portasm.s79

超好的嵌入式操作系统学习代码

/*
	FreeRTOS.org V4.5.0 - Copyright (C) 2003-2007 Richard Barry.

	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.

	Also see http://www.SafeRTOS.com for an IEC 61508 compliant version along
	with commercial development and support options.
	***************************************************************************
*/

		RSEG ICODE:CODE
		CODE32

	EXTERN vTaskSwitchContext

	PUBLIC vPortYieldProcessor
	PUBLIC vPortStartFirstTask

#include "ISR_Support.h"

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Starting the first task is just a matter of restoring the context that
; was created by pxPortInitialiseStack().
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
vPortStartFirstTask:
	portRESTORE_CONTEXT

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Manual context switch function.  This is the SWI hander.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
vPortYieldProcessor:
	ADD		LR, LR, #4			; Add 4 to the LR to make the LR appear exactly
								; as if the context was saved during and IRQ
								; handler.
								
	portSAVE_CONTEXT			; Save the context of the current task...
	LDR R0, =vTaskSwitchContext	; before selecting the next task to execute.
	MOV     lr, pc
	BX R0
	portRESTORE_CONTEXT			; Restore the context of the selected task.

	END