EK-TM4C1294XL定时器如何不用中断输出指定频率的方波脉冲

各位老师,我想采用EK-TM4C1294XLTimer5 T5CCP0 PB2输出指定频率的方波脉冲,作了下面的程序,但一直无输出,不知道问题在哪里,请给与指正.

main()

{

// Set the clocking to run directly from the crystal at 120MHz.

    g_ui32SysClock = MAP_SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ | SYSCTL_OSC_MAIN |SYSCTL_USE_PLL|SYSCTL_CFG_VCO_480), 120000000);

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER5);

    ROM_GPIOPinTypeTimer(GPIO_PORTB_BASE, GPIO_PIN_2);

    ROM_GPIOPinConfigure(GPIO_PB2_T5CCP0);

    ROM_GPIODirModeSet(GPIO_PORTB_BASE, GPIO_PIN_2, GPIO_DIR_MODE_OUT);

    ROM_TimerConfigure(TIMER5_BASE, TIMER_CFG_PERIODIC);

    ROM_TimerLoadSet(TIMER5_BASE, TIMER_A, g_ui32SysClock/2);

    ROM_TimerEnable(TIMER5_BASE, TIMER_A);

    while(1)
    {
    }

}