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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.

;    ***NOTE*** The exception to the GPL is included to allow you to distribute

;    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