| ;/*
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| ; * FreeRTOS Kernel <DEVELOPMENT BRANCH>
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| ; * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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| ; *
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| ; * SPDX-License-Identifier: MIT |
| ; * |
| ; * Permission is hereby granted, free of charge, to any person obtaining a copy of
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| ; * this software and associated documentation files (the "Software"), to deal in
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| ; * the Software without restriction, including without limitation the rights to
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| ; * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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| ; * the Software, and to permit persons to whom the Software is furnished to do so,
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| ; * subject to the following conditions:
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| ; *
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| ; * The above copyright notice and this permission notice shall be included in all
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| ; * copies or substantial portions of the Software.
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| ; *
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| ; * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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| ; * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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| ; * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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| ; * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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| ; * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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| ; * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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| ; *
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| ; * https://www.FreeRTOS.org
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| ; * https://github.com/FreeRTOS
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| ; *
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| ; */
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|
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| INCLUDE portmacro.inc
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| IMPORT vTaskSwitchContext
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| IMPORT xTaskIncrementTick
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| EXPORT vPortYieldProcessor
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| EXPORT vPortStartFirstTask
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| EXPORT vPreemptiveTick
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| EXPORT vPortYield
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| VICVECTADDR EQU 0xFFFFF030
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| T0IR EQU 0xE0004000
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| T0MATCHBIT EQU 0x00000001
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| ARM
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| AREA PORT_ASM, CODE, READONLY
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| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| ; Starting the first task is done by just restoring the context
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| ; setup by pxPortInitialiseStack
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| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| vPortStartFirstTask
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| PRESERVE8
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| portRESTORE_CONTEXT
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| vPortYield
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| PRESERVE8
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| SVC 0
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| bx lr
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| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| ; Interrupt service routine for the SWI interrupt. The vector table is
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| ; configured in the startup.s file.
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| ;
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| ; vPortYieldProcessor() is used to manually force a context switch. The
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| ; SWI interrupt is generated by a call to taskYIELD() or portYIELD().
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| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| vPortYieldProcessor
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| PRESERVE8
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| ; Within an IRQ ISR the link register has an offset from the true return
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| ; address, but an SWI ISR does not. Add the offset manually so the same
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| ; ISR return code can be used in both cases.
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| ADD LR, LR, #4
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| ; Perform the context switch.
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| portSAVE_CONTEXT ; Save current task context
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| LDR R0, =vTaskSwitchContext ; Get the address of the context switch function
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| MOV LR, PC ; Store the return address
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| BX R0 ; Call the contedxt switch function
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| portRESTORE_CONTEXT ; restore the context of the selected task
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| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| ; Interrupt service routine for preemptive scheduler tick timer
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| ; Only used if portUSE_PREEMPTION is set to 1 in portmacro.h
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| ;
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| ; Uses timer 0 of LPC21XX Family
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| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| vPreemptiveTick
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| PRESERVE8
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| portSAVE_CONTEXT ; Save the context of the current task.
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| LDR R0, =xTaskIncrementTick ; Increment the tick count.
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| MOV LR, PC ; This may make a delayed task ready
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| BX R0 ; to run.
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| CMP R0, #0
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| BEQ SkipContextSwitch
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| LDR R0, =vTaskSwitchContext ; Find the highest priority task that
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| MOV LR, PC ; is ready to run.
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| BX R0
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| SkipContextSwitch
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| MOV R0, #T0MATCHBIT ; Clear the timer event
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| LDR R1, =T0IR
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| STR R0, [R1]
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| LDR R0, =VICVECTADDR ; Acknowledge the interrupt
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| STR R0,[R0]
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| portRESTORE_CONTEXT ; Restore the context of the highest
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| ; priority task that is ready to run.
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| END
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