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/*
FreeRTOS V7.1.1 - Copyright (C) 2012 Real Time Engineers Ltd.
***************************************************************************
* *
* FreeRTOS tutorial books are available in pdf and paperback. *
* Complete, revised, and edited pdf reference manuals are also *
* available. *
* *
* Purchasing FreeRTOS documentation will not only help you, by *
* ensuring you get running as quickly as possible and with an *
* in-depth knowledge of how to use FreeRTOS, it will also help *
* the FreeRTOS project to continue with its mission of providing *
* professional grade, cross platform, de facto standard solutions *
* for microcontrollers - completely free of charge! *
* *
* >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
* *
* Thank you for using FreeRTOS, and thank you for your support! *
* *
***************************************************************************
This file is part of the FreeRTOS distribution.
FreeRTOS is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License (version 2) as published by the
Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
>>>NOTE<<< The modification to the GPL is included to allow you to
distribute a combined work that includes FreeRTOS without being obliged to
provide the source code for proprietary components outside of the FreeRTOS
kernel. FreeRTOS is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details. You should have received a copy of the GNU General Public
License and the FreeRTOS license exception along with FreeRTOS; if not it
can be viewed here: http://www.freertos.org/a00114.html and also obtained
by writing to Richard Barry, contact details for whom are available on the
FreeRTOS WEB site.
1 tab == 4 spaces!
***************************************************************************
* *
* Having a problem? Start by reading the FAQ "My application does *
* not run, what could be wrong? *
* *
* http://www.FreeRTOS.org/FAQHelp.html *
* *
***************************************************************************
http://www.FreeRTOS.org - Documentation, training, latest information,
license and contact details.
http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
including FreeRTOS+Trace - an indispensable productivity tool.
Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell
the code with commercial support, indemnification, and middleware, under
the OpenRTOS brand: http://www.OpenRTOS.com. High Integrity Systems also
provide a safety engineered and independently SIL3 certified version under
the SafeRTOS brand: http://www.SafeRTOS.com.
*/
/*
Changes from V2.6.1
+ Replaced the sUsingPreemption variable with the configUSE_PREEMPTION
macro to be consistent with the later ports.
Changes from V4.0.1
+ Add function prvSetTickFrequencyDefault() to set the DOS tick back to
its proper value when the scheduler exits.
*/
#include <stdlib.h>
#include <dos.h>
#include <setjmp.h>
#include "FreeRTOS.h"
#include "task.h"
#include "portasm.h"
/*-----------------------------------------------------------
* Implementation of functions defined in portable.h for the industrial
* PC port.
*----------------------------------------------------------*/
/*lint -e950 Non ANSI reserved words okay in this file only. */
#define portTIMER_INT_NUMBER 0x08
/* Setup hardware for required tick interrupt rate. */
static void prvSetTickFrequency( unsigned long ulTickRateHz );
/* Restore hardware to as it was prior to starting the scheduler. */
static void prvExitFunction( void );
/* Either chain to the DOS tick (which itself clears the PIC) or clear the PIC
directly. We chain to the DOS tick as close as possible to the standard DOS
tick rate. */
static void prvPortResetPIC( void );
/* The ISR used depends on whether the preemptive or cooperative
scheduler is being used. */
#if( configUSE_PREEMPTION == 1 )
/* Tick service routine used by the scheduler when preemptive scheduling is
being used. */
static void __interrupt __far prvPreemptiveTick( void );
#else
/* Tick service routine used by the scheduler when cooperative scheduling is
being used. */
static void __interrupt __far prvNonPreemptiveTick( void );
#endif
/* Trap routine used by taskYIELD() to manually cause a context switch. */
static void __interrupt __far prvYieldProcessor( void );
/* Set the tick frequency back so the floppy drive works correctly when the
scheduler exits. */
static void prvSetTickFrequencyDefault( void );
/*lint -e956 File scopes necessary here. */
/* Used to signal when to chain to the DOS tick, and when to just clear the PIC ourselves. */
static short sDOSTickCounter;
/* Set true when the vectors are set so the scheduler will service the tick. */
static portBASE_TYPE xSchedulerRunning = pdFALSE;
/* Points to the original routine installed on the vector we use for manual context switches. This is then used to restore the original routine during prvExitFunction(). */
static void ( __interrupt __far *pxOldSwitchISR )();
/* Points to the original routine installed on the vector we use to chain to the DOS tick. This is then used to restore the original routine during prvExitFunction(). */
static void ( __interrupt __far *pxOldSwitchISRPlus1 )();
/* Used to restore the original DOS context when the scheduler is ended. */
static jmp_buf xJumpBuf;
/*lint +e956 */
/*-----------------------------------------------------------*/
portBASE_TYPE xPortStartScheduler( void )
{
pxISR pxOriginalTickISR;
/* This is called with interrupts already disabled. */
/* Remember what was on the interrupts we are going to use
so we can put them back later if required. */
pxOldSwitchISR = _dos_getvect( portSWITCH_INT_NUMBER );
pxOriginalTickISR = _dos_getvect( portTIMER_INT_NUMBER );
pxOldSwitchISRPlus1 = _dos_getvect( portSWITCH_INT_NUMBER + 1 );
prvSetTickFrequency( configTICK_RATE_HZ );
/* Put our manual switch (yield) function on a known
vector. */
_dos_setvect( portSWITCH_INT_NUMBER, prvYieldProcessor );
/* Put the old tick on a different interrupt number so we can
call it when we want. */
_dos_setvect( portSWITCH_INT_NUMBER + 1, pxOriginalTickISR );
/* The ISR used depends on whether the preemptive or cooperative
scheduler is being used. */
#if( configUSE_PREEMPTION == 1 )
{
/* Put our tick switch function on the timer interrupt. */
_dos_setvect( portTIMER_INT_NUMBER, prvPreemptiveTick );
}
#else
{
/* We want the timer interrupt to just increment the tick count. */
_dos_setvect( portTIMER_INT_NUMBER, prvNonPreemptiveTick );
}
#endif
/* Setup a counter that is used to call the DOS interrupt as close
to it's original frequency as can be achieved given our chosen tick
frequency. */
sDOSTickCounter = portTICKS_PER_DOS_TICK;
/* Clean up function if we want to return to DOS. */
if( setjmp( xJumpBuf ) != 0 )
{
prvExitFunction();
xSchedulerRunning = pdFALSE;
}
else
{
xSchedulerRunning = pdTRUE;
/* Kick off the scheduler by setting up the context of the first task. */
portFIRST_CONTEXT();
}
return xSchedulerRunning;
}
/*-----------------------------------------------------------*/
/* The ISR used depends on whether the preemptive or cooperative
scheduler is being used. */
#if( configUSE_PREEMPTION == 1 )
static void __interrupt __far prvPreemptiveTick( void )
{
/* Get the scheduler to update the task states following the tick. */
vTaskIncrementTick();
/* Switch in the context of the next task to be run. */
portSWITCH_CONTEXT();
/* Reset the PIC ready for the next time. */
prvPortResetPIC();
}
#else
static void __interrupt __far prvNonPreemptiveTick( void )
{
/* Same as preemptive tick, but the cooperative scheduler is being used
so we don't have to switch in the context of the next task. */
vTaskIncrementTick();
prvPortResetPIC();
}
#endif
/*-----------------------------------------------------------*/
static void __interrupt __far prvYieldProcessor( void )
{
/* Switch in the context of the next task to be run. */
portSWITCH_CONTEXT();
}
/*-----------------------------------------------------------*/
static void prvPortResetPIC( void )
{
/* We are going to call the DOS tick interrupt at as close a
frequency to the normal DOS tick as possible. */
/* WE SHOULD NOT DO THIS IF YIELD WAS CALLED. */
--sDOSTickCounter;
if( sDOSTickCounter <= 0 )
{
sDOSTickCounter = ( short ) portTICKS_PER_DOS_TICK;
__asm{ int portSWITCH_INT_NUMBER + 1 };
}
else
{
/* Reset the PIC as the DOS tick is not being called to
do it. */
__asm
{
mov al, 20H
out 20H, al
};
}
}
/*-----------------------------------------------------------*/
void vPortEndScheduler( void )
{
/* Jump back to the processor state prior to starting the
scheduler. This means we are not going to be using a
task stack frame so the task can be deleted. */
longjmp( xJumpBuf, 1 );
}
/*-----------------------------------------------------------*/
static void prvExitFunction( void )
{
void ( __interrupt __far *pxOriginalTickISR )();
/* Interrupts should be disabled here anyway - but no
harm in making sure. */
portDISABLE_INTERRUPTS();
if( xSchedulerRunning == pdTRUE )
{
/* Set the DOS tick back onto the timer ticker. */
pxOriginalTickISR = _dos_getvect( portSWITCH_INT_NUMBER + 1 );
_dos_setvect( portTIMER_INT_NUMBER, pxOriginalTickISR );
prvSetTickFrequencyDefault();
/* Put back the switch interrupt routines that was in place
before the scheduler started. */
_dos_setvect( portSWITCH_INT_NUMBER, pxOldSwitchISR );
_dos_setvect( portSWITCH_INT_NUMBER + 1, pxOldSwitchISRPlus1 );
}
/* The tick timer is back how DOS wants it. We can re-enable
interrupts without the scheduler being called. */
portENABLE_INTERRUPTS();
}
/*-----------------------------------------------------------*/
static void prvSetTickFrequency( unsigned long ulTickRateHz )
{
const unsigned short usPIT_MODE = ( unsigned short ) 0x43;
const unsigned short usPIT0 = ( unsigned short ) 0x40;
const unsigned long ulPIT_CONST = ( unsigned long ) 1193180UL;
const unsigned short us8254_CTR0_MODE3 = ( unsigned short ) 0x36;
unsigned long ulOutput;
/* Setup the 8245 to tick at the wanted frequency. */
portOUTPUT_BYTE( usPIT_MODE, us8254_CTR0_MODE3 );
ulOutput = ulPIT_CONST / ulTickRateHz;
portOUTPUT_BYTE( usPIT0, ( unsigned short )( ulOutput & ( unsigned long ) 0xff ) );
ulOutput >>= 8;
portOUTPUT_BYTE( usPIT0, ( unsigned short ) ( ulOutput & ( unsigned long ) 0xff ) );
}
/*-----------------------------------------------------------*/
static void prvSetTickFrequencyDefault( void )
{
const unsigned short usPIT_MODE = ( unsigned short ) 0x43;
const unsigned short usPIT0 = ( unsigned short ) 0x40;
const unsigned short us8254_CTR0_MODE3 = ( unsigned short ) 0x36;
portOUTPUT_BYTE( usPIT_MODE, us8254_CTR0_MODE3 );
portOUTPUT_BYTE( usPIT0,0 );
portOUTPUT_BYTE( usPIT0,0 );
}
/*lint +e950 */
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