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;/*
;    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.
;
;    ***************************************************************************
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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.
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;    a combined work that includes FreeRTOS without being obliged to provide the
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;*/
 
	INCLUDE portmacro.inc
 
	IMPORT	vTaskSwitchContext
	IMPORT	vTaskIncrementTick
 
	EXPORT	vPortYieldProcessor
	EXPORT	vPortStartFirstTask
	EXPORT	vPreemptiveTick
	EXPORT	vPortYield
 
 
VICVECTADDR	EQU	0xFFFFF030
T0IR		EQU	0xE0004000
T0MATCHBIT	EQU	0x00000001
 
	ARM
	AREA	PORT_ASM, CODE, READONLY
 
 
 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Starting the first task is done by just restoring the context 
; setup by pxPortInitialiseStack
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
vPortStartFirstTask
 
	PRESERVE8
 
	portRESTORE_CONTEXT
 
vPortYield
 
	PRESERVE8
 
	SVC 0
	bx lr
 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Interrupt service routine for the SWI interrupt.  The vector table is
; configured in the startup.s file.
;
; vPortYieldProcessor() is used to manually force a context switch.  The
; SWI interrupt is generated by a call to taskYIELD() or portYIELD().
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
vPortYieldProcessor
 
	PRESERVE8
 
	; Within an IRQ ISR the link register has an offset from the true return 
	; address, but an SWI ISR does not.  Add the offset manually so the same 
	; ISR return code can be used in both cases.
	ADD	LR, LR, #4
 
	; Perform the context switch.
	portSAVE_CONTEXT					; Save current task context				
	LDR R0, =vTaskSwitchContext			; Get the address of the context switch function
	MOV LR, PC							; Store the return address
	BX	R0								; Call the contedxt switch function
	portRESTORE_CONTEXT					; restore the context of the selected task	
 
 
 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Interrupt service routine for preemptive scheduler tick timer
; Only used if portUSE_PREEMPTION is set to 1 in portmacro.h
;
; Uses timer 0 of LPC21XX Family
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;	
 
vPreemptiveTick
 
	PRESERVE8
 
	portSAVE_CONTEXT					; Save the context of the current task.	
 
	LDR R0, =vTaskIncrementTick			; Increment the tick count.  
	MOV LR, PC							; This may make a delayed task ready
	BX R0								; to run.
 
	LDR R0, =vTaskSwitchContext			; Find the highest priority task that 
	MOV LR, PC							; is ready to run.
	BX R0
 
	MOV R0, #T0MATCHBIT					; Clear the timer event
	LDR R1, =T0IR
	STR R0, [R1] 
 
	LDR	R0, =VICVECTADDR				; Acknowledge the interrupt	
	STR	R0,[R0]
 
	portRESTORE_CONTEXT					; Restore the context of the highest 
										; priority task that is ready to run.
	END