2 FreeRTOS.org V4.6.1 - 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 a version that has been certified for use
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32 in safety critical systems, plus commercial licensing, development and
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34 ***************************************************************************
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37 /*-----------------------------------------------------------
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38 * Implementation of functions defined in portable.h for the Cygnal port.
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39 *----------------------------------------------------------*/
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41 /* Standard includes. */
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44 /* Scheduler includes. */
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45 #include "FreeRTOS.h"
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48 /* Constants required to setup timer 2 to produce the RTOS tick. */
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49 #define portCLOCK_DIVISOR ( ( unsigned portLONG ) 12 )
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50 #define portMAX_TIMER_VALUE ( ( unsigned portLONG ) 0xffff )
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51 #define portENABLE_TIMER ( ( unsigned portCHAR ) 0x04 )
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52 #define portTIMER_2_INTERRUPT_ENABLE ( ( unsigned portCHAR ) 0x20 )
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54 /* The value used in the IE register when a task first starts. */
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55 #define portGLOBAL_INTERRUPT_BIT ( ( portSTACK_TYPE ) 0x80 )
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57 /* The value used in the PSW register when a task first starts. */
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58 #define portINITIAL_PSW ( ( portSTACK_TYPE ) 0x00 )
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60 /* Macro to clear the timer 2 interrupt flag. */
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61 #define portCLEAR_INTERRUPT_FLAG() TMR2CN &= ~0x80;
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63 /* Used during a context switch to store the size of the stack being copied
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65 data static unsigned portCHAR ucStackBytes;
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67 /* Used during a context switch to point to the next byte in XRAM from/to which
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68 a RAM byte is to be copied. */
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69 xdata static portSTACK_TYPE * data pxXRAMStack;
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71 /* Used during a context switch to point to the next byte in RAM from/to which
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72 an XRAM byte is to be copied. */
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73 data static portSTACK_TYPE * data pxRAMStack;
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75 /* We require the address of the pxCurrentTCB variable, but don't want to know
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76 any details of its type. */
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77 typedef void tskTCB;
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78 extern volatile tskTCB * volatile pxCurrentTCB;
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81 * Setup the hardware to generate an interrupt off timer 2 at the required
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84 static void prvSetupTimerInterrupt( void );
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86 /*-----------------------------------------------------------*/
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88 * Macro that copies the current stack from internal RAM to XRAM. This is
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89 * required as the 8051 only contains enough internal RAM for a single stack,
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90 * but we have a stack for every task.
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92 #define portCOPY_STACK_TO_XRAM() \
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94 /* pxCurrentTCB points to a TCB which itself points to the location into \
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95 which the first stack byte should be copied. Set pxXRAMStack to point \
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96 to the location into which the first stack byte is to be copied. */ \
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97 pxXRAMStack = ( xdata portSTACK_TYPE * ) *( ( xdata portSTACK_TYPE ** ) pxCurrentTCB ); \
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99 /* Set pxRAMStack to point to the first byte to be coped from the stack. */ \
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100 pxRAMStack = ( data portSTACK_TYPE * data ) configSTACK_START; \
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102 /* Calculate the size of the stack we are about to copy from the current \
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103 stack pointer value. */ \
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104 ucStackBytes = SP - ( configSTACK_START - 1 ); \
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106 /* Before starting to copy the stack, store the calculated stack size so \
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107 the stack can be restored when the task is resumed. */ \
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108 *pxXRAMStack = ucStackBytes; \
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110 /* Copy each stack byte in turn. pxXRAMStack is incremented first as we \
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111 have already stored the stack size into XRAM. */ \
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112 while( ucStackBytes ) \
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115 *pxXRAMStack = *pxRAMStack; \
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120 /*-----------------------------------------------------------*/
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123 * Macro that copies the stack of the task being resumed from XRAM into
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126 #define portCOPY_XRAM_TO_STACK() \
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128 /* Setup the pointers as per portCOPY_STACK_TO_XRAM(), but this time to \
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129 copy the data back out of XRAM and into the stack. */ \
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130 pxXRAMStack = ( xdata portSTACK_TYPE * ) *( ( xdata portSTACK_TYPE ** ) pxCurrentTCB ); \
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131 pxRAMStack = ( data portSTACK_TYPE * data ) ( configSTACK_START - 1 ); \
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133 /* The first value stored in XRAM was the size of the stack - i.e. the \
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134 number of bytes we need to copy back. */ \
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135 ucStackBytes = pxXRAMStack[ 0 ]; \
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137 /* Copy the required number of bytes back into the stack. */ \
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142 *pxRAMStack = *pxXRAMStack; \
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144 } while( ucStackBytes ); \
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146 /* Restore the stack pointer ready to use the restored stack. */ \
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147 SP = ( unsigned portCHAR ) pxRAMStack; \
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149 /*-----------------------------------------------------------*/
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152 * Macro to push the current execution context onto the stack, before the stack
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153 * is moved to XRAM.
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155 #define portSAVE_CONTEXT() \
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158 /* Push ACC first, as when restoring the context it must be restored \
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159 last (it is used to set the IE register). */ \
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161 /* Store the IE register then disable interrupts. */ \
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182 /*-----------------------------------------------------------*/
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185 * Macro that restores the execution context from the stack. The execution
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186 * context was saved into the stack before the stack was copied into XRAM.
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188 #define portRESTORE_CONTEXT() \
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204 /* The next byte of the stack is the IE register. Only the global \
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205 enable bit forms part of the task context. Pop off the IE then set \
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206 the global enable bit to match that of the stored IE register. */ \
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214 /* Finally pop off the ACC, which was the first register saved. */ \
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219 /*-----------------------------------------------------------*/
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222 * See header file for description.
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224 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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226 unsigned portLONG ulAddress;
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227 portSTACK_TYPE *pxStartOfStack;
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229 /* Leave space to write the size of the stack as the first byte. */
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230 pxStartOfStack = pxTopOfStack;
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233 /* Place a few bytes of known values on the bottom of the stack.
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234 This is just useful for debugging and can be uncommented if required.
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235 *pxTopOfStack = 0x11;
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237 *pxTopOfStack = 0x22;
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239 *pxTopOfStack = 0x33;
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243 /* Simulate how the stack would look after a call to the scheduler tick
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246 The return address that would have been pushed by the MCU. */
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247 ulAddress = ( unsigned portLONG ) pxCode;
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248 *pxTopOfStack = ( portSTACK_TYPE ) ulAddress;
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251 *pxTopOfStack = ( portSTACK_TYPE ) ( ulAddress );
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254 /* Next all the registers will have been pushed by portSAVE_CONTEXT(). */
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255 *pxTopOfStack = 0xaa; /* acc */
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258 /* We want tasks to start with interrupts enabled. */
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259 *pxTopOfStack = portGLOBAL_INTERRUPT_BIT;
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262 /* The function parameters will be passed in the DPTR and B register as
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263 a three byte generic pointer is used. */
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264 ulAddress = ( unsigned portLONG ) pvParameters;
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265 *pxTopOfStack = ( portSTACK_TYPE ) ulAddress; /* DPL */
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268 *pxTopOfStack = ( portSTACK_TYPE ) ulAddress; /* DPH */
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271 *pxTopOfStack = ( portSTACK_TYPE ) ulAddress; /* b */
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274 /* The remaining registers are straight forward. */
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275 *pxTopOfStack = 0x02; /* R2 */
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277 *pxTopOfStack = 0x03; /* R3 */
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279 *pxTopOfStack = 0x04; /* R4 */
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281 *pxTopOfStack = 0x05; /* R5 */
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283 *pxTopOfStack = 0x06; /* R6 */
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285 *pxTopOfStack = 0x07; /* R7 */
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287 *pxTopOfStack = 0x00; /* R0 */
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289 *pxTopOfStack = 0x01; /* R1 */
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291 *pxTopOfStack = 0x00; /* PSW */
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293 *pxTopOfStack = 0xbb; /* BP */
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295 /* Dont increment the stack size here as we don't want to include
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296 the stack size byte as part of the stack size count.
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298 Finally we place the stack size at the beginning. */
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299 *pxStartOfStack = ( portSTACK_TYPE ) ( pxTopOfStack - pxStartOfStack );
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301 /* Unlike most ports, we return the start of the stack as this is where the
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302 size of the stack is stored. */
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303 return pxStartOfStack;
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305 /*-----------------------------------------------------------*/
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308 * See header file for description.
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310 portBASE_TYPE xPortStartScheduler( void )
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312 /* Setup timer 2 to generate the RTOS tick. */
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313 prvSetupTimerInterrupt();
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315 /* Make sure we start with the expected SFR page. This line should not
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316 really be required. */
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319 /* Copy the stack for the first task to execute from XRAM into the stack,
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320 restore the task context from the new stack, then start running the task. */
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321 portCOPY_XRAM_TO_STACK();
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322 portRESTORE_CONTEXT();
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324 /* Should never get here! */
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327 /*-----------------------------------------------------------*/
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329 void vPortEndScheduler( void )
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331 /* Not implemented for this port. */
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333 /*-----------------------------------------------------------*/
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336 * Manual context switch. The first thing we do is save the registers so we
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337 * can use a naked attribute.
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339 void vPortYield( void ) _naked
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341 /* Save the execution context onto the stack, then copy the entire stack
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342 to XRAM. This is necessary as the internal RAM is only large enough to
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343 hold one stack, and we want one per task.
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345 PERFORMANCE COULD BE IMPROVED BY ONLY COPYING TO XRAM IF A TASK SWITCH
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347 portSAVE_CONTEXT();
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348 portCOPY_STACK_TO_XRAM();
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350 /* Call the standard scheduler context switch function. */
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351 vTaskSwitchContext();
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353 /* Copy the stack of the task about to execute from XRAM into RAM and
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354 restore it's context ready to run on exiting. */
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355 portCOPY_XRAM_TO_STACK();
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356 portRESTORE_CONTEXT();
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358 /*-----------------------------------------------------------*/
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360 #if configUSE_PREEMPTION == 1
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361 void vTimer2ISR( void ) interrupt 5 _naked
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363 /* Preemptive context switch function triggered by the timer 2 ISR.
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364 This does the same as vPortYield() (see above) with the addition
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365 of incrementing the RTOS tick count. */
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367 portSAVE_CONTEXT();
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368 portCOPY_STACK_TO_XRAM();
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370 vTaskIncrementTick();
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371 vTaskSwitchContext();
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373 portCLEAR_INTERRUPT_FLAG();
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374 portCOPY_XRAM_TO_STACK();
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375 portRESTORE_CONTEXT();
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378 void vTimer2ISR( void ) interrupt 5
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380 /* When using the cooperative scheduler the timer 2 ISR is only
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381 required to increment the RTOS tick count. */
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383 vTaskIncrementTick();
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384 portCLEAR_INTERRUPT_FLAG();
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387 /*-----------------------------------------------------------*/
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389 static void prvSetupTimerInterrupt( void )
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391 unsigned portCHAR ucOriginalSFRPage;
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393 /* Constants calculated to give the required timer capture values. */
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394 const unsigned portLONG ulTicksPerSecond = configCPU_CLOCK_HZ / portCLOCK_DIVISOR;
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395 const unsigned portLONG ulCaptureTime = ulTicksPerSecond / configTICK_RATE_HZ;
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396 const unsigned portLONG ulCaptureValue = portMAX_TIMER_VALUE - ulCaptureTime;
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397 const unsigned portCHAR ucLowCaptureByte = ( unsigned portCHAR ) ( ulCaptureValue & ( unsigned portLONG ) 0xff );
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398 const unsigned portCHAR ucHighCaptureByte = ( unsigned portCHAR ) ( ulCaptureValue >> ( unsigned portLONG ) 8 );
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400 /* NOTE: This uses a timer only present on 8052 architecture. */
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402 /* Remember the current SFR page so we can restore it at the end of the
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404 ucOriginalSFRPage = SFRPAGE;
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407 /* TMR2CF can be left in its default state. */
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408 TMR2CF = ( unsigned portCHAR ) 0;
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410 /* Setup the overflow reload value. */
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411 RCAP2L = ucLowCaptureByte;
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412 RCAP2H = ucHighCaptureByte;
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414 /* The initial load is performed manually. */
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415 TMR2L = ucLowCaptureByte;
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416 TMR2H = ucHighCaptureByte;
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418 /* Enable the timer 2 interrupts. */
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419 IE |= portTIMER_2_INTERRUPT_ENABLE;
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421 /* Interrupts are disabled when this is called so the timer can be started
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423 TMR2CN = portENABLE_TIMER;
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425 /* Restore the original SFR page. */
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426 SFRPAGE = ucOriginalSFRPage;
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