/*
FreeRTOS . org V5 .1 .1 - Copyright ( C ) 2003 - 2008 Richard Barry .
This file is part of the FreeRTOS . org distribution .
FreeRTOS . org is free software ; you can redistribute it and / or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation ; either version 2 of the License , or
( at your option ) any later version .
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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
along with FreeRTOS . org ; if not , write to the Free Software
Foundation , Inc . , 59 Temple Place , Suite 330 , Boston , MA 02111 - 1307 USA
A special exception to the GPL can be applied should you wish to distribute
a combined work that includes FreeRTOS . org , without being obliged to provide
the source code for any proprietary components . See the licensing section
of http : //www.FreeRTOS.org for full details of how and when the exception
can be applied .
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* *
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Please ensure to read the configuration and relevant port sections of the
online documentation .
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*/
/*
Changes from V1 .00 :
+ Call to taskYIELD ( ) from within tick ISR has been replaced by the more
efficient portSWITCH_CONTEXT ( ) .
+ ISR function definitions renamed to include the prv prefix .
Changes from V1 .2 .0 :
+ portRESET_PIC ( ) is now called last thing before the end of the preemptive
tick routine .
Changes from V2 .6 .1
+ Replaced the sUsingPreemption variable with the configUSE_PREEMPTION
macro to be consistent with the later ports .
*/
/*-----------------------------------------------------------
* Implementation of functions defined in portable . h for the Flashlite 186
* port .
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
# include <stdlib.h>
# include <i86.h>
# include <dos.h>
# include <setjmp.h>
# include "FreeRTOS.h"
# include "task.h"
# include "portasm.h"
/*lint -e950 Non ANSI reserved words okay in this file only. */
# define portTIMER_EOI_TYPE ( 8 )
# define portRESET_PIC() portOUTPUT_WORD( ( unsigned portSHORT ) 0xff22, portTIMER_EOI_TYPE )
# define portTIMER_INT_NUMBER 0x12
# define portTIMER_1_CONTROL_REGISTER ( ( unsigned portSHORT ) 0xff5e )
# define portTIMER_0_CONTROL_REGISTER ( ( unsigned portSHORT ) 0xff56 )
# define portTIMER_INTERRUPT_ENABLE ( ( unsigned portSHORT ) 0x2000 )
/* Setup the hardware to generate the required tick frequency. */
static void prvSetTickFrequency ( unsigned portLONG ulTickRateHz ) ;
/* Set the hardware back to the state as per before the scheduler started. */
static void prvExitFunction ( void ) ;
# 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 ) ;
/*lint -e956 File scopes necessary here. */
/* Set true when the vectors are set so the scheduler will service the tick. */
static portSHORT sSchedulerRunning = 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 ) ( ) ;
/* Used to restore the original DOS context when the scheduler is ended. */
static jmp_buf xJumpBuf ;
/*lint +e956 */
/*-----------------------------------------------------------*/
portBASE_TYPE xPortStartScheduler ( void )
{
/* 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 ) ;
/* Put our manual switch (yield) function on a known
vector . */
_dos_setvect ( portSWITCH_INT_NUMBER , prvYieldProcessor ) ;
# 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
prvSetTickFrequency ( configTICK_RATE_HZ ) ;
/* Clean up function if we want to return to DOS. */
if ( setjmp ( xJumpBuf ) ! = 0 )
{
prvExitFunction ( ) ;
sSchedulerRunning = pdFALSE ;
}
else
{
sSchedulerRunning = pdTRUE ;
/* Kick off the scheduler by setting up the context of the first task. */
portFIRST_CONTEXT ( ) ;
}
return sSchedulerRunning ;
}
/*-----------------------------------------------------------*/
/* The tick ISR used depend on whether or not the preemptive or cooperative
kernel 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. */
portRESET_PIC ( ) ;
}
# 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 ( ) ;
portRESET_PIC ( ) ;
}
# endif
/*-----------------------------------------------------------*/
static void __interrupt __far prvYieldProcessor ( void )
{
/* Switch in the context of the next task to be run. */
portSWITCH_CONTEXT ( ) ;
}
/*-----------------------------------------------------------*/
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 )
{
const unsigned portSHORT usTimerDisable = 0x0000 ;
unsigned portSHORT usTimer0Control ;
/* Interrupts should be disabled here anyway - but no
harm in making sure . */
portDISABLE_INTERRUPTS ( ) ;
if ( sSchedulerRunning = = pdTRUE )
{
/* Put back the switch interrupt routines that was in place
before the scheduler started . */
_dos_setvect ( portSWITCH_INT_NUMBER , pxOldSwitchISR ) ;
}
/* Disable the timer used for the tick to ensure the scheduler is
not called before restoring interrupts . There was previously nothing
on this timer so there is no old ISR to restore . */
portOUTPUT_WORD ( portTIMER_1_CONTROL_REGISTER , usTimerDisable ) ;
/* Restart the DOS tick. */
usTimer0Control = portINPUT_WORD ( portTIMER_0_CONTROL_REGISTER ) ;
usTimer0Control | = portTIMER_INTERRUPT_ENABLE ;
portOUTPUT_WORD ( portTIMER_0_CONTROL_REGISTER , usTimer0Control ) ;
portENABLE_INTERRUPTS ( ) ;
/* This will free up all the memory used by the scheduler.
exiting back to dos with INT21 AH = 4 CH will do this anyway so
it is not necessary to call this . */
vTaskCleanUpResources ( ) ;
}
/*-----------------------------------------------------------*/
static void prvSetTickFrequency ( unsigned portLONG ulTickRateHz )
{
const unsigned portSHORT usMaxCountRegister = 0xff5a ;
const unsigned portSHORT usTimerPriorityRegister = 0xff32 ;
const unsigned portSHORT usTimerEnable = 0xC000 ;
const unsigned portSHORT usRetrigger = 0x0001 ;
const unsigned portSHORT usTimerHighPriority = 0x0000 ;
unsigned portSHORT usTimer0Control ;
/* ( CPU frequency / 4 ) / clock 2 max count [inpw( 0xff62 ) = 7] */
const unsigned portLONG ulClockFrequency = 0x7f31a0 ;
unsigned portLONG ulTimerCount = ulClockFrequency / ulTickRateHz ;
portOUTPUT_WORD ( portTIMER_1_CONTROL_REGISTER , usTimerEnable | portTIMER_INTERRUPT_ENABLE | usRetrigger ) ;
portOUTPUT_WORD ( usMaxCountRegister , ( unsigned portSHORT ) ulTimerCount ) ;
portOUTPUT_WORD ( usTimerPriorityRegister , usTimerHighPriority ) ;
/* Stop the DOS tick - don't do this if you want to maintain a TOD clock. */
usTimer0Control = portINPUT_WORD ( portTIMER_0_CONTROL_REGISTER ) ;
usTimer0Control & = ~ portTIMER_INTERRUPT_ENABLE ;
portOUTPUT_WORD ( portTIMER_0_CONTROL_REGISTER , usTimer0Control ) ;
}
/*lint +e950 */
