2 FreeRTOS.org V4.3.0 - 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 for an IEC 61508 compliant version along
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32 with commercial development and support options.
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33 ***************************************************************************
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36 /* Scheduler includes. */
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37 #include "FreeRTOS.h"
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41 /*-----------------------------------------------------------
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42 * Implementation of functions defined in portable.h for the HCS12 port.
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43 *----------------------------------------------------------*/
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47 * Configure a timer to generate the RTOS tick at the frequency specified
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48 * within FreeRTOSConfig.h.
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50 static void prvSetupTimerInterrupt( void );
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52 /* Interrupt service routines have to be in non-banked memory - as does the
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53 scheduler startup function. */
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54 #pragma CODE_SEG __NEAR_SEG NON_BANKED
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56 /* Manual context switch function. This is the SWI ISR. */
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57 void interrupt vPortYield( void );
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59 /* Tick context switch function. This is the timer ISR. */
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60 void interrupt vPortTickInterrupt( void );
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62 /* Simply called by xPortStartScheduler(). xPortStartScheduler() does not
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63 start the scheduler directly because the header file containing the
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64 xPortStartScheduler() prototype is part of the common kernel code, and
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65 therefore cannot use the CODE_SEG pragma. */
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66 static portBASE_TYPE xBankedStartScheduler( void );
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68 #pragma CODE_SEG DEFAULT
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70 /* Calls to portENTER_CRITICAL() can be nested. When they are nested the
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71 critical section should not be left (i.e. interrupts should not be re-enabled)
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72 until the nesting depth reaches 0. This variable simply tracks the nesting
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73 depth. Each task maintains it's own critical nesting depth variable so
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74 uxCriticalNesting is saved and restored from the task stack during a context
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76 volatile unsigned portBASE_TYPE uxCriticalNesting = 0xff;
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78 /*-----------------------------------------------------------*/
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81 * See header file for description.
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83 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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86 Place a few bytes of known values on the bottom of the stack.
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87 This can be uncommented to provide useful stack markers when debugging.
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89 *pxTopOfStack = ( portSTACK_TYPE ) 0x11;
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91 *pxTopOfStack = ( portSTACK_TYPE ) 0x22;
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93 *pxTopOfStack = ( portSTACK_TYPE ) 0x33;
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99 /* Setup the initial stack of the task. The stack is set exactly as
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100 expected by the portRESTORE_CONTEXT() macro. In this case the stack as
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101 expected by the HCS12 RTI instruction. */
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104 /* The address of the task function is placed in the stack byte at a time. */
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105 *pxTopOfStack = ( portSTACK_TYPE ) *( ((portSTACK_TYPE *) (&pxCode) ) + 1 );
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107 *pxTopOfStack = ( portSTACK_TYPE ) *( ((portSTACK_TYPE *) (&pxCode) ) + 0 );
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110 /* Next are all the registers that form part of the task context. */
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113 *pxTopOfStack = ( portSTACK_TYPE ) 0xff;
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115 *pxTopOfStack = ( portSTACK_TYPE ) 0xee;
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119 *pxTopOfStack = ( portSTACK_TYPE ) 0xdd;
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121 *pxTopOfStack = ( portSTACK_TYPE ) 0xcc;
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124 /* A register contains parameter high byte. */
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125 *pxTopOfStack = ( portSTACK_TYPE ) *( ((portSTACK_TYPE *) (&pvParameters) ) + 0 );
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128 /* B register contains parameter low byte. */
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129 *pxTopOfStack = ( portSTACK_TYPE ) *( ((portSTACK_TYPE *) (&pvParameters) ) + 1 );
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132 /* CCR: Note that when the task starts interrupts will be enabled since
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133 "I" bit of CCR is cleared */
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134 *pxTopOfStack = ( portSTACK_TYPE ) 0x00;
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137 #ifdef BANKED_MODEL
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138 /* The page of the task. */
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139 *pxTopOfStack = ( portSTACK_TYPE ) ( ( int ) pxCode );
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143 /* Finally the critical nesting depth is initialised with 0 (not within
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144 a critical section). */
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145 *pxTopOfStack = ( portSTACK_TYPE ) 0x00;
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147 return pxTopOfStack;
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149 /*-----------------------------------------------------------*/
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151 void vPortEndScheduler( void )
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153 /* It is unlikely that the HCS12 port will get stopped. */
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155 /*-----------------------------------------------------------*/
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157 static void prvSetupTimerInterrupt( void )
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159 TickTimer_SetFreqHz( configTICK_RATE_HZ );
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160 TickTimer_Enable();
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162 /*-----------------------------------------------------------*/
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164 portBASE_TYPE xPortStartScheduler( void )
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166 /* xPortStartScheduler() does not start the scheduler directly because
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167 the header file containing the xPortStartScheduler() prototype is part
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168 of the common kernel code, and therefore cannot use the CODE_SEG pragma.
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169 Instead it simply calls the locally defined xBankedStartScheduler() -
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170 which does use the CODE_SEG pragma. */
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172 return xBankedStartScheduler();
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174 /*-----------------------------------------------------------*/
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176 #pragma CODE_SEG __NEAR_SEG NON_BANKED
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178 static portBASE_TYPE xBankedStartScheduler( void )
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180 /* Configure the timer that will generate the RTOS tick. Interrupts are
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181 disabled when this function is called. */
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182 prvSetupTimerInterrupt();
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184 /* Restore the context of the first task. */
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185 portRESTORE_CONTEXT();
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187 /* Simulate the end of an interrupt to start the scheduler off. */
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190 /* Should not get here! */
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193 /*-----------------------------------------------------------*/
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196 * Context switch functions. These are both interrupt service routines.
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200 * Manual context switch forced by calling portYIELD(). This is the SWI
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203 void interrupt vPortYield( void )
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205 portSAVE_CONTEXT();
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206 vTaskSwitchContext();
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207 portRESTORE_CONTEXT();
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209 /*-----------------------------------------------------------*/
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212 * RTOS tick interrupt service routine. If the cooperative scheduler is
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213 * being used then this simply increments the tick count. If the
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214 * preemptive scheduler is being used a context switch can occur.
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216 void interrupt vPortTickInterrupt( void )
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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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232 /* Restore the context of a task - which may be a different task
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233 to that interrupted. */
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234 portRESTORE_CONTEXT();
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238 vTaskIncrementTick();
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244 #pragma CODE_SEG DEFAULT
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