Source/portable/Paradigm/Tern_EE/small/port.c

/*
	FreeRTOS.org V5.2.0 - Copyright (C) 2003-2009 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 (version 2) as published
	by the Free Software Foundation and modified by the FreeRTOS exception.

	FreeRTOS.org 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 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 is included to allow you 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.


	***************************************************************************
	*                                                                         *
	* Get the FreeRTOS eBook!  See http://www.FreeRTOS.org/Documentation      *
	*                                                                         *
	* This is a concise, step by step, 'hands on' guide that describes both   *
	* general multitasking concepts and FreeRTOS specifics. It presents and   *
	* explains numerous examples that are written using the FreeRTOS API.     *
	* Full source code for all the examples is provided in an accompanying    *
	* .zip file.                                                              *
	*                                                                         *
	***************************************************************************

	1 tab == 4 spaces!

	Please ensure to read the configuration and relevant port sections of the
	online documentation.

	http://www.FreeRTOS.org - Documentation, latest information, license and
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	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 portPRESCALE_VALUE ( 16 )
#define portTIMER_COMPARE ( configCPU_CLOCK_HZ  / ( configTICK_RATE_HZ * 4UL ) )

/* From the RDC data sheet. */
#define portENABLE_TIMER_AND_INTERRUPT 	( unsigned portSHORT ) 0xe00b
#define portENABLE_TIMER				( unsigned portSHORT ) 0xC001

/* 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 );

/*-----------------------------------------------------------*/
/* See header file for description. */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
portSTACK_TYPE DS_Reg = 0;

	/* We need the true data segment. */
	__asm{	MOV DS_Reg, DS };

	/* 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_OFF( pvParameters );
	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--;

	*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;
}
/*-----------------------------------------------------------*/

/* 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. */
		portEND_SWITCHING_ISR();

		/* 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. */
	portEND_SWITCHING_ISR();
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
	/* Not implemented. */
}
/*-----------------------------------------------------------*/

static void prvSetupTimerInterrupt( void )
{
const unsigned portLONG ulCompareValue = portTIMER_COMPARE;
unsigned portSHORT usTimerCompare;

	usTimerCompare = ( unsigned portSHORT ) ( ulCompareValue >> 4 );
    t2_init( portENABLE_TIMER, portPRESCALE_VALUE, NULL );

	#if( configUSE_PREEMPTION == 1 )
		/* Tick service routine used by the scheduler when preemptive scheduling is
		being used. */
		t1_init( portENABLE_TIMER_AND_INTERRUPT, usTimerCompare, usTimerCompare, prvPreemptiveTick );
	#else
		/* Tick service routine used by the scheduler when cooperative scheduling is
		being used. */
		t1_init( portENABLE_TIMER_AND_INTERRUPT, usTimerCompare, usTimerCompare, prvNonPreemptiveTick );
	#endif
}