[参考译文] TMS320F28035：关于切换到备用时钟。

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https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/1320865/tms320f28035-about-switching-to-an-alternative-clock

你好。
请告诉我在检测到 MISS_CLOCK 时切换到备用时钟的情况。
PLL_INITIAL (6、2)使用20M_XTAL 生成60MHz 系统时钟。
对于切换测试，运行以下代码，该过程将继续执行 NMI_ISR()。
NmiIntruptRegs.NMIFLGFRC.bit.CLOCKFAIL = 1；

我们知道、有必要重新配置 PLL 才能在该函数内切换到内部 OSC1。
这种理解是否正确？
我想使用内部 OSC1并使用 PLL_Initial (12、2)生成一个60MHz 系统时钟。
但是、当执行此函数时、CPU 将停止。
相反、如果未执行此函数、CPU 将继续运行。
XTAL->OSC1在未复位 PLL 的情况下切换是否成功？

祝你一切

​

__interrupt void nmi_isr(void)
{
    PLL_Initial(12, 2);     // CLK=10M*12/2=60M  XTAL->OSC1

    EALLOW;
    NmiIntruptRegs.NMIFLGCLR.bit.CLOCKFAIL = 1;
    NmiIntruptRegs.NMIFLGCLR.bit.NMIINT = 1;
    EDIS;
}

void 
PLL_Initial(Uint16 val, Uint16 divsel)
{
   volatile Uint16 iVol;

   //
   // Make sure the PLL is not running in limp mode
   //
   if (SysCtrlRegs.PLLSTS.bit.MCLKSTS != 0)
   {
        EALLOW;
        
        //
        // OSCCLKSRC1 failure detected. PLL running in limp mode.
        // Re-enable missing clock logic.
        //
        SysCtrlRegs.PLLSTS.bit.MCLKCLR = 1;
        EDIS;
        
        //
        // Replace this line with a call to an appropriate
        // SystemShutdown(); function.
        __asm("        ESTOP0");     // Uncomment for debugging purposes
    }

    //
    // DIVSEL MUST be 0 before PLLCR can be changed from
    // 0x0000. It is set to 0 by an external reset XRSn
    // This puts us in 1/4
    //
    if (SysCtrlRegs.PLLSTS.bit.DIVSEL != 0)
    {
        EALLOW;
        SysCtrlRegs.PLLSTS.bit.DIVSEL = 0;
        EDIS;
    }

    //
    // Change the PLLCR
    //
    if (SysCtrlRegs.PLLCR.bit.DIV != val)
    {
        EALLOW;
        
        //
        // Before setting PLLCR turn off missing clock detect logic
        //
        SysCtrlRegs.PLLSTS.bit.MCLKOFF = 1;
        SysCtrlRegs.PLLCR.bit.DIV = val;
        EDIS;

        //
        // Optional: Wait for PLL to lock.
        //
        // During this time the CPU will switch to OSCCLK/2 until
        // the PLL is stable.  Once the PLL is stable the CPU will
        // switch to the new PLL value.
        //
        // This time-to-lock is monitored by a PLL lock counter.
        //
        // Code is not required to sit and wait for the PLL to lock.
        // However, if the code does anything that is timing critical,
        // and requires the correct clock be locked, then it is best to
        // wait until this switching has completed.
        //
        
        //
        // Wait for the PLL lock bit to be set.
        //

        //
        // The watchdog should be disabled before this loop, or fed within
        // the loop via ServiceDog().
        //

        //
        // Uncomment to disable the watchdog
        //
        DisableDog();

        while(SysCtrlRegs.PLLSTS.bit.PLLLOCKS != 1)
        {
            //
            // Uncomment to service the watchdog
            //
            // ServiceDog();
        }

        EALLOW;
        SysCtrlRegs.PLLSTS.bit.MCLKOFF = 0;
        EDIS;
    }

    //
    // If switching to 1/2
    //
    if((divsel == 1)||(divsel == 2))
    {
        EALLOW;
        SysCtrlRegs.PLLSTS.bit.DIVSEL = divsel;
        EDIS;
    }

    //
    // If switching to 1/1
    // * First go to 1/2 and let the power settle
    //   The time required will depend on the system, this is only an example
    // * Then switch to 1/1
    //
    if(divsel == 3)
    {
        EALLOW;
        SysCtrlRegs.PLLSTS.bit.DIVSEL = 2;
        DELAY_US(50L);
        SysCtrlRegs.PLLSTS.bit.DIVSEL = 3;
        EDIS;
    }
}