MSP430G2553 DCO clock totally inaccurate - ~1 MHz instead of 8Mhz

I just let one of the pins toggling in a while loop, and I measured it with oscilloscope. Here is the whole code:

static void Clock_Init(void);
void Port_Create (void);

int main(void)
{
WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer

Clock_Init();
Port_Create();
__enable_interrupt(); // enable maskable interrupts

LED_GREEN_OFF;
LED_RED_OFF;

/* should never return */
while(1U)
{
P2OUT ^= BIT1;
}
}

static void Clock_Init(void)
{
if (CALBC1_1MHZ ==0xFF || CALDCO_1MHZ == 0xFF)
{
while(1); // If cal constants erased, trap CPU!!
}
__delay_cycles(10000);
BCSCTL1 &= ~BIT1;
BCSCTL1 |= BIT3 + BIT2 + BIT0;
DCOCTL &= ~BIT7;
DCOCTL |= BIT6 + BIT5;

BCSCTL2 = 0;
BCSCTL3 = 0;

}

void Port_Create (void)
{
P1DIR &= ~BIT3; // Input : ADC
P2DIR |= BIT0 | BIT1 | BIT5; // Output : LED_RED, LED_GREEN, PWM_LED
P3DIR |= BIT5; // Output : PWM_FAN
P3DIR &= ~BIT6; // Input : FAN_TACH
P2DIR &= ~BIT4; // Input : DALI_RX
P2DIR |= BIT3; // Output : DALI_TX
}

Michal,

that is not the way you can measure your clock frequency. Toggling a pin takes more than one CPU cycle, so your pin will not toggle at the same frequency your processor is running. You have to lead the clock out of your processor to one of the portpins. This is a special function. Look at P1.4 of the MSP430G2553 - one of it's special functions is SMCLK. If you enable it the processor will output the buffered SMCLK on that pin. Try the following code and measure the frequency at P1.4 of the device.

#include "msp430g2553.h"

void main( void )
{
  WDTCTL  = WDTPW | WDTHOLD; // Stop watchdog timer
  
  BCSCTL1 = CALBC1_8MHZ;     // Set range to 8MHz
  DCOCTL  = CALDCO_8MHZ;     // Set DCO step and modulation to 8MHz

  P1SEL |= 0x10;             // Enable special function for P1.4 - SMCLK
  P1OUT |= 0x10;             // Set P1.4 to output direction

  while( 1 )
  {
  }
}

Dennis

That is correct, but he wrote he tried the calibrated frequencies as well and he also told, that they did not work, either - so I would recommend to start from there and see if the clock works as expected in general.