外部晶振无法使用

user4994727

我是用的28027芯片，时钟配置如下：

CLK_disableOsc1(clkHandle);	
	
CLK_setOscSrc(clkHandle,CLK_OscSrc_External);  
	
CLK_disableClkIn(clkHandle);   

CLK_enableCrystalOsc(clkHandle);
	
CLK_disableOsc2(clkHandle);

PLL_setup(pllHandle, PLL_Multiplier_6, PLL_DivideSelect_ClkIn_by_2);

PLL_setup函数如下：

void PLL_setup(PLL_Handle pllHandle, const PLL_Multiplier_e clkMult, const PLL_DivideSelect_e divSelect)  
{

    if(PLL_getClkStatus(pllHandle) == PLL_ClkStatus_Missing)
    {
        // The clock is missing so we cannot setup the PLL correctly
        asm(" ESTOP0");
    }

    // Set divider to max value (/4) for safety
    PLL_setDivider(pllHandle, PLL_DivideSelect_ClkIn_by_4);

    // Set the desired multiplier
    PLL_setMultiplier(pllHandle, clkMult);

    while(PLL_getLockStatus(pllHandle) != PLL_LockStatus_Done)
    {
    }

    // Set the desired divider
    PLL_setDivider(pllHandle, divSelect);

} // end of PLL_setup() function

使用外部20M晶振，按照手册配置的外部电路；编译通过，但是烧写程序时，烧写进去了，但是仿真开始，就会执行到下面的语句，仿真停止

 if(PLL_getClkStatus(pllHandle) == PLL_ClkStatus_Missing)
    {
        // The clock is missing so we cannot setup the PLL correctly
        asm(" ESTOP0");
    }