MSP430 BasicTimer1 / Stabile Uhr-Clock mit 32kHz Uhrenquarz

  WDTCTL = WDTPW + WDTHOLD;    // Stop watchdog timer

  FLL_CTL0 &= ~XTS_FLL;        // XT1 0 low-frequency

  _BIC_SR(OSCOFF);             // turn on XT1 oscillator

  do                           // wait in loop until crystal is stable

   IFG1 &= ~OFIFG;

  while (IFG1 & OFIFG);

  FLL_CTL1 &= ~FLL_DIV0;       // ACLK = XT1

  FLL_CTL1 &= ~FLL_DIV1;

  IFG1 &= ~OFIFG;              // clear osc. fault int. flag

  FLL_CTL1 &= ~SELM0;          // set DCO as MCLK

  FLL_CTL1 &= ~SELM1;

  BTCTL = BTIP2;     // BT1 interrupt freq. = 1024Hz 

                     // aus ACLK = 32.768kHz

  _EINT();              // Enable interrupts

  _BIS_SR(LPM3_bits + GIE);     // in Low Power Mode 3