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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37 /*-----------------------------------------------------------
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38 * Implementation of functions defined in portable.h for the Tern EE 186
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40 *----------------------------------------------------------*/
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42 /* Library includes. */
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43 #include <embedded.h>
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46 /* Scheduler includes. */
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47 #include "FreeRTOS.h"
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49 #include "portasm.h"
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51 /* The timer increments every four clocks, hence the divide by 4. */
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52 #define portPRESCALE_VALUE ( 16 )
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53 #define portTIMER_COMPARE ( configCPU_CLOCK_HZ / ( configTICK_RATE_HZ * 4UL ) )
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55 /* From the RDC data sheet. */
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56 #define portENABLE_TIMER_AND_INTERRUPT ( unsigned portSHORT ) 0xe00b
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57 #define portENABLE_TIMER ( unsigned portSHORT ) 0xC001
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59 /* Interrupt control. */
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60 #define portEIO_REGISTER 0xff22
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61 #define portCLEAR_INTERRUPT 0x0008
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63 /* Setup the hardware to generate the required tick frequency. */
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64 static void prvSetupTimerInterrupt( void );
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66 /* The ISR used depends on whether the preemptive or cooperative scheduler
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68 #if( configUSE_PREEMPTION == 1 )
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69 /* Tick service routine used by the scheduler when preemptive scheduling is
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71 static void __interrupt __far prvPreemptiveTick( void );
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73 /* Tick service routine used by the scheduler when cooperative scheduling is
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75 static void __interrupt __far prvNonPreemptiveTick( void );
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78 /* Trap routine used by taskYIELD() to manually cause a context switch. */
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79 static void __interrupt __far prvYieldProcessor( void );
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81 /*-----------------------------------------------------------*/
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82 /* 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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85 portSTACK_TYPE DS_Reg = 0;
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87 /* We need the true data segment. */
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88 __asm{ MOV DS_Reg, DS };
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90 /* Place a few bytes of known values on the bottom of the stack.
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91 This is just useful for debugging. */
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93 *pxTopOfStack = 0x1111;
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95 *pxTopOfStack = 0x2222;
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97 *pxTopOfStack = 0x3333;
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100 /* We are going to start the scheduler using a return from interrupt
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101 instruction to load the program counter, so first there would be the
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102 function call with parameters preamble. */
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104 *pxTopOfStack = FP_OFF( pvParameters );
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106 *pxTopOfStack = FP_OFF( pxCode );
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109 /* Next the status register and interrupt return address. */
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110 *pxTopOfStack = portINITIAL_SW;
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112 *pxTopOfStack = FP_SEG( pxCode );
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114 *pxTopOfStack = FP_OFF( pxCode );
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117 /* The remaining registers would be pushed on the stack by our context
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118 switch function. These are loaded with values simply to make debugging
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120 *pxTopOfStack = ( portSTACK_TYPE ) 0xAAAA; /* AX */
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122 *pxTopOfStack = ( portSTACK_TYPE ) 0xBBBB; /* BX */
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124 *pxTopOfStack = ( portSTACK_TYPE ) 0xCCCC; /* CX */
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126 *pxTopOfStack = ( portSTACK_TYPE ) 0xDDDD; /* DX */
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128 *pxTopOfStack = ( portSTACK_TYPE ) 0xEEEE; /* ES */
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131 *pxTopOfStack = DS_Reg; /* DS */
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133 *pxTopOfStack = ( portSTACK_TYPE ) 0x0123; /* SI */
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135 *pxTopOfStack = ( portSTACK_TYPE ) 0xDDDD; /* DI */
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137 *pxTopOfStack = ( portSTACK_TYPE ) 0xBBBB; /* BP */
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139 return pxTopOfStack;
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141 /*-----------------------------------------------------------*/
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143 portBASE_TYPE xPortStartScheduler( void )
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145 /* This is called with interrupts already disabled. */
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147 /* Put our manual switch (yield) function on a known
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149 setvect( portSWITCH_INT_NUMBER, prvYieldProcessor );
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151 /* Setup the tick interrupt. */
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152 prvSetupTimerInterrupt();
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154 /* Kick off the scheduler by setting up the context of the first task. */
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155 portFIRST_CONTEXT();
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157 /* Should not get here! */
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160 /*-----------------------------------------------------------*/
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162 /* The ISR used depends on whether the preemptive or cooperative scheduler
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164 #if( configUSE_PREEMPTION == 1 )
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165 static void __interrupt __far prvPreemptiveTick( void )
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167 /* Get the scheduler to update the task states following the tick. */
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168 vTaskIncrementTick();
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170 /* Switch in the context of the next task to be run. */
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171 portEND_SWITCHING_ISR();
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173 /* Reset interrupt. */
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174 outport( portEIO_REGISTER, portCLEAR_INTERRUPT );
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177 static void __interrupt __far prvNonPreemptiveTick( void )
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179 /* Same as preemptive tick, but the cooperative scheduler is being used
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180 so we don't have to switch in the context of the next task. */
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181 vTaskIncrementTick();
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182 /* Reset interrupt. */
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183 outport( portEIO_REGISTER, portCLEAR_INTERRUPT );
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186 /*-----------------------------------------------------------*/
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188 static void __interrupt __far prvYieldProcessor( void )
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190 /* Switch in the context of the next task to be run. */
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191 portEND_SWITCHING_ISR();
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193 /*-----------------------------------------------------------*/
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195 void vPortEndScheduler( void )
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197 /* Not implemented. */
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199 /*-----------------------------------------------------------*/
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201 static void prvSetupTimerInterrupt( void )
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203 const unsigned portLONG ulCompareValue = portTIMER_COMPARE;
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204 unsigned portSHORT usTimerCompare;
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206 usTimerCompare = ( unsigned portSHORT ) ( ulCompareValue >> 4 );
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207 t2_init( portENABLE_TIMER, portPRESCALE_VALUE, NULL );
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209 #if( configUSE_PREEMPTION == 1 )
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210 /* Tick service routine used by the scheduler when preemptive scheduling is
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212 t1_init( portENABLE_TIMER_AND_INTERRUPT, usTimerCompare, usTimerCompare, prvPreemptiveTick );
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214 /* Tick service routine used by the scheduler when cooperative scheduling is
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216 t1_init( portENABLE_TIMER_AND_INTERRUPT, usTimerCompare, usTimerCompare, prvNonPreemptiveTick );
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