2 FreeRTOS.org V4.0.5 - Copyright (C) 2003 - 2005 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 /* GCC/HCS12 port by Jefferson L Smith, 2005 */
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35 /* Scheduler includes. */
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36 #include "FreeRTOS.h"
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40 #include <sys/ports_def.h>
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42 /*-----------------------------------------------------------
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43 * Implementation of functions defined in portable.h for the HCS12 port.
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44 *----------------------------------------------------------*/
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48 * Configure a timer to generate the RTOS tick at the frequency specified
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49 * within FreeRTOSConfig.h.
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51 static void prvSetupTimerInterrupt( void );
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53 /* NOTE: Interrupt service routines must be in non-banked memory - as does the
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54 scheduler startup function. */
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55 #define ATTR_NEAR __attribute__((near))
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57 /* Manual context switch function. This is the SWI ISR. */
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58 // __attribute__((interrupt))
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59 void ATTR_NEAR vPortYield( void );
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61 /* Tick context switch function. This is the timer ISR. */
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62 // __attribute__((interrupt))
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63 void ATTR_NEAR vPortTickInterrupt( void );
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65 /* Function in non-banked memory which actually switches to first task. */
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66 portBASE_TYPE ATTR_NEAR xStartSchedulerNear( void );
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68 /* Calls to portENTER_CRITICAL() can be nested. When they are nested the
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69 critical section should not be left (i.e. interrupts should not be re-enabled)
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70 until the nesting depth reaches 0. This variable simply tracks the nesting
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71 depth. Each task maintains it's own critical nesting depth variable so
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72 uxCriticalNesting is saved and restored from the task stack during a context
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74 volatile unsigned portBASE_TYPE uxCriticalNesting = 0x80; // un-initialized
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76 /*-----------------------------------------------------------*/
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79 * See header file for description.
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81 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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85 /* Setup the initial stack of the task. The stack is set exactly as
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86 expected by the portRESTORE_CONTEXT() macro. In this case the stack as
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87 expected by the HCS12 RTI instruction. */
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90 /* The address of the task function is placed in the stack byte at a time. */
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91 *pxTopOfStack = ( portSTACK_TYPE ) *( ((portSTACK_TYPE *) (&pxCode) ) + 1 );
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92 *--pxTopOfStack = ( portSTACK_TYPE ) *( ((portSTACK_TYPE *) (&pxCode) ) + 0 );
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94 /* Next are all the registers that form part of the task context. */
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97 *--pxTopOfStack = ( portSTACK_TYPE ) 0xff;
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98 *--pxTopOfStack = ( portSTACK_TYPE ) 0xee;
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101 *--pxTopOfStack = ( portSTACK_TYPE ) 0xdd;
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102 *--pxTopOfStack = ( portSTACK_TYPE ) 0xcc;
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104 /* A register contains parameter high byte. */
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105 *--pxTopOfStack = ( portSTACK_TYPE ) *( ((portSTACK_TYPE *) (&pvParameters) ) + 0 );
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107 /* B register contains parameter low byte. */
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108 *--pxTopOfStack = ( portSTACK_TYPE ) *( ((portSTACK_TYPE *) (&pvParameters) ) + 1 );
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110 /* CCR: Note that when the task starts interrupts will be enabled since
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111 "I" bit of CCR is cleared */
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112 *--pxTopOfStack = ( portSTACK_TYPE ) 0x80; // keeps Stop disabled (MCU default)
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114 /* tmp softregs used by GCC. Values right now don't matter. */
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116 movw _.frame, 2,-%0 \n\
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117 movw _.tmp, 2,-%0 \n\
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118 movw _.z, 2,-%0 \n\
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119 movw _.xy, 2,-%0 \n\
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120 ;movw _.d2, 2,-%0 \n\
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121 ;movw _.d1, 2,-%0 \n\
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122 ": "=A"(pxTopOfStack) : "0"(pxTopOfStack) );
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124 #ifdef BANKED_MODEL
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125 /* The page of the task. */
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126 *--pxTopOfStack = 0x30; // can only directly start in PPAGE 0x30
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129 /* The critical nesting depth is initialised with 0 (meaning not in
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130 a critical section). */
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131 *--pxTopOfStack = ( portSTACK_TYPE ) 0x00;
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134 return pxTopOfStack;
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136 /*-----------------------------------------------------------*/
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138 void vPortEndScheduler( void )
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140 /* It is unlikely that the HCS12 port will get stopped. */
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142 /*-----------------------------------------------------------*/
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144 static void prvSetupTimerInterrupt( void )
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146 /* Enable hardware RTI timer */
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147 /* Ignores configTICK_RATE_HZ */
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148 RTICTL = 0x50; // 16 MHz xtal: 976.56 Hz, 1024mS
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149 CRGINT |= 0x80; // RTIE
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151 /*-----------------------------------------------------------*/
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153 portBASE_TYPE xPortStartScheduler( void )
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155 /* xPortStartScheduler() does not start the scheduler directly because
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156 the header file containing the xPortStartScheduler() prototype is part
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157 of the common kernel code, and therefore cannot use the CODE_SEG pragma.
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158 Instead it simply calls the locally defined xNearStartScheduler() -
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159 which does use the CODE_SEG pragma. */
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162 __asm ("jmp xStartSchedulerNear ; will never return": "=d"(d));
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165 /*-----------------------------------------------------------*/
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167 portBASE_TYPE xStartSchedulerNear( void )
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169 /* Configure the timer that will generate the RTOS tick. Interrupts are
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170 disabled when this function is called. */
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171 prvSetupTimerInterrupt();
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173 /* Restore the context of the first task. */
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174 portRESTORE_CONTEXT();
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178 /* Should not get here! */
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181 /*-----------------------------------------------------------*/
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184 * Context switch functions. These are interrupt service routines.
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188 * Manual context switch forced by calling portYIELD(). This is the SWI
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191 void vPortYield( void )
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194 /* NOTE: This is the trap routine (swi) although not defined as a trap.
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195 It will fill the stack the same way as an ISR in order to mix preemtion
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196 and cooperative yield. */
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198 portSAVE_CONTEXT();
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199 vTaskSwitchContext();
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200 portRESTORE_CONTEXT();
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204 /*-----------------------------------------------------------*/
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207 * RTOS tick interrupt service routine. If the cooperative scheduler is
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208 * being used then this simply increments the tick count. If the
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209 * preemptive scheduler is being used a context switch can occur.
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211 void vPortTickInterrupt( void )
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215 /* Clear tick timer flag */
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218 #if configUSE_PREEMPTION == 1
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220 /* A context switch might happen so save the context. */
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221 portSAVE_CONTEXT();
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223 /* Increment the tick ... */
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224 vTaskIncrementTick();
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226 /* ... then see if the new tick value has necessitated a
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228 vTaskSwitchContext();
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230 /* Restore the context of a task - which may be a different task
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231 to that interrupted. */
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232 portRESTORE_CONTEXT();
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236 vTaskIncrementTick();
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