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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36 + Call to taskYIELD() from within tick ISR has been replaced by the more
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37 efficient portSWITCH_CONTEXT().
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38 + ISR function definitions renamed to include the prv prefix.
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42 + Replaced the sUsingPreemption variable with the configUSE_PREEMPTION
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43 macro to be consistent with the later ports.
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46 /*-----------------------------------------------------------
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47 * Implementation of functions defined in portable.h for the Flashlite 186
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49 *----------------------------------------------------------*/
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55 #include "FreeRTOS.h"
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57 #include "portasm.h"
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59 /*lint -e950 Non ANSI reserved words okay in this file only. */
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61 #define portTIMER_EOI_TYPE ( 8 )
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62 #define portRESET_PIC() portOUTPUT_WORD( ( unsigned portSHORT ) 0xff22, portTIMER_EOI_TYPE )
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63 #define portTIMER_INT_NUMBER 0x12
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65 #define portTIMER_1_CONTROL_REGISTER ( ( unsigned portSHORT ) 0xff5e )
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66 #define portTIMER_0_CONTROL_REGISTER ( ( unsigned portSHORT ) 0xff56 )
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67 #define portTIMER_INTERRUPT_ENABLE ( ( unsigned portSHORT ) 0x2000 )
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69 /* Setup the hardware to generate the required tick frequency. */
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70 static void prvSetTickFrequency( unsigned portLONG ulTickRateHz );
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72 /* Set the hardware back to the state as per before the scheduler started. */
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73 static void prvExitFunction( void );
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75 /* The ISR used depends on whether the preemptive or cooperative scheduler
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77 #if( configUSE_PREEMPTION == 1 )
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78 /* Tick service routine used by the scheduler when preemptive scheduling is
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80 static void __interrupt __far prvPreemptiveTick( void );
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82 /* Tick service routine used by the scheduler when cooperative scheduling is
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84 static void __interrupt __far prvNonPreemptiveTick( void );
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87 /* Trap routine used by taskYIELD() to manually cause a context switch. */
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88 static void __interrupt __far prvYieldProcessor( void );
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90 /*lint -e956 File scopes necessary here. */
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92 /* Set true when the vectors are set so the scheduler will service the tick. */
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93 static portBASE_TYPE xSchedulerRunning = pdFALSE;
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95 /* Points to the original routine installed on the vector we use for manual
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96 context switches. This is then used to restore the original routine during
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97 prvExitFunction(). */
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98 static void ( __interrupt __far *pxOldSwitchISR )();
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100 /* Used to restore the original DOS context when the scheduler is ended. */
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101 static jmp_buf xJumpBuf;
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105 /*-----------------------------------------------------------*/
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106 portBASE_TYPE xPortStartScheduler( void )
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108 /* This is called with interrupts already disabled. */
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110 /* Remember what was on the interrupts we are going to use
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111 so we can put them back later if required. */
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112 pxOldSwitchISR = _dos_getvect( portSWITCH_INT_NUMBER );
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114 /* Put our manual switch (yield) function on a known
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116 _dos_setvect( portSWITCH_INT_NUMBER, prvYieldProcessor );
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118 #if( configUSE_PREEMPTION == 1 )
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120 /* Put our tick switch function on the timer interrupt. */
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121 _dos_setvect( portTIMER_INT_NUMBER, prvPreemptiveTick );
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125 /* We want the timer interrupt to just increment the tick count. */
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126 _dos_setvect( portTIMER_INT_NUMBER, prvNonPreemptiveTick );
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130 prvSetTickFrequency( configTICK_RATE_HZ );
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132 /* Clean up function if we want to return to DOS. */
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133 if( setjmp( xJumpBuf ) != 0 )
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136 xSchedulerRunning = pdFALSE;
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140 xSchedulerRunning = pdTRUE;
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142 /* Kick off the scheduler by setting up the context of the first task. */
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143 portFIRST_CONTEXT();
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146 return xSchedulerRunning;
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148 /*-----------------------------------------------------------*/
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150 /* The ISR used depends on whether the preemptive or cooperative scheduler
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152 #if( configUSE_PREEMPTION == 1 )
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153 static void __interrupt __far prvPreemptiveTick( void )
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155 /* Get the scheduler to update the task states following the tick. */
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156 vTaskIncrementTick();
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158 /* Switch in the context of the next task to be run. */
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159 portSWITCH_CONTEXT();
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161 /* Reset the PIC ready for the next time. */
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165 static void __interrupt __far prvNonPreemptiveTick( void )
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167 /* Same as preemptive tick, but the cooperative scheduler is being used
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168 so we don't have to switch in the context of the next task. */
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169 vTaskIncrementTick();
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173 /*-----------------------------------------------------------*/
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175 static void __interrupt __far prvYieldProcessor( void )
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177 /* Switch in the context of the next task to be run. */
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178 portSWITCH_CONTEXT();
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180 /*-----------------------------------------------------------*/
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182 void vPortEndScheduler( void )
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184 /* Jump back to the processor state prior to starting the
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185 scheduler. This means we are not going to be using a
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186 task stack frame so the task can be deleted. */
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187 longjmp( xJumpBuf, 1 );
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189 /*-----------------------------------------------------------*/
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191 static void prvExitFunction( void )
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193 const unsigned portSHORT usTimerDisable = 0x0000;
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194 unsigned portSHORT usTimer0Control;
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196 /* Interrupts should be disabled here anyway - but no
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197 harm in making sure. */
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198 portDISABLE_INTERRUPTS();
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199 if( xSchedulerRunning == pdTRUE )
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201 /* Put back the switch interrupt routines that was in place
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202 before the scheduler started. */
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203 _dos_setvect( portSWITCH_INT_NUMBER, pxOldSwitchISR );
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206 /* Disable the timer used for the tick to ensure the scheduler is
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207 not called before restoring interrupts. There was previously nothing
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208 on this timer so there is no old ISR to restore. */
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209 portOUTPUT_WORD( portTIMER_1_CONTROL_REGISTER, usTimerDisable );
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211 /* Restart the DOS tick. */
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212 usTimer0Control = portINPUT_WORD( portTIMER_0_CONTROL_REGISTER );
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213 usTimer0Control |= portTIMER_INTERRUPT_ENABLE;
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214 portOUTPUT_WORD( portTIMER_0_CONTROL_REGISTER, usTimer0Control );
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217 portENABLE_INTERRUPTS();
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219 /* This will free up all the memory used by the scheduler.
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220 exiting back to dos with INT21 AH=4CH will do this anyway so
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221 it is not necessary to call this. */
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222 vTaskCleanUpResources();
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224 /*-----------------------------------------------------------*/
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226 static void prvSetTickFrequency( unsigned portLONG ulTickRateHz )
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228 const unsigned portSHORT usMaxCountRegister = 0xff5a;
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229 const unsigned portSHORT usTimerPriorityRegister = 0xff32;
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230 const unsigned portSHORT usTimerEnable = 0xC000;
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231 const unsigned portSHORT usRetrigger = 0x0001;
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232 const unsigned portSHORT usTimerHighPriority = 0x0000;
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233 unsigned portSHORT usTimer0Control;
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235 /* ( CPU frequency / 4 ) / clock 2 max count [inpw( 0xff62 ) = 7] */
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237 const unsigned portLONG ulClockFrequency = ( unsigned portLONG ) 0x7f31a0UL;
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239 unsigned portLONG ulTimerCount = ulClockFrequency / ulTickRateHz;
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241 portOUTPUT_WORD( portTIMER_1_CONTROL_REGISTER, usTimerEnable | portTIMER_INTERRUPT_ENABLE | usRetrigger );
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242 portOUTPUT_WORD( usMaxCountRegister, ( unsigned portSHORT ) ulTimerCount );
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243 portOUTPUT_WORD( usTimerPriorityRegister, usTimerHighPriority );
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245 /* Stop the DOS tick - don't do this if you want to maintain a TOD clock. */
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246 usTimer0Control = portINPUT_WORD( portTIMER_0_CONTROL_REGISTER );
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247 usTimer0Control &= ~portTIMER_INTERRUPT_ENABLE;
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248 portOUTPUT_WORD( portTIMER_0_CONTROL_REGISTER, usTimer0Control );
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