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jeremybenn |
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FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.
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***************************************************************************
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* *
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* If you are: *
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* *
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* + New to FreeRTOS, *
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* + Wanting to learn FreeRTOS or multitasking in general quickly *
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* + Looking for basic training, *
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* + Wanting to improve your FreeRTOS skills and productivity *
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* *
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* then take a look at the FreeRTOS books - available as PDF or paperback *
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* *
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* "Using the FreeRTOS Real Time Kernel - a Practical Guide" *
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* http://www.FreeRTOS.org/Documentation *
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* *
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* A pdf reference manual is also available. Both are usually delivered *
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* to your inbox within 20 minutes to two hours when purchased between 8am *
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* and 8pm GMT (although please allow up to 24 hours in case of *
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* exceptional circumstances). Thank you for your support! *
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* *
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***************************************************************************
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This file is part of the FreeRTOS distribution.
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FreeRTOS is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License (version 2) as published by the
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Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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***NOTE*** The exception to the GPL is included to allow you to distribute
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a combined work that includes FreeRTOS without being obliged to provide the
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source code for proprietary components outside of the FreeRTOS kernel.
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FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details. You should have received a copy of the GNU General Public
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License and the FreeRTOS license exception along with FreeRTOS; if not it
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can be viewed here: http://www.freertos.org/a00114.html and also obtained
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by writing to Richard Barry, contact details for whom are available on the
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FreeRTOS WEB site.
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1 tab == 4 spaces!
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http://www.FreeRTOS.org - Documentation, latest information, license and
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contact details.
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http://www.SafeRTOS.com - A version that is certified for use in safety
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critical systems.
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http://www.OpenRTOS.com - Commercial support, development, porting,
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licensing and training services.
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*/
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/*
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Changes from V1.00:
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+ Call to taskYIELD() from within tick ISR has been replaced by the more
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efficient portSWITCH_CONTEXT().
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+ ISR function definitions renamed to include the prv prefix.
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Changes from V2.6.1
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+ Replaced the sUsingPreemption variable with the configUSE_PREEMPTION
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macro to be consistent with the later ports.
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*/
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/*-----------------------------------------------------------
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* Implementation of functions defined in portable.h for the Flashlite 186
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* port.
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*----------------------------------------------------------*/
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#include <dos.h>
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#include <stdlib.h>
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#include <setjmp.h>
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#include "FreeRTOS.h"
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#include "task.h"
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#include "portasm.h"
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/*lint -e950 Non ANSI reserved words okay in this file only. */
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#define portTIMER_EOI_TYPE ( 8 )
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#define portRESET_PIC() portOUTPUT_WORD( ( unsigned short ) 0xff22, portTIMER_EOI_TYPE )
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#define portTIMER_INT_NUMBER 0x12
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#define portTIMER_1_CONTROL_REGISTER ( ( unsigned short ) 0xff5e )
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#define portTIMER_0_CONTROL_REGISTER ( ( unsigned short ) 0xff56 )
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#define portTIMER_INTERRUPT_ENABLE ( ( unsigned short ) 0x2000 )
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/* Setup the hardware to generate the required tick frequency. */
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static void prvSetTickFrequency( unsigned long ulTickRateHz );
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/* Set the hardware back to the state as per before the scheduler started. */
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static void prvExitFunction( void );
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/* The ISR used depends on whether the preemptive or cooperative scheduler
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is being used. */
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#if( configUSE_PREEMPTION == 1 )
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/* Tick service routine used by the scheduler when preemptive scheduling is
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being used. */
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static void __interrupt __far prvPreemptiveTick( void );
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#else
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/* Tick service routine used by the scheduler when cooperative scheduling is
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being used. */
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static void __interrupt __far prvNonPreemptiveTick( void );
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#endif
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/* Trap routine used by taskYIELD() to manually cause a context switch. */
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static void __interrupt __far prvYieldProcessor( void );
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/*lint -e956 File scopes necessary here. */
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/* Set true when the vectors are set so the scheduler will service the tick. */
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static portBASE_TYPE xSchedulerRunning = pdFALSE;
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/* Points to the original routine installed on the vector we use for manual
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context switches. This is then used to restore the original routine during
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prvExitFunction(). */
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static void ( __interrupt __far *pxOldSwitchISR )();
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/* Used to restore the original DOS context when the scheduler is ended. */
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static jmp_buf xJumpBuf;
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/*lint +e956 */
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/*-----------------------------------------------------------*/
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portBASE_TYPE xPortStartScheduler( void )
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{
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/* This is called with interrupts already disabled. */
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/* Remember what was on the interrupts we are going to use
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so we can put them back later if required. */
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pxOldSwitchISR = _dos_getvect( portSWITCH_INT_NUMBER );
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/* Put our manual switch (yield) function on a known
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vector. */
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_dos_setvect( portSWITCH_INT_NUMBER, prvYieldProcessor );
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#if( configUSE_PREEMPTION == 1 )
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{
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/* Put our tick switch function on the timer interrupt. */
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_dos_setvect( portTIMER_INT_NUMBER, prvPreemptiveTick );
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}
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#else
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{
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/* We want the timer interrupt to just increment the tick count. */
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_dos_setvect( portTIMER_INT_NUMBER, prvNonPreemptiveTick );
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}
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#endif
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prvSetTickFrequency( configTICK_RATE_HZ );
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/* Clean up function if we want to return to DOS. */
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if( setjmp( xJumpBuf ) != 0 )
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{
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prvExitFunction();
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xSchedulerRunning = pdFALSE;
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}
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else
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{
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xSchedulerRunning = pdTRUE;
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/* Kick off the scheduler by setting up the context of the first task. */
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portFIRST_CONTEXT();
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}
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return xSchedulerRunning;
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}
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/*-----------------------------------------------------------*/
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/* The ISR used depends on whether the preemptive or cooperative scheduler
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is being used. */
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#if( configUSE_PREEMPTION == 1 )
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static void __interrupt __far prvPreemptiveTick( void )
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{
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/* Get the scheduler to update the task states following the tick. */
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vTaskIncrementTick();
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/* Switch in the context of the next task to be run. */
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portSWITCH_CONTEXT();
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/* Reset the PIC ready for the next time. */
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portRESET_PIC();
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}
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#else
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static void __interrupt __far prvNonPreemptiveTick( void )
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{
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/* Same as preemptive tick, but the cooperative scheduler is being used
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so we don't have to switch in the context of the next task. */
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vTaskIncrementTick();
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portRESET_PIC();
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}
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#endif
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/*-----------------------------------------------------------*/
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static void __interrupt __far prvYieldProcessor( void )
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{
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/* Switch in the context of the next task to be run. */
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portSWITCH_CONTEXT();
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}
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/*-----------------------------------------------------------*/
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void vPortEndScheduler( void )
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{
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/* Jump back to the processor state prior to starting the
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scheduler. This means we are not going to be using a
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task stack frame so the task can be deleted. */
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longjmp( xJumpBuf, 1 );
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}
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/*-----------------------------------------------------------*/
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static void prvExitFunction( void )
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{
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const unsigned short usTimerDisable = 0x0000;
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unsigned short usTimer0Control;
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/* Interrupts should be disabled here anyway - but no
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harm in making sure. */
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portDISABLE_INTERRUPTS();
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if( xSchedulerRunning == pdTRUE )
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{
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/* Put back the switch interrupt routines that was in place
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before the scheduler started. */
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_dos_setvect( portSWITCH_INT_NUMBER, pxOldSwitchISR );
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}
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/* Disable the timer used for the tick to ensure the scheduler is
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not called before restoring interrupts. There was previously nothing
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on this timer so there is no old ISR to restore. */
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portOUTPUT_WORD( portTIMER_1_CONTROL_REGISTER, usTimerDisable );
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/* Restart the DOS tick. */
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usTimer0Control = portINPUT_WORD( portTIMER_0_CONTROL_REGISTER );
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usTimer0Control |= portTIMER_INTERRUPT_ENABLE;
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portOUTPUT_WORD( portTIMER_0_CONTROL_REGISTER, usTimer0Control );
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portENABLE_INTERRUPTS();
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/* This will free up all the memory used by the scheduler.
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exiting back to dos with INT21 AH=4CH will do this anyway so
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it is not necessary to call this. */
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vTaskCleanUpResources();
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}
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/*-----------------------------------------------------------*/
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static void prvSetTickFrequency( unsigned long ulTickRateHz )
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{
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const unsigned short usMaxCountRegister = 0xff5a;
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const unsigned short usTimerPriorityRegister = 0xff32;
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const unsigned short usTimerEnable = 0xC000;
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const unsigned short usRetrigger = 0x0001;
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const unsigned short usTimerHighPriority = 0x0000;
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unsigned short usTimer0Control;
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/* ( CPU frequency / 4 ) / clock 2 max count [inpw( 0xff62 ) = 7] */
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const unsigned long ulClockFrequency = ( unsigned long ) 0x7f31a0UL;
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unsigned long ulTimerCount = ulClockFrequency / ulTickRateHz;
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portOUTPUT_WORD( portTIMER_1_CONTROL_REGISTER, usTimerEnable | portTIMER_INTERRUPT_ENABLE | usRetrigger );
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portOUTPUT_WORD( usMaxCountRegister, ( unsigned short ) ulTimerCount );
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portOUTPUT_WORD( usTimerPriorityRegister, usTimerHighPriority );
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/* Stop the DOS tick - don't do this if you want to maintain a TOD clock. */
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usTimer0Control = portINPUT_WORD( portTIMER_0_CONTROL_REGISTER );
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usTimer0Control &= ~portTIMER_INTERRUPT_ENABLE;
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portOUTPUT_WORD( portTIMER_0_CONTROL_REGISTER, usTimer0Control );
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}
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/*lint +e950 */
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