port.c

freemodbus-v1-1-1-0.zip v1.1.1版本的代码 支持多个平台

/*
    FreeRTOS V4.1.1 - Copyright (C) 2003-2005 Richard Barry.
    Modification for STR71X/GCC -  Copyright (C) 2006 Christian Walter.

    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 as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    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
    along with FreeRTOS; 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, 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.

    ***************************************************************************
    See http://www.FreeRTOS.org for documentation, latest information, license 
    and contact details.  Please ensure to read the configuration and relevant 
    port sections of the online documentation.
    ***************************************************************************
*/

/* ----------------------- Standard includes --------------------------------*/
#include <stdlib.h>

/* ----------------------- FreeRTOS includes --------------------------------*/
#include "FreeRTOS.h"
#include "task.h"

/* ----------------------- System includes ----------------------------------*/
#include "eic.h"
#include "wdg.h"

#define portINITIAL_SPSR        ( ( portSTACK_TYPE ) 0x1f )     /* System mode, ARM mode, interrupts enabled. */
#define portTHUMB_MODE_BIT      ( ( portSTACK_TYPE ) 0x20 )
#define portINSTRUCTION_SIZE    ( ( portSTACK_TYPE ) 4 )
#define portNO_CRITICAL_SECTION_NESTING \
  ( ( portSTACK_TYPE ) 0 )

/* ----------------------- Prototypes ---------------------------------------*/

/* Setup the timer to generate the tick interrupts. */
static void     prvSetupTimerInterrupt( void );

/* The scheduler can only be started from ARM mode, so 
 * vPortISRStartFirstSTask() is defined in portISR.c. 
 */
extern void     vPortISRStartFirstTask( void );

/* ----------------------- Start Implementation -----------------------------*/
/* 
 * Initialise the stack of a task to look exactly as if a call to 
 * portSAVE_CONTEXT had been called.
 *
 * See header file for description. 
 */
portSTACK_TYPE *
pxPortInitialiseStack( portSTACK_TYPE * pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
    portSTACK_TYPE *pxOriginalTOS;

    pxOriginalTOS = pxTopOfStack;

    /* Setup the initial stack of the task.  The stack is set exactly as 
     * expected by the portRESTORE_CONTEXT() macro. 
     */

    /* First on the stack is the return address - which in this case is the
     * start of the task.  The offset is added to make the return address appear
     * as it would within an IRQ ISR. 
     */
    *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;
    pxTopOfStack--;

    *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa;      /* R14 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS;   /* Stack used when task starts goes in R13. */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212;      /* R12 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111;      /* R11 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010;      /* R10 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909;      /* R9 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808;      /* R8 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707;      /* R7 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606;      /* R6 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505;      /* R5 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404;      /* R4 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303;      /* R3 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202;      /* R2 */
    pxTopOfStack--;
    *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101;      /* R1 */
    pxTopOfStack--;

    /* When the task starts is will expect to find the function parameter in
     * R0. 
     */
    *pxTopOfStack = ( portSTACK_TYPE ) pvParameters;    /* R0 */
    pxTopOfStack--;

    /* The last thing onto the stack is the status register, which is set for
     * system mode, with interrupts enabled. 
     */
    *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;

#ifdef THUMB_INTERWORK
    {
        /* We want the task to start in thumb mode. */
        *pxTopOfStack |= portTHUMB_MODE_BIT;
    }
#endif

    pxTopOfStack--;

    /* Some optimisation levels use the stack differently to others.  This 
     * means the interrupt flags cannot always be stored on the stack and will
     * instead be stored in a variable, which is then saved as part of the
     * tasks context. 
     */
    *pxTopOfStack = portNO_CRITICAL_SECTION_NESTING;

    return pxTopOfStack;
}

portBASE_TYPE
xPortStartScheduler( void )
{
    /* Start the timer that generates the tick ISR.  Interrupts are disabled
       here already. */
    prvSetupTimerInterrupt(  );

    /* Start the first task. */
    vPortISRStartFirstTask(  );

    /* Should not get here! */
    return 0;
}

void
vPortEndScheduler( void )
{
    /* It is unlikely that the ARM port will require this function as there
       is nothing to return to.  */
}

/* 
 * Setup timer 3 to generate ticks at the required frequency.
 */
static void
prvSetupTimerInterrupt( void )
{
    /* Set the watchdog up to generate a periodic tick. */
    WDG_ECITConfig( DISABLE );
    WDG_CntOnOffConfig( DISABLE );
    WDG_PeriodValueConfig( configTICK_RATE_HZ );

    /* Setup the tick interrupt in the EIC. */
    EIC_IRQChannelPriorityConfig( WDG_IRQChannel, 1 );
    EIC_IRQChannelConfig( WDG_IRQChannel, ENABLE );
    EIC_IRQConfig( ENABLE );
    WDG_ECITConfig( ENABLE );

    /* Start the timer - interrupts are actually disabled at this point so
       it is safe to do this here. */
    WDG_CntOnOffConfig( ENABLE );
}