systick.c

基于 Cortex-M3 (ARM) 内核使用之 uC/OS-II 作业系统,此例程可移植于 Cortex-M3 (ARM)内核的微处理器上的应用,于 Keil MDK 3.15b以上 工程编译,而

//*****************************************************************************
//
// systick.c - Driver for the SysTick timer in NVIC.
//
// Copyright (c) 2005,2006 Luminary Micro, Inc.  All rights reserved.
//
// Software License Agreement
//
// Luminary Micro, Inc. (LMI) is supplying this software for use solely and
// exclusively on LMI's Stellaris Family of microcontroller products.
//
// The software is owned by LMI and/or its suppliers, and is protected under
// applicable copyright laws.  All rights are reserved.  Any use in violation
// of the foregoing restrictions may subject the user to criminal sanctions
// under applicable laws, as well as to civil liability for the breach of the
// terms and conditions of this license.
//
// THIS SOFTWARE IS PROVIDED "AS IS".  NO WARRANTIES, WHETHER EXPRESS, IMPLIED
// OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE.
// LMI SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR
// CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
//
// This is part of revision 852 of the Stellaris Driver Library.
//
//*****************************************************************************

//*****************************************************************************
//
//! \addtogroup systick_api
//! @{
//
//*****************************************************************************

#include "hw_ints.h"
#include "hw_nvic.h"
#include "hw_types.h"
#include "debug.h"
#include "interrupt.h"
#include "systick.h"

//*****************************************************************************
//
//! Enables the SysTick counter.
//!
//! This will start the SysTick counter.  If an interrupt.handler has been
//! registered, it will be called when the SysTick counter rolls over.
//!
//! \return None.
//
//*****************************************************************************
void
SysTickEnable(void)
{
    //
    // Enable SysTick.
    //
    HWREG(NVIC_ST_CTRL) |= NVIC_ST_CTRL_CLK_SRC | NVIC_ST_CTRL_ENABLE;
}

//*****************************************************************************
//
//! Disables the SysTick counter.
//!
//! This will stop the SysTick counter.  If an interrupt.handler has been
//! registered, it will no longer be called until SysTick is restarted.
//!
//! \return None.
//
//*****************************************************************************
void
SysTickDisable(void)
{
    //
    // Disable SysTick.
    //
    HWREG(NVIC_ST_CTRL) &= ~(NVIC_ST_CTRL_ENABLE);
}

//*****************************************************************************
//
//! Registers an interrupt.handler for the SysTick interrupt.
//!
//! \param pfnHandler is a pointer to the function to be called when the
//! SysTick interrupt occurs.
//!
//! This sets the handler to be called when a SysTick interrupt occurs.
//!
//! \sa IntRegister() for important information about registering interrupt
//! handlers.
//!
//! \return None.
//
//*****************************************************************************
void
SysTickIntRegister(void (*pfnHandler)(void))
{
    //
    // Register the interrupt.handler, returning an error if an error occurs.
    //
    IntRegister(FAULT_SYSTICK, pfnHandler);

    //
    // Enable the SysTick interrupt.
    //
    HWREG(NVIC_ST_CTRL) |= NVIC_ST_CTRL_INTEN;
}

//*****************************************************************************
//
//! Unregisters the interrupt.handler for the SysTick interrupt.
//!
//! This function will clear the handler to be called when a SysTick interrupt
//! occurs.
//!
//! \sa IntRegister() for important information about registering interrupt
//! handlers.
//!
//! \return None.
//
//*****************************************************************************
void
SysTickIntUnregister(void)
{
    //
    // Disable the SysTick interrupt.
    //
    HWREG(NVIC_ST_CTRL) &= ~(NVIC_ST_CTRL_INTEN);

    //
    // Unregister the interrupt.handler.
    //
    IntUnregister(FAULT_SYSTICK);
}

//*****************************************************************************
//
//! Enables the SysTick interrupt.
//!
//! This function will enable the SysTick interrupt, allowing it to be
//! reflected to the processor.
//!
//! \return None.
//
//*****************************************************************************
void
SysTickIntEnable(void)
{
    //
    // Enable the SysTick interrupt.
    //
    HWREG(NVIC_ST_CTRL) |= NVIC_ST_CTRL_INTEN;
}

//*****************************************************************************
//
//! Disables the SysTick interrupt.
//!
//! This function will disable the SysTick interrupt, preventing it from being
//! reflected to the processor.
//!
//! \return None.
//
//*****************************************************************************
void
SysTickIntDisable(void)
{
    //
    // Disable the SysTick interrupt.
    //
    HWREG(NVIC_ST_CTRL) &= ~(NVIC_ST_CTRL_INTEN);
}

//*****************************************************************************
//
//! Sets the period of the SysTick counter.
//!
//! \param ulPeriod is the number of clock ticks in each period of the SysTick
//! counter; must be between 1 and 16,777,216, inclusive.
//!
//! This function sets the rate at which the SysTick counter wraps; this
//! equates to the number of processor clocks between interrupts.
//!
//! \return None.
//
//*****************************************************************************
void
SysTickPeriodSet(unsigned long ulPeriod)
{
    //
    // Check the arguments.
    //
    ASSERT((ulPeriod > 0) && (ulPeriod <= 16777216));

    //
    // Set the period of the SysTick counter.
    //
    HWREG(NVIC_ST_RELOAD) = ulPeriod - 1;
}

//*****************************************************************************
//
//! Gets the period of the SysTick counter.
//!
//! This function returns the rate at which the SysTick counter wraps; this
//! equates to the number of processor clocks between interrupts.
//!
//! \return Returns the period of the SysTick counter.
//
//*****************************************************************************
unsigned long
SysTickPeriodGet(void)
{
    //
    // Return the period of the SysTick counter.
    //
    return(HWREG(NVIC_ST_RELOAD) + 1);
}

//*****************************************************************************
//
//! Gets the current value of the SysTick counter.
//!
//! This function returns the current value of the SysTick counter; this will
//! be a value between the period - 1 and zero, inclusive.
//!
//! \return Returns the current value of the SysTick counter.
//
//*****************************************************************************
unsigned long
SysTickValueGet(void)
{
    //
    // Return the current value of the SysTick counter.
    //
    return(HWREG(NVIC_ST_CURRENT));
}

//*****************************************************************************
//
// Close the Doxygen group.
//! @}
//
//*****************************************************************************