[参考译文] TM4C129ENCZAD：无法将通用计时器清零。

您好！

 我无法重现您的问题。 我尝试将0x1234、0x5678和0xABCD 写入 TAV 寄存器、并且我可以看到 TAR 寄存器更新为相同的值。 请参见下文。  

下面是我在 TivaWare 示例中使用的修改后的代码。 如果我在循环中不断写入不同的值、那么我还可以在寄存器窗口中看到 TAV 变化。

int
main(void)
{
    //
    // Run from the PLL at 120 MHz.
    // Note: SYSCTL_CFG_VCO_240 is a new setting provided in TivaWare 2.2.x and
    // later to better reflect the actual VCO speed due to SYSCTL#22.
    //
    g_ui32SysClock = MAP_SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
                                             SYSCTL_OSC_MAIN |
                                             SYSCTL_USE_PLL |
                                             SYSCTL_CFG_VCO_240), 120000000);

    //
    // Enable the peripherals used by this example.
    //
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOL);

    //
    // Configure the GPIO to be CCP pins for the Timer peripheral.
    //
    MAP_GPIOPinConfigure(GPIO_PL4_T0CCP0);
    MAP_GPIOPinConfigure(GPIO_PL5_T0CCP1);

    //
    // Configure the GPIO for the Timer peripheral.
    //
    MAP_GPIOPinTypeTimer(GPIO_PORTL_BASE, GPIO_PIN_4 | GPIO_PIN_5);

    //
    // Initialize the UART and write initial status.
    //
    ConfigureUART();
    UARTprintf("Edge Capture Example for measuring the high period of an"
               "input signal.\n");
    UARTprintf("Input a square wave onto pins PL4 and PL5 of the "
               "EK-TM4C1294XL.\n");

    //
    // Initialize Timers A yo run as periodic up-count edge capture
    // timers.  This will split the 32-bit timer into two 16-bit timers.
    //
    MAP_TimerConfigure(TIMER0_BASE, (TIMER_CFG_SPLIT_PAIR |
            TIMER_CFG_A_CAP_COUNT_UP ));

    //
    // To use the timer in Edge Time mode, it must be preloaded with initial
    // values.  If the prescaler is used, then it must be preloaded as well.
    // Since we want to use all 24-bits for both timers it will be loaded with
    // the maximum of 0xFFFF for the 16-bit wide split timers, and 0xFF to add
    // the additional 8-bits to the split timers with the prescaler.
    //
    MAP_TimerLoadSet(TIMER0_BASE, TIMER_BOTH, 0xFFFF);
    MAP_TimerPrescaleSet(TIMER0_BASE, TIMER_BOTH, 0xFF);

    //
    // Configure Timer A to trigger on a Positive Edge
    //
    MAP_TimerControlEvent(TIMER0_BASE, TIMER_A, TIMER_EVENT_POS_EDGE);

    //
    // Clear the interrupt status flag.  This is done to make sure the
    // interrupt flag is cleared before we enable it.
    //
    MAP_TimerIntClear(TIMER0_BASE, TIMER_CAPA_EVENT );

    //
    // Enable the Timer A interrupts for Capture Events.
    //
    MAP_TimerIntEnable(TIMER0_BASE, TIMER_CAPA_EVENT );

    //
    // Enable the interrupts for Timer A  on the processor (NVIC).
    //
    MAP_IntEnable(INT_TIMER0A);

    //
    // Enable processor interrupts.
    //
    MAP_IntMasterEnable();

    HWREG(TIMER0_BASE + TIMER_O_TAV) = 0x00001234;
    HWREG(TIMER0_BASE + TIMER_O_TAV) = 0x00005678;
    HWREG(TIMER0_BASE + TIMER_O_TAV) = 0x0000abcd;


    //
    // Enable both Timer A to begin the application.
    //
    MAP_TimerEnable(TIMER0_BASE, TIMER_A);

    while(1)
    {
        HWREG(TIMER0_BASE + TIMER_O_TAV) = 0x00001234;
        SysCtlDelay(10000);
        HWREG(TIMER0_BASE + TIMER_O_TAV) = 0x00005678;
        SysCtlDelay(10000);
        HWREG(TIMER0_BASE + TIMER_O_TAV) = 0x0000ABCD;
        SysCtlDelay(10000);

    }

}