portable/GCC/ATMega323/port.c - third_party/github/FreeRTOS/FreeRTOS-Kernel - Git at Google

 /*
  * FreeRTOS Kernel V10.3.1
  * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of
  * this software and associated documentation files (the "Software"), to deal in
  * the Software without restriction, including without limitation the rights to
  * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
  * the Software, and to permit persons to whom the Software is furnished to do so,
  * subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in all
  * copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
  * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  *
  * http://www.FreeRTOS.org
  * http://aws.amazon.com/freertos
  *
  * 1 tab == 4 spaces!
  */

 /*

 Changes from V2.6.0

 	+ AVR port - Replaced the inb() and outb() functions with direct memory
 	  access.  This allows the port to be built with the 20050414 build of
 	  WinAVR.
 */

 #include <stdlib.h>
 #include <avr/interrupt.h>

 #include "FreeRTOS.h"
 #include "task.h"

 /*-----------------------------------------------------------
  * Implementation of functions defined in portable.h for the AVR port.
  *----------------------------------------------------------*/

 /* Start tasks with interrupts enables. */
 #define portFLAGS_INT_ENABLED					( ( StackType_t ) 0x80 )

 /* Hardware constants for timer 1. */
 #define portCLEAR_COUNTER_ON_MATCH				( ( uint8_t ) 0x08 )
 #define portPRESCALE_64							( ( uint8_t ) 0x03 )
 #define portCLOCK_PRESCALER						( ( uint32_t ) 64 )
 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE	( ( uint8_t ) 0x10 )

 /*-----------------------------------------------------------*/

 /* We require the address of the pxCurrentTCB variable, but don't want to know
 any details of its type. */
 typedef void TCB_t;
 extern volatile TCB_t * volatile pxCurrentTCB;

 /*-----------------------------------------------------------*/

 /*
  * Macro to save all the general purpose registers, the save the stack pointer
  * into the TCB.
  *
  * The first thing we do is save the flags then disable interrupts.  This is to
  * guard our stack against having a context switch interrupt after we have already
  * pushed the registers onto the stack - causing the 32 registers to be on the
  * stack twice.
  *
  * r1 is set to zero as the compiler expects it to be thus, however some
  * of the math routines make use of R1.
  *
  * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
  * so we need not worry about reading/writing to the stack pointer.
  */

 #define portSAVE_CONTEXT()									\
 	asm volatile (	"push	r0						\n\t"	\
 					"in		r0, __SREG__			\n\t"	\
 					"cli							\n\t"	\
 					"push	r0						\n\t"	\
 					"push	r1						\n\t"	\
 					"clr	r1						\n\t"	\
 					"push	r2						\n\t"	\
 					"push	r3						\n\t"	\
 					"push	r4						\n\t"	\
 					"push	r5						\n\t"	\
 					"push	r6						\n\t"	\
 					"push	r7						\n\t"	\
 					"push	r8						\n\t"	\
 					"push	r9						\n\t"	\
 					"push	r10						\n\t"	\
 					"push	r11						\n\t"	\
 					"push	r12						\n\t"	\
 					"push	r13						\n\t"	\
 					"push	r14						\n\t"	\
 					"push	r15						\n\t"	\
 					"push	r16						\n\t"	\
 					"push	r17						\n\t"	\
 					"push	r18						\n\t"	\
 					"push	r19						\n\t"	\
 					"push	r20						\n\t"	\
 					"push	r21						\n\t"	\
 					"push	r22						\n\t"	\
 					"push	r23						\n\t"	\
 					"push	r24						\n\t"	\
 					"push	r25						\n\t"	\
 					"push	r26						\n\t"	\
 					"push	r27						\n\t"	\
 					"push	r28						\n\t"	\
 					"push	r29						\n\t"	\
 					"push	r30						\n\t"	\
 					"push	r31						\n\t"	\
 					"lds	r26, pxCurrentTCB		\n\t"	\
 					"lds	r27, pxCurrentTCB + 1	\n\t"	\
 					"in		r0, 0x3d				\n\t"	\
 					"st		x+, r0					\n\t"	\
 					"in		r0, 0x3e				\n\t"	\
 					"st		x+, r0					\n\t"	\
 				);

 /*
  * Opposite to portSAVE_CONTEXT().  Interrupts will have been disabled during
  * the context save so we can write to the stack pointer.
  */

 #define portRESTORE_CONTEXT()								\
 	asm volatile (	"lds	r26, pxCurrentTCB		\n\t"	\
 					"lds	r27, pxCurrentTCB + 1	\n\t"	\
 					"ld		r28, x+					\n\t"	\
 					"out	__SP_L__, r28			\n\t"	\
 					"ld		r29, x+					\n\t"	\
 					"out	__SP_H__, r29			\n\t"	\
 					"pop	r31						\n\t"	\
 					"pop	r30						\n\t"	\
 					"pop	r29						\n\t"	\
 					"pop	r28						\n\t"	\
 					"pop	r27						\n\t"	\
 					"pop	r26						\n\t"	\
 					"pop	r25						\n\t"	\
 					"pop	r24						\n\t"	\
 					"pop	r23						\n\t"	\
 					"pop	r22						\n\t"	\
 					"pop	r21						\n\t"	\
 					"pop	r20						\n\t"	\
 					"pop	r19						\n\t"	\
 					"pop	r18						\n\t"	\
 					"pop	r17						\n\t"	\
 					"pop	r16						\n\t"	\
 					"pop	r15						\n\t"	\
 					"pop	r14						\n\t"	\
 					"pop	r13						\n\t"	\
 					"pop	r12						\n\t"	\
 					"pop	r11						\n\t"	\
 					"pop	r10						\n\t"	\
 					"pop	r9						\n\t"	\
 					"pop	r8						\n\t"	\
 					"pop	r7						\n\t"	\
 					"pop	r6						\n\t"	\
 					"pop	r5						\n\t"	\
 					"pop	r4						\n\t"	\
 					"pop	r3						\n\t"	\
 					"pop	r2						\n\t"	\
 					"pop	r1						\n\t"	\
 					"pop	r0						\n\t"	\
 					"out	__SREG__, r0			\n\t"	\
 					"pop	r0						\n\t"	\
 				);

 /*-----------------------------------------------------------*/

 /*
  * Perform hardware setup to enable ticks from timer 1, compare match A.
  */
 static void prvSetupTimerInterrupt( void );
 /*-----------------------------------------------------------*/

 /*
  * See header file for description.
  */
 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
 {
 uint16_t usAddress;

 	/* Place a few bytes of known values on the bottom of the stack.
 	This is just useful for debugging. */

 	*pxTopOfStack = 0x11;
 	pxTopOfStack--;
 	*pxTopOfStack = 0x22;
 	pxTopOfStack--;
 	*pxTopOfStack = 0x33;
 	pxTopOfStack--;

 	/* Simulate how the stack would look after a call to vPortYield() generated by
 	the compiler. */

 	/*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */

 	/* The start of the task code will be popped off the stack last, so place
 	it on first. */
 	usAddress = ( uint16_t ) pxCode;
 	*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 	pxTopOfStack--;

 	usAddress >>= 8;
 	*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 	pxTopOfStack--;

 	/* Next simulate the stack as if after a call to portSAVE_CONTEXT().
 	portSAVE_CONTEXT places the flags on the stack immediately after r0
 	to ensure the interrupts get disabled as soon as possible, and so ensuring
 	the stack use is minimal should a context switch interrupt occur. */
 	*pxTopOfStack = ( StackType_t ) 0x00;	/* R0 */
 	pxTopOfStack--;
 	*pxTopOfStack = portFLAGS_INT_ENABLED;
 	pxTopOfStack--;


 	/* Now the remaining registers.   The compiler expects R1 to be 0. */
 	*pxTopOfStack = ( StackType_t ) 0x00;	/* R1 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x02;	/* R2 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x03;	/* R3 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x04;	/* R4 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x05;	/* R5 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x06;	/* R6 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x07;	/* R7 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x08;	/* R8 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x09;	/* R9 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x10;	/* R10 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x11;	/* R11 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x12;	/* R12 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x13;	/* R13 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x14;	/* R14 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x15;	/* R15 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x16;	/* R16 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x17;	/* R17 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x18;	/* R18 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x19;	/* R19 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x20;	/* R20 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x21;	/* R21 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x22;	/* R22 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x23;	/* R23 */
 	pxTopOfStack--;

 	/* Place the parameter on the stack in the expected location. */
 	usAddress = ( uint16_t ) pvParameters;
 	*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 	pxTopOfStack--;

 	usAddress >>= 8;
 	*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 	pxTopOfStack--;

 	*pxTopOfStack = ( StackType_t ) 0x26;	/* R26 X */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x27;	/* R27 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x28;	/* R28 Y */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x29;	/* R29 */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x30;	/* R30 Z */
 	pxTopOfStack--;
 	*pxTopOfStack = ( StackType_t ) 0x031;	/* R31 */
 	pxTopOfStack--;

 	/*lint +e950 +e611 +e923 */

 	return pxTopOfStack;
 }
 /*-----------------------------------------------------------*/

 BaseType_t xPortStartScheduler( void )
 {
 	/* Setup the hardware to generate the tick. */
 	prvSetupTimerInterrupt();

 	/* Restore the context of the first task that is going to run. */
 	portRESTORE_CONTEXT();

 	/* Simulate a function call end as generated by the compiler.  We will now
 	jump to the start of the task the context of which we have just restored. */
 	asm volatile ( "ret" );

 	/* Should not get here. */
 	return pdTRUE;
 }
 /*-----------------------------------------------------------*/

 void vPortEndScheduler( void )
 {
 	/* It is unlikely that the AVR port will get stopped.  If required simply
 	disable the tick interrupt here. */
 }
 /*-----------------------------------------------------------*/

 /*
  * Manual context switch.  The first thing we do is save the registers so we
  * can use a naked attribute.
  */
 void vPortYield( void ) __attribute__ ( ( naked ) );
 void vPortYield( void )
 {
 	portSAVE_CONTEXT();
 	vTaskSwitchContext();
 	portRESTORE_CONTEXT();

 	asm volatile ( "ret" );
 }
 /*-----------------------------------------------------------*/

 /*
  * Context switch function used by the tick.  This must be identical to
  * vPortYield() from the call to vTaskSwitchContext() onwards.  The only
  * difference from vPortYield() is the tick count is incremented as the
  * call comes from the tick ISR.
  */
 void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
 void vPortYieldFromTick( void )
 {
 	portSAVE_CONTEXT();
 	if( xTaskIncrementTick() != pdFALSE )
 	{
 		vTaskSwitchContext();
 	}
 	portRESTORE_CONTEXT();

 	asm volatile ( "ret" );
 }
 /*-----------------------------------------------------------*/

 /*
  * Setup timer 1 compare match A to generate a tick interrupt.
  */
 static void prvSetupTimerInterrupt( void )
 {
 uint32_t ulCompareMatch;
 uint8_t ucHighByte, ucLowByte;

 	/* Using 16bit timer 1 to generate the tick.  Correct fuses must be
 	selected for the configCPU_CLOCK_HZ clock. */

 	ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;

 	/* We only have 16 bits so have to scale to get our required tick rate. */
 	ulCompareMatch /= portCLOCK_PRESCALER;

 	/* Adjust for correct value. */
 	ulCompareMatch -= ( uint32_t ) 1;

 	/* Setup compare match value for compare match A.  Interrupts are disabled
 	before this is called so we need not worry here. */
 	ucLowByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
 	ulCompareMatch >>= 8;
 	ucHighByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
 	OCR1AH = ucHighByte;
 	OCR1AL = ucLowByte;

 	/* Setup clock source and compare match behaviour. */
 	ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
 	TCCR1B = ucLowByte;

 	/* Enable the interrupt - this is okay as interrupt are currently globally
 	disabled. */
 	ucLowByte = TIMSK;
 	ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
 	TIMSK = ucLowByte;
 }
 /*-----------------------------------------------------------*/

 #if configUSE_PREEMPTION == 1

 	/*
 	 * Tick ISR for preemptive scheduler.  We can use a naked attribute as
 	 * the context is saved at the start of vPortYieldFromTick().  The tick
 	 * count is incremented after the context is saved.
 	 */
 	void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
 	void SIG_OUTPUT_COMPARE1A( void )
 	{
 		vPortYieldFromTick();
 		asm volatile ( "reti" );
 	}
 #else

 	/*
 	 * Tick ISR for the cooperative scheduler.  All this does is increment the
 	 * tick count.  We don't need to switch context, this can only be done by
 	 * manual calls to taskYIELD();
 	 */
 	void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal ) );
 	void SIG_OUTPUT_COMPARE1A( void )
 	{
 		xTaskIncrementTick();
 	}
 #endif
	/*
	* FreeRTOS Kernel V10.3.1
	* Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy of
	* this software and associated documentation files (the "Software"), to deal in
	* the Software without restriction, including without limitation the rights to
	* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
	* the Software, and to permit persons to whom the Software is furnished to do so,
	* subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in all
	* copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
	* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
	* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
	* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
	* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
	*
	* http://www.FreeRTOS.org
	* http://aws.amazon.com/freertos
	*
	* 1 tab == 4 spaces!
	*/

	/*

	Changes from V2.6.0

	+ AVR port - Replaced the inb() and outb() functions with direct memory
	access. This allows the port to be built with the 20050414 build of
	WinAVR.
	*/

	#include <stdlib.h>
	#include <avr/interrupt.h>

	#include "FreeRTOS.h"
	#include "task.h"

	/*-----------------------------------------------------------
	* Implementation of functions defined in portable.h for the AVR port.
	----------------------------------------------------------/

	/* Start tasks with interrupts enables. */
	#define portFLAGS_INT_ENABLED ( ( StackType_t ) 0x80 )

	/* Hardware constants for timer 1. */
	#define portCLEAR_COUNTER_ON_MATCH ( ( uint8_t ) 0x08 )
	#define portPRESCALE_64 ( ( uint8_t ) 0x03 )
	#define portCLOCK_PRESCALER ( ( uint32_t ) 64 )
	#define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( uint8_t ) 0x10 )

	/-----------------------------------------------------------/

	/* We require the address of the pxCurrentTCB variable, but don't want to know
	any details of its type. */
	typedef void TCB_t;
	extern volatile TCB_t * volatile pxCurrentTCB;

	/-----------------------------------------------------------/

	/*
	* Macro to save all the general purpose registers, the save the stack pointer
	* into the TCB.
	*
	* The first thing we do is save the flags then disable interrupts. This is to
	* guard our stack against having a context switch interrupt after we have already
	* pushed the registers onto the stack - causing the 32 registers to be on the
	* stack twice.
	*
	* r1 is set to zero as the compiler expects it to be thus, however some
	* of the math routines make use of R1.
	*
	* The interrupts will have been disabled during the call to portSAVE_CONTEXT()
	* so we need not worry about reading/writing to the stack pointer.
	*/

	#define portSAVE_CONTEXT() \
	asm volatile ( "push r0 \n\t" \
	"in r0, __SREG__ \n\t" \
	"cli \n\t" \
	"push r0 \n\t" \
	"push r1 \n\t" \
	"clr r1 \n\t" \
	"push r2 \n\t" \
	"push r3 \n\t" \
	"push r4 \n\t" \
	"push r5 \n\t" \
	"push r6 \n\t" \
	"push r7 \n\t" \
	"push r8 \n\t" \
	"push r9 \n\t" \
	"push r10 \n\t" \
	"push r11 \n\t" \
	"push r12 \n\t" \
	"push r13 \n\t" \
	"push r14 \n\t" \
	"push r15 \n\t" \
	"push r16 \n\t" \
	"push r17 \n\t" \
	"push r18 \n\t" \
	"push r19 \n\t" \
	"push r20 \n\t" \
	"push r21 \n\t" \
	"push r22 \n\t" \
	"push r23 \n\t" \
	"push r24 \n\t" \
	"push r25 \n\t" \
	"push r26 \n\t" \
	"push r27 \n\t" \
	"push r28 \n\t" \
	"push r29 \n\t" \
	"push r30 \n\t" \
	"push r31 \n\t" \
	"lds r26, pxCurrentTCB \n\t" \
	"lds r27, pxCurrentTCB + 1 \n\t" \
	"in r0, 0x3d \n\t" \
	"st x+, r0 \n\t" \
	"in r0, 0x3e \n\t" \
	"st x+, r0 \n\t" \
	);

	/*
	* Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
	* the context save so we can write to the stack pointer.
	*/

	#define portRESTORE_CONTEXT() \
	asm volatile ( "lds r26, pxCurrentTCB \n\t" \
	"lds r27, pxCurrentTCB + 1 \n\t" \
	"ld r28, x+ \n\t" \
	"out __SP_L__, r28 \n\t" \
	"ld r29, x+ \n\t" \
	"out __SP_H__, r29 \n\t" \
	"pop r31 \n\t" \
	"pop r30 \n\t" \
	"pop r29 \n\t" \
	"pop r28 \n\t" \
	"pop r27 \n\t" \
	"pop r26 \n\t" \
	"pop r25 \n\t" \
	"pop r24 \n\t" \
	"pop r23 \n\t" \
	"pop r22 \n\t" \
	"pop r21 \n\t" \
	"pop r20 \n\t" \
	"pop r19 \n\t" \
	"pop r18 \n\t" \
	"pop r17 \n\t" \
	"pop r16 \n\t" \
	"pop r15 \n\t" \
	"pop r14 \n\t" \
	"pop r13 \n\t" \
	"pop r12 \n\t" \
	"pop r11 \n\t" \
	"pop r10 \n\t" \
	"pop r9 \n\t" \
	"pop r8 \n\t" \
	"pop r7 \n\t" \
	"pop r6 \n\t" \
	"pop r5 \n\t" \
	"pop r4 \n\t" \
	"pop r3 \n\t" \
	"pop r2 \n\t" \
	"pop r1 \n\t" \
	"pop r0 \n\t" \
	"out __SREG__, r0 \n\t" \
	"pop r0 \n\t" \
	);

	/-----------------------------------------------------------/

	/*
	* Perform hardware setup to enable ticks from timer 1, compare match A.
	*/
	static void prvSetupTimerInterrupt( void );
	/-----------------------------------------------------------/

	/*
	* See header file for description.
	*/
	StackType_t pxPortInitialiseStack( StackType_t pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
	{
	uint16_t usAddress;

	/* Place a few bytes of known values on the bottom of the stack.
	This is just useful for debugging. */

	*pxTopOfStack = 0x11;
	pxTopOfStack--;
	*pxTopOfStack = 0x22;
	pxTopOfStack--;
	*pxTopOfStack = 0x33;
	pxTopOfStack--;

	/* Simulate how the stack would look after a call to vPortYield() generated by
	the compiler. */

	/lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. /

	/* The start of the task code will be popped off the stack last, so place
	it on first. */
	usAddress = ( uint16_t ) pxCode;
	*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
	pxTopOfStack--;

	usAddress >>= 8;
	*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
	pxTopOfStack--;

	/* Next simulate the stack as if after a call to portSAVE_CONTEXT().
	portSAVE_CONTEXT places the flags on the stack immediately after r0
	to ensure the interrupts get disabled as soon as possible, and so ensuring
	the stack use is minimal should a context switch interrupt occur. */
	pxTopOfStack = ( StackType_t ) 0x00; / R0 */
	pxTopOfStack--;
	*pxTopOfStack = portFLAGS_INT_ENABLED;
	pxTopOfStack--;


	/* Now the remaining registers. The compiler expects R1 to be 0. */
	pxTopOfStack = ( StackType_t ) 0x00; / R1 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x02; / R2 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x03; / R3 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x04; / R4 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x05; / R5 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x06; / R6 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x07; / R7 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x08; / R8 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x09; / R9 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x10; / R10 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x11; / R11 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x12; / R12 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x13; / R13 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x14; / R14 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x15; / R15 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x16; / R16 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x17; / R17 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x18; / R18 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x19; / R19 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x20; / R20 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x21; / R21 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x22; / R22 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x23; / R23 */
	pxTopOfStack--;

	/* Place the parameter on the stack in the expected location. */
	usAddress = ( uint16_t ) pvParameters;
	*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
	pxTopOfStack--;

	usAddress >>= 8;
	*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
	pxTopOfStack--;

	pxTopOfStack = ( StackType_t ) 0x26; / R26 X */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x27; / R27 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x28; / R28 Y */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x29; / R29 */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x30; / R30 Z */
	pxTopOfStack--;
	pxTopOfStack = ( StackType_t ) 0x031; / R31 */
	pxTopOfStack--;

	/lint +e950 +e611 +e923 /

	return pxTopOfStack;
	}
	/-----------------------------------------------------------/

	BaseType_t xPortStartScheduler( void )
	{
	/* Setup the hardware to generate the tick. */
	prvSetupTimerInterrupt();

	/* Restore the context of the first task that is going to run. */
	portRESTORE_CONTEXT();

	/* Simulate a function call end as generated by the compiler. We will now
	jump to the start of the task the context of which we have just restored. */
	asm volatile ( "ret" );

	/* Should not get here. */
	return pdTRUE;
	}
	/-----------------------------------------------------------/

	void vPortEndScheduler( void )
	{
	/* It is unlikely that the AVR port will get stopped. If required simply
	disable the tick interrupt here. */
	}
	/-----------------------------------------------------------/

	/*
	* Manual context switch. The first thing we do is save the registers so we
	* can use a naked attribute.
	*/
	void vPortYield( void ) __attribute__ ( ( naked ) );
	void vPortYield( void )
	{
	portSAVE_CONTEXT();
	vTaskSwitchContext();
	portRESTORE_CONTEXT();

	asm volatile ( "ret" );
	}
	/-----------------------------------------------------------/

	/*
	* Context switch function used by the tick. This must be identical to
	* vPortYield() from the call to vTaskSwitchContext() onwards. The only
	* difference from vPortYield() is the tick count is incremented as the
	* call comes from the tick ISR.
	*/
	void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
	void vPortYieldFromTick( void )
	{
	portSAVE_CONTEXT();
	if( xTaskIncrementTick() != pdFALSE )
	{
	vTaskSwitchContext();
	}
	portRESTORE_CONTEXT();

	asm volatile ( "ret" );
	}
	/-----------------------------------------------------------/

	/*
	* Setup timer 1 compare match A to generate a tick interrupt.
	*/
	static void prvSetupTimerInterrupt( void )
	{
	uint32_t ulCompareMatch;
	uint8_t ucHighByte, ucLowByte;

	/* Using 16bit timer 1 to generate the tick. Correct fuses must be
	selected for the configCPU_CLOCK_HZ clock. */

	ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;

	/* We only have 16 bits so have to scale to get our required tick rate. */
	ulCompareMatch /= portCLOCK_PRESCALER;

	/* Adjust for correct value. */
	ulCompareMatch -= ( uint32_t ) 1;

	/* Setup compare match value for compare match A. Interrupts are disabled
	before this is called so we need not worry here. */
	ucLowByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
	ulCompareMatch >>= 8;
	ucHighByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
	OCR1AH = ucHighByte;
	OCR1AL = ucLowByte;

	/* Setup clock source and compare match behaviour. */
	ucLowByte = portCLEAR_COUNTER_ON_MATCH \| portPRESCALE_64;
	TCCR1B = ucLowByte;

	/* Enable the interrupt - this is okay as interrupt are currently globally
	disabled. */
	ucLowByte = TIMSK;
	ucLowByte \|= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
	TIMSK = ucLowByte;
	}
	/-----------------------------------------------------------/

	#if configUSE_PREEMPTION == 1

	/*
	* Tick ISR for preemptive scheduler. We can use a naked attribute as
	* the context is saved at the start of vPortYieldFromTick(). The tick
	* count is incremented after the context is saved.
	*/
	void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
	void SIG_OUTPUT_COMPARE1A( void )
	{
	vPortYieldFromTick();
	asm volatile ( "reti" );
	}
	#else

	/*
	* Tick ISR for the cooperative scheduler. All this does is increment the
	* tick count. We don't need to switch context, this can only be done by
	* manual calls to taskYIELD();
	*/
	void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal ) );
	void SIG_OUTPUT_COMPARE1A( void )
	{
	xTaskIncrementTick();
	}
	#endif