CCS/MSP430F6659: Use an external 20 MHz crystal on XT1

Tool/software: Code Composer Studio

Hello TI community,

I have a serious problem with a 20 MHz crystal which I soldered on the XT1 pads of the MSP-TS430PZ100USB evaluation board.

I have a second HF crystal with 4 MHz soldered on XT2.

The 4Mhz crystal works fine, the 20MHz crystal does not work. I have added 2 capacitors of 22pF according to the formula C1=C2=(2*Cload)-Cparasitic=(2*12pF)-2pF

I have sourced the ACLK with XT2 and routed to P1.0: I can measure a nice 4Mhz squrewave there.

I have sourced the SMCLK with XT1 and routed to P3.4: I can see a DC voltage with some random oscillations (very small) on the pin as soon as I run my code.

Another problem is my MCLK: when I want to modify the SELM bits of the UCSCTL4 register manually, the programm crashes. Also when I use library functions and TI example codes, these problems remain.

Please help me, I am busy since a week with the same issue and I am running out of time.

Here is the code:

#include "driverlib.h"
//*****************************************************************************
//
//Target frequency for MCLK in kHz
//
//*****************************************************************************
#define UCS_DESIRED_MCLK_FREQUENCY_IN_KHZ   20000
//*****************************************************************************
//
//MCLK/FLLRef Ratio (desired frequency / FLL reference clock frequency)
//
//*****************************************************************************
#define UCS_MCLK_FLLREF_RATIO   609
//*****************************************************************************´

//*****************************************************************************
//
//XT Crystal Frequencies being used
//
//*****************************************************************************
#define UCS_XT1_CRYSTAL_FREQUENCY       20000000
#define UCS_XT2_CRYSTAL_FREQUENCY        4000000


//Variable to store current Clock values
uint32_t clockValue = 0;

//Variable to store status of Oscillator fault flags
uint16_t status;

//Variable to store returned STATUS_SUCCESS or STATUS_FAIL
uint8_t returnValue = 0;


void set_clock_frequencies()
{

    // SMCLK on Port 3.4 (Pin#46)
    GPIO_setAsPeripheralModuleFunctionOutputPin(
            GPIO_PORT_P3,
            GPIO_PIN4
            );

    // ACLK on P1.0 (Pin#34)
    GPIO_setAsPeripheralModuleFunctionOutputPin(
            GPIO_PORT_P1,
            GPIO_PIN0
            );

    //Startup HF XT2 crystal Port select XT2
    GPIO_setAsPeripheralModuleFunctionInputPin(
        GPIO_PORT_P7,
        GPIO_PIN2 + GPIO_PIN3
        );



    // Set VCore = 3 for 20MHz clock
    PMM_setVCore(PMM_CORE_LEVEL_3);

    //Set DCO; FLL reference = REFO
    UCS_initClockSignal(
        UCS_FLLREF,
        UCS_REFOCLK_SELECT,
        UCS_CLOCK_DIVIDER_1
        );

    //Set Ratio and Desired MCLK Frequency and initialize DCO
    UCS_initFLLSettle(
        UCS_DESIRED_MCLK_FREQUENCY_IN_KHZ,
        UCS_MCLK_FLLREF_RATIO
        );

    status = UCS_turnOnHFXT1WithTimeout(UCS_XT1_DRIVE_2, 5000);

    status = UCS_turnOnXT2WithTimeout(UCS_XT2_DRIVE_4MHZ_8MHZ, 5000);

#if 0
    // Set MCLK with library function
    UCS_initClockSignal(           // INSIDE THE FUNTION, PROGRAM CRASHES
        UCS_MCLK,
        UCS_DCOCLK_SELECT,
        UCS_CLOCK_DIVIDER_1
        );
#endif
#if 0
    // Set MCLK manually --> problem remains

    // Clear Register
    UCSCTL4 &= ~(SELM_7);
    // Set XT1 CLK as MCLK source
    UCSCTL4 |= SELM__XT1CLK;        // HERE PROGRAM CRASHES
    // MCLK Source Divider f(MCLK)/1
    UCSCTL5 |= DIVM_0;

    // Breakpoint here
    status = status;
#endif

    //Set SMCLK
    UCS_initClockSignal(
        UCS_SMCLK,
        UCS_XT1CLK_SELECT,
        UCS_CLOCK_DIVIDER_1
        );

    //Set ACLK
    UCS_initClockSignal(
        UCS_ACLK,
        UCS_XT2CLK_SELECT,
        UCS_CLOCK_DIVIDER_1
        );


    // Enable global oscillator fault flag
    SFR_clearInterrupt(SFR_OSCILLATOR_FAULT_INTERRUPT);
    SFR_enableInterrupt(SFR_OSCILLATOR_FAULT_INTERRUPT);

    // Enable global interrupt
    __bis_SR_register(GIE);


    // Verify if the Clock settings are as expected
    UCS_setExternalClockSource(UCS_XT1_CRYSTAL_FREQUENCY, UCS_XT2_CRYSTAL_FREQUENCY);
    clockValue = UCS_getSMCLK();
    clockValue = UCS_getMCLK();
    clockValue = UCS_getACLK();

}


#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=UNMI_VECTOR
__interrupt
#elif defined(__GNUC__)
__attribute__((interrupt(UNMI_VECTOR)))
#endif
void NMI_ISR(void)
{
    do
    {
        // If it still can't clear the oscillator fault flags after the timeout,
        // trap and wait here.
        status = UCS_clearAllOscFlagsWithTimeout(1000);
    }
    while(status != 0);
}

void NMI_ISR(void)
{
    do
    {
        // If it still can't clear the oscillator fault flags after the timeout,
        // trap and wait here.
        status = UCS_clearAllOscFlagsWithTimeout(1000);
    }
    while(status != 0);
}

PS:

When I commented The MCLK modification, as you can see in the code, the program does not crash.

And if I apply the DCO clock to SMCLK (Pin 3.4), I can measure 20MHz. Problem: too much jitter, thatswhy I badly need to use a 20MHz crystal at XT1.

Thx for your help in advance,

with kind regards,

Stefan