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MSP430F5XX 库 时钟配置问题

user4959119
Genius 4890 points


在使用MSP430F5XX的库，发现定时器demo中没有系统时钟的初始化代码，上来就是配置定时器的参数，这是怎么回事？

void main(void)
{
    //Stop WDT
    WDT_A_hold(WDT_A_BASE);

    //Set P1.0 to output direction
    GPIO_setAsOutputPin(
        GPIO_PORT_P1,
        GPIO_PIN0
        );

    //Start timer in continuous mode sourced by ACLK
    Timer_A_clearTimerInterrupt(TIMER_A1_BASE);

    Timer_A_initContinuousModeParam param = {0};
    param.clockSource = TIMER_A_CLOCKSOURCE_ACLK;
    param.clockSourceDivider = TIMER_A_CLOCKSOURCE_DIVIDER_1;
    param.timerInterruptEnable_TAIE = TIMER_A_TAIE_INTERRUPT_ENABLE;
    param.timerClear = TIMER_A_DO_CLEAR;
    param.startTimer = true;
    Timer_A_initContinuousMode(TIMER_A1_BASE, &param);

    //Enter LPM0, enable interrupts
    __bis_SR_register(LPM0_bits + GIE);

    //For debugger
    __no_operation();
}

  • 0
    Guru 67475 points

    这个例程里定时器使用的是ACLK，ACLK默认上电时开启的，例程里也没有涉及到其他的ACLK的频率，所以不需要初始化。

    如果使用其他时钟或不是默认的频率，要注意先配置时钟。

  • 0
    TI__Guru**** 252096 points

    您可以看一下ucs.h内的说明

    //! This function initializes each of the clock signals. The user must ensure
//! that this function is called for each clock signal. If not, the default
//! state is assumed for the particular clock signal. Refer MSP430Ware
//! documentation for UCS module or Device Family User's Guide for details of
//! default clock signal states.

    //*****************************************************************************
//
//! \brief Initializes a clock signal
//!
//! This function initializes each of the clock signals. The user must ensure
//! that this function is called for each clock signal. If not, the default
//! state is assumed for the particular clock signal. Refer MSP430Ware
//! documentation for UCS module or Device Family User's Guide for details of
//! default clock signal states.
//!
//! \param selectedClockSignal selected clock signal
//!        Valid values are:
//!        - \b UCS_ACLK
//!        - \b UCS_MCLK
//!        - \b UCS_SMCLK
//!        - \b UCS_FLLREF
//! \param clockSource is clock source for the selectedClockSignal
//!        Valid values are:
//!        - \b UCS_XT1CLK_SELECT
//!        - \b UCS_VLOCLK_SELECT
//!        - \b UCS_REFOCLK_SELECT
//!        - \b UCS_DCOCLK_SELECT
//!        - \b UCS_DCOCLKDIV_SELECT
//!        - \b UCS_XT2CLK_SELECT
//! \param clockSourceDivider selected the clock divider to calculate
//!        clocksignal from clock source.
//!        Valid values are:
//!        - \b UCS_CLOCK_DIVIDER_1 [Default]
//!        - \b UCS_CLOCK_DIVIDER_2
//!        - \b UCS_CLOCK_DIVIDER_4
//!        - \b UCS_CLOCK_DIVIDER_8
//!        - \b UCS_CLOCK_DIVIDER_12 - [Valid only for UCS_FLLREF]
//!        - \b UCS_CLOCK_DIVIDER_16
//!        - \b UCS_CLOCK_DIVIDER_32 - [Not valid for UCS_FLLREF]
//!
//! Modified bits of \b UCSCTL5 register, bits of \b UCSCTL4 register and bits
//! of \b UCSCTL3 register.
//!
//! \return None
//
//*****************************************************************************
extern void UCS_initClockSignal(uint8_t selectedClockSignal,
                                uint16_t clockSource,
                                uint16_t clockSourceDivider);

  • 0 回复 Susan Yang
    Genius 4890 points
    嗯明白了，另外定时器参数 compareOutputMode是什么意思？我不想有任何外部输出，选择bit就可以了吗？
  • 0 回复 user4959119
    TI__Guru**** 252096 points
    uint16_t compareOutputMode;

    //! Is the count to be compared with in compare mode
  • 0 回复 Susan Yang
    Genius 4890 points

    我指的是这个，默认的bitValue是啥含义？

    //! - \b TIMER_A_OUTPUTMODE_OUTBITVALUE [Default]
    //! - \b TIMER_A_OUTPUTMODE_SET
    //! - \b TIMER_A_OUTPUTMODE_TOGGLE_RESET
    //! - \b TIMER_A_OUTPUTMODE_SET_RESET
    //! - \b TIMER_A_OUTPUTMODE_TOGGLE
    //! - \b TIMER_A_OUTPUTMODE_RESET
    //! - \b TIMER_A_OUTPUTMODE_TOGGLE_SET
    //! - \b TIMER_A_OUTPUTMODE_RESET_SET
    uint16_t compareOutputMode;

  • 0 回复 user4959119
    TI__Guru**** 252096 points
    TIMER_A_OUTPUTMODE_OUTBITVALUE 表示 输出由TACCTLx的OUT位直接控制
  • 0 回复 user4959119
    Guru 67475 points

    建议楼主先找个msp430f5的教程看一下，然后再对照数据手册看例程，就很容易理解了。

    http://bbs.21ic.com/icview-584664-1-1.html