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jeremybenn |
;/*
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; FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.
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;
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; ***************************************************************************
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; * *
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; * If you are: *
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; * *
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; * + New to FreeRTOS, *
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; * + Wanting to learn FreeRTOS or multitasking in general quickly *
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; * + Looking for basic training, *
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; * + Wanting to improve your FreeRTOS skills and productivity *
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; * *
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; * then take a look at the FreeRTOS books - available as PDF or paperback *
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; * *
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; * "Using the FreeRTOS Real Time Kernel - a Practical Guide" *
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; * http://www.FreeRTOS.org/Documentation *
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; * *
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; * A pdf reference manual is also available. Both are usually delivered *
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; * to your inbox within 20 minutes to two hours when purchased between 8am *
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; * and 8pm GMT (although please allow up to 24 hours in case of *
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; * exceptional circumstances). Thank you for your support! *
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; * *
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; ***************************************************************************
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;
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; This file is part of the FreeRTOS distribution.
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;
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; FreeRTOS is free software; you can redistribute it and/or modify it under
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; the terms of the GNU General Public License (version 2) as published by the
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; Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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; ***NOTE*** The exception to the GPL is included to allow you to distribute
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; a combined work that includes FreeRTOS without being obliged to provide the
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; source code for proprietary components outside of the FreeRTOS kernel.
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; FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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; FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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; more details. You should have received a copy of the GNU General Public
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; License and the FreeRTOS license exception along with FreeRTOS; if not it
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; can be viewed here: http://www.freertos.org/a00114.html and also obtained
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; by writing to Richard Barry, contact details for whom are available on the
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; FreeRTOS WEB site.
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;
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; 1 tab == 4 spaces!
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;
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; http://www.FreeRTOS.org - Documentation, latest information, license and
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; contact details.
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;
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; http://www.SafeRTOS.com - A version that is certified for use in safety
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; critical systems.
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;
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; http://www.OpenRTOS.com - Commercial support, development, porting,
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; licensing and training services.
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;*/
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#include
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; Declare all extern symbols here - including any ISRs that are referenced in
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; the vector table.
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; ISR functions
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; -------------
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EXTERN SIG_OUTPUT_COMPARE1A
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EXTERN SIG_UART_RECV
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EXTERN SIG_UART_DATA
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; Functions used by scheduler
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; ---------------------------
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EXTERN vTaskSwitchContext
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EXTERN pxCurrentTCB
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EXTERN vTaskIncrementTick
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EXTERN uxCriticalNesting
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; Functions implemented in this file
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; ----------------------------------
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PUBLIC vPortYield
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PUBLIC vPortYieldFromTick
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PUBLIC vPortStart
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; Interrupt vector table.
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; -----------------------
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;
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; For simplicity the RTOS tick interrupt routine uses the __task keyword.
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; As the IAR compiler does not permit a function to be declared using both
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; __task and __interrupt, the use of __task necessitates that the interrupt
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; vector table be setup manually.
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;
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; To write an ISR, implement the ISR function using the __interrupt keyword
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; but do not install the interrupt using the "#pragma vector=ABC" method.
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; Instead manually place the name of the ISR in the vector table using an
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; ORG and jmp instruction as demonstrated below.
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; You will also have to add an EXTERN statement at the top of the file.
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ASEG
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ORG TIMER1_COMPA_vect ; Vector address
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jmp SIG_OUTPUT_COMPARE1A ; ISR
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ORG USART_RXC_vect ; Vector address
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jmp SIG_UART_RECV ; ISR
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ORG USART_UDRE_vect ; Vector address
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jmp SIG_UART_DATA ; ISR
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RSEG CODE
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; Saving and Restoring a Task Context and Task Switching
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; ------------------------------------------------------
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;
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; The IAR compiler does not fully support inline assembler, so saving and
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; restoring a task context has to be written in an asm file.
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;
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; vPortYield() and vPortYieldFromTick() are usually written in C. Doing
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; so in this case would required calls to be made to portSAVE_CONTEXT() and
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; portRESTORE_CONTEXT(). This is dis-advantageous as the context switch
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; function would require two extra jump and return instructions over the
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; WinAVR equivalent.
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;
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; To avoid this I have opted to implement both vPortYield() and
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; vPortYieldFromTick() in this assembly file. For convenience
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; portSAVE_CONTEXT and portRESTORE_CONTEXT are implemented as macros.
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portSAVE_CONTEXT MACRO
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st -y, r0 ; First save the r0 register - we need to use this.
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in r0, SREG ; Obtain the SREG value so we can disable interrupts...
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cli ; ... as soon as possible.
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st -y, r0 ; Store the SREG as it was before we disabled interrupts.
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in r0, SPL ; Next store the hardware stack pointer. The IAR...
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st -y, r0 ; ... compiler uses the hardware stack as a call stack ...
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in r0, SPH ; ... only.
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st -y, r0
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st -y, r1 ; Now store the rest of the registers. Dont store the ...
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st -y, r2 ; ... the Y register here as it is used as the software
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st -y, r3 ; stack pointer and will get saved into the TCB.
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st -y, r4
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st -y, r5
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st -y, r6
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st -y, r7
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st -y, r8
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st -y, r9
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st -y, r10
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st -y, r11
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st -y, r12
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st -y, r13
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st -y, r14
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st -y, r15
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st -y, r16
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st -y, r17
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st -y, r18
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st -y, r19
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st -y, r20
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st -y, r21
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st -y, r22
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st -y, r23
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st -y, r24
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st -y, r25
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st -y, r26
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st -y, r27
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st -y, r30
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st -y, r31
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lds r0, uxCriticalNesting
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st -y, r0 ; Store the critical nesting counter.
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lds r26, pxCurrentTCB ; Finally save the software stack pointer (Y ...
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lds r27, pxCurrentTCB + 1 ; ... register) into the TCB.
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st x+, r28
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st x+, r29
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ENDM
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portRESTORE_CONTEXT MACRO
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lds r26, pxCurrentTCB
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lds r27, pxCurrentTCB + 1 ; Restore the software stack pointer from ...
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ld r28, x+ ; the TCB into the software stack pointer (...
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ld r29, x+ ; ... the Y register).
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ld r0, y+
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sts uxCriticalNesting, r0
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ld r31, y+ ; Restore the registers down to R0. The Y
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ld r30, y+ ; register is missing from this list as it
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ld r27, y+ ; has already been restored.
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ld r26, y+
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ld r25, y+
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ld r24, y+
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ld r23, y+
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ld r22, y+
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ld r21, y+
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ld r20, y+
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ld r19, y+
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ld r18, y+
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ld r17, y+
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ld r16, y+
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ld r15, y+
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ld r14, y+
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ld r13, y+
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ld r12, y+
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ld r11, y+
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ld r10, y+
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ld r9, y+
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ld r8, y+
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ld r7, y+
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ld r6, y+
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ld r5, y+
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ld r4, y+
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ld r3, y+
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ld r2, y+
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ld r1, y+
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ld r0, y+ ; The next thing on the stack is the ...
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out SPH, r0 ; ... hardware stack pointer.
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ld r0, y+
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out SPL, r0
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ld r0, y+ ; Next there is the SREG register.
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out SREG, r0
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ld r0, y+ ; Finally we have finished with r0, so restore r0.
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ENDM
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; vPortYield() and vPortYieldFromTick()
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; -------------------------------------
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;
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; Manual and preemptive context switch functions respectively.
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; The IAR compiler does not fully support inline assembler,
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; so these are implemented here rather than the more usually
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; place of within port.c.
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vPortYield:
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portSAVE_CONTEXT ; Save the context of the current task.
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call vTaskSwitchContext ; Call the scheduler.
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portRESTORE_CONTEXT ; Restore the context of whichever task the ...
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ret ; ... scheduler decided should run.
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vPortYieldFromTick:
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portSAVE_CONTEXT ; Save the context of the current task.
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call vTaskIncrementTick ; Call the timer tick function.
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call vTaskSwitchContext ; Call the scheduler.
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portRESTORE_CONTEXT ; Restore the context of whichever task the ...
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ret ; ... scheduler decided should run.
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; vPortStart()
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; ------------
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;
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; Again due to the lack of inline assembler, this is required
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; to get access to the portRESTORE_CONTEXT macro.
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vPortStart:
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portRESTORE_CONTEXT
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ret
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; Just a filler for unused interrupt vectors.
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vNoISR:
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reti
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END
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