2 FreeRTOS.org V4.1.3 - Copyright (C) 2003-2006 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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30 ***************************************************************************
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33 /*-----------------------------------------------------------
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34 * Implementation of functions defined in portable.h for the Cygnal port.
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35 *----------------------------------------------------------*/
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37 /* Standard includes. */
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40 /* Scheduler includes. */
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41 #include "FreeRTOS.h"
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44 /* Constants required to setup timer 2 to produce the RTOS tick. */
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45 #define portCLOCK_DIVISOR ( ( unsigned portLONG ) 12 )
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46 #define portMAX_TIMER_VALUE ( ( unsigned portLONG ) 0xffff )
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47 #define portENABLE_TIMER ( ( unsigned portCHAR ) 0x04 )
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48 #define portTIMER_2_INTERRUPT_ENABLE ( ( unsigned portCHAR ) 0x20 )
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50 /* The value used in the IE register when a task first starts. */
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51 #define portGLOBAL_INTERRUPT_BIT ( ( portSTACK_TYPE ) 0x80 )
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53 /* The value used in the PSW register when a task first starts. */
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54 #define portINITIAL_PSW ( ( portSTACK_TYPE ) 0x00 )
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56 /* Macro to clear the timer 2 interrupt flag. */
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57 #define portCLEAR_INTERRUPT_FLAG() TMR2CN &= ~0x80;
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59 /* Used during a context switch to store the size of the stack being copied
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61 data static unsigned portCHAR ucStackBytes;
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63 /* Used during a context switch to point to the next byte in XRAM from/to which
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64 a RAM byte is to be copied. */
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65 xdata static portSTACK_TYPE * data pxXRAMStack;
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67 /* Used during a context switch to point to the next byte in RAM from/to which
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68 an XRAM byte is to be copied. */
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69 data static portSTACK_TYPE * data pxRAMStack;
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71 /* We require the address of the pxCurrentTCB variable, but don't want to know
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72 any details of its type. */
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73 typedef void tskTCB;
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74 extern volatile tskTCB * volatile pxCurrentTCB;
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77 * Setup the hardware to generate an interrupt off timer 2 at the required
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80 static void prvSetupTimerInterrupt( void );
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82 /*-----------------------------------------------------------*/
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84 * Macro that copies the current stack from internal RAM to XRAM. This is
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85 * required as the 8051 only contains enough internal RAM for a single stack,
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86 * but we have a stack for every task.
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88 #define portCOPY_STACK_TO_XRAM() \
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90 /* pxCurrentTCB points to a TCB which itself points to the location into \
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91 which the first stack byte should be copied. Set pxXRAMStack to point \
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92 to the location into which the first stack byte is to be copied. */ \
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93 pxXRAMStack = ( xdata portSTACK_TYPE * ) *( ( xdata portSTACK_TYPE ** ) pxCurrentTCB ); \
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95 /* Set pxRAMStack to point to the first byte to be coped from the stack. */ \
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96 pxRAMStack = ( data portSTACK_TYPE * data ) configSTACK_START; \
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98 /* Calculate the size of the stack we are about to copy from the current \
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99 stack pointer value. */ \
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100 ucStackBytes = SP - ( configSTACK_START - 1 ); \
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102 /* Before starting to copy the stack, store the calculated stack size so \
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103 the stack can be restored when the task is resumed. */ \
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104 *pxXRAMStack = ucStackBytes; \
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106 /* Copy each stack byte in turn. pxXRAMStack is incremented first as we \
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107 have already stored the stack size into XRAM. */ \
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108 while( ucStackBytes ) \
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111 *pxXRAMStack = *pxRAMStack; \
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116 /*-----------------------------------------------------------*/
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119 * Macro that copies the stack of the task being resumed from XRAM into
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122 #define portCOPY_XRAM_TO_STACK() \
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124 /* Setup the pointers as per portCOPY_STACK_TO_XRAM(), but this time to \
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125 copy the data back out of XRAM and into the stack. */ \
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126 pxXRAMStack = ( xdata portSTACK_TYPE * ) *( ( xdata portSTACK_TYPE ** ) pxCurrentTCB ); \
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127 pxRAMStack = ( data portSTACK_TYPE * data ) ( configSTACK_START - 1 ); \
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129 /* The first value stored in XRAM was the size of the stack - i.e. the \
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130 number of bytes we need to copy back. */ \
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131 ucStackBytes = pxXRAMStack[ 0 ]; \
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133 /* Copy the required number of bytes back into the stack. */ \
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138 *pxRAMStack = *pxXRAMStack; \
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140 } while( ucStackBytes ); \
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142 /* Restore the stack pointer ready to use the restored stack. */ \
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143 SP = ( unsigned portCHAR ) pxRAMStack; \
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145 /*-----------------------------------------------------------*/
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148 * Macro to push the current execution context onto the stack, before the stack
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149 * is moved to XRAM.
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151 #define portSAVE_CONTEXT() \
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154 /* Push ACC first, as when restoring the context it must be restored \
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155 last (it is used to set the IE register). */ \
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157 /* Store the IE register then disable interrupts. */ \
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178 /*-----------------------------------------------------------*/
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181 * Macro that restores the execution context from the stack. The execution
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182 * context was saved into the stack before the stack was copied into XRAM.
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184 #define portRESTORE_CONTEXT() \
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200 /* The next byte of the stack is the IE register. Only the global \
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201 enable bit forms part of the task context. Pop off the IE then set \
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202 the global enable bit to match that of the stored IE register. */ \
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210 /* Finally pop off the ACC, which was the first register saved. */ \
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215 /*-----------------------------------------------------------*/
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218 * See header file for description.
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220 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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222 unsigned portLONG ulAddress;
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223 portSTACK_TYPE *pxStartOfStack;
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225 /* Leave space to write the size of the stack as the first byte. */
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226 pxStartOfStack = pxTopOfStack;
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229 /* Place a few bytes of known values on the bottom of the stack.
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230 This is just useful for debugging and can be uncommented if required.
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231 *pxTopOfStack = 0x11;
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233 *pxTopOfStack = 0x22;
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235 *pxTopOfStack = 0x33;
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239 /* Simulate how the stack would look after a call to the scheduler tick
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242 The return address that would have been pushed by the MCU. */
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243 ulAddress = ( unsigned portLONG ) pxCode;
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244 *pxTopOfStack = ( portSTACK_TYPE ) ulAddress;
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247 *pxTopOfStack = ( portSTACK_TYPE ) ( ulAddress );
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250 /* Next all the registers will have been pushed by portSAVE_CONTEXT(). */
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251 *pxTopOfStack = 0xaa; /* acc */
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254 /* We want tasks to start with interrupts enabled. */
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255 *pxTopOfStack = portGLOBAL_INTERRUPT_BIT;
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258 /* The function parameters will be passed in the DPTR and B register as
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259 a three byte generic pointer is used. */
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260 ulAddress = ( unsigned portLONG ) pvParameters;
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261 *pxTopOfStack = ( portSTACK_TYPE ) ulAddress; /* DPL */
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264 *pxTopOfStack = ( portSTACK_TYPE ) ulAddress; /* DPH */
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267 *pxTopOfStack = ( portSTACK_TYPE ) ulAddress; /* b */
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270 /* The remaining registers are straight forward. */
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271 *pxTopOfStack = 0x02; /* R2 */
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273 *pxTopOfStack = 0x03; /* R3 */
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275 *pxTopOfStack = 0x04; /* R4 */
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277 *pxTopOfStack = 0x05; /* R5 */
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279 *pxTopOfStack = 0x06; /* R6 */
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281 *pxTopOfStack = 0x07; /* R7 */
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283 *pxTopOfStack = 0x00; /* R0 */
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285 *pxTopOfStack = 0x01; /* R1 */
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287 *pxTopOfStack = 0x00; /* PSW */
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289 *pxTopOfStack = 0xbb; /* BP */
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291 /* Dont increment the stack size here as we don't want to include
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292 the stack size byte as part of the stack size count.
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294 Finally we place the stack size at the beginning. */
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295 *pxStartOfStack = ( portSTACK_TYPE ) ( pxTopOfStack - pxStartOfStack );
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297 /* Unlike most ports, we return the start of the stack as this is where the
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298 size of the stack is stored. */
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299 return pxStartOfStack;
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301 /*-----------------------------------------------------------*/
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304 * See header file for description.
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306 portBASE_TYPE xPortStartScheduler( void )
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308 /* Setup timer 2 to generate the RTOS tick. */
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309 prvSetupTimerInterrupt();
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311 /* Make sure we start with the expected SFR page. This line should not
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312 really be required. */
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315 /* Copy the stack for the first task to execute from XRAM into the stack,
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316 restore the task context from the new stack, then start running the task. */
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317 portCOPY_XRAM_TO_STACK();
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318 portRESTORE_CONTEXT();
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320 /* Should never get here! */
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323 /*-----------------------------------------------------------*/
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325 void vPortEndScheduler( void )
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327 /* Not implemented for this port. */
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329 /*-----------------------------------------------------------*/
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332 * Manual context switch. The first thing we do is save the registers so we
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333 * can use a naked attribute.
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335 void vPortYield( void ) _naked
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337 /* Save the execution context onto the stack, then copy the entire stack
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338 to XRAM. This is necessary as the internal RAM is only large enough to
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339 hold one stack, and we want one per task.
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341 PERFORMANCE COULD BE IMPROVED BY ONLY COPYING TO XRAM IF A TASK SWITCH
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343 portSAVE_CONTEXT();
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344 portCOPY_STACK_TO_XRAM();
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346 /* Call the standard scheduler context switch function. */
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347 vTaskSwitchContext();
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349 /* Copy the stack of the task about to execute from XRAM into RAM and
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350 restore it's context ready to run on exiting. */
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351 portCOPY_XRAM_TO_STACK();
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352 portRESTORE_CONTEXT();
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354 /*-----------------------------------------------------------*/
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356 #if configUSE_PREEMPTION == 1
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357 void vTimer2ISR( void ) interrupt 5 _naked
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359 /* Preemptive context switch function triggered by the timer 2 ISR.
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360 This does the same as vPortYield() (see above) with the addition
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361 of incrementing the RTOS tick count. */
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363 portSAVE_CONTEXT();
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364 portCOPY_STACK_TO_XRAM();
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366 vTaskIncrementTick();
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367 vTaskSwitchContext();
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369 portCLEAR_INTERRUPT_FLAG();
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370 portCOPY_XRAM_TO_STACK();
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371 portRESTORE_CONTEXT();
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374 void vTimer2ISR( void ) interrupt 5
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376 /* When using the cooperative scheduler the timer 2 ISR is only
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377 required to increment the RTOS tick count. */
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379 vTaskIncrementTick();
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380 portCLEAR_INTERRUPT_FLAG();
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383 /*-----------------------------------------------------------*/
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385 static void prvSetupTimerInterrupt( void )
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387 unsigned portCHAR ucOriginalSFRPage;
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389 /* Constants calculated to give the required timer capture values. */
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390 const unsigned portLONG ulTicksPerSecond = configCPU_CLOCK_HZ / portCLOCK_DIVISOR;
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391 const unsigned portLONG ulCaptureTime = ulTicksPerSecond / configTICK_RATE_HZ;
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392 const unsigned portLONG ulCaptureValue = portMAX_TIMER_VALUE - ulCaptureTime;
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393 const unsigned portCHAR ucLowCaptureByte = ( unsigned portCHAR ) ( ulCaptureValue & ( unsigned portLONG ) 0xff );
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394 const unsigned portCHAR ucHighCaptureByte = ( unsigned portCHAR ) ( ulCaptureValue >> ( unsigned portLONG ) 8 );
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396 /* NOTE: This uses a timer only present on 8052 architecture. */
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398 /* Remember the current SFR page so we can restore it at the end of the
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400 ucOriginalSFRPage = SFRPAGE;
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403 /* TMR2CF can be left in its default state. */
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404 TMR2CF = ( unsigned portCHAR ) 0;
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406 /* Setup the overflow reload value. */
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407 RCAP2L = ucLowCaptureByte;
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408 RCAP2H = ucHighCaptureByte;
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410 /* The initial load is performed manually. */
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411 TMR2L = ucLowCaptureByte;
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412 TMR2H = ucHighCaptureByte;
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414 /* Enable the timer 2 interrupts. */
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415 IE |= portTIMER_2_INTERRUPT_ENABLE;
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417 /* Interrupts are disabled when this is called so the timer can be started
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419 TMR2CN = portENABLE_TIMER;
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421 /* Restore the original SFR page. */
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422 SFRPAGE = ucOriginalSFRPage;
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