2 FreeRTOS.org V4.8.0 - Copyright (C) 2003-2008 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 ***************************************************************************
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29 * SAVE TIME AND MONEY! Why not get us to quote to get FreeRTOS.org *
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30 * running on your hardware - or even write all or part of your application*
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31 * for you? See http://www.OpenRTOS.com for details. *
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33 ***************************************************************************
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34 ***************************************************************************
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36 Please ensure to read the configuration and relevant port sections of the
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37 online documentation.
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39 http://www.FreeRTOS.org - Documentation, latest information, license and
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42 http://www.SafeRTOS.com - A version that is certified for use in safety
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45 http://www.OpenRTOS.com - Commercial support, development, porting,
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46 licensing and training services.
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50 /*-----------------------------------------------------------
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51 * Implementation of functions defined in portable.h for the ARM7 port
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52 * using the Keil compiler.
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54 * Components that can be compiled to either ARM or THUMB mode are
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55 * contained in this file. The ISR routines, which can only be compiled
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56 * to ARM mode are contained in portISR.c.
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57 *----------------------------------------------------------*/
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62 + Bug fix - The prescale value for the timer setup is now written to T0PR
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63 instead of T0PC. This bug would have had no effect unless a prescale
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64 value was actually used.
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67 /* Standard includes. */
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70 /* Scheduler includes. */
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71 #include "FreeRTOS.h"
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74 /* Constants required to setup the initial task context. */
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75 #define portINITIAL_SPSR ( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
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76 #define portTHUMB_MODE_BIT ( ( portSTACK_TYPE ) 0x20 )
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77 #define portINSTRUCTION_SIZE ( ( portSTACK_TYPE ) 4 )
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78 #define portNO_CRITICAL_SECTION_NESTING ( ( portSTACK_TYPE ) 0 )
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80 /* Constants required to setup the tick ISR. */
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81 #define portENABLE_TIMER ( ( unsigned portCHAR ) 0x01 )
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82 #define portPRESCALE_VALUE 0x00
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83 #define portINTERRUPT_ON_MATCH ( ( unsigned portLONG ) 0x01 )
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84 #define portRESET_COUNT_ON_MATCH ( ( unsigned portLONG ) 0x02 )
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86 /* Constants required to setup the VIC for the tick ISR. */
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87 #define portTIMER_VIC_CHANNEL ( ( unsigned portLONG ) 0x0004 )
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88 #define portTIMER_VIC_CHANNEL_BIT ( ( unsigned portLONG ) 0x0010 )
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89 #define portTIMER_VIC_ENABLE ( ( unsigned portLONG ) 0x0020 )
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91 /*-----------------------------------------------------------*/
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93 /* Setup the timer to generate the tick interrupts. */
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94 static void prvSetupTimerInterrupt( void );
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97 * The scheduler can only be started from ARM mode, so
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98 * vPortISRStartFirstSTask() is defined in portISR.c.
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100 extern void vPortISRStartFirstTask( void );
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102 /*-----------------------------------------------------------*/
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105 * See header file for description.
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107 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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109 portSTACK_TYPE *pxOriginalTOS;
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111 /* Setup the initial stack of the task. The stack is set exactly as
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112 expected by the portRESTORE_CONTEXT() macro.
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114 Remember where the top of the (simulated) stack is before we place
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116 pxOriginalTOS = pxTopOfStack;
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118 /* First on the stack is the return address - which in this case is the
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119 start of the task. The offset is added to make the return address appear
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120 as it would within an IRQ ISR. */
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121 *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;
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124 *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa; /* R14 */
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126 *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
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128 *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212; /* R12 */
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130 *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111; /* R11 */
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132 *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010; /* R10 */
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134 *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909; /* R9 */
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136 *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808; /* R8 */
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138 *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707; /* R7 */
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140 *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606; /* R6 */
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142 *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505; /* R5 */
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144 *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404; /* R4 */
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146 *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303; /* R3 */
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148 *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202; /* R2 */
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150 *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101; /* R1 */
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152 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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155 /* The last thing onto the stack is the status register, which is set for
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156 system mode, with interrupts enabled. */
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157 *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;
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159 #ifdef KEIL_THUMB_INTERWORK
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161 /* We want the task to start in thumb mode. */
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162 *pxTopOfStack |= portTHUMB_MODE_BIT;
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168 /* The code generated by the Keil compiler does not maintain separate
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169 stack and frame pointers. The portENTER_CRITICAL macro cannot therefore
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170 use the stack as per other ports. Instead a variable is used to keep
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171 track of the critical section nesting. This variable has to be stored
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172 as part of the task context and is initially set to zero. */
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173 *pxTopOfStack = portNO_CRITICAL_SECTION_NESTING;
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175 return pxTopOfStack;
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177 /*-----------------------------------------------------------*/
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179 portBASE_TYPE xPortStartScheduler( void )
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181 /* Start the timer that generates the tick ISR. */
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182 prvSetupTimerInterrupt();
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184 /* Start the first task. This is done from portISR.c as ARM mode must be
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186 vPortISRStartFirstTask();
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188 /* Should not get here! */
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191 /*-----------------------------------------------------------*/
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193 void vPortEndScheduler( void )
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195 /* It is unlikely that the ARM port will require this function as there
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196 is nothing to return to. If this is required - stop the tick ISR then
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197 return back to main. */
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199 /*-----------------------------------------------------------*/
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201 static void prvSetupTimerInterrupt( void )
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203 unsigned portLONG ulCompareMatch;
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205 /* A 1ms tick does not require the use of the timer prescale. This is
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206 defaulted to zero but can be used if necessary. */
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207 T0PR = portPRESCALE_VALUE;
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209 /* Calculate the match value required for our wanted tick rate. */
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210 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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212 /* Protect against divide by zero. Using an if() statement still results
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213 in a warning - hence the #if. */
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214 #if portPRESCALE_VALUE != 0
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216 ulCompareMatch /= ( portPRESCALE_VALUE + 1 );
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220 T0MR0 = ulCompareMatch;
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222 /* Generate tick with timer 0 compare match. */
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223 T0MCR = portRESET_COUNT_ON_MATCH | portINTERRUPT_ON_MATCH;
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225 /* Setup the VIC for the timer. */
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226 VICIntSelect &= ~( portTIMER_VIC_CHANNEL_BIT );
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227 VICIntEnable |= portTIMER_VIC_CHANNEL_BIT;
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229 /* The ISR installed depends on whether the preemptive or cooperative
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230 scheduler is being used. */
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231 #if configUSE_PREEMPTION == 1
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233 #ifdef KEIL_THUMB_INTERWORK
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234 extern void ( vPreemptiveTick )( void ) __arm __task;
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236 extern void ( vPreemptiveTick )( void ) __task;
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239 VICVectAddr0 = ( unsigned portLONG ) vPreemptiveTick;
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243 extern void ( vNonPreemptiveTick )( void ) __irq;
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245 VICVectAddr0 = ( portLONG ) vNonPreemptiveTick;
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249 VICVectCntl0 = portTIMER_VIC_CHANNEL | portTIMER_VIC_ENABLE;
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251 /* Start the timer - interrupts are disabled when this function is called
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252 so it is okay to do this here. */
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253 T0TCR = portENABLE_TIMER;
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255 /*-----------------------------------------------------------*/
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