/*
    FreeRTOS V7.4.1 - Copyright (C) 2013 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.

    ***************************************************************************
     *                                                                       *
     *    FreeRTOS tutorial books are available in pdf and paperback.        *
     *    Complete, revised, and edited pdf reference manuals are also       *
     *    available.                                                         *
     *                                                                       *
     *    Purchasing FreeRTOS documentation will not only help you, by       *
     *    ensuring you get running as quickly as possible and with an        *
     *    in-depth knowledge of how to use FreeRTOS, it will also help       *
     *    the FreeRTOS project to continue with its mission of providing     *
     *    professional grade, cross platform, de facto standard solutions    *
     *    for microcontrollers - completely free of charge!                  *
     *                                                                       *
     *    >>> See http://www.FreeRTOS.org/Documentation for details. <<<     *
     *                                                                       *
     *    Thank you for using FreeRTOS, and thank you for your support!      *
     *                                                                       *
    ***************************************************************************


    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
    provide the source code for proprietary components outside of the FreeRTOS
    kernel.

    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
    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 Real Time Engineers Ltd., contact details for whom are available
    on the FreeRTOS WEB site.

    1 tab == 4 spaces!

    ***************************************************************************
     *                                                                       *
     *    Having a problem?  Start by reading the FAQ "My application does   *
     *    not run, what could be wrong?"                                     *
     *                                                                       *
     *    http://www.FreeRTOS.org/FAQHelp.html                               *
     *                                                                       *
    ***************************************************************************


    http://www.FreeRTOS.org - Documentation, books, training, latest versions, 
    license and Real Time Engineers Ltd. contact details.

    http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
    including FreeRTOS+Trace - an indispensable productivity tool, and our new
    fully thread aware and reentrant UDP/IP stack.

    http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High 
    Integrity Systems, who sell the code with commercial support, 
    indemnification and middleware, under the OpenRTOS brand.
    
    http://www.SafeRTOS.com - High Integrity Systems also provide a safety 
    engineered and independently SIL3 certified version for use in safety and 
    mission critical applications that require provable dependability.
*/

#include "PriorityDefinitions.h"

	PUBLIC _prvStartFirstTask
	PUBLIC ___interrupt_27

	EXTERN _pxCurrentTCB
	EXTERN _vTaskSwitchContext

	RSEG CODE:CODE(4)

_prvStartFirstTask:

		/* When starting the scheduler there is nothing that needs moving to the
		interrupt stack because the function is not called from an interrupt.
		Just ensure the current stack is the user stack. */
		SETPSW		U

		/* Obtain the location of the stack associated with which ever task
		pxCurrentTCB is currently pointing to. */
		MOV.L		#_pxCurrentTCB, R15
		MOV.L		[R15], R15
		MOV.L		[R15], R0

		/* Restore the registers from the stack of the task pointed to by
		pxCurrentTCB. */
		POP			R15

		/* Accumulator low 32 bits. */
		MVTACLO		R15
		POP			R15

		/* Accumulator high 32 bits. */
		MVTACHI		R15
		POP			R15

		/* Floating point status word. */
		MVTC		R15, FPSW

		/* R1 to R15 - R0 is not included as it is the SP. */
		POPM		R1-R15

		/* This pops the remaining registers. */
		RTE
		NOP
		NOP

/*-----------------------------------------------------------*/

/* The software interrupt - overwrite the default 'weak' definition. */
___interrupt_27:

		/* Re-enable interrupts. */
		SETPSW		I

		/* Move the data that was automatically pushed onto the interrupt stack when
		the interrupt occurred from the interrupt stack to the user stack.

		R15 is saved before it is clobbered. */
		PUSH.L		R15

		/* Read the user stack pointer. */
		MVFC		USP, R15

		/* Move the address down to the data being moved. */
		SUB			#12, R15
		MVTC		R15, USP

		/* Copy the data across, R15, then PC, then PSW. */
		MOV.L		[ R0 ], [ R15 ]
		MOV.L 		4[ R0 ], 4[ R15 ]
		MOV.L		8[ R0 ], 8[ R15 ]

		/* Move the interrupt stack pointer to its new correct position. */
		ADD		#12, R0

		/* All the rest of the registers are saved directly to the user stack. */
		SETPSW		U

		/* Save the rest of the general registers (R15 has been saved already). */
		PUSHM		R1-R14

		/* Save the FPSW and accumulator. */
		MVFC		FPSW, R15
		PUSH.L		R15
		MVFACHI 	R15
		PUSH.L		R15

		/* Middle word. */
		MVFACMI	R15

		/* Shifted left as it is restored to the low order word. */
		SHLL		#16, R15
		PUSH.L		R15

		/* Save the stack pointer to the TCB. */
		MOV.L		#_pxCurrentTCB, R15
		MOV.L		[ R15 ], R15
		MOV.L		R0, [ R15 ]

		/* Ensure the interrupt mask is set to the syscall priority while the kernel
		structures are being accessed. */
		MVTIPL		#configMAX_SYSCALL_INTERRUPT_PRIORITY

		/* Select the next task to run. */
		BSR.A		_vTaskSwitchContext

		/* Reset the interrupt mask as no more data structure access is required. */
		MVTIPL		#configKERNEL_INTERRUPT_PRIORITY

		/* Load the stack pointer of the task that is now selected as the Running
		state task from its TCB. */
		MOV.L		#_pxCurrentTCB,R15
		MOV.L		[ R15 ], R15
		MOV.L		[ R15 ], R0

		/* Restore the context of the new task.  The PSW (Program Status Word) and
		PC will be popped by the RTE instruction. */
		POP			R15
		MVTACLO 	R15
		POP			R15
		MVTACHI 	R15
		POP			R15
		MVTC		R15, FPSW
		POPM		R1-R15
		RTE
		NOP
		NOP

/*-----------------------------------------------------------*/

		END