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/*
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
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.
*/
/*
Changes from V1.00:
+ pxPortInitialiseStack() now initialises the stack of new tasks to the
same format used by the compiler. This allows the compiler generated
interrupt mechanism to be used for context switches.
Changes from V2.4.2:
+ pvPortMalloc and vPortFree have been removed. The projects now use
the definitions from the source/portable/MemMang directory.
Changes from V2.6.1:
+ usPortCheckFreeStackSpace() has been moved to tasks.c.
*/
#include <stdlib.h>
#include "FreeRTOS.h"
/*-----------------------------------------------------------*/
/* See header file for description. */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
portSTACK_TYPE DS_Reg = 0, *pxOriginalSP;
/* 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--;
*pxTopOfStack = 0x4444;
pxTopOfStack--;
*pxTopOfStack = 0x5555;
pxTopOfStack--;
/*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
/* We are going to start the scheduler using a return from interrupt
instruction to load the program counter, so first there would be the
status register and interrupt return address. We make this the start
of the task. */
*pxTopOfStack = portINITIAL_SW;
pxTopOfStack--;
*pxTopOfStack = FP_SEG( pxCode );
pxTopOfStack--;
*pxTopOfStack = FP_OFF( pxCode );
pxTopOfStack--;
/* We are going to setup the stack for the new task to look like
the stack frame was setup by a compiler generated ISR. We need to know
the address of the existing stack top to place in the SP register within
the stack frame. pxOriginalSP holds SP before (simulated) pusha was
called. */
pxOriginalSP = 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 = FP_OFF( pvParameters ); /* AX */
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xCCCC; /* CX */
pxTopOfStack--;
*pxTopOfStack = FP_SEG( pvParameters ); /* DX */
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xBBBB; /* BX */
pxTopOfStack--;
*pxTopOfStack = FP_OFF( pxOriginalSP ); /* SP */
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xBBBB; /* BP */
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0x0123; /* SI */
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xDDDD; /* DI */
/* We need the true data segment. */
__asm{ MOV DS_Reg, DS };
pxTopOfStack--;
*pxTopOfStack = DS_Reg; /* DS */
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xEEEE; /* ES */
/* The AX register is pushed again twice - don't know why. */
pxTopOfStack--;
*pxTopOfStack = FP_OFF( pvParameters ); /* AX */
pxTopOfStack--;
*pxTopOfStack = FP_OFF( pvParameters ); /* AX */
#ifdef DEBUG_BUILD
/* The compiler adds space to each ISR stack if building to
include debug information. Presumably this is used by the
debugger - we don't need to initialise it to anything just
make sure it is there. */
pxTopOfStack--;
#endif
/*lint +e950 +e611 +e923 */
return pxTopOfStack;
}
/*-----------------------------------------------------------*/
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