代码：
#include <lm3s8962.h>


void Delay(void)
{
    unsigned long Tmp = 0xFFFFFF;
   
    while(--Tmp);   
}

int main(void)
{
    unsigned long RCC;
    unsigned long RCC2;

    RCC = SYSCTL_RCC_R;
    RCC2 = SYSCTL_RCC2_R;

    RCC |= SYSCTL_RCC_BYPASS;
    RCC &= ~SYSCTL_RCC_USESYSDIV;
    RCC2 |= SYSCTL_RCC2_BYPASS2;

    SYSCTL_RCC_R = RCC;
    SYSCTL_RCC2_R = RCC2;

    RCC &= ~SYSCTL_RCC_MOSCDIS;
    RCC |= SYSCTL_RCC_IOSCDIS;
    SYSCTL_RCC_R = RCC;

    Delay();

    RCC |= SYSCTL_RCC_XTAL_8MHZ;
    RCC |= SYSCTL_RCC_OSCSRC_MAIN;
    RCC &= ~SYSCTL_RCC_PWRDN;
    SYSCTL_RCC_R = RCC;

    Delay();

    RCC &= ~SYSCTL_RCC_SYSDIV_16;
    RCC |= SYSCTL_RCC_SYSDIV_4;
    RCC |= SYSCTL_RCC_USESYSDIV;
    SYSCTL_RCC_R = RCC;     //--------------运行了这句KEIL出错

    while((SYSCTL_RIS_R & SYSCTL_RIS_PLLLRIS) == 0);

    RCC &= ~SYSCTL_RCC_BYPASS;
    RCC = SYSCTL_RCC_R;
    SYSCTL_RCC_R = RCC;

    while(1);
}

首先问题是这样：
无论用KEIL3或者KEIL4，运行完SYSCTL_RCC_R = RCC;  就会马上出错
另外，将Delay延长点也一样出错的。

板是8962 EV KIT，用8M主晶振，想倍频到50M
此帖出自小平头技术问答