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/*

    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.

    ***************************************************************************

    *                                                                         *

    * If you are:                                                             *

    *                                                                         *

    *    + New to FreeRTOS,                                                   *

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    *                                                                         *

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    *                                                                         *

    *        "Using the FreeRTOS Real Time Kernel - a Practical Guide"        *

    *                  http://www.FreeRTOS.org/Documentation                  *

    *                                                                         *

    * A pdf reference manual is also available.  Both are usually delivered   *

    * to your inbox within 20 minutes to two hours when purchased between 8am *

    * and 8pm GMT (although please allow up to 24 hours in case of            *

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    *                                                                         *

    ***************************************************************************

    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 exception 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!

    http://www.FreeRTOS.org - Documentation, latest information, license and

    contact details.

    http://www.SafeRTOS.com - A version that is certified for use in safety

    critical systems.

    http://www.OpenRTOS.com - Commercial support, development, porting,

    licensing and training services.

*/

/*-----------------------------------------------------------

 * Implementation of functions defined in portable.h for the Tern EE 186

 * port.

 *----------------------------------------------------------*/

/* Library includes. */

#include <embedded.h>

#include <ae.h>

/* Scheduler includes. */

#include "FreeRTOS.h"

#include "task.h"

#include "portasm.h"

/* The timer increments every four clocks, hence the divide by 4. */

#define portTIMER_COMPARE ( unsigned short ) ( ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) / ( unsigned long ) 4 )

/* From the RDC data sheet. */

#define portENABLE_TIMER_AND_INTERRUPT ( unsigned short ) 0xe001

/* Interrupt control. */

#define portEIO_REGISTER 0xff22

#define portCLEAR_INTERRUPT 0x0008

/* Setup the hardware to generate the required tick frequency. */

static void prvSetupTimerInterrupt( 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 );

/* The timer initialisation functions leave interrupts enabled,

which is not what we want.  This ISR is installed temporarily in case

the timer fires before we get a change to disable interrupts again. */

static void __interrupt __far prvDummyISR( void );

/*-----------------------------------------------------------*/

/* See header file for description. */

portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )

{

portSTACK_TYPE DS_Reg = 0;

        /* Place a few bytes of known values on the bottom of the stack.

        This is just useful for debugging. */

        *pxTopOfStack = 0x1111;

        pxTopOfStack--;

        *pxTopOfStack = 0x2222;

        pxTopOfStack--;

        *pxTopOfStack = 0x3333;

        pxTopOfStack--;

        /* We are going to start the scheduler using a return from interrupt

        instruction to load the program counter, so first there would be the

        function call with parameters preamble. */

        *pxTopOfStack = FP_SEG( pvParameters );

        pxTopOfStack--;

        *pxTopOfStack = FP_OFF( pvParameters );

        pxTopOfStack--;

        *pxTopOfStack = FP_SEG( pxCode );

        pxTopOfStack--;

        *pxTopOfStack = FP_OFF( pxCode );

        pxTopOfStack--;

        /* Next the status register and interrupt return address. */

        *pxTopOfStack = portINITIAL_SW;

        pxTopOfStack--;

        *pxTopOfStack = FP_SEG( pxCode );

        pxTopOfStack--;

        *pxTopOfStack = FP_OFF( pxCode );

        pxTopOfStack--;

        /* The remaining registers would be pushed on the stack by our context

        switch function.  These are loaded with values simply to make debugging

        easier. */

        *pxTopOfStack = ( portSTACK_TYPE ) 0xAAAA;      /* AX */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xBBBB;      /* BX */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xCCCC;      /* CX */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xDDDD;      /* DX */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xEEEE;      /* ES */

        pxTopOfStack--;

        /* We need the true data segment. */

        __asm{  MOV DS_Reg, DS };

        *pxTopOfStack = DS_Reg;                                         /* DS */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x0123;      /* SI */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xDDDD;      /* DI */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xBBBB;      /* BP */

        return pxTopOfStack;

}

/*-----------------------------------------------------------*/

portBASE_TYPE xPortStartScheduler( void )

{

        /* This is called with interrupts already disabled. */

        /* Put our manual switch (yield) function on a known

        vector. */

        setvect( portSWITCH_INT_NUMBER, prvYieldProcessor );

        /* Setup the tick interrupt. */

        prvSetupTimerInterrupt();

        /* Kick off the scheduler by setting up the context of the first task. */

        portFIRST_CONTEXT();

        /* Should not get here! */

        return pdFALSE;

}

/*-----------------------------------------------------------*/

static void __interrupt __far prvDummyISR( void )

{

        /* The timer initialisation functions leave interrupts enabled,

        which is not what we want.  This ISR is installed temporarily in case

        the timer fires before we get a change to disable interrupts again. */

        outport( portEIO_REGISTER, portCLEAR_INTERRUPT );

}

/*-----------------------------------------------------------*/

/* 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 interrupt. */

                outport( portEIO_REGISTER, portCLEAR_INTERRUPT );

        }

#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();

                /* Reset interrupt. */

                outport( portEIO_REGISTER, portCLEAR_INTERRUPT );

        }

#endif

/*-----------------------------------------------------------*/

static void __interrupt __far prvYieldProcessor( void )

{

        /* Switch in the context of the next task to be run. */

        portSWITCH_CONTEXT();

}

/*-----------------------------------------------------------*/

void vPortEndScheduler( void )

{

        /* Not implemented. */

}

/*-----------------------------------------------------------*/

static void prvSetupTimerInterrupt( void )

{

const unsigned short usTimerACompare = portTIMER_COMPARE, usTimerAMode = portENABLE_TIMER_AND_INTERRUPT;

const unsigned short usT2_IRQ = 0x13;

        /* Configure the timer, the dummy handler is used here as the init

        function leaves interrupts enabled. */

        t2_init( usTimerAMode, usTimerACompare, prvDummyISR );

        /* Disable interrupts again before installing the real handlers. */

        portDISABLE_INTERRUPTS();

        #if( configUSE_PREEMPTION == 1 )

                /* Tick service routine used by the scheduler when preemptive scheduling is

                being used. */

                setvect( usT2_IRQ, prvPreemptiveTick );

        #else

                /* Tick service routine used by the scheduler when cooperative scheduling is

                being used. */

                setvect( usT2_IRQ, prvNonPreemptiveTick );

        #endif

}