FreeRTOS provides completely free yet professionally developed, *
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10 * robust, strictly quality controlled, supported, and cross *
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11 * platform software that has become a de facto standard. *
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13 * Help yourself get started quickly and support the FreeRTOS *
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14 * project by purchasing a FreeRTOS tutorial book, reference *
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15 * manual, or both from: http://www.FreeRTOS.org/Documentation *
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19 ***************************************************************************
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21 This file is part of the FreeRTOS distribution.
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23 FreeRTOS is free software; you can redistribute it and/or modify it under
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24 the terms of the GNU General Public License (version 2) as published by the
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25 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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27 >>! NOTE: The modification to the GPL is included to allow you to !<<
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28 >>! distribute a combined work that includes FreeRTOS without being !<<
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29 >>! obliged to provide the source code for proprietary components !<<
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30 >>! outside of the FreeRTOS kernel. !<<
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32 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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33 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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34 FOR A PARTICULAR PURPOSE. Full license text is available from the following
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35 link: http://www.freertos.org/a00114.html
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39 ***************************************************************************
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41 * Having a problem? Start by reading the FAQ "My application does *
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42 * not run, what could be wrong?" *
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44 * http://www.FreeRTOS.org/FAQHelp.html *
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46 ***************************************************************************
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48 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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49 license and Real Time Engineers Ltd. contact details.
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51 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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52 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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53 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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55 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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56 Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS
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57 licenses offer ticketed support, indemnification and middleware.
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59 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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60 engineered and independently SIL3 certified version for use in safety and
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61 mission critical applications that require provable dependability.
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66 /*-----------------------------------------------------------
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67 * Implementation of functions defined in portable.h for the Cygnal port.
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68 *----------------------------------------------------------*/
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70 /* Standard includes. */
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73 /* Scheduler includes. */
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74 #include "FreeRTOS.h"
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77 /* Constants required to setup timer 2 to produce the RTOS tick. */
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78 #define portCLOCK_DIVISOR ( ( uint32_t ) 12 )
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79 #define portMAX_TIMER_VALUE ( ( uint32_t ) 0xffff )
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80 #define portENABLE_TIMER ( ( uint8_t ) 0x04 )
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81 #define portTIMER_2_INTERRUPT_ENABLE ( ( uint8_t ) 0x20 )
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83 /* The value used in the IE register when a task first starts. */
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84 #define portGLOBAL_INTERRUPT_BIT ( ( StackType_t ) 0x80 )
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86 /* The value used in the PSW register when a task first starts. */
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87 #define portINITIAL_PSW ( ( StackType_t ) 0x00 )
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89 /* Macro to clear the timer 2 interrupt flag. */
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90 #define portCLEAR_INTERRUPT_FLAG() TMR2CN &= ~0x80;
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92 /* Used during a context switch to store the size of the stack being copied
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94 data static uint8_t ucStackBytes;
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96 /* Used during a context switch to point to the next byte in XRAM from/to which
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97 a RAM byte is to be copied. */
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98 xdata static StackType_t * data pxXRAMStack;
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100 /* Used during a context switch to point to the next byte in RAM from/to which
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101 an XRAM byte is to be copied. */
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102 data static StackType_t * data pxRAMStack;
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104 /* We require the address of the pxCurrentTCB variable, but don't want to know
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105 any details of its type. */
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106 typedef void TCB_t;
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107 extern volatile TCB_t * volatile pxCurrentTCB;
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110 * Setup the hardware to generate an interrupt off timer 2 at the required
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113 static void prvSetupTimerInterrupt( void );
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115 /*-----------------------------------------------------------*/
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117 * Macro that copies the current stack from internal RAM to XRAM. This is
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118 * required as the 8051 only contains enough internal RAM for a single stack,
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119 * but we have a stack for every task.
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121 #define portCOPY_STACK_TO_XRAM() \
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123 /* pxCurrentTCB points to a TCB which itself points to the location into \
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124 which the first stack byte should be copied. Set pxXRAMStack to point \
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125 to the location into which the first stack byte is to be copied. */ \
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126 pxXRAMStack = ( xdata StackType_t * ) *( ( xdata StackType_t ** ) pxCurrentTCB ); \
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128 /* Set pxRAMStack to point to the first byte to be coped from the stack. */ \
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129 pxRAMStack = ( data StackType_t * data ) configSTACK_START; \
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131 /* Calculate the size of the stack we are about to copy from the current \
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132 stack pointer value. */ \
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133 ucStackBytes = SP - ( configSTACK_START - 1 ); \
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135 /* Before starting to copy the stack, store the calculated stack size so \
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136 the stack can be restored when the task is resumed. */ \
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137 *pxXRAMStack = ucStackBytes; \
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139 /* Copy each stack byte in turn. pxXRAMStack is incremented first as we \
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140 have already stored the stack size into XRAM. */ \
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141 while( ucStackBytes ) \
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144 *pxXRAMStack = *pxRAMStack; \
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149 /*-----------------------------------------------------------*/
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152 * Macro that copies the stack of the task being resumed from XRAM into
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155 #define portCOPY_XRAM_TO_STACK() \
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157 /* Setup the pointers as per portCOPY_STACK_TO_XRAM(), but this time to \
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158 copy the data back out of XRAM and into the stack. */ \
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159 pxXRAMStack = ( xdata StackType_t * ) *( ( xdata StackType_t ** ) pxCurrentTCB ); \
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160 pxRAMStack = ( data StackType_t * data ) ( configSTACK_START - 1 ); \
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162 /* The first value stored in XRAM was the size of the stack - i.e. the \
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163 number of bytes we need to copy back. */ \
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164 ucStackBytes = pxXRAMStack[ 0 ]; \
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166 /* Copy the required number of bytes back into the stack. */ \
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171 *pxRAMStack = *pxXRAMStack; \
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173 } while( ucStackBytes ); \
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175 /* Restore the stack pointer ready to use the restored stack. */ \
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176 SP = ( uint8_t ) pxRAMStack; \
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178 /*-----------------------------------------------------------*/
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181 * Macro to push the current execution context onto the stack, before the stack
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182 * is moved to XRAM.
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184 #define portSAVE_CONTEXT() \
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187 /* Push ACC first, as when restoring the context it must be restored \
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188 last (it is used to set the IE register). */ \
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190 /* Store the IE register then disable interrupts. */ \
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211 /*-----------------------------------------------------------*/
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214 * Macro that restores the execution context from the stack. The execution
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215 * context was saved into the stack before the stack was copied into XRAM.
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217 #define portRESTORE_CONTEXT() \
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233 /* The next byte of the stack is the IE register. Only the global \
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234 enable bit forms part of the task context. Pop off the IE then set \
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235 the global enable bit to match that of the stored IE register. */ \
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243 /* Finally pop off the ACC, which was the first register saved. */ \
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248 /*-----------------------------------------------------------*/
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251 * See header file for description.
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253 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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255 uint32_t ulAddress;
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256 StackType_t *pxStartOfStack;
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258 /* Leave space to write the size of the stack as the first byte. */
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259 pxStartOfStack = pxTopOfStack;
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262 /* Place a few bytes of known values on the bottom of the stack.
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263 This is just useful for debugging and can be uncommented if required.
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264 *pxTopOfStack = 0x11;
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266 *pxTopOfStack = 0x22;
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268 *pxTopOfStack = 0x33;
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272 /* Simulate how the stack would look after a call to the scheduler tick
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275 The return address that would have been pushed by the MCU. */
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276 ulAddress = ( uint32_t ) pxCode;
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277 *pxTopOfStack = ( StackType_t ) ulAddress;
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280 *pxTopOfStack = ( StackType_t ) ( ulAddress );
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283 /* Next all the registers will have been pushed by portSAVE_CONTEXT(). */
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284 *pxTopOfStack = 0xaa; /* acc */
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287 /* We want tasks to start with interrupts enabled. */
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288 *pxTopOfStack = portGLOBAL_INTERRUPT_BIT;
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291 /* The function parameters will be passed in the DPTR and B register as
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292 a three byte generic pointer is used. */
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293 ulAddress = ( uint32_t ) pvParameters;
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294 *pxTopOfStack = ( StackType_t ) ulAddress; /* DPL */
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297 *pxTopOfStack = ( StackType_t ) ulAddress; /* DPH */
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300 *pxTopOfStack = ( StackType_t ) ulAddress; /* b */
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303 /* The remaining registers are straight forward. */
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304 *pxTopOfStack = 0x02; /* R2 */
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306 *pxTopOfStack = 0x03; /* R3 */
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308 *pxTopOfStack = 0x04; /* R4 */
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310 *pxTopOfStack = 0x05; /* R5 */
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312 *pxTopOfStack = 0x06; /* R6 */
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314 *pxTopOfStack = 0x07; /* R7 */
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316 *pxTopOfStack = 0x00; /* R0 */
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318 *pxTopOfStack = 0x01; /* R1 */
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320 *pxTopOfStack = 0x00; /* PSW */
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322 *pxTopOfStack = 0xbb; /* BP */
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324 /* Dont increment the stack size here as we don't want to include
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325 the stack size byte as part of the stack size count.
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327 Finally we place the stack size at the beginning. */
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328 *pxStartOfStack = ( StackType_t ) ( pxTopOfStack - pxStartOfStack );
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330 /* Unlike most ports, we return the start of the stack as this is where the
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331 size of the stack is stored. */
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332 return pxStartOfStack;
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334 /*-----------------------------------------------------------*/
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337 * See header file for description.
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339 BaseType_t xPortStartScheduler( void )
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341 /* Setup timer 2 to generate the RTOS tick. */
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342 prvSetupTimerInterrupt();
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344 /* Make sure we start with the expected SFR page. This line should not
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345 really be required. */
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348 /* Copy the stack for the first task to execute from XRAM into the stack,
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349 restore the task context from the new stack, then start running the task. */
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350 portCOPY_XRAM_TO_STACK();
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351 portRESTORE_CONTEXT();
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353 /* Should never get here! */
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356 /*-----------------------------------------------------------*/
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358 void vPortEndScheduler( void )
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360 /* Not implemented for this port. */
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362 /*-----------------------------------------------------------*/
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365 * Manual context switch. The first thing we do is save the registers so we
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366 * can use a naked attribute.
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368 void vPortYield( void ) _naked
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370 /* Save the execution context onto the stack, then copy the entire stack
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371 to XRAM. This is necessary as the internal RAM is only large enough to
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372 hold one stack, and we want one per task.
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374 PERFORMANCE COULD BE IMPROVED BY ONLY COPYING TO XRAM IF A TASK SWITCH
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376 portSAVE_CONTEXT();
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377 portCOPY_STACK_TO_XRAM();
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379 /* Call the standard scheduler context switch function. */
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380 vTaskSwitchContext();
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382 /* Copy the stack of the task about to execute from XRAM into RAM and
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383 restore it's context ready to run on exiting. */
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384 portCOPY_XRAM_TO_STACK();
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385 portRESTORE_CONTEXT();
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387 /*-----------------------------------------------------------*/
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389 #if configUSE_PREEMPTION == 1
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390 void vTimer2ISR( void ) interrupt 5 _naked
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392 /* Preemptive context switch function triggered by the timer 2 ISR.
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393 This does the same as vPortYield() (see above) with the addition
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394 of incrementing the RTOS tick count. */
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396 portSAVE_CONTEXT();
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397 portCOPY_STACK_TO_XRAM();
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399 if( xTaskIncrementTick() != pdFALSE )
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401 vTaskSwitchContext();
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404 portCLEAR_INTERRUPT_FLAG();
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405 portCOPY_XRAM_TO_STACK();
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406 portRESTORE_CONTEXT();
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409 void vTimer2ISR( void ) interrupt 5
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411 /* When using the cooperative scheduler the timer 2 ISR is only
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412 required to increment the RTOS tick count. */
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414 xTaskIncrementTick();
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415 portCLEAR_INTERRUPT_FLAG();
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418 /*-----------------------------------------------------------*/
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420 static void prvSetupTimerInterrupt( void )
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422 uint8_t ucOriginalSFRPage;
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424 /* Constants calculated to give the required timer capture values. */
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425 const uint32_t ulTicksPerSecond = configCPU_CLOCK_HZ / portCLOCK_DIVISOR;
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426 const uint32_t ulCaptureTime = ulTicksPerSecond / configTICK_RATE_HZ;
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427 const uint32_t ulCaptureValue = portMAX_TIMER_VALUE - ulCaptureTime;
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428 const uint8_t ucLowCaptureByte = ( uint8_t ) ( ulCaptureValue & ( uint32_t ) 0xff );
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429 const uint8_t ucHighCaptureByte = ( uint8_t ) ( ulCaptureValue >> ( uint32_t ) 8 );
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431 /* NOTE: This uses a timer only present on 8052 architecture. */
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433 /* Remember the current SFR page so we can restore it at the end of the
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435 ucOriginalSFRPage = SFRPAGE;
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438 /* TMR2CF can be left in its default state. */
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439 TMR2CF = ( uint8_t ) 0;
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441 /* Setup the overflow reload value. */
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442 RCAP2L = ucLowCaptureByte;
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443 RCAP2H = ucHighCaptureByte;
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445 /* The initial load is performed manually. */
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446 TMR2L = ucLowCaptureByte;
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447 TMR2H = ucHighCaptureByte;
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449 /* Enable the timer 2 interrupts. */
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450 IE |= portTIMER_2_INTERRUPT_ENABLE;
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452 /* Interrupts are disabled when this is called so the timer can be started
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454 TMR2CN = portENABLE_TIMER;
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456 /* Restore the original SFR page. */
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457 SFRPAGE = ucOriginalSFRPage;
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