5xx Parts: Disabling FLL Hardware and Modulator

Hmmm... I cannot confirm that. When SCG0 is set, there is no automatic modification of UCSCTL0 in my appliaction. Maybe it takes some cycles until the FLL is really inactive... did you check the behaviour once your app is running?
Johannes

Hi Johannes.

Thanks for the reply. I'm glad its working for someone at least! [:)] Most likely I'm just doing it wrong.

I added a while (1) { temp = UCSCTL0; } before the following lines

  UCSCTL1 &= ~DISMOD;
  __bic_SR_register(SCG0|SCG1);                 // Enable the FLL control loop

and UCSCTL0 still changes all the time after running in the while loop. When I force the value to zero using the debugger, the debugger reports back a non-zero value. The value of "temp" is also nonzero.

So other people can follow along, I decided to post the code I am playing with. It's pretty much a cut and paste from the msp430x54x_UCS_2.c sample code:

volatile uint16 temp;
void main(void) {
  WDTCTL = WDTPW+WDTHOLD;                   // Stop WDT
  P1DIR |= BIT0;                            // P1.0 output
  P11DIR |= 0x07;                           // ACLK, MCLK, SMCLK set out to pins
  P11SEL |= 0x07;                           // P11.0,1,2 for debugging purposes.

  UCSCTL3 |= SELREF_2;                      // Set DCO FLL reference = REFO
  UCSCTL4 |= SELA_2;                        // Set ACLK = REFO

  __bis_SR_register(SCG0|SCG1);                 // Disable the FLL control loop
  UCSCTL1 |= DISMOD;
  UCSCTL0 = 0x0000;                                         // Set lowest possible DCOx, MODx
  UCSCTL1 = (DISMOD|DCORSEL_5);             // Select DCO range 16MHz operation
  UCSCTL2 = FLLD_1 + 249;                            // Set DCO Multiplier for 8MHz
                                                                                // (N + 1) * FLLRef = Fdco
                                                                                // (249 + 1) * 32768 = 8MHz
                                                                                // Set FLL Div = fDCOCLK/2
  while (1){
  temp = UCSCTL0;
  }

}

Just loaded your code on one of my boards (F5419 Rev L). And the result (I think you will not like to hear that [:)] : The temp variable stays at 0. Maybe your Debugger is the problem? Try this one and see if the _NOP() gets reaches (place a breakpoint at the _NOP())

  while (1)
  {
  temp = UCSCTL0;
 
  if (temp != 0) break;
  }
 _NOP();

In case that does not work, too: To help you out of frustration: I have my problems with the FLL, too. [:S] (See other posting)

Regards,
Johannes

Well it sounds like I am doing it right then. I am using an old experimental part from a year back (X430F5438) while I am waiting for some real MSP430F5438s to arrive, so maybe that's the issue.

I'll give an update when I get some samples of the real chips.