FreeRTOS/Source/portable/oWatcom/16BitDOS/common/portasm.h

/*
    FreeRTOS V7.3.0 - Copyright (C) 2012 Real Time Engineers Ltd.

    FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME.  PLEASE VISIT 
    http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    ***************************************************************************
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     *    for microcontrollers - completely free of charge!                  *
     *                                                                       *
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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 modification to the GPL is included to allow you to
    distribute a combined work that includes FreeRTOS without being obliged to
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    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.

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    ***************************************************************************
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*/

typedef void tskTCB;
extern volatile tskTCB * volatile pxCurrentTCB;
extern void vTaskSwitchContext( void );

/* 
 * Saves the stack pointer for one task into its TCB, calls 
 * vTaskSwitchContext() to update the TCB being used, then restores the stack 
 * from the new TCB read to run the task. 
 */
void portSWITCH_CONTEXT( void );

/*
 * Load the stack pointer from the TCB of the task which is going to be first
 * to execute.  Then force an IRET so the registers and IP are popped off the
 * stack.
 */
void portFIRST_CONTEXT( void );

/* There are slightly different versions depending on whether you are building
to include debugger information.  If debugger information is used then there
are a couple of extra bytes left of the ISR stack (presumably for use by the
debugger).  The true stack pointer is then stored in the bp register.  We add
2 to the stack pointer to remove the extra bytes before we restore our context. */

#ifdef DEBUG_BUILD

	#pragma aux portSWITCH_CONTEXT =	"mov	ax, seg pxCurrentTCB"														\
										"mov	ds, ax"																		\
										"les	bx, pxCurrentTCB"			/* Save the stack pointer into the TCB. */		\
										"mov	es:0x2[ bx ], ss"															\
										"mov	es:[ bx ], sp"																\
										"call	vTaskSwitchContext"			/* Perform the switch. */						\
										"mov	ax, seg pxCurrentTCB"		/* Restore the stack pointer from the TCB. */	\
										"mov	ds, ax"																		\
										"les	bx, dword ptr pxCurrentTCB"													\
										"mov	ss, es:[ bx + 2 ]"															\
										"mov	sp, es:[ bx ]"																\
										"mov	bp, sp"						/* Prepair the bp register for the restoration of the SP in the compiler generated portion of the ISR */	\
										"add	bp, 0x0002"

										

	#pragma aux portFIRST_CONTEXT =		"mov	ax, seg pxCurrentTCB"			\
										"mov	ds, ax"							\
										"les	bx, dword ptr pxCurrentTCB"		\
										"mov	ss, es:[ bx + 2 ]"				\
										"mov	sp, es:[ bx ]"					\
										"add	sp, 0x0002"						/* Remove the extra bytes that exist in debug builds before restoring the context. */ \
										"pop	ax"								\
										"pop	ax"								\
										"pop	es"								\
										"pop	ds"								\
										"popa"									\
										"iret"									
#else

	#pragma aux portSWITCH_CONTEXT =	"mov	ax, seg pxCurrentTCB"														\
										"mov	ds, ax"																		\
										"les	bx, pxCurrentTCB"			/* Save the stack pointer into the TCB. */		\
										"mov	es:0x2[ bx ], ss"															\
										"mov	es:[ bx ], sp"																\
										"call	vTaskSwitchContext"			/* Perform the switch. */						\
										"mov	ax, seg pxCurrentTCB"		/* Restore the stack pointer from the TCB. */	\
										"mov	ds, ax"																		\
										"les	bx, dword ptr pxCurrentTCB"													\
										"mov	ss, es:[ bx + 2 ]"															\
										"mov	sp, es:[ bx ]"
										

	#pragma aux portFIRST_CONTEXT =		"mov	ax, seg pxCurrentTCB"			\
										"mov	ds, ax"							\
										"les	bx, dword ptr pxCurrentTCB"		\
										"mov	ss, es:[ bx + 2 ]"				\
										"mov	sp, es:[ bx ]"					\
										"pop	ax"								\
										"pop	ax"								\
										"pop	es"								\
										"pop	ds"								\
										"popa"									\
										"iret"									
#endif