port.c

一个免费的嵌入式操作系统。

/*
	FreeRTOS V2.2.0 - Copyright (C) 2003, 2004 Richard Barry.

	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 as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	FreeRTOS is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with FreeRTOS; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

	A special exception to the GPL can be applied should you wish to distribute
	a combined work that includes FreeRTOS, without being obliged to provide
	the source code for any proprietary components.  See the licensing section 
	of http://www.FreeRTOS.org for full details of how and when the exception
	can be applied.

	***************************************************************************
	See http://www.FreeRTOS.org for documentation, latest information, license 
	and contact details.  Please ensure to read the configuration and relevant 
	port sections of the online documentation.
	***************************************************************************
*/

/* 
Changes between V1.2.4 and V1.2.5

	+ Introduced portGLOBAL_INTERRUPT_FLAG definition to test the global 
	  interrupt flag setting.  Using the two bits defined within
	  portINITAL_INTERRUPT_STATE was causing the w register to get clobbered
	  before the test was performed.

Changes from V1.2.5

	+ Set the interrupt vector address to 0x08.  Previously it was at the
	  incorrect address for compatibility mode of 0x18.

Changes from V2.1.1

	+ PCLATU and PCLATH are now saved as part of the context.  This allows
	  function pointers to be used within tasks.  Thanks to Javier Espeche
	  for the enhancement. 
*/

/* Scheduler include files. */
#include "projdefs.h"
#include "portable.h"
#include "task.h"

/* MPLAB library include file. */
#include "timers.h"

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

/* Hardware setup for tick. */
#define portTIMER_FOSC_SCALE			( ( unsigned portLONG ) 4 )

/* Initial interrupt enable state for newly created tasks.  This value is
copied into INTCON when a task switches in for the first time. */
#define portINITAL_INTERRUPT_STATE			0xc0

/* Just the bit within INTCON for the global interrupt flag. */
#define portGLOBAL_INTERRUPT_FLAG			0x80

/* Constant used for context switch macro when we require the interrupt 
enable state to be unchanged when the interrupted task is switched back in. */
#define portINTERRUPTS_UNCHANGED			0x00

/* Some memory areas get saved as part of the task context.  These memory
area's get used by the compiler for temporary storage, especially when 
performing mathematical operations, or when using 32bit data types.  This
constant defines the size of memory area which must be saved. */
#define portCOMPILER_MANAGED_MEMORY_SIZE	0x13

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

/* IO port constants. */
#define portBIT_SET		( ( unsigned portCHAR ) 1 )
#define portBIT_CLEAR	( ( unsigned portCHAR ) 0 )

/*
 * The serial port ISR's are defined in serial.c, but are called from portable
 * as they use the same vector as the tick ISR.
 */
void vSerialTxISR( void );
void vSerialRxISR( void );

/*
 * Perform hardware setup to enable ticks.
 */
static void prvSetupTimerInterrupt( void );

/* 
 * ISR to maintain the tick, and perform tick context switches if the
 * preemptive scheduler is being used.
 */
static void prvTickISR( void );

/*
 * ISR placed on the low priority vector.  This calls the appropriate ISR for
 * the actual interrupt.
 */
static void prvLowInterrupt( void );

/* 
 * Macro that pushes all the registers that make up the context of a task onto
 * the stack, then saves the new top of stack into the TCB.
 * 
 * If this is called from an ISR then the interrupt enable bits must have been 
 * set for the ISR to ever get called.  Therefore we want to save the INTCON
 * register with the enable bits forced to be set - and ucForcedInterruptFlags 
 * must contain these bit settings.  This means the interrupts will again be
 * enabled when the interrupted task is switched back in.
 *
 * If this is called from a manual context switch (i.e. from a call to yield),
 * then we want to save the INTCON so it is restored with its current state,
 * and ucForcedInterruptFlags must be 0.  This allows a yield from within
 * a critical section.
 *
 * The compiler uses some locations at the bottom of the memory for temporary
 * storage during math and other computations.  This is especially true if
 * 32bit data types are utilised (as they are by the scheduler).  The .tmpdata
 * and MATH_DATA sections have to be stored in there entirety as part of a task
 * context.  This macro stores from data address 0x00 to 
 * portCOMPILER_MANAGED_MEMORY_SIZE.  This is sufficient for the demo 
 * applications but you should check the map file for your project to ensure 
 * this is sufficient for your needs.  It is not clear whether this size is 
 * fixed for all compilations or has the potential to be program specific.
 */
#define	portSAVE_CONTEXT( ucForcedInterruptFlags )								\
{																				\
	_asm																		\
		/* Save the status and WREG registers first, as these will get modified	\
		by the operations below. */												\
		MOVFF	WREG, PREINC1													\
		MOVFF   STATUS, PREINC1													\
		/* Save the INTCON register with the appropriate bits forced if			\
		necessary - as described above. */										\
		MOVFF	INTCON, WREG													\
		IORLW	ucForcedInterruptFlags											\
		MOVFF	WREG, PREINC1													\
	_endasm																		\
																				\
	portDISABLE_INTERRUPTS();													\
																				\
	_asm																		\
		/* Store the necessary registers to the stack. */						\
		MOVFF	BSR, PREINC1													\
		MOVFF	FSR2L, PREINC1													\
		MOVFF	FSR2H, PREINC1													\
		MOVFF	FSR0L, PREINC1													\
		MOVFF	FSR0H, PREINC1													\
		MOVFF	TBLPTRU, PREINC1												\
		MOVFF	TBLPTRH, PREINC1												\
		MOVFF	TBLPTRL, PREINC1												\
		MOVFF	PRODH, PREINC1													\
		MOVFF	PRODL, PREINC1													\
		MOVFF	PCLATU, PREINC1													\
		MOVFF	PCLATH, PREINC1													\
		/* Store the .tempdata and MATH_DATA areas as described above. */		\
		CLRF	FSR0L, 0														\
		CLRF	FSR0H, 0														\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	POSTINC0, PREINC1												\
		MOVFF	INDF0, PREINC1													\
		MOVFF	FSR0L, PREINC1													\
		MOVFF	FSR0H, PREINC1													\
		/* Store the hardware stack pointer in a temp register before we		\
		modify it. */															\
		MOVFF	STKPTR, FSR0L													\
	_endasm																		\
																				\
		/* Store each address from the hardware stack. */						\
		while( STKPTR > ( unsigned portCHAR ) 0 )								\
		{																		\
			_asm																\
				MOVFF	TOSL, PREINC1											\
				MOVFF	TOSH, PREINC1											\
				MOVFF	TOSU, PREINC1											\
				POP																\
			_endasm																\
		}																		\
																				\
	_asm																		\
		/* Store the number of addresses on the hardware stack (from the		\
		temporary register). */													\
		MOVFF	FSR0L, PREINC1													\
		MOVF	PREINC1, 1, 0													\
	_endasm																		\
																				\
	/* Save the new top of the software stack in the TCB. */					\
	_asm																		\
		MOVFF	pxCurrentTCB, FSR0L												\
		MOVFF	pxCurrentTCB + 1, FSR0H											\
		MOVFF	FSR1L, POSTINC0													\
		MOVFF	FSR1H, POSTINC0													\
	_endasm																		\
}
/*-----------------------------------------------------------*/

/*
 * This is the reverse of portSAVE_CONTEXT.  See portSAVE_CONTEXT for more
 * details.
 */
#define portRESTORE_CONTEXT()													\
{																				\
	_asm																		\
		/* Set FSR0 to point to pxCurrentTCB->pxTopOfStack. */					\
		MOVFF	pxCurrentTCB, FSR0L												\
		MOVFF	pxCurrentTCB + 1, FSR0H											\
																				\
		/* De-reference FSR0 to set the address it holds into FSR1.				\
		(i.e. *( pxCurrentTCB->pxTopOfStack ) ). */								\
		MOVFF	POSTINC0, FSR1L													\
		MOVFF	POSTINC0, FSR1H													\
																				\
		/* How many return addresses are there on the hardware stack?  Discard	\
		the first byte as we are pointing to the next free space. */			\
		MOVFF	POSTDEC1, FSR0L													\
		MOVFF	POSTDEC1, FSR0L													\
	_endasm																		\
																				\
	/* Fill the hardware stack from our software stack. */						\
	STKPTR = 0;																	\
																				\
	while( STKPTR < FSR0L )														\
	{																			\
		_asm																	\
			PUSH																\
			MOVF	POSTDEC1, 0, 0												\
			MOVWF	TOSU, 0														\
			MOVF	POSTDEC1, 0, 0												\
			MOVWF	TOSH, 0														\
			MOVF	POSTDEC1, 0, 0												\
			MOVWF	TOSL, 0														\
		_endasm																	\
	}																			\
																				\
	_asm																		\
		/* Restore the .tmpdata and MATH_DATA memory. */						\
		MOVFF	POSTDEC1, FSR0H													\
		MOVFF	POSTDEC1, FSR0L													\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, POSTDEC0												\
		MOVFF	POSTDEC1, INDF0													\
		/* Restore the other registers forming the tasks context. */			\
		MOVFF	POSTDEC1, PCLATH												\
		MOVFF	POSTDEC1, PCLATU												\
		MOVFF	POSTDEC1, PRODL													\
		MOVFF	POSTDEC1, PRODH													\
		MOVFF	POSTDEC1, TBLPTRL												\
		MOVFF	POSTDEC1, TBLPTRH												\
		MOVFF	POSTDEC1, TBLPTRU												\
		MOVFF	POSTDEC1, FSR0H													\
		MOVFF	POSTDEC1, FSR0L													\
		MOVFF	POSTDEC1, FSR2H													\
		MOVFF	POSTDEC1, FSR2L													\
		MOVFF	POSTDEC1, BSR													\
		/* The next byte is the INTCON register.  Read this into WREG as some	\
		manipulation is required. */											\